diff --git a/Documentation/dev-core-plugins.txt b/Documentation/dev-core-plugins.txt
index 04e2420..aa519806 100644
--- a/Documentation/dev-core-plugins.txt
+++ b/Documentation/dev-core-plugins.txt
@@ -155,6 +155,52 @@
    link:https://www.gerritcodereview.com/news.html[project news].
 --
 
+[[removing]]
+=== Removing Core Plugins
+
+A core plugin could be subject to NOT be considered core anymore if:
+
+1. Does not respect the license:
++
+The plugin code or the libraries used are not following anymore the
+Apache License Version 2.0.
+
+2. Is out of scope:
++
+The plugin functionality has gone outside the Gerrit-related scope,
+has a clear scope or conflict with other core plugins or existing and
+planned Gerrit core features.
+
+NOTE: The plugin would need to remain core until the planned replacement gets
+implemented. Otherwise the feature is likely missing between the removal and
+planned implementation times.
+
+3. Is not relevant:
++
+The plugin functionality is no more relevant to a majority of the Gerrit community:
++
+--
+** An out of the box Gerrit installation won’t be missing anything if the plugin is
+   not installed.
+** It isn’t anymore used by most sites.
+** Multiple parties (different organizations/companies) have abandoned the use of
+   the plugin and agree that it should not be anymore a core plugin.
+** If the same or similar functionality is provided by multiple plugins, the plugin
+   is not a clear recommended solution anymore by the community.
+** Whether a plugin is no more relevant to a majority of the Gerrit community must be
+   discussed on a case-by-case basis. In case of doubt, it’s up to the engineering
+   steering committee to make a decision.
+--
+
+4. Degraded code quality:
++
+The plugin code maintenance is lacking and has not anymore good test coverage.
+Maintaining the plugin code creates a significant overhead for the Gerrit maintainers.
+
+5. Outdated documentation:
++
+The plugin functionality documented is significantly outdated.
+
 GERRIT
 ------
 Part of link:index.html[Gerrit Code Review]
diff --git a/java/com/google/gerrit/acceptance/GerritServer.java b/java/com/google/gerrit/acceptance/GerritServer.java
index 2d62608..07aab3b 100644
--- a/java/com/google/gerrit/acceptance/GerritServer.java
+++ b/java/com/google/gerrit/acceptance/GerritServer.java
@@ -30,6 +30,9 @@
 import com.google.gerrit.acceptance.config.GlobalPluginConfigs;
 import com.google.gerrit.acceptance.testsuite.account.AccountOperations;
 import com.google.gerrit.acceptance.testsuite.account.AccountOperationsImpl;
+import com.google.gerrit.acceptance.testsuite.change.ChangeOperations;
+import com.google.gerrit.acceptance.testsuite.change.ChangeOperationsImpl;
+import com.google.gerrit.acceptance.testsuite.change.PerPatchsetOperationsImpl;
 import com.google.gerrit.acceptance.testsuite.group.GroupOperations;
 import com.google.gerrit.acceptance.testsuite.group.GroupOperationsImpl;
 import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
@@ -506,6 +509,8 @@
             bind(GroupOperations.class).to(GroupOperationsImpl.class);
             bind(ProjectOperations.class).to(ProjectOperationsImpl.class);
             bind(RequestScopeOperations.class).to(RequestScopeOperationsImpl.class);
+            bind(ChangeOperations.class).to(ChangeOperationsImpl.class);
+            factory(PerPatchsetOperationsImpl.Factory.class);
             factory(PushOneCommit.Factory.class);
             install(InProcessProtocol.module());
             install(new NoSshModule());
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/ChangeOperations.java b/java/com/google/gerrit/acceptance/testsuite/change/ChangeOperations.java
new file mode 100644
index 0000000..cc96d5b
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/ChangeOperations.java
@@ -0,0 +1,115 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+import com.google.gerrit.entities.Change;
+import com.google.gerrit.entities.PatchSet;
+
+/**
+ * An aggregation of operations on changes for test purposes.
+ *
+ * <p>To execute the operations, no Gerrit permissions are necessary.
+ *
+ * <p><strong>Note:</strong> This interface is not implemented using the REST or extension API.
+ * Hence, it cannot be used for testing those APIs.
+ */
+public interface ChangeOperations {
+
+  /**
+   * Starts the fluent chain for querying or modifying a change. Please see the methods of {@link
+   * PerChangeOperations} for details on possible operations.
+   *
+   * @return an aggregation of operations on a specific change
+   */
+  PerChangeOperations change(Change.Id changeId);
+
+  /**
+   * Starts the fluent chain to create a change. The returned builder can be used to specify the
+   * attributes of the new change. To create the change for real, {@link
+   * TestChangeCreation.Builder#create()} must be called.
+   *
+   * <p>Example:
+   *
+   * <pre>
+   * Change.Id createdChangeId = changeOperations
+   *     .newChange()
+   *     .file("file1")
+   *     .content("Line 1\nLine2\n")
+   *     .create();
+   * </pre>
+   *
+   * <p><strong>Note:</strong> There must be at least one existing user and repository.
+   *
+   * @return a builder to create the new change
+   */
+  TestChangeCreation.Builder newChange();
+
+  /** An aggregation of methods on a specific change. */
+  interface PerChangeOperations {
+
+    /**
+     * Checks whether the change exists.
+     *
+     * @return {@code true} if the change exists
+     */
+    boolean exists();
+
+    /**
+     * Retrieves the change.
+     *
+     * <p><strong>Note:</strong> This call will fail with an exception if the requested change
+     * doesn't exist. If you want to check for the existence of a change, use {@link #exists()}
+     * instead.
+     *
+     * @return the corresponding {@code TestChange}
+     */
+    TestChange get();
+
+    /**
+     * Starts the fluent chain to create a new patchset. The returned builder can be used to specify
+     * the attributes of the new patchset. To create the patchset for real, {@link
+     * TestPatchsetCreation.Builder#create()} must be called.
+     *
+     * <p>Example:
+     *
+     * <pre>
+     * PatchSet.Id createdPatchsetId = changeOperations
+     *     .change(changeId)
+     *     .newPatchset()
+     *     .file("file1")
+     *     .content("Line 1\nLine2\n")
+     *     .create();
+     * </pre>
+     *
+     * @return builder to create a new patchset
+     */
+    TestPatchsetCreation.Builder newPatchset();
+
+    /**
+     * Starts the fluent chain for querying or modifying a patchset. Please see the methods of
+     * {@link PerPatchsetOperations} for details on possible operations.
+     *
+     * @return an aggregation of operations on a specific patchset
+     */
+    PerPatchsetOperations patchset(PatchSet.Id patchsetId);
+
+    /**
+     * Like {@link #patchset(PatchSet.Id)} but for the current patchset.
+     *
+     * @return an aggregation of operations on a specific patchset
+     */
+    PerPatchsetOperations currentPatchset();
+  }
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/ChangeOperationsImpl.java b/java/com/google/gerrit/acceptance/testsuite/change/ChangeOperationsImpl.java
new file mode 100644
index 0000000..3bd6475
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/ChangeOperationsImpl.java
@@ -0,0 +1,412 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+import static com.google.common.base.Preconditions.checkState;
+import static com.google.common.collect.ImmutableList.toImmutableList;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Streams;
+import com.google.gerrit.entities.Account;
+import com.google.gerrit.entities.Change;
+import com.google.gerrit.entities.PatchSet;
+import com.google.gerrit.entities.Project;
+import com.google.gerrit.entities.RefNames;
+import com.google.gerrit.extensions.restapi.BadRequestException;
+import com.google.gerrit.extensions.restapi.RestApiException;
+import com.google.gerrit.server.ChangeUtil;
+import com.google.gerrit.server.GerritPersonIdent;
+import com.google.gerrit.server.IdentifiedUser;
+import com.google.gerrit.server.account.AccountResolver;
+import com.google.gerrit.server.change.ChangeFinder;
+import com.google.gerrit.server.change.ChangeInserter;
+import com.google.gerrit.server.change.PatchSetInserter;
+import com.google.gerrit.server.edit.tree.TreeCreator;
+import com.google.gerrit.server.edit.tree.TreeModification;
+import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.gerrit.server.notedb.ChangeNotes;
+import com.google.gerrit.server.notedb.Sequences;
+import com.google.gerrit.server.project.ProjectCache;
+import com.google.gerrit.server.update.BatchUpdate;
+import com.google.gerrit.server.update.UpdateException;
+import com.google.gerrit.server.util.CommitMessageUtil;
+import com.google.gerrit.server.util.time.TimeUtil;
+import com.google.inject.Inject;
+import java.io.IOException;
+import java.sql.Timestamp;
+import java.util.Arrays;
+import java.util.Date;
+import java.util.Objects;
+import java.util.Optional;
+import org.eclipse.jgit.errors.ConfigInvalidException;
+import org.eclipse.jgit.lib.CommitBuilder;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectInserter;
+import org.eclipse.jgit.lib.PersonIdent;
+import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevWalk;
+import org.eclipse.jgit.util.ChangeIdUtil;
+
+/**
+ * The implementation of {@link ChangeOperations}.
+ *
+ * <p>There is only one implementation of {@link ChangeOperations}. Nevertheless, we keep the
+ * separation between interface and implementation to enhance clarity.
+ */
+public class ChangeOperationsImpl implements ChangeOperations {
+  private final Sequences seq;
+  private final ChangeInserter.Factory changeInserterFactory;
+  private final PatchSetInserter.Factory patchsetInserterFactory;
+  private final GitRepositoryManager repositoryManager;
+  private final AccountResolver resolver;
+  private final IdentifiedUser.GenericFactory userFactory;
+  private final PersonIdent serverIdent;
+  private final BatchUpdate.Factory batchUpdateFactory;
+  private final ProjectCache projectCache;
+  private final ChangeFinder changeFinder;
+  private final PerPatchsetOperationsImpl.Factory perPatchsetOperationsFactory;
+
+  @Inject
+  public ChangeOperationsImpl(
+      Sequences seq,
+      ChangeInserter.Factory changeInserterFactory,
+      PatchSetInserter.Factory patchsetInserterFactory,
+      GitRepositoryManager repositoryManager,
+      AccountResolver resolver,
+      IdentifiedUser.GenericFactory userFactory,
+      @GerritPersonIdent PersonIdent serverIdent,
+      BatchUpdate.Factory batchUpdateFactory,
+      ProjectCache projectCache,
+      ChangeFinder changeFinder,
+      PerPatchsetOperationsImpl.Factory perPatchsetOperationsFactory) {
+    this.seq = seq;
+    this.changeInserterFactory = changeInserterFactory;
+    this.patchsetInserterFactory = patchsetInserterFactory;
+    this.repositoryManager = repositoryManager;
+    this.resolver = resolver;
+    this.userFactory = userFactory;
+    this.serverIdent = serverIdent;
+    this.batchUpdateFactory = batchUpdateFactory;
+    this.projectCache = projectCache;
+    this.changeFinder = changeFinder;
+    this.perPatchsetOperationsFactory = perPatchsetOperationsFactory;
+  }
+
+  @Override
+  public PerChangeOperations change(Change.Id changeId) {
+    return new PerChangeOperationsImpl(changeId);
+  }
+
+  @Override
+  public TestChangeCreation.Builder newChange() {
+    return TestChangeCreation.builder(this::createChange);
+  }
+
+  private Change.Id createChange(TestChangeCreation changeCreation) throws Exception {
+    Change.Id changeId = Change.id(seq.nextChangeId());
+    Project.NameKey project = getTargetProject(changeCreation);
+
+    try (Repository repository = repositoryManager.openRepository(project);
+        ObjectInserter objectInserter = repository.newObjectInserter();
+        RevWalk revWalk = new RevWalk(objectInserter.newReader())) {
+      Timestamp now = TimeUtil.nowTs();
+      IdentifiedUser changeOwner = getChangeOwner(changeCreation);
+      PersonIdent authorAndCommitter =
+          changeOwner.newCommitterIdent(now, serverIdent.getTimeZone());
+      ObjectId commitId =
+          createCommit(repository, revWalk, objectInserter, changeCreation, authorAndCommitter);
+
+      String refName = RefNames.fullName(changeCreation.branch());
+      ChangeInserter inserter = getChangeInserter(changeId, refName, commitId);
+
+      try (BatchUpdate batchUpdate = batchUpdateFactory.create(project, changeOwner, now)) {
+        batchUpdate.setRepository(repository, revWalk, objectInserter);
+        batchUpdate.insertChange(inserter);
+        batchUpdate.execute();
+      }
+      return changeId;
+    }
+  }
+
+  private Project.NameKey getTargetProject(TestChangeCreation changeCreation) {
+    if (changeCreation.project().isPresent()) {
+      return changeCreation.project().get();
+    }
+
+    return getArbitraryProject();
+  }
+
+  private Project.NameKey getArbitraryProject() {
+    Project.NameKey allProjectsName = projectCache.getAllProjects().getNameKey();
+    Project.NameKey allUsersName = projectCache.getAllUsers().getNameKey();
+    Optional<Project.NameKey> arbitraryProject =
+        projectCache.all().stream()
+            .filter(
+                name ->
+                    !Objects.equals(name, allProjectsName) && !Objects.equals(name, allUsersName))
+            .findFirst();
+    checkState(
+        arbitraryProject.isPresent(),
+        "At least one repository must be available on the Gerrit server");
+    return arbitraryProject.get();
+  }
+
+  private IdentifiedUser getChangeOwner(TestChangeCreation changeCreation)
+      throws IOException, ConfigInvalidException {
+    if (changeCreation.owner().isPresent()) {
+      return userFactory.create(changeCreation.owner().get());
+    }
+
+    return getArbitraryUser();
+  }
+
+  private IdentifiedUser getArbitraryUser() throws ConfigInvalidException, IOException {
+    ImmutableSet<Account.Id> foundAccounts = resolver.resolveIgnoreVisibility("").asIdSet();
+    checkState(
+        !foundAccounts.isEmpty(),
+        "At least one user account must be available on the Gerrit server");
+    return userFactory.create(foundAccounts.iterator().next());
+  }
+
+  private ObjectId createCommit(
+      Repository repository,
+      RevWalk revWalk,
+      ObjectInserter objectInserter,
+      TestChangeCreation changeCreation,
+      PersonIdent authorAndCommitter)
+      throws IOException, BadRequestException {
+    Optional<ObjectId> branchTip = getTip(repository, changeCreation.branch());
+
+    ObjectId tree =
+        createNewTree(
+            repository,
+            revWalk,
+            branchTip.orElse(ObjectId.zeroId()),
+            changeCreation.treeModifications());
+
+    String commitMessage = correctCommitMessage(changeCreation.commitMessage());
+
+    ImmutableList<ObjectId> parentCommitIds = Streams.stream(branchTip).collect(toImmutableList());
+    return createCommit(
+        objectInserter,
+        tree,
+        parentCommitIds,
+        authorAndCommitter,
+        authorAndCommitter,
+        commitMessage);
+  }
+
+  private Optional<ObjectId> getTip(Repository repository, String branch) throws IOException {
+    Optional<Ref> ref = Optional.ofNullable(repository.findRef(branch));
+    return ref.map(Ref::getObjectId);
+  }
+
+  private static ObjectId createNewTree(
+      Repository repository,
+      RevWalk revWalk,
+      ObjectId baseCommitId,
+      ImmutableList<TreeModification> treeModifications)
+      throws IOException {
+    TreeCreator treeCreator = getTreeCreator(revWalk, baseCommitId);
+    treeCreator.addTreeModifications(treeModifications);
+    return treeCreator.createNewTreeAndGetId(repository);
+  }
+
+  private static TreeCreator getTreeCreator(RevWalk revWalk, ObjectId baseCommitId)
+      throws IOException {
+    if (ObjectId.zeroId().equals(baseCommitId)) {
+      return TreeCreator.basedOnEmptyTree();
+    }
+    RevCommit baseCommit = revWalk.parseCommit(baseCommitId);
+    return TreeCreator.basedOn(baseCommit);
+  }
+
+  private String correctCommitMessage(String desiredCommitMessage) throws BadRequestException {
+    String commitMessage = CommitMessageUtil.checkAndSanitizeCommitMessage(desiredCommitMessage);
+
+    if (ChangeIdUtil.indexOfChangeId(commitMessage, "\n") == -1) {
+      ObjectId id = CommitMessageUtil.generateChangeId();
+      commitMessage = ChangeIdUtil.insertId(commitMessage, id);
+    }
+
+    return commitMessage;
+  }
+
+  private ObjectId createCommit(
+      ObjectInserter objectInserter,
+      ObjectId tree,
+      ImmutableList<ObjectId> parentCommitIds,
+      PersonIdent author,
+      PersonIdent committer,
+      String commitMessage)
+      throws IOException {
+    CommitBuilder builder = new CommitBuilder();
+    builder.setTreeId(tree);
+    builder.setParentIds(parentCommitIds);
+    builder.setAuthor(author);
+    builder.setCommitter(committer);
+    builder.setMessage(commitMessage);
+    ObjectId newCommitId = objectInserter.insert(builder);
+    objectInserter.flush();
+    return newCommitId;
+  }
+
+  private ChangeInserter getChangeInserter(Change.Id changeId, String refName, ObjectId commitId) {
+    ChangeInserter inserter = changeInserterFactory.create(changeId, commitId, refName);
+    inserter.setMessage(String.format("Uploaded patchset %d.", inserter.getPatchSetId().get()));
+    return inserter;
+  }
+
+  private class PerChangeOperationsImpl implements PerChangeOperations {
+
+    private final Change.Id changeId;
+
+    public PerChangeOperationsImpl(Change.Id changeId) {
+      this.changeId = changeId;
+    }
+
+    @Override
+    public boolean exists() {
+      return changeFinder.findOne(changeId).isPresent();
+    }
+
+    @Override
+    public TestChange get() {
+      return toTestChange(getChangeNotes().getChange());
+    }
+
+    private ChangeNotes getChangeNotes() {
+      Optional<ChangeNotes> changeNotes = changeFinder.findOne(changeId);
+      checkState(changeNotes.isPresent(), "Tried to get non-existing test change.");
+      return changeNotes.get();
+    }
+
+    private TestChange toTestChange(Change change) {
+      return TestChange.builder()
+          .numericChangeId(change.getId())
+          .changeId(change.getKey().get())
+          .build();
+    }
+
+    @Override
+    public TestPatchsetCreation.Builder newPatchset() {
+      return TestPatchsetCreation.builder(this::createPatchset);
+    }
+
+    private PatchSet.Id createPatchset(TestPatchsetCreation patchsetCreation)
+        throws IOException, RestApiException, UpdateException {
+      ChangeNotes changeNotes = getChangeNotes();
+      Project.NameKey project = changeNotes.getProjectName();
+      try (Repository repository = repositoryManager.openRepository(project);
+          ObjectInserter objectInserter = repository.newObjectInserter();
+          RevWalk revWalk = new RevWalk(objectInserter.newReader())) {
+        Timestamp now = TimeUtil.nowTs();
+        ObjectId newPatchsetCommit =
+            createPatchsetCommit(
+                repository, revWalk, objectInserter, changeNotes, patchsetCreation, now);
+
+        PatchSet.Id patchsetId =
+            ChangeUtil.nextPatchSetId(repository, changeNotes.getCurrentPatchSet().id());
+        PatchSetInserter patchSetInserter =
+            getPatchSetInserter(changeNotes, newPatchsetCommit, patchsetId);
+
+        IdentifiedUser changeOwner = userFactory.create(changeNotes.getChange().getOwner());
+        try (BatchUpdate batchUpdate = batchUpdateFactory.create(project, changeOwner, now)) {
+          batchUpdate.setRepository(repository, revWalk, objectInserter);
+          batchUpdate.addOp(changeId, patchSetInserter);
+          batchUpdate.execute();
+        }
+        return patchsetId;
+      }
+    }
+
+    private ObjectId createPatchsetCommit(
+        Repository repository,
+        RevWalk revWalk,
+        ObjectInserter objectInserter,
+        ChangeNotes changeNotes,
+        TestPatchsetCreation patchsetCreation,
+        Timestamp now)
+        throws IOException {
+      ObjectId oldPatchsetCommitId = changeNotes.getCurrentPatchSet().commitId();
+      RevCommit oldPatchsetCommit = repository.parseCommit(oldPatchsetCommitId);
+
+      ObjectId tree =
+          createNewTree(
+              repository, revWalk, oldPatchsetCommitId, patchsetCreation.treeModifications());
+
+      String commitMessage = oldPatchsetCommit.getFullMessage();
+
+      ImmutableList<ObjectId> parentCommitIds = getParents(oldPatchsetCommit);
+      PersonIdent author = getAuthor(oldPatchsetCommit);
+      PersonIdent committer = getCommitter(oldPatchsetCommit, now);
+      return createCommit(objectInserter, tree, parentCommitIds, author, committer, commitMessage);
+    }
+
+    private PersonIdent getAuthor(RevCommit oldPatchsetCommit) {
+      return Optional.ofNullable(oldPatchsetCommit.getAuthorIdent()).orElse(serverIdent);
+    }
+
+    private PersonIdent getCommitter(RevCommit oldPatchsetCommit, Timestamp now) {
+      PersonIdent oldPatchsetCommitter =
+          Optional.ofNullable(oldPatchsetCommit.getCommitterIdent()).orElse(serverIdent);
+      if (asSeconds(now) == asSeconds(oldPatchsetCommitter.getWhen())) {
+        /* We need to ensure that the resulting commit SHA-1 is different from the old patchset.
+         * In real situations, this automatically happens as two patchsets won't have exactly the
+         * same commit timestamp even when the tree and commit message are the same. In tests,
+         * we can easily end up with the same timestamp as Git uses second precision for timestamps.
+         * We could of course require that tests must use TestTimeUtil#setClockStep but
+         * that would be an unnecessary nuisance for test writers. Hence, go with a simple solution
+         * here and simply add a second. */
+        now = Timestamp.from(now.toInstant().plusSeconds(1));
+      }
+      return new PersonIdent(oldPatchsetCommitter, now);
+    }
+
+    private long asSeconds(Date date) {
+      return date.getTime() / 1000;
+    }
+
+    private ImmutableList<ObjectId> getParents(RevCommit oldPatchsetCommit) {
+      return Arrays.stream(oldPatchsetCommit.getParents())
+          .map(ObjectId::toObjectId)
+          .collect(toImmutableList());
+    }
+
+    private PatchSetInserter getPatchSetInserter(
+        ChangeNotes changeNotes, ObjectId newPatchsetCommit, PatchSet.Id patchsetId) {
+      PatchSetInserter patchSetInserter =
+          patchsetInserterFactory.create(changeNotes, patchsetId, newPatchsetCommit);
+      patchSetInserter.setCheckAddPatchSetPermission(false);
+      patchSetInserter.setMessage(String.format("Uploaded patchset %d.", patchsetId.get()));
+      return patchSetInserter;
+    }
+
+    @Override
+    public PerPatchsetOperations patchset(PatchSet.Id patchsetId) {
+      return perPatchsetOperationsFactory.create(getChangeNotes(), patchsetId);
+    }
+
+    @Override
+    public PerPatchsetOperations currentPatchset() {
+      ChangeNotes changeNotes = getChangeNotes();
+      return perPatchsetOperationsFactory.create(
+          changeNotes, changeNotes.getChange().currentPatchSetId());
+    }
+  }
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/FileContentBuilder.java b/java/com/google/gerrit/acceptance/testsuite/change/FileContentBuilder.java
new file mode 100644
index 0000000..bae8407
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/FileContentBuilder.java
@@ -0,0 +1,60 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import com.google.common.base.Strings;
+import com.google.gerrit.common.RawInputUtil;
+import com.google.gerrit.server.edit.tree.ChangeFileContentModification;
+import com.google.gerrit.server.edit.tree.DeleteFileModification;
+import com.google.gerrit.server.edit.tree.RenameFileModification;
+import com.google.gerrit.server.edit.tree.TreeModification;
+import java.util.function.Consumer;
+
+/** Builder to simplify file content specification. */
+public class FileContentBuilder<T> {
+  private final T builder;
+  private final String filePath;
+  private final Consumer<TreeModification> modificationToBuilderAdder;
+
+  FileContentBuilder(
+      T builder, String filePath, Consumer<TreeModification> modificationToBuilderAdder) {
+    checkNotNull(Strings.emptyToNull(filePath), "File path must not be null or empty.");
+    this.builder = builder;
+    this.filePath = filePath;
+    this.modificationToBuilderAdder = modificationToBuilderAdder;
+  }
+
+  /** Content of the file. Must not be empty. */
+  public T content(String content) {
+    checkNotNull(
+        Strings.emptyToNull(content),
+        "Empty file content is not supported. Adjust test API if necessary.");
+    modificationToBuilderAdder.accept(
+        new ChangeFileContentModification(filePath, RawInputUtil.create(content)));
+    return builder;
+  }
+
+  public T delete() {
+    modificationToBuilderAdder.accept(new DeleteFileModification(filePath));
+    return builder;
+  }
+
+  public T renameTo(String newFilePath) {
+    modificationToBuilderAdder.accept(new RenameFileModification(filePath, newFilePath));
+    return builder;
+  }
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/PerPatchsetOperations.java b/java/com/google/gerrit/acceptance/testsuite/change/PerPatchsetOperations.java
new file mode 100644
index 0000000..c095551
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/PerPatchsetOperations.java
@@ -0,0 +1,28 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package com.google.gerrit.acceptance.testsuite.change;
+
+/** An aggregation of methods on a specific patchset. */
+public interface PerPatchsetOperations {
+
+  /**
+   * Retrieves the patchset.
+   *
+   * <p><strong>Note:</strong> This call will fail with an exception if the requested patchset
+   * doesn't exist.
+   *
+   * @return the corresponding {@code TestPatchset}
+   */
+  TestPatchset get();
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/PerPatchsetOperationsImpl.java b/java/com/google/gerrit/acceptance/testsuite/change/PerPatchsetOperationsImpl.java
new file mode 100644
index 0000000..8c9a495
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/PerPatchsetOperationsImpl.java
@@ -0,0 +1,48 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+import com.google.gerrit.entities.PatchSet;
+import com.google.gerrit.server.notedb.ChangeNotes;
+import com.google.inject.Inject;
+import com.google.inject.assistedinject.Assisted;
+
+/**
+ * The implementation of {@link PerPatchsetOperations}.
+ *
+ * <p>There is only one implementation of {@link PerPatchsetOperations}. Nevertheless, we keep the
+ * separation between interface and implementation to enhance clarity.
+ */
+public class PerPatchsetOperationsImpl implements PerPatchsetOperations {
+  private final ChangeNotes changeNotes;
+  private final PatchSet.Id patchsetId;
+
+  public interface Factory {
+    PerPatchsetOperationsImpl create(ChangeNotes changeNotes, PatchSet.Id patchsetId);
+  }
+
+  @Inject
+  private PerPatchsetOperationsImpl(
+      @Assisted ChangeNotes changeNotes, @Assisted PatchSet.Id patchsetId) {
+    this.changeNotes = changeNotes;
+    this.patchsetId = patchsetId;
+  }
+
+  @Override
+  public TestPatchset get() {
+    PatchSet patchset = changeNotes.getPatchSets().get(patchsetId);
+    return TestPatchset.builder().patchsetId(patchsetId).commitId(patchset.commitId()).build();
+  }
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/TestChange.java b/java/com/google/gerrit/acceptance/testsuite/change/TestChange.java
new file mode 100644
index 0000000..ea2acaa
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/TestChange.java
@@ -0,0 +1,48 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+import com.google.auto.value.AutoValue;
+import com.google.gerrit.entities.Change;
+
+/** Representation of a change used for testing purposes. */
+@AutoValue
+public abstract class TestChange {
+
+  /**
+   * The numeric change ID, sometimes also called change number or legacy change ID. Unique per
+   * host.
+   */
+  public abstract Change.Id numericChangeId();
+
+  /**
+   * The Change-Id as specified in the commit message. Consists of an {@code I} followed by a 40-hex
+   * string. Only unique per project-branch.
+   */
+  public abstract String changeId();
+
+  static Builder builder() {
+    return new AutoValue_TestChange.Builder();
+  }
+
+  @AutoValue.Builder
+  abstract static class Builder {
+    abstract Builder numericChangeId(Change.Id numericChangeId);
+
+    abstract Builder changeId(String changeId);
+
+    abstract TestChange build();
+  }
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/TestChangeCreation.java b/java/com/google/gerrit/acceptance/testsuite/change/TestChangeCreation.java
new file mode 100644
index 0000000..65db967
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/TestChangeCreation.java
@@ -0,0 +1,89 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableList;
+import com.google.gerrit.acceptance.testsuite.ThrowingFunction;
+import com.google.gerrit.entities.Account;
+import com.google.gerrit.entities.Change;
+import com.google.gerrit.entities.Project;
+import com.google.gerrit.server.edit.tree.TreeModification;
+import java.util.Optional;
+import org.eclipse.jgit.lib.Constants;
+
+/** Initial attributes of the change. If not provided, arbitrary values will be used. */
+@AutoValue
+public abstract class TestChangeCreation {
+  public abstract Optional<Project.NameKey> project();
+
+  public abstract String branch();
+
+  public abstract Optional<Account.Id> owner();
+
+  public abstract String commitMessage();
+
+  public abstract ImmutableList<TreeModification> treeModifications();
+
+  abstract ThrowingFunction<TestChangeCreation, Change.Id> changeCreator();
+
+  public static Builder builder(ThrowingFunction<TestChangeCreation, Change.Id> changeCreator) {
+    return new AutoValue_TestChangeCreation.Builder()
+        .changeCreator(changeCreator)
+        .branch(Constants.R_HEADS + Constants.MASTER)
+        .commitMessage("A test change");
+  }
+
+  @AutoValue.Builder
+  public abstract static class Builder {
+    /** Target project/Repository of the change. Must be an existing project. */
+    public abstract Builder project(Project.NameKey project);
+
+    /**
+     * Target branch of the change. Neither needs to exist nor needs to point to an actual commit.
+     */
+    public abstract Builder branch(String branch);
+
+    /** The change owner. Must be an existing user account. */
+    public abstract Builder owner(Account.Id owner);
+
+    /**
+     * The commit message. The message may contain a {@code Change-Id} footer but does not need to.
+     * If the footer is absent, it will be generated.
+     */
+    public abstract Builder commitMessage(String commitMessage);
+
+    /** Modified file of the change. The file content is specified via the returned builder. */
+    public FileContentBuilder<Builder> file(String filePath) {
+      return new FileContentBuilder<>(this, filePath, treeModificationsBuilder()::add);
+    }
+
+    abstract ImmutableList.Builder<TreeModification> treeModificationsBuilder();
+
+    abstract Builder changeCreator(ThrowingFunction<TestChangeCreation, Change.Id> changeCreator);
+
+    abstract TestChangeCreation autoBuild();
+
+    /**
+     * Creates the change.
+     *
+     * @return the {@code Change.Id} of the created change
+     */
+    public Change.Id create() {
+      TestChangeCreation changeUpdate = autoBuild();
+      return changeUpdate.changeCreator().applyAndThrowSilently(changeUpdate);
+    }
+  }
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/TestPatchset.java b/java/com/google/gerrit/acceptance/testsuite/change/TestPatchset.java
new file mode 100644
index 0000000..1ba242a
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/TestPatchset.java
@@ -0,0 +1,43 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+import com.google.auto.value.AutoValue;
+import com.google.gerrit.entities.PatchSet;
+import org.eclipse.jgit.lib.ObjectId;
+
+/** Representation of a patchset used for testing purposes. */
+@AutoValue
+public abstract class TestPatchset {
+
+  /** The numeric patchset ID. */
+  public abstract PatchSet.Id patchsetId();
+
+  /** The commit SHA-1 of the patchset. */
+  public abstract ObjectId commitId();
+
+  static Builder builder() {
+    return new AutoValue_TestPatchset.Builder();
+  }
+
+  @AutoValue.Builder
+  abstract static class Builder {
+    abstract Builder patchsetId(PatchSet.Id patchsetId);
+
+    abstract Builder commitId(ObjectId commitId);
+
+    abstract TestPatchset build();
+  }
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/change/TestPatchsetCreation.java b/java/com/google/gerrit/acceptance/testsuite/change/TestPatchsetCreation.java
new file mode 100644
index 0000000..571b1e1
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/testsuite/change/TestPatchsetCreation.java
@@ -0,0 +1,61 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableList;
+import com.google.gerrit.acceptance.testsuite.ThrowingFunction;
+import com.google.gerrit.entities.PatchSet;
+import com.google.gerrit.server.edit.tree.TreeModification;
+
+/** Initial attributes of the patchset. If not provided, arbitrary values will be used. */
+@AutoValue
+public abstract class TestPatchsetCreation {
+
+  public abstract ImmutableList<TreeModification> treeModifications();
+
+  abstract ThrowingFunction<TestPatchsetCreation, PatchSet.Id> patchsetCreator();
+
+  public static TestPatchsetCreation.Builder builder(
+      ThrowingFunction<TestPatchsetCreation, PatchSet.Id> patchsetCreator) {
+    return new AutoValue_TestPatchsetCreation.Builder().patchsetCreator(patchsetCreator);
+  }
+
+  @AutoValue.Builder
+  public abstract static class Builder {
+
+    /** Modified file of the patchset. The file content is specified via the returned builder. */
+    public FileContentBuilder<Builder> file(String filePath) {
+      return new FileContentBuilder<>(this, filePath, treeModificationsBuilder()::add);
+    }
+
+    abstract ImmutableList.Builder<TreeModification> treeModificationsBuilder();
+
+    abstract TestPatchsetCreation.Builder patchsetCreator(
+        ThrowingFunction<TestPatchsetCreation, PatchSet.Id> patchsetCreator);
+
+    abstract TestPatchsetCreation autoBuild();
+
+    /**
+     * Creates the patchset.
+     *
+     * @return the {@code PatchSet.Id} of the created patchset
+     */
+    public PatchSet.Id create() {
+      TestPatchsetCreation patchsetCreation = autoBuild();
+      return patchsetCreation.patchsetCreator().applyAndThrowSilently(patchsetCreation);
+    }
+  }
+}
diff --git a/java/com/google/gerrit/acceptance/testsuite/project/ProjectOperationsImpl.java b/java/com/google/gerrit/acceptance/testsuite/project/ProjectOperationsImpl.java
index c894059..e4d594b 100644
--- a/java/com/google/gerrit/acceptance/testsuite/project/ProjectOperationsImpl.java
+++ b/java/com/google/gerrit/acceptance/testsuite/project/ProjectOperationsImpl.java
@@ -14,6 +14,7 @@
 
 package com.google.gerrit.acceptance.testsuite.project;
 
+import static com.google.common.collect.ImmutableList.toImmutableList;
 import static com.google.gerrit.entities.RefNames.REFS_CONFIG;
 import static com.google.gerrit.server.project.ProjectConfig.PROJECT_CONFIG;
 import static java.nio.charset.StandardCharsets.UTF_8;
@@ -43,12 +44,10 @@
 import com.google.inject.Inject;
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Collections;
 import org.apache.commons.lang.RandomStringUtils;
 import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.junit.TestRepository;
 import org.eclipse.jgit.lib.Config;
-import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectLoader;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
@@ -91,7 +90,8 @@
 
     CreateProjectArgs args = new CreateProjectArgs();
     args.setProjectName(name);
-    args.branch = Collections.singletonList(Constants.R_HEADS + Constants.MASTER);
+    args.branch =
+        projectCreation.branches().stream().map(RefNames::fullName).collect(toImmutableList());
     args.createEmptyCommit = projectCreation.createEmptyCommit().orElse(true);
     projectCreation.parent().ifPresent(p -> args.newParent = p);
     // ProjectCreator wants non-null owner IDs.
@@ -211,9 +211,7 @@
     }
 
     private RevCommit headOrNull(String branch) {
-      if (!branch.startsWith(Constants.R_REFS)) {
-        branch = RefNames.REFS_HEADS + branch;
-      }
+      branch = RefNames.fullName(branch);
 
       try (Repository repo = repoManager.openRepository(nameKey);
           RevWalk rw = new RevWalk(repo)) {
diff --git a/java/com/google/gerrit/acceptance/testsuite/project/TestProjectCreation.java b/java/com/google/gerrit/acceptance/testsuite/project/TestProjectCreation.java
index 99e045c..2649dea 100644
--- a/java/com/google/gerrit/acceptance/testsuite/project/TestProjectCreation.java
+++ b/java/com/google/gerrit/acceptance/testsuite/project/TestProjectCreation.java
@@ -15,10 +15,14 @@
 package com.google.gerrit.acceptance.testsuite.project;
 
 import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Sets;
 import com.google.gerrit.acceptance.testsuite.ThrowingFunction;
 import com.google.gerrit.entities.Project;
 import com.google.gerrit.extensions.client.SubmitType;
 import java.util.Optional;
+import java.util.Set;
+import org.eclipse.jgit.lib.Constants;
 
 @AutoValue
 public abstract class TestProjectCreation {
@@ -27,6 +31,8 @@
 
   public abstract Optional<Project.NameKey> parent();
 
+  public abstract ImmutableSet<String> branches();
+
   public abstract Optional<Boolean> createEmptyCommit();
 
   public abstract Optional<SubmitType> submitType();
@@ -35,7 +41,9 @@
 
   public static Builder builder(
       ThrowingFunction<TestProjectCreation, Project.NameKey> projectCreator) {
-    return new AutoValue_TestProjectCreation.Builder().projectCreator(projectCreator);
+    return new AutoValue_TestProjectCreation.Builder()
+        .branches(Constants.R_HEADS + Constants.MASTER)
+        .projectCreator(projectCreator);
   }
 
   @AutoValue.Builder
@@ -46,6 +54,17 @@
 
     public abstract TestProjectCreation.Builder submitType(SubmitType submitType);
 
+    /**
+     * Branches which should be created in the repository (with an empty root commit). The
+     * "refs/heads/" prefix of the branch name can be omitted. The specified branches are ignored if
+     * {@link #noEmptyCommit()} is used.
+     */
+    public TestProjectCreation.Builder branches(String branch1, String... otherBranches) {
+      return branches(Sets.union(ImmutableSet.of(branch1), ImmutableSet.copyOf(otherBranches)));
+    }
+
+    abstract TestProjectCreation.Builder branches(Set<String> branches);
+
     public abstract TestProjectCreation.Builder createEmptyCommit(boolean value);
 
     /** Skips the empty commit on creation. This means that project's branches will not exist. */
diff --git a/java/com/google/gerrit/extensions/common/testing/CommitInfoSubject.java b/java/com/google/gerrit/extensions/common/testing/CommitInfoSubject.java
index d6fcb37..d344e18 100644
--- a/java/com/google/gerrit/extensions/common/testing/CommitInfoSubject.java
+++ b/java/com/google/gerrit/extensions/common/testing/CommitInfoSubject.java
@@ -18,11 +18,13 @@
 import static com.google.gerrit.extensions.common.testing.GitPersonSubject.gitPersons;
 import static com.google.gerrit.truth.ListSubject.elements;
 
+import com.google.common.truth.Correspondence;
 import com.google.common.truth.FailureMetadata;
 import com.google.common.truth.StringSubject;
 import com.google.common.truth.Subject;
 import com.google.gerrit.extensions.common.CommitInfo;
 import com.google.gerrit.truth.ListSubject;
+import com.google.gerrit.truth.NullAwareCorrespondence;
 
 public class CommitInfoSubject extends Subject {
 
@@ -65,4 +67,8 @@
     isNotNull();
     return check("message").that(commitInfo.message);
   }
+
+  public static Correspondence<CommitInfo, String> hasCommit() {
+    return NullAwareCorrespondence.transforming(commitInfo -> commitInfo.commit, "hasCommit");
+  }
 }
diff --git a/java/com/google/gerrit/server/config/PluginConfig.java b/java/com/google/gerrit/server/config/PluginConfig.java
index 7dd981c..2459d0b 100644
--- a/java/com/google/gerrit/server/config/PluginConfig.java
+++ b/java/com/google/gerrit/server/config/PluginConfig.java
@@ -61,6 +61,13 @@
         pluginName, copyConfig(cfg), Optional.ofNullable(projectConfig), groupReferences.build());
   }
 
+  public static PluginConfig createFromGerritConfig(String pluginName, Config cfg) {
+    // There is no need to make a defensive copy here because this value won't be cached.
+    // gerrit.config uses baseConfig's (a member of Config) which would also make defensive copies
+    // fail.
+    return new AutoValue_PluginConfig(pluginName, cfg, Optional.empty(), ImmutableMap.of());
+  }
+
   PluginConfig withInheritance(ProjectState.Factory projectStateFactory) {
     checkState(projectConfig().isPresent(), "no project config provided");
 
diff --git a/java/com/google/gerrit/server/config/PluginConfigFactory.java b/java/com/google/gerrit/server/config/PluginConfigFactory.java
index 0028d63..a9abd1e 100644
--- a/java/com/google/gerrit/server/config/PluginConfigFactory.java
+++ b/java/com/google/gerrit/server/config/PluginConfigFactory.java
@@ -111,7 +111,7 @@
       cfgSnapshot = FileSnapshot.save(configFile);
       cfg = cfgProvider.get();
     }
-    return PluginConfig.create(pluginName, cfg, null);
+    return PluginConfig.createFromGerritConfig(pluginName, cfg);
   }
 
   /**
diff --git a/java/com/google/gerrit/server/edit/ChangeEditModifier.java b/java/com/google/gerrit/server/edit/ChangeEditModifier.java
index 48683ea..a05c392 100644
--- a/java/com/google/gerrit/server/edit/ChangeEditModifier.java
+++ b/java/com/google/gerrit/server/edit/ChangeEditModifier.java
@@ -498,7 +498,7 @@
       throws BadRequestException, IOException, InvalidChangeOperationException {
     ObjectId newTreeId;
     try {
-      TreeCreator treeCreator = new TreeCreator(baseCommit);
+      TreeCreator treeCreator = TreeCreator.basedOn(baseCommit);
       treeCreator.addTreeModifications(treeModifications);
       newTreeId = treeCreator.createNewTreeAndGetId(repository);
     } catch (InvalidPathException e) {
diff --git a/java/com/google/gerrit/server/edit/tree/ChangeFileContentModification.java b/java/com/google/gerrit/server/edit/tree/ChangeFileContentModification.java
index 0adacd8..4821a7a 100644
--- a/java/com/google/gerrit/server/edit/tree/ChangeFileContentModification.java
+++ b/java/com/google/gerrit/server/edit/tree/ChangeFileContentModification.java
@@ -18,6 +18,7 @@
 import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.ImmutableList;
 import com.google.common.flogger.FluentLogger;
 import com.google.common.io.ByteStreams;
 import com.google.gerrit.extensions.restapi.RawInput;
@@ -33,7 +34,6 @@
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectInserter;
 import org.eclipse.jgit.lib.Repository;
-import org.eclipse.jgit.revwalk.RevCommit;
 
 /** A {@code TreeModification} which changes the content of a file. */
 public class ChangeFileContentModification implements TreeModification {
@@ -48,7 +48,8 @@
   }
 
   @Override
-  public List<DirCacheEditor.PathEdit> getPathEdits(Repository repository, RevCommit baseCommit) {
+  public List<DirCacheEditor.PathEdit> getPathEdits(
+      Repository repository, ObjectId treeId, ImmutableList<? extends ObjectId> parents) {
     DirCacheEditor.PathEdit changeContentEdit = new ChangeContent(filePath, newContent, repository);
     return Collections.singletonList(changeContentEdit);
   }
diff --git a/java/com/google/gerrit/server/edit/tree/DeleteFileModification.java b/java/com/google/gerrit/server/edit/tree/DeleteFileModification.java
index feffb70..3b7826c 100644
--- a/java/com/google/gerrit/server/edit/tree/DeleteFileModification.java
+++ b/java/com/google/gerrit/server/edit/tree/DeleteFileModification.java
@@ -14,11 +14,12 @@
 
 package com.google.gerrit.server.edit.tree;
 
+import com.google.common.collect.ImmutableList;
 import java.util.Collections;
 import java.util.List;
 import org.eclipse.jgit.dircache.DirCacheEditor;
+import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Repository;
-import org.eclipse.jgit.revwalk.RevCommit;
 
 /** A {@code TreeModification} which deletes a file. */
 public class DeleteFileModification implements TreeModification {
@@ -30,7 +31,8 @@
   }
 
   @Override
-  public List<DirCacheEditor.PathEdit> getPathEdits(Repository repository, RevCommit baseCommit) {
+  public List<DirCacheEditor.PathEdit> getPathEdits(
+      Repository repository, ObjectId treeId, ImmutableList<? extends ObjectId> parents) {
     DirCacheEditor.DeletePath deletePathEdit = new DirCacheEditor.DeletePath(filePath);
     return Collections.singletonList(deletePathEdit);
   }
diff --git a/java/com/google/gerrit/server/edit/tree/RenameFileModification.java b/java/com/google/gerrit/server/edit/tree/RenameFileModification.java
index b847599..d4412e4 100644
--- a/java/com/google/gerrit/server/edit/tree/RenameFileModification.java
+++ b/java/com/google/gerrit/server/edit/tree/RenameFileModification.java
@@ -14,13 +14,12 @@
 
 package com.google.gerrit.server.edit.tree;
 
+import com.google.common.collect.ImmutableList;
 import java.io.IOException;
-import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import org.eclipse.jgit.dircache.DirCacheEditor;
+import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Repository;
-import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.treewalk.TreeWalk;
 
@@ -36,19 +35,23 @@
   }
 
   @Override
-  public List<DirCacheEditor.PathEdit> getPathEdits(Repository repository, RevCommit baseCommit)
+  public List<DirCacheEditor.PathEdit> getPathEdits(
+      Repository repository, ObjectId treeId, ImmutableList<? extends ObjectId> parents)
       throws IOException {
+    if (ObjectId.zeroId().equals(treeId)) {
+      return ImmutableList.of();
+    }
+
     try (RevWalk revWalk = new RevWalk(repository)) {
-      revWalk.parseHeaders(baseCommit);
       try (TreeWalk treeWalk =
-          TreeWalk.forPath(revWalk.getObjectReader(), currentFilePath, baseCommit.getTree())) {
+          TreeWalk.forPath(revWalk.getObjectReader(), currentFilePath, treeId)) {
         if (treeWalk == null) {
-          return Collections.emptyList();
+          return ImmutableList.of();
         }
         DirCacheEditor.DeletePath deletePathEdit = new DirCacheEditor.DeletePath(currentFilePath);
         AddPath addPathEdit =
             new AddPath(newFilePath, treeWalk.getFileMode(0), treeWalk.getObjectId(0));
-        return Arrays.asList(deletePathEdit, addPathEdit);
+        return ImmutableList.of(deletePathEdit, addPathEdit);
       }
     }
   }
diff --git a/java/com/google/gerrit/server/edit/tree/RestoreFileModification.java b/java/com/google/gerrit/server/edit/tree/RestoreFileModification.java
index 393a866..730664b 100644
--- a/java/com/google/gerrit/server/edit/tree/RestoreFileModification.java
+++ b/java/com/google/gerrit/server/edit/tree/RestoreFileModification.java
@@ -14,10 +14,12 @@
 
 package com.google.gerrit.server.edit.tree;
 
+import com.google.common.collect.ImmutableList;
 import java.io.IOException;
 import java.util.Collections;
 import java.util.List;
 import org.eclipse.jgit.dircache.DirCacheEditor;
+import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevWalk;
@@ -36,16 +38,16 @@
   }
 
   @Override
-  public List<DirCacheEditor.PathEdit> getPathEdits(Repository repository, RevCommit baseCommit)
+  public List<DirCacheEditor.PathEdit> getPathEdits(
+      Repository repository, ObjectId treeId, ImmutableList<? extends ObjectId> parents)
       throws IOException {
-    if (baseCommit.getParentCount() == 0) {
+    if (parents.isEmpty()) {
       DirCacheEditor.DeletePath deletePath = new DirCacheEditor.DeletePath(filePath);
       return Collections.singletonList(deletePath);
     }
 
-    RevCommit base = baseCommit.getParent(0);
     try (RevWalk revWalk = new RevWalk(repository)) {
-      revWalk.parseHeaders(base);
+      RevCommit base = revWalk.parseCommit(parents.get(0));
       try (TreeWalk treeWalk =
           TreeWalk.forPath(revWalk.getObjectReader(), filePath, base.getTree())) {
         if (treeWalk == null) {
diff --git a/java/com/google/gerrit/server/edit/tree/TreeCreator.java b/java/com/google/gerrit/server/edit/tree/TreeCreator.java
index e6caf97..3c400ec 100644
--- a/java/com/google/gerrit/server/edit/tree/TreeCreator.java
+++ b/java/com/google/gerrit/server/edit/tree/TreeCreator.java
@@ -16,6 +16,7 @@
 
 import static java.util.Objects.requireNonNull;
 
+import com.google.common.collect.ImmutableList;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
@@ -31,15 +32,26 @@
 
 /**
  * A creator for a new Git tree. To create the new tree, the tree of another commit is taken as a
- * basis and modified.
+ * basis and modified. Alternatively, an empty tree can serve as base.
  */
 public class TreeCreator {
 
-  private final RevCommit baseCommit;
+  private final ObjectId baseTreeId;
+  private final ImmutableList<? extends ObjectId> baseParents;
   private final List<TreeModification> treeModifications = new ArrayList<>();
 
-  public TreeCreator(RevCommit baseCommit) {
-    this.baseCommit = requireNonNull(baseCommit, "baseCommit is required");
+  public static TreeCreator basedOn(RevCommit baseCommit) {
+    requireNonNull(baseCommit, "baseCommit is required");
+    return new TreeCreator(baseCommit.getTree(), ImmutableList.copyOf(baseCommit.getParents()));
+  }
+
+  public static TreeCreator basedOnEmptyTree() {
+    return new TreeCreator(ObjectId.zeroId(), ImmutableList.of());
+  }
+
+  private TreeCreator(ObjectId baseTreeId, ImmutableList<? extends ObjectId> baseParents) {
+    this.baseTreeId = requireNonNull(baseTreeId, "baseTree is required");
+    this.baseParents = baseParents;
   }
 
   /**
@@ -78,8 +90,9 @@
     try (ObjectReader objectReader = repository.newObjectReader()) {
       DirCache dirCache = DirCache.newInCore();
       DirCacheBuilder dirCacheBuilder = dirCache.builder();
-      dirCacheBuilder.addTree(
-          new byte[0], DirCacheEntry.STAGE_0, objectReader, baseCommit.getTree());
+      if (!ObjectId.zeroId().equals(baseTreeId)) {
+        dirCacheBuilder.addTree(new byte[0], DirCacheEntry.STAGE_0, objectReader, baseTreeId);
+      }
       dirCacheBuilder.finish();
       return dirCache;
     }
@@ -88,7 +101,8 @@
   private List<DirCacheEditor.PathEdit> getPathEdits(Repository repository) throws IOException {
     List<DirCacheEditor.PathEdit> pathEdits = new ArrayList<>();
     for (TreeModification treeModification : treeModifications) {
-      pathEdits.addAll(treeModification.getPathEdits(repository, baseCommit));
+      pathEdits.addAll(
+          treeModification.getPathEdits(repository, baseTreeId, ImmutableList.copyOf(baseParents)));
     }
     return pathEdits;
   }
diff --git a/java/com/google/gerrit/server/edit/tree/TreeModification.java b/java/com/google/gerrit/server/edit/tree/TreeModification.java
index 2656707..68fd7ea 100644
--- a/java/com/google/gerrit/server/edit/tree/TreeModification.java
+++ b/java/com/google/gerrit/server/edit/tree/TreeModification.java
@@ -15,11 +15,12 @@
 package com.google.gerrit.server.edit.tree;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.ImmutableList;
 import java.io.IOException;
 import java.util.List;
 import org.eclipse.jgit.dircache.DirCacheEditor;
+import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Repository;
-import org.eclipse.jgit.revwalk.RevCommit;
 
 /** A specific modification of a Git tree. */
 public interface TreeModification {
@@ -30,11 +31,14 @@
    * shouldn't be changed.
    *
    * @param repository the affected Git repository
-   * @param baseCommit the commit to whose tree this modification is applied
+   * @param treeId tree to which the modification is applied. A value of {@code ObjectId.zero()}
+   *     indicates an empty tree.
+   * @param parents parent commits of the commit to whose tree this modification is applied
    * @return an ordered list of necessary {@code PathEdit}s
    * @throws IOException if problems arise when accessing the repository
    */
-  List<DirCacheEditor.PathEdit> getPathEdits(Repository repository, RevCommit baseCommit)
+  List<DirCacheEditor.PathEdit> getPathEdits(
+      Repository repository, ObjectId treeId, ImmutableList<? extends ObjectId> parents)
       throws IOException;
 
   /**
diff --git a/java/com/google/gerrit/server/project/ProjectCacheImpl.java b/java/com/google/gerrit/server/project/ProjectCacheImpl.java
index 663c9aa..d2e1086 100644
--- a/java/com/google/gerrit/server/project/ProjectCacheImpl.java
+++ b/java/com/google/gerrit/server/project/ProjectCacheImpl.java
@@ -56,7 +56,6 @@
 import com.google.inject.name.Named;
 import java.io.IOException;
 import java.time.Duration;
-import java.util.Objects;
 import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.ExecutionException;
@@ -224,9 +223,7 @@
   @Override
   public Set<AccountGroup.UUID> guessRelevantGroupUUIDs() {
     try (Timer0.Context ignored = guessRelevantGroupsLatency.start()) {
-      return all().stream()
-          .map(n -> byName.getIfPresent(n))
-          .filter(Objects::nonNull)
+      return byName.asMap().values().stream()
           .flatMap(p -> p.getConfig().getAllGroupUUIDs().stream())
           // getAllGroupUUIDs shouldn't really return null UUIDs, but harden
           // against them just in case there is a bug or corner case.
diff --git a/java/com/google/gerrit/truth/MapSubject.java b/java/com/google/gerrit/truth/MapSubject.java
index 95a0e0c..4eba753 100644
--- a/java/com/google/gerrit/truth/MapSubject.java
+++ b/java/com/google/gerrit/truth/MapSubject.java
@@ -17,6 +17,7 @@
 import static com.google.common.truth.Truth.assertAbout;
 
 import com.google.common.truth.FailureMetadata;
+import com.google.common.truth.IntegerSubject;
 import com.google.common.truth.IterableSubject;
 import com.google.common.truth.Subject;
 import java.util.Map;
@@ -51,4 +52,9 @@
     isNotNull();
     return check("values()").that(map.values());
   }
+
+  public IntegerSubject size() {
+    isNotNull();
+    return check("size()").that(map.size());
+  }
 }
diff --git a/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java b/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java
index c88dbff..da2c048 100644
--- a/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java
+++ b/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java
@@ -872,6 +872,40 @@
   }
 
   @Test
+  public void ownerNotAddedAsReviewerToAttentionSet() throws Exception {
+    PushOneCommit.Result r = createChange();
+    change(r).current().review(ReviewInput.approve());
+    assertThat(getAttentionSetUpdatesForUser(r, admin)).isEmpty();
+  }
+
+  @Test
+  public void ownerNotAddedAsReviewerToAttentionSetWithoutAutomaticRules() throws Exception {
+    PushOneCommit.Result r = createChange();
+    change(r).current().review(ReviewInput.approve().blockAutomaticAttentionSetRules());
+    assertThat(getAttentionSetUpdatesForUser(r, admin)).isEmpty();
+  }
+
+  @Test
+  public void uploaderNotAddedAsReviewerToAttentionSet() throws Exception {
+    PushOneCommit.Result r = createChange();
+    amendChangeWithUploader(r, project, user);
+    requestScopeOperations.setApiUser(user.id());
+
+    change(r).current().review(ReviewInput.recommend());
+    assertThat(getAttentionSetUpdatesForUser(r, user)).isEmpty();
+  }
+
+  @Test
+  public void uploaderNotAddedAsReviewerToAttentionSetWithoutAutomaticRules() throws Exception {
+    PushOneCommit.Result r = createChange();
+    amendChangeWithUploader(r, project, user);
+    requestScopeOperations.setApiUser(user.id());
+
+    change(r).current().review(ReviewInput.recommend().blockAutomaticAttentionSetRules());
+    assertThat(getAttentionSetUpdatesForUser(r, user)).isEmpty();
+  }
+
+  @Test
   public void attentionSetStillChangesWithIgnoreAutomaticAttentionSetRulesWithInputList()
       throws Exception {
     PushOneCommit.Result r = createChange();
diff --git a/javatests/com/google/gerrit/acceptance/testsuite/change/ChangeOperationsImplTest.java b/javatests/com/google/gerrit/acceptance/testsuite/change/ChangeOperationsImplTest.java
new file mode 100644
index 0000000..4783db7
--- /dev/null
+++ b/javatests/com/google/gerrit/acceptance/testsuite/change/ChangeOperationsImplTest.java
@@ -0,0 +1,462 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.testsuite.change;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.gerrit.acceptance.testsuite.project.TestProjectUpdate.permissionKey;
+import static com.google.gerrit.extensions.common.testing.CommitInfoSubject.assertThat;
+import static com.google.gerrit.extensions.common.testing.CommitInfoSubject.hasCommit;
+import static com.google.gerrit.extensions.restapi.testing.BinaryResultSubject.assertThat;
+import static com.google.gerrit.testing.GerritJUnit.assertThrows;
+import static com.google.gerrit.truth.MapSubject.assertThatMap;
+
+import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.testsuite.account.AccountOperations;
+import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
+import com.google.gerrit.acceptance.testsuite.request.RequestScopeOperations;
+import com.google.gerrit.entities.Account;
+import com.google.gerrit.entities.Change;
+import com.google.gerrit.entities.PatchSet;
+import com.google.gerrit.entities.Permission;
+import com.google.gerrit.entities.Project;
+import com.google.gerrit.extensions.client.ChangeKind;
+import com.google.gerrit.extensions.common.ChangeInfo;
+import com.google.gerrit.extensions.common.CommitInfo;
+import com.google.gerrit.extensions.common.FileInfo;
+import com.google.gerrit.extensions.common.RevisionInfo;
+import com.google.gerrit.extensions.restapi.BinaryResult;
+import com.google.gerrit.extensions.restapi.RestApiException;
+import com.google.inject.Inject;
+import java.util.Map;
+import org.eclipse.jgit.lib.ObjectId;
+import org.junit.Test;
+
+public class ChangeOperationsImplTest extends AbstractDaemonTest {
+
+  @Inject private ChangeOperations changeOperations;
+  @Inject private ProjectOperations projectOperations;
+  @Inject private AccountOperations accountOperations;
+  @Inject private RequestScopeOperations requestScopeOperations;
+
+  @Test
+  public void changeCanBeCreatedWithoutSpecifyingAnyParameters() throws Exception {
+    Change.Id numericChangeId = changeOperations.newChange().create();
+
+    ChangeInfo change = getChangeFromServer(numericChangeId);
+    assertThat(change._number).isEqualTo(numericChangeId.get());
+    assertThat(change.changeId).isNotEmpty();
+  }
+
+  @Test
+  public void changeCanBeCreatedEvenWithRequestScopeOfArbitraryUser() throws Exception {
+    Account.Id user = accountOperations.newAccount().create();
+
+    requestScopeOperations.setApiUser(user);
+    Change.Id numericChangeId = changeOperations.newChange().create();
+
+    ChangeInfo change = getChangeFromServer(numericChangeId);
+    assertThat(change._number).isEqualTo(numericChangeId.get());
+  }
+
+  @Test
+  public void twoChangesWithoutAnyParametersDoNotClash() {
+    Change.Id changeId1 = changeOperations.newChange().create();
+    Change.Id changeId2 = changeOperations.newChange().create();
+
+    TestChange change1 = changeOperations.change(changeId1).get();
+    TestChange change2 = changeOperations.change(changeId2).get();
+    assertThat(change1.numericChangeId()).isNotEqualTo(change2.numericChangeId());
+    assertThat(change1.changeId()).isNotEqualTo(change2.changeId());
+  }
+
+  @Test
+  public void twoSubsequentlyCreatedChangesDoNotDependOnEachOther() throws Exception {
+    Change.Id changeId1 = changeOperations.newChange().create();
+    Change.Id changeId2 = changeOperations.newChange().create();
+
+    ChangeInfo change1 = getChangeFromServer(changeId1);
+    ChangeInfo change2 = getChangeFromServer(changeId2);
+    CommitInfo currentPatchsetCommit1 = change1.revisions.get(change1.currentRevision).commit;
+    CommitInfo currentPatchsetCommit2 = change2.revisions.get(change2.currentRevision).commit;
+    assertThat(currentPatchsetCommit1)
+        .parents()
+        .comparingElementsUsing(hasCommit())
+        .doesNotContain(currentPatchsetCommit2.commit);
+    assertThat(currentPatchsetCommit2)
+        .parents()
+        .comparingElementsUsing(hasCommit())
+        .doesNotContain(currentPatchsetCommit1.commit);
+  }
+
+  @Test
+  public void createdChangeHasAtLeastOnePatchset() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    assertThatMap(change.revisions).size().isAtLeast(1);
+  }
+
+  @Test
+  public void createdChangeIsInSpecifiedProject() throws Exception {
+    Project.NameKey project = projectOperations.newProject().create();
+    Change.Id changeId = changeOperations.newChange().project(project).create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    assertThat(change.project).isEqualTo(project.get());
+  }
+
+  @Test
+  public void changeCanBeCreatedInEmptyRepository() throws Exception {
+    Project.NameKey project = projectOperations.newProject().noEmptyCommit().create();
+    Change.Id changeId = changeOperations.newChange().project(project).create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    assertThat(change.project).isEqualTo(project.get());
+  }
+
+  @Test
+  public void createdChangeHasSpecifiedTargetBranch() throws Exception {
+    Project.NameKey project = projectOperations.newProject().branches("test-branch").create();
+    Change.Id changeId =
+        changeOperations.newChange().project(project).branch("test-branch").create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    assertThat(change.branch).isEqualTo("test-branch");
+  }
+
+  @Test
+  public void createdChangeUsesTipOfTargetBranchAsParentByDefault() throws Exception {
+    Project.NameKey project = projectOperations.newProject().branches("test-branch").create();
+    ObjectId parentCommitId = projectOperations.project(project).getHead("test-branch").getId();
+    Change.Id changeId =
+        changeOperations.newChange().project(project).branch("test-branch").create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    CommitInfo currentPatchsetCommit = change.revisions.get(change.currentRevision).commit;
+    assertThat(currentPatchsetCommit)
+        .parents()
+        .onlyElement()
+        .commit()
+        .isEqualTo(parentCommitId.getName());
+  }
+
+  @Test
+  public void createdChangeHasSpecifiedOwner() throws Exception {
+    Account.Id changeOwner = accountOperations.newAccount().create();
+    Change.Id changeId = changeOperations.newChange().owner(changeOwner).create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    assertThat(change.owner._accountId).isEqualTo(changeOwner.get());
+  }
+
+  @Test
+  public void changeOwnerDoesNotNeedAnyPermissionsForChangeCreation() throws Exception {
+    Account.Id changeOwner = accountOperations.newAccount().create();
+    Project.NameKey project = projectOperations.newProject().branches("test-branch").create();
+    // Remove any read and push permissions which might potentially exist. Without read, users
+    // shouldn't be able to do anything. The newly created project should only inherit from
+    // All-Projects.
+    projectOperations
+        .project(project)
+        .forUpdate()
+        .remove(permissionKey(Permission.READ).ref("refs/heads/test-branch"))
+        .remove(permissionKey(Permission.PUSH).ref("refs/heads/test-branch"))
+        .update();
+    projectOperations
+        .allProjectsForUpdate()
+        .remove(permissionKey(Permission.READ).ref("refs/heads/test-branch"))
+        .remove(permissionKey(Permission.PUSH).ref("refs/heads/test-branch"))
+        .update();
+
+    Change.Id changeId =
+        changeOperations
+            .newChange()
+            .owner(changeOwner)
+            .branch("test-branch")
+            .project(project)
+            .create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    assertThat(change.owner._accountId).isEqualTo(changeOwner.get());
+  }
+
+  @Test
+  public void createdChangeHasSpecifiedCommitMessage() throws Exception {
+    Change.Id changeId =
+        changeOperations
+            .newChange()
+            .commitMessage("Summary line\n\nDetailed description.")
+            .create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    CommitInfo currentPatchsetCommit = change.revisions.get(change.currentRevision).commit;
+    assertThat(currentPatchsetCommit).message().startsWith("Summary line\n\nDetailed description.");
+  }
+
+  @Test
+  public void changeCannotBeCreatedWithoutCommitMessage() {
+    assertThrows(
+        IllegalStateException.class, () -> changeOperations.newChange().commitMessage("").create());
+  }
+
+  @Test
+  public void commitMessageOfCreatedChangeAutomaticallyGetsChangeId() throws Exception {
+    Change.Id changeId =
+        changeOperations
+            .newChange()
+            .commitMessage("Summary line\n\nDetailed description.")
+            .create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    CommitInfo currentPatchsetCommit = change.revisions.get(change.currentRevision).commit;
+    assertThat(currentPatchsetCommit).message().contains("Change-Id:");
+  }
+
+  @Test
+  public void changeIdSpecifiedInCommitMessageIsKeptForCreatedChange() throws Exception {
+    Change.Id changeId =
+        changeOperations
+            .newChange()
+            .commitMessage("Summary line\n\nChange-Id: I0123456789012345678901234567890123456789")
+            .create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    CommitInfo currentPatchsetCommit = change.revisions.get(change.currentRevision).commit;
+    assertThat(currentPatchsetCommit)
+        .message()
+        .contains("Change-Id: I0123456789012345678901234567890123456789");
+    assertThat(change.changeId).isEqualTo("I0123456789012345678901234567890123456789");
+  }
+
+  @Test
+  public void createdChangeHasSpecifiedFiles() throws Exception {
+    Change.Id changeId =
+        changeOperations
+            .newChange()
+            .file("file1")
+            .content("Line 1")
+            .file("path/to/file2.txt")
+            .content("Line one")
+            .create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    Map<String, FileInfo> files = change.revisions.get(change.currentRevision).files;
+    assertThatMap(files).keys().containsExactly("file1", "path/to/file2.txt");
+    BinaryResult fileContent1 = gApi.changes().id(changeId.get()).current().file("file1").content();
+    assertThat(fileContent1).asString().isEqualTo("Line 1");
+    BinaryResult fileContent2 =
+        gApi.changes().id(changeId.get()).current().file("path/to/file2.txt").content();
+    assertThat(fileContent2).asString().isEqualTo("Line one");
+  }
+
+  @Test
+  public void existingChangeCanBeCheckedForExistence() {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    boolean exists = changeOperations.change(changeId).exists();
+
+    assertThat(exists).isTrue();
+  }
+
+  @Test
+  public void notExistingChangeCanBeCheckedForExistence() {
+    Change.Id changeId = Change.id(123456789);
+
+    boolean exists = changeOperations.change(changeId).exists();
+
+    assertThat(exists).isFalse();
+  }
+
+  @Test
+  public void retrievingNotExistingChangeFails() {
+    Change.Id changeId = Change.id(123456789);
+    assertThrows(IllegalStateException.class, () -> changeOperations.change(changeId).get());
+  }
+
+  @Test
+  public void numericChangeIdOfExistingChangeCanBeRetrieved() {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    TestChange change = changeOperations.change(changeId).get();
+    assertThat(change.numericChangeId()).isEqualTo(changeId);
+  }
+
+  @Test
+  public void changeIdOfExistingChangeCanBeRetrieved() {
+    Change.Id changeId =
+        changeOperations
+            .newChange()
+            .commitMessage("Summary line\n\nChange-Id: I0123456789012345678901234567890123456789")
+            .create();
+
+    TestChange change = changeOperations.change(changeId).get();
+    assertThat(change.changeId()).isEqualTo("I0123456789012345678901234567890123456789");
+  }
+
+  @Test
+  public void currentPatchsetOfExistingChangeCanBeRetrieved() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    TestPatchset patchset = changeOperations.change(changeId).currentPatchset().get();
+
+    ChangeInfo expectedChange = getChangeFromServer(changeId);
+    String expectedCommitId = expectedChange.currentRevision;
+    int expectedPatchsetNumber = expectedChange.revisions.get(expectedCommitId)._number;
+    assertThat(patchset.commitId()).isEqualTo(ObjectId.fromString(expectedCommitId));
+    assertThat(patchset.patchsetId()).isEqualTo(PatchSet.id(changeId, expectedPatchsetNumber));
+  }
+
+  @Test
+  public void earlierPatchsetOfExistingChangeCanBeRetrieved() {
+    Change.Id changeId = changeOperations.newChange().create();
+    PatchSet.Id earlierPatchsetId =
+        changeOperations.change(changeId).currentPatchset().get().patchsetId();
+    PatchSet.Id currentPatchsetId = changeOperations.change(changeId).newPatchset().create();
+
+    TestPatchset earlierPatchset =
+        changeOperations.change(changeId).patchset(earlierPatchsetId).get();
+
+    assertThat(earlierPatchset.patchsetId()).isEqualTo(earlierPatchsetId);
+    assertThat(earlierPatchset.patchsetId()).isNotEqualTo(currentPatchsetId);
+  }
+
+  @Test
+  public void newPatchsetCanBeCreatedWithoutSpecifyingAnyParameters() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+    ChangeInfo unmodifiedChange = getChangeFromServer(changeId);
+    int originalPatchsetCount = unmodifiedChange.revisions.size();
+
+    PatchSet.Id patchsetId = changeOperations.change(changeId).newPatchset().create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    assertThatMap(change.revisions).hasSize(originalPatchsetCount + 1);
+    RevisionInfo currentRevision = change.revisions.get(change.currentRevision);
+    assertThat(currentRevision._number).isEqualTo(patchsetId.get());
+  }
+
+  @Test
+  public void newPatchsetIsCopyOfPreviousPatchsetByDefault() throws Exception {
+    Change.Id changeId = changeOperations.newChange().create();
+
+    PatchSet.Id patchsetId = changeOperations.change(changeId).newPatchset().create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    RevisionInfo patchsetRevision = getRevision(change, patchsetId);
+    assertThat(patchsetRevision.kind).isEqualTo(ChangeKind.NO_CHANGE);
+  }
+
+  @Test
+  public void newPatchsetCanHaveReplacedFileContent() throws Exception {
+    Change.Id changeId = changeOperations.newChange().file("file1").content("Line 1").create();
+
+    PatchSet.Id patchsetId =
+        changeOperations
+            .change(changeId)
+            .newPatchset()
+            .file("file1")
+            .content("Different content")
+            .create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    Map<String, FileInfo> files = change.revisions.get(change.currentRevision).files;
+    assertThatMap(files).keys().containsExactly("file1");
+    BinaryResult fileContent = getFileContent(changeId, patchsetId, "file1");
+    assertThat(fileContent).asString().isEqualTo("Different content");
+  }
+
+  @Test
+  public void newPatchsetCanHaveAdditionalFile() throws Exception {
+    Change.Id changeId = changeOperations.newChange().file("file1").content("Line 1").create();
+
+    PatchSet.Id patchsetId =
+        changeOperations
+            .change(changeId)
+            .newPatchset()
+            .file("file2")
+            .content("My file content")
+            .create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    Map<String, FileInfo> files = change.revisions.get(change.currentRevision).files;
+    assertThatMap(files).keys().containsExactly("file1", "file2");
+    BinaryResult fileContent = getFileContent(changeId, patchsetId, "file2");
+    assertThat(fileContent).asString().isEqualTo("My file content");
+  }
+
+  @Test
+  public void newPatchsetCanHaveLessFiles() throws Exception {
+    Change.Id changeId =
+        changeOperations
+            .newChange()
+            .file("file1")
+            .content("Line 1")
+            .file("file2")
+            .content("Line one")
+            .create();
+
+    changeOperations.change(changeId).newPatchset().file("file2").delete().create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    Map<String, FileInfo> files = change.revisions.get(change.currentRevision).files;
+    assertThatMap(files).keys().containsExactly("file1");
+  }
+
+  @Test
+  public void newPatchsetCanHaveRenamedFile() throws Exception {
+    Change.Id changeId =
+        changeOperations
+            .newChange()
+            .file("file1")
+            .content("Line 1")
+            .file("file2")
+            .content("Line one")
+            .create();
+
+    PatchSet.Id patchsetId =
+        changeOperations
+            .change(changeId)
+            .newPatchset()
+            .file("file2")
+            .renameTo("renamed file")
+            .create();
+
+    ChangeInfo change = getChangeFromServer(changeId);
+    Map<String, FileInfo> files = change.revisions.get(change.currentRevision).files;
+    assertThatMap(files).keys().containsExactly("file1", "renamed file");
+    BinaryResult fileContent = getFileContent(changeId, patchsetId, "renamed file");
+    assertThat(fileContent).asString().isEqualTo("Line one");
+  }
+
+  private ChangeInfo getChangeFromServer(Change.Id changeId) throws RestApiException {
+    return gApi.changes().id(changeId.get()).get();
+  }
+
+  private RevisionInfo getRevision(ChangeInfo change, PatchSet.Id patchsetId) {
+    return change.revisions.values().stream()
+        .filter(revision -> revision._number == patchsetId.get())
+        .findAny()
+        .orElseThrow(
+            () ->
+                new IllegalStateException(
+                    String.format(
+                        "Change %d doesn't have specified patchset %d.",
+                        change._number, patchsetId.get())));
+  }
+
+  private BinaryResult getFileContent(Change.Id changeId, PatchSet.Id patchsetId, String filePath)
+      throws RestApiException {
+    return gApi.changes().id(changeId.get()).revision(patchsetId.get()).file(filePath).content();
+  }
+}
diff --git a/javatests/com/google/gerrit/acceptance/testsuite/project/ProjectOperationsImplTest.java b/javatests/com/google/gerrit/acceptance/testsuite/project/ProjectOperationsImplTest.java
index 76b8826..62dfc63 100644
--- a/javatests/com/google/gerrit/acceptance/testsuite/project/ProjectOperationsImplTest.java
+++ b/javatests/com/google/gerrit/acceptance/testsuite/project/ProjectOperationsImplTest.java
@@ -36,6 +36,7 @@
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableListMultimap;
+import com.google.common.truth.Correspondence;
 import com.google.gerrit.acceptance.AbstractDaemonTest;
 import com.google.gerrit.acceptance.testsuite.project.TestProjectUpdate.TestPermission;
 import com.google.gerrit.entities.Permission;
@@ -43,6 +44,7 @@
 import com.google.gerrit.extensions.api.projects.BranchInfo;
 import com.google.gerrit.extensions.api.projects.ConfigInput;
 import com.google.gerrit.server.project.ProjectConfig;
+import com.google.gerrit.truth.NullAwareCorrespondence;
 import com.google.inject.Inject;
 import java.util.List;
 import org.eclipse.jgit.junit.TestRepository;
@@ -82,6 +84,36 @@
   }
 
   @Test
+  public void specifiedBranchesAreCreatedInNewProject() throws Exception {
+    Project.NameKey project =
+        projectOperations
+            .newProject()
+            .branches("test-branch", "refs/heads/another-test-branch")
+            .create();
+
+    List<BranchInfo> branches = gApi.projects().name(project.get()).branches().get();
+    assertThat(branches)
+        .comparingElementsUsing(hasBranchName())
+        .containsAtLeast("refs/heads/test-branch", "refs/heads/another-test-branch");
+  }
+
+  @Test
+  public void specifiedBranchesAreNotCreatedInNewProjectIfNoEmptyCommitRequested()
+      throws Exception {
+    Project.NameKey project =
+        projectOperations
+            .newProject()
+            .branches("test-branch", "refs/heads/another-test-branch")
+            .noEmptyCommit()
+            .create();
+
+    List<BranchInfo> branches = gApi.projects().name(project.get()).branches().get();
+    assertThat(branches)
+        .comparingElementsUsing(hasBranchName())
+        .containsNoneOf("refs/heads/test-branch", "refs/heads/another-test-branch");
+  }
+
+  @Test
   public void getProjectConfig() throws Exception {
     Project.NameKey key = projectOperations.newProject().create();
     assertThat(projectOperations.project(key).getProjectConfig().getProject().getDescription())
@@ -571,4 +603,8 @@
       tr.delete(REFS_CONFIG);
     }
   }
+
+  private static Correspondence<BranchInfo, String> hasBranchName() {
+    return NullAwareCorrespondence.transforming(branch -> branch.ref, "hasName");
+  }
 }
diff --git a/javatests/com/google/gerrit/server/edit/tree/TreeCreatorTest.java b/javatests/com/google/gerrit/server/edit/tree/TreeCreatorTest.java
new file mode 100644
index 0000000..926c345
--- /dev/null
+++ b/javatests/com/google/gerrit/server/edit/tree/TreeCreatorTest.java
@@ -0,0 +1,110 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.edit.tree;
+
+import static com.google.common.truth.Truth.assertThat;
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
+
+import com.google.common.collect.ImmutableList;
+import com.google.gerrit.common.RawInputUtil;
+import org.eclipse.jgit.internal.storage.dfs.DfsRepositoryDescription;
+import org.eclipse.jgit.internal.storage.dfs.InMemoryRepository;
+import org.eclipse.jgit.junit.TestRepository;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectReader;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.revwalk.RevObject;
+import org.eclipse.jgit.revwalk.RevTree;
+import org.eclipse.jgit.revwalk.RevWalk;
+import org.eclipse.jgit.treewalk.TreeWalk;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class TreeCreatorTest {
+
+  private Repository repository;
+  private TestRepository<?> testRepository;
+
+  @Before
+  public void setUp() throws Exception {
+    repository = new InMemoryRepository(new DfsRepositoryDescription("Test Repository"));
+    testRepository = new TestRepository<>(repository);
+  }
+
+  @After
+  public void tearDown() throws Exception {
+    if (testRepository != null) {
+      testRepository.close();
+    }
+  }
+
+  @Test
+  public void fileContentModificationWorksWithEmptyTree() throws Exception {
+    TreeCreator treeCreator = TreeCreator.basedOnEmptyTree();
+    treeCreator.addTreeModifications(
+        ImmutableList.of(
+            new ChangeFileContentModification("file.txt", RawInputUtil.create("Line 1"))));
+    ObjectId newTreeId = treeCreator.createNewTreeAndGetId(repository);
+
+    String fileContent = getFileContent(newTreeId, "file.txt");
+    assertThat(fileContent).isEqualTo("Line 1");
+  }
+
+  @Test
+  public void renameFileModificationDoesNotComplainAboutEmptyTree() throws Exception {
+    TreeCreator treeCreator = TreeCreator.basedOnEmptyTree();
+    treeCreator.addTreeModifications(
+        ImmutableList.of(new RenameFileModification("oldfileName", "newFileName")));
+    ObjectId newTreeId = treeCreator.createNewTreeAndGetId(repository);
+
+    assertThat(isEmptyTree(newTreeId)).isTrue();
+  }
+
+  @Test
+  public void deleteFileModificationDoesNotComplainAboutEmptyTree() throws Exception {
+    TreeCreator treeCreator = TreeCreator.basedOnEmptyTree();
+    treeCreator.addTreeModifications(ImmutableList.of(new DeleteFileModification("file.txt")));
+    ObjectId newTreeId = treeCreator.createNewTreeAndGetId(repository);
+
+    assertThat(isEmptyTree(newTreeId)).isTrue();
+  }
+
+  @Test
+  public void restoreFileModificationDoesNotComplainAboutEmptyTree() throws Exception {
+    TreeCreator treeCreator = TreeCreator.basedOnEmptyTree();
+    treeCreator.addTreeModifications(ImmutableList.of(new RestoreFileModification("file.txt")));
+    ObjectId newTreeId = treeCreator.createNewTreeAndGetId(repository);
+
+    assertThat(isEmptyTree(newTreeId)).isTrue();
+  }
+
+  private String getFileContent(ObjectId treeId, String filePath) throws Exception {
+    try (RevWalk revWalk = new RevWalk(repository);
+        ObjectReader reader = revWalk.getObjectReader()) {
+      RevTree revTree = revWalk.parseTree(treeId);
+      RevObject revObject = testRepository.get(revTree, filePath);
+      return new String(reader.open(revObject, OBJ_BLOB).getBytes(), UTF_8);
+    }
+  }
+
+  private boolean isEmptyTree(ObjectId treeId) throws Exception {
+    try (TreeWalk treeWalk = new TreeWalk(repository)) {
+      treeWalk.reset(treeId);
+      return !treeWalk.next();
+    }
+  }
+}
diff --git a/polygerrit-ui/app/.eslintrc.js b/polygerrit-ui/app/.eslintrc.js
index bf1fcc6..6d19ac9 100644
--- a/polygerrit-ui/app/.eslintrc.js
+++ b/polygerrit-ui/app/.eslintrc.js
@@ -268,6 +268,8 @@
       "rules": {
         // The following rules is required to match internal google rules
         "@typescript-eslint/restrict-plus-operands": "error",
+        // https://github.com/mysticatea/eslint-plugin-node/blob/master/docs/rules/no-unsupported-features/node-builtins.md
+        "node/no-unsupported-features/node-builtins": "off",
       },
       "parserOptions": {
         "project": path.resolve(__dirname, "./tsconfig_eslint.json"),
diff --git a/polygerrit-ui/app/constants/constants.ts b/polygerrit-ui/app/constants/constants.ts
index 32e1bed..00acc05 100644
--- a/polygerrit-ui/app/constants/constants.ts
+++ b/polygerrit-ui/app/constants/constants.ts
@@ -146,3 +146,12 @@
   FIRST_NAME = 'FIRST_NAME',
   FULL_NAME = 'FULL_NAME',
 }
+
+/**
+ * @desc The state of the projects
+ */
+export enum ProjectState {
+  ACTIVE = 'ACTIVE',
+  READ_ONLY = 'READ_ONLY',
+  HIDDEN = 'HIDDEN',
+}
diff --git a/polygerrit-ui/app/elements/core/gr-navigation/gr-navigation.js b/polygerrit-ui/app/elements/core/gr-navigation/gr-navigation.js
deleted file mode 100644
index 3203e0c..0000000
--- a/polygerrit-ui/app/elements/core/gr-navigation/gr-navigation.js
+++ /dev/null
@@ -1,784 +0,0 @@
-/**
- * @license
- * Copyright (C) 2017 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-// Navigation parameters object format:
-//
-// Each object has a `view` property with a value from GerritNav.View. The
-// remaining properties depend on the value used for view.
-//
-//  - GerritNav.View.CHANGE:
-//    - `changeNum`, required, String: the numeric ID of the change.
-//    - `project`, optional, String: the project name.
-//    - `patchNum`, optional, Number: the patch for the right-hand-side of
-//        the diff.
-//    - `basePatchNum`, optional, Number: the patch for the left-hand-side
-//        of the diff. If `basePatchNum` is provided, then `patchNum` must
-//        also be provided.
-//    - `edit`, optional, Boolean: whether or not to load the file list with
-//        edit controls.
-//    - `messageHash`, optional, String: the hash of the change message to
-//        scroll to.
-//
-// - GerritNav.View.SEARCH:
-//    - `query`, optional, String: the literal search query. If provided,
-//        the string will be used as the query, and all other params will be
-//        ignored.
-//    - `owner`, optional, String: the owner name.
-//    - `project`, optional, String: the project name.
-//    - `branch`, optional, String: the branch name.
-//    - `topic`, optional, String: the topic name.
-//    - `hashtag`, optional, String: the hashtag name.
-//    - `statuses`, optional, Array<String>: the list of change statuses to
-//        search for. If more than one is provided, the search will OR them
-//        together.
-//    - `offset`, optional, Number: the offset for the query.
-//
-//  - GerritNav.View.DIFF:
-//    - `changeNum`, required, String: the numeric ID of the change.
-//    - `path`, required, String: the filepath of the diff.
-//    - `patchNum`, required, Number: the patch for the right-hand-side of
-//        the diff.
-//    - `basePatchNum`, optional, Number: the patch for the left-hand-side
-//        of the diff. If `basePatchNum` is provided, then `patchNum` must
-//        also be provided.
-//    - `lineNum`, optional, Number: the line number to be selected on load.
-//    - `leftSide`, optional, Boolean: if a `lineNum` is provided, a value
-//        of true selects the line from base of the patch range. False by
-//        default.
-//
-//  - GerritNav.View.GROUP:
-//    - `groupId`, required, String: the ID of the group.
-//    - `detail`, optional, String: the name of the group detail view.
-//      Takes any value from GerritNav.GroupDetailView.
-//
-//  - GerritNav.View.REPO:
-//    - `repoName`, required, String: the name of the repo
-//    - `detail`, optional, String: the name of the repo detail view.
-//      Takes any value from GerritNav.RepoDetailView.
-//
-//  - GerritNav.View.DASHBOARD
-//    - `repo`, optional, String.
-//    - `sections`, optional, Array of objects with `title` and `query`
-//      strings.
-//    - `user`, optional, String.
-//
-//  - GerritNav.View.ROOT:
-//    - no possible parameters.
-
-const uninitialized = () => {
-  console.warn('Use of uninitialized routing');
-};
-
-const EDIT_PATCHNUM = 'edit';
-const PARENT_PATCHNUM = 'PARENT';
-
-const USER_PLACEHOLDER_PATTERN = /\${user}/g;
-
-// NOTE: These queries are tested in Java. Any changes made to definitions
-// here require corresponding changes to:
-// javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
-const DEFAULT_SECTIONS = [
-  {
-    // Changes with unpublished draft comments. This section is omitted when
-    // viewing other users, so we don't need to filter anything out.
-    name: 'Has draft comments',
-    query: 'has:draft',
-    selfOnly: true,
-    hideIfEmpty: true,
-    suffixForDashboard: 'limit:10',
-  },
-  {
-    // Changes where the user is in the attention set.
-    name: 'Your Turn',
-    query: 'attention:${user}',
-    hideIfEmpty: false,
-    suffixForDashboard: 'limit:25',
-    attentionSetOnly: true,
-  },
-  {
-    // Changes that are assigned to the viewed user.
-    name: 'Assigned reviews',
-    query: 'assignee:${user} (-is:wip OR owner:self OR assignee:self) ' +
-        'is:open -is:ignored',
-    hideIfEmpty: true,
-    suffixForDashboard: 'limit:25',
-    assigneeOnly: true,
-  },
-  {
-    // WIP open changes owned by viewing user. This section is omitted when
-    // viewing other users, so we don't need to filter anything out.
-    name: 'Work in progress',
-    query: 'is:open owner:${user} is:wip',
-    selfOnly: true,
-    hideIfEmpty: true,
-    suffixForDashboard: 'limit:25',
-  },
-  {
-    // Non-WIP open changes owned by viewed user. Filter out changes ignored
-    // by the viewing user.
-    name: 'Outgoing reviews',
-    query: 'is:open owner:${user} -is:wip -is:ignored',
-    isOutgoing: true,
-    suffixForDashboard: 'limit:25',
-  },
-  {
-    // Non-WIP open changes not owned by the viewed user, that the viewed user
-    // is associated with (as either a reviewer or the assignee). Changes
-    // ignored by the viewing user are filtered out.
-    name: 'Incoming reviews',
-    query: 'is:open -owner:${user} -is:wip -is:ignored ' +
-        '(reviewer:${user} OR assignee:${user})',
-    suffixForDashboard: 'limit:25',
-  },
-  {
-    // Open changes the viewed user is CCed on. Changes ignored by the viewing
-    // user are filtered out.
-    name: 'CCed on',
-    query: 'is:open -is:ignored cc:${user}',
-    suffixForDashboard: 'limit:10',
-  },
-  {
-    name: 'Recently closed',
-    // Closed changes where viewed user is owner, reviewer, or assignee.
-    // Changes ignored by the viewing user are filtered out, and so are WIP
-    // changes not owned by the viewing user (the one instance of
-    // 'owner:self' is intentional and implements this logic).
-    query: 'is:closed -is:ignored (-is:wip OR owner:self) ' +
-        '(owner:${user} OR reviewer:${user} OR assignee:${user} ' +
-        'OR cc:${user})',
-    suffixForDashboard: '-age:4w limit:10',
-  },
-];
-
-// TODO(dmfilippov) Convert to class, extract consts, give better name and
-// expose as a service from appContext
-export const GerritNav = {
-
-  View: {
-    ADMIN: 'admin',
-    AGREEMENTS: 'agreements',
-    CHANGE: 'change',
-    DASHBOARD: 'dashboard',
-    DIFF: 'diff',
-    DOCUMENTATION_SEARCH: 'documentation-search',
-    EDIT: 'edit',
-    GROUP: 'group',
-    PLUGIN_SCREEN: 'plugin-screen',
-    REPO: 'repo',
-    ROOT: 'root',
-    SEARCH: 'search',
-    SETTINGS: 'settings',
-  },
-
-  GroupDetailView: {
-    MEMBERS: 'members',
-    LOG: 'log',
-  },
-
-  RepoDetailView: {
-    ACCESS: 'access',
-    BRANCHES: 'branches',
-    COMMANDS: 'commands',
-    DASHBOARDS: 'dashboards',
-    TAGS: 'tags',
-  },
-
-  WeblinkType: {
-    CHANGE: 'change',
-    FILE: 'file',
-    PATCHSET: 'patchset',
-  },
-
-  /** @type {Function} */
-  _navigate: uninitialized,
-
-  /** @type {Function} */
-  _generateUrl: uninitialized,
-
-  /** @type {Function} */
-  _generateWeblinks: uninitialized,
-
-  /** @type {Function} */
-  mapCommentlinks: uninitialized,
-
-  /**
-   * @param {number=} patchNum
-   * @param {number|string=} basePatchNum
-   */
-  _checkPatchRange(patchNum, basePatchNum) {
-    if (basePatchNum && !patchNum) {
-      throw new Error('Cannot use base patch number without patch number.');
-    }
-  },
-
-  /**
-   * Setup router implementation.
-   *
-   * @param {function(!string, boolean=)} navigate the router-abstracted equivalent of
-   *     `window.location.href = ...` or window.location.replace(...). The
-   *     string is a new location and boolean defines is it redirect or not
-   *     (true means redirect, i.e. equivalent of window.location.replace).
-   * @param {function(!Object): string} generateUrl generates a URL given
-   *     navigation parameters, detailed in the file header.
-   * @param {function(!Object): string} generateWeblinks weblinks generator
-   *     function takes single payload parameter with type property that
-   *  determines which
-   *     part of the UI is the consumer of the weblinks. type property can
-   *     be one of file, change, or patchset.
-   *     - For file type, payload will also contain string properties: repo,
-   *         commit, file.
-   *     - For patchset type, payload will also contain string properties:
-   *         repo, commit.
-   *     - For change type, payload will also contain string properties:
-   *         repo, commit. If server provides weblinks, those will be passed
-   *         as options.weblinks property on the main payload object.
-   * @param {function(!Object): Object} mapCommentlinks provides an escape
-   *     hatch to modify the commentlinks object, e.g. if it contains any
-   *     relative URLs.
-   */
-  setup(navigate, generateUrl, generateWeblinks, mapCommentlinks) {
-    this._navigate = navigate;
-    this._generateUrl = generateUrl;
-    this._generateWeblinks = generateWeblinks;
-    this.mapCommentlinks = mapCommentlinks;
-  },
-
-  destroy() {
-    this._navigate = uninitialized;
-    this._generateUrl = uninitialized;
-    this._generateWeblinks = uninitialized;
-    this.mapCommentlinks = uninitialized;
-  },
-
-  /**
-   * Generate a URL for the given route parameters.
-   *
-   * @param {Object} params
-   * @return {string}
-   */
-  _getUrlFor(params) {
-    return this._generateUrl(params);
-  },
-
-  getUrlForSearchQuery(query, opt_offset) {
-    return this._getUrlFor({
-      view: GerritNav.View.SEARCH,
-      query,
-      offset: opt_offset,
-    });
-  },
-
-  /**
-   * @param {!string} project The name of the project.
-   * @param {boolean=} opt_openOnly When true, only search open changes in
-   *     the project.
-   * @param {string=} opt_host The host in which to search.
-   * @return {string}
-   */
-  getUrlForProjectChanges(project, opt_openOnly, opt_host) {
-    return this._getUrlFor({
-      view: GerritNav.View.SEARCH,
-      project,
-      statuses: opt_openOnly ? ['open'] : [],
-      host: opt_host,
-    });
-  },
-
-  /**
-   * @param {string} branch The name of the branch.
-   * @param {string} project The name of the project.
-   * @param {string=} opt_status The status to search.
-   * @param {string=} opt_host The host in which to search.
-   * @return {string}
-   */
-  getUrlForBranch(branch, project, opt_status, opt_host) {
-    return this._getUrlFor({
-      view: GerritNav.View.SEARCH,
-      branch,
-      project,
-      statuses: opt_status ? [opt_status] : undefined,
-      host: opt_host,
-    });
-  },
-
-  /**
-   * @param {string} topic The name of the topic.
-   * @param {string=} opt_host The host in which to search.
-   * @return {string}
-   */
-  getUrlForTopic(topic, opt_host) {
-    return this._getUrlFor({
-      view: GerritNav.View.SEARCH,
-      topic,
-      statuses: ['open', 'merged'],
-      host: opt_host,
-    });
-  },
-
-  /**
-   * @param {string} hashtag The name of the hashtag.
-   * @return {string}
-   */
-  getUrlForHashtag(hashtag) {
-    return this._getUrlFor({
-      view: GerritNav.View.SEARCH,
-      hashtag,
-      statuses: ['open', 'merged'],
-    });
-  },
-
-  /**
-   * Navigate to a search for changes with the given status.
-   *
-   * @param {string} status
-   */
-  navigateToStatusSearch(status) {
-    this._navigate(this._getUrlFor({
-      view: GerritNav.View.SEARCH,
-      statuses: [status],
-    }));
-  },
-
-  /**
-   * Navigate to a search query
-   *
-   * @param {string} query
-   * @param {number=} opt_offset
-   */
-  navigateToSearchQuery(query, opt_offset) {
-    return this._navigate(this.getUrlForSearchQuery(query, opt_offset));
-  },
-
-  /**
-   * Navigate to the user's dashboard
-   */
-  navigateToUserDashboard() {
-    return this._navigate(this.getUrlForUserDashboard('self'));
-  },
-
-  /**
-   * @param {!Object} change The change object.
-   * @param {number=} opt_patchNum
-   * @param {number|string=} opt_basePatchNum The string 'PARENT' can be
-   *     used for none.
-   * @param {boolean=} opt_isEdit
-   * @param {string=} opt_messageHash
-   * @return {string}
-   */
-  getUrlForChange(change, opt_patchNum, opt_basePatchNum, opt_isEdit,
-      opt_messageHash) {
-    if (opt_basePatchNum === PARENT_PATCHNUM) {
-      opt_basePatchNum = undefined;
-    }
-
-    this._checkPatchRange(opt_patchNum, opt_basePatchNum);
-    return this._getUrlFor({
-      view: GerritNav.View.CHANGE,
-      changeNum: change._number,
-      project: change.project,
-      patchNum: opt_patchNum,
-      basePatchNum: opt_basePatchNum,
-      edit: opt_isEdit,
-      host: change.internalHost || undefined,
-      messageHash: opt_messageHash,
-    });
-  },
-
-  /**
-   * @param {number} changeNum
-   * @param {string} project The name of the project.
-   * @param {number=} opt_patchNum
-   * @return {string}
-   */
-  getUrlForChangeById(changeNum, project, opt_patchNum) {
-    return this._getUrlFor({
-      view: GerritNav.View.CHANGE,
-      changeNum,
-      project,
-      patchNum: opt_patchNum,
-    });
-  },
-
-  /**
-   * @param {!Object} change The change object.
-   * @param {number=} opt_patchNum
-   * @param {number|string=} opt_basePatchNum The string 'PARENT' can be
-   *     used for none.
-   * @param {boolean=} opt_isEdit
-   * @param {boolean=} opt_redirect redirect to a change - if true, the current
-   *     location (i.e. page which makes redirect) is not added to a history.
-   *     I.e. back/forward buttons skip current location
-   *
-   */
-  navigateToChange(change, opt_patchNum, opt_basePatchNum, opt_isEdit,
-      opt_redirect) {
-    this._navigate(this.getUrlForChange(change, opt_patchNum,
-        opt_basePatchNum, opt_isEdit), opt_redirect);
-  },
-
-  /**
-   * @param {{ _number: number, project: string }} change The change object.
-   * @param {string} path The file path.
-   * @param {number=} opt_patchNum
-   * @param {number|string=} opt_basePatchNum The string 'PARENT' can be
-   *     used for none.
-   * @param {number|string=} opt_lineNum
-   * @return {string}
-   */
-  getUrlForDiff(change, path, opt_patchNum, opt_basePatchNum, opt_lineNum) {
-    return this.getUrlForDiffById(change._number, change.project, path,
-        opt_patchNum, opt_basePatchNum, opt_lineNum);
-  },
-
-  /**
-   * @param {number} changeNum
-   * @param {string} project The name of the project.
-   * @param {string} path The file path.
-   * @param {number} patchNum
-   * @param {number} commentId
-   * @return {string}
-   */
-  getUrlForComment(changeNum, project, commentId) {
-    return this._getUrlFor({
-      view: GerritNav.View.DIFF,
-      changeNum,
-      project,
-      commentId,
-    });
-  },
-
-  /**
-   * @param {number} changeNum
-   * @param {string} project The name of the project.
-   * @param {string} path The file path.
-   * @param {number=} opt_patchNum
-   * @param {number|string=} opt_basePatchNum The string 'PARENT' can be
-   *     used for none.
-   * @param {number=} opt_lineNum
-   * @param {boolean=} opt_leftSide
-   * @return {string}
-   */
-  getUrlForDiffById(changeNum, project, path, opt_patchNum,
-      opt_basePatchNum, opt_lineNum, opt_leftSide) {
-    if (opt_basePatchNum === PARENT_PATCHNUM) {
-      opt_basePatchNum = undefined;
-    }
-
-    this._checkPatchRange(opt_patchNum, opt_basePatchNum);
-    return this._getUrlFor({
-      view: GerritNav.View.DIFF,
-      changeNum,
-      project,
-      path,
-      patchNum: opt_patchNum,
-      basePatchNum: opt_basePatchNum,
-      lineNum: opt_lineNum,
-      leftSide: opt_leftSide,
-    });
-  },
-
-  /**
-   * @param {{ _number: number, project: string }} change The change object.
-   * @param {string} path The file path.
-   * @param {number=} opt_patchNum
-   * @param {number=} opt_lineNum
-   * @return {string}
-   */
-  getEditUrlForDiff(change, path, opt_patchNum, opt_lineNum) {
-    return this.getEditUrlForDiffById(change._number, change.project, path,
-        opt_patchNum, opt_lineNum);
-  },
-
-  /**
-   * @param {number} changeNum
-   * @param {string} project The name of the project.
-   * @param {string} path The file path.
-   * @param {number|string=} opt_patchNum The patchNum the file content
-   *    should be based on, or ${EDIT_PATCHNUM} if left undefined.
-   * @param {number=} opt_lineNum The line number to pass to the inline editor.
-   * @return {string}
-   */
-  getEditUrlForDiffById(changeNum, project, path, opt_patchNum, opt_lineNum) {
-    return this._getUrlFor({
-      view: GerritNav.View.EDIT,
-      changeNum,
-      project,
-      path,
-      patchNum: opt_patchNum || EDIT_PATCHNUM,
-      lineNum: opt_lineNum,
-    });
-  },
-
-  /**
-   * @param {!Object} change The change object.
-   * @param {string} path The file path.
-   * @param {number=} opt_patchNum
-   * @param {number|string=} opt_basePatchNum The string 'PARENT' can be
-   *     used for none.
-   */
-  navigateToDiff(change, path, opt_patchNum, opt_basePatchNum) {
-    this._navigate(this.getUrlForDiff(change, path, opt_patchNum,
-        opt_basePatchNum));
-  },
-
-  /**
-   * @param {string} owner The name of the owner.
-   * @return {string}
-   */
-  getUrlForOwner(owner) {
-    return this._getUrlFor({
-      view: GerritNav.View.SEARCH,
-      owner,
-    });
-  },
-
-  /**
-   * @param {string} user The name of the user.
-   * @return {string}
-   */
-  getUrlForUserDashboard(user) {
-    return this._getUrlFor({
-      view: GerritNav.View.DASHBOARD,
-      user,
-    });
-  },
-
-  /**
-   * @return {string}
-   */
-  getUrlForRoot() {
-    return this._getUrlFor({
-      view: GerritNav.View.ROOT,
-    });
-  },
-
-  /**
-   * @param {string} repo The name of the repo.
-   * @param {string} dashboard The ID of the dashboard, in the form of
-   *     '<ref>:<path>'.
-   * @return {string}
-   */
-  getUrlForRepoDashboard(repo, dashboard) {
-    return this._getUrlFor({
-      view: GerritNav.View.DASHBOARD,
-      repo,
-      dashboard,
-    });
-  },
-
-  /**
-   * Navigate to an arbitrary relative URL.
-   *
-   * @param {string} relativeUrl
-   */
-  navigateToRelativeUrl(relativeUrl) {
-    if (!relativeUrl.startsWith('/')) {
-      throw new Error('navigateToRelativeUrl with non-relative URL');
-    }
-    this._navigate(relativeUrl);
-  },
-
-  /**
-   * @param {string} repoName
-   * @return {string}
-   */
-  getUrlForRepo(repoName) {
-    return this._getUrlFor({
-      view: GerritNav.View.REPO,
-      repoName,
-    });
-  },
-
-  /**
-   * Navigate to a repo settings page.
-   *
-   * @param {string} repoName
-   */
-  navigateToRepo(repoName) {
-    this._navigate(this.getUrlForRepo(repoName));
-  },
-
-  /**
-   * @param {string} repoName
-   * @return {string}
-   */
-  getUrlForRepoTags(repoName) {
-    return this._getUrlFor({
-      view: GerritNav.View.REPO,
-      repoName,
-      detail: GerritNav.RepoDetailView.TAGS,
-    });
-  },
-
-  /**
-   * @param {string} repoName
-   * @return {string}
-   */
-  getUrlForRepoBranches(repoName) {
-    return this._getUrlFor({
-      view: GerritNav.View.REPO,
-      repoName,
-      detail: GerritNav.RepoDetailView.BRANCHES,
-    });
-  },
-
-  /**
-   * @param {string} repoName
-   * @return {string}
-   */
-  getUrlForRepoAccess(repoName) {
-    return this._getUrlFor({
-      view: GerritNav.View.REPO,
-      repoName,
-      detail: GerritNav.RepoDetailView.ACCESS,
-    });
-  },
-
-  /**
-   * @param {string} repoName
-   * @return {string}
-   */
-  getUrlForRepoCommands(repoName) {
-    return this._getUrlFor({
-      view: GerritNav.View.REPO,
-      repoName,
-      detail: GerritNav.RepoDetailView.COMMANDS,
-    });
-  },
-
-  /**
-   * @param {string} repoName
-   * @return {string}
-   */
-  getUrlForRepoDashboards(repoName) {
-    return this._getUrlFor({
-      view: GerritNav.View.REPO,
-      repoName,
-      detail: GerritNav.RepoDetailView.DASHBOARDS,
-    });
-  },
-
-  /**
-   * @param {string} groupId
-   * @return {string}
-   */
-  getUrlForGroup(groupId) {
-    return this._getUrlFor({
-      view: GerritNav.View.GROUP,
-      groupId,
-    });
-  },
-
-  /**
-   * @param {string} groupId
-   * @return {string}
-   */
-  getUrlForGroupLog(groupId) {
-    return this._getUrlFor({
-      view: GerritNav.View.GROUP,
-      groupId,
-      detail: GerritNav.GroupDetailView.LOG,
-    });
-  },
-
-  /**
-   * @param {string} groupId
-   * @return {string}
-   */
-  getUrlForGroupMembers(groupId) {
-    return this._getUrlFor({
-      view: GerritNav.View.GROUP,
-      groupId,
-      detail: GerritNav.GroupDetailView.MEMBERS,
-    });
-  },
-
-  getUrlForSettings() {
-    return this._getUrlFor({view: GerritNav.View.SETTINGS});
-  },
-
-  /**
-   * @param {string} repo
-   * @param {string} commit
-   * @param {string} file
-   * @param {Object=} opt_options
-   * @return {
-   *   Array<{label: string, url: string}>|
-   *   {label: string, url: string}
-   *  }
-   */
-  getFileWebLinks(repo, commit, file, opt_options) {
-    const params = {type: GerritNav.WeblinkType.FILE, repo, commit, file};
-    if (opt_options) {
-      params.options = opt_options;
-    }
-    return [].concat(this._generateWeblinks(params));
-  },
-
-  /**
-   * @param {string} repo
-   * @param {string} commit
-   * @param {Object=} opt_options
-   * @return {{label: string, url: string}}
-   */
-  getPatchSetWeblink(repo, commit, opt_options) {
-    const params = {type: GerritNav.WeblinkType.PATCHSET, repo, commit};
-    if (opt_options) {
-      params.options = opt_options;
-    }
-    const result = this._generateWeblinks(params);
-    if (Array.isArray(result)) {
-      return result.pop();
-    } else {
-      return result;
-    }
-  },
-
-  /**
-   * @param {string} repo
-   * @param {string} commit
-   * @param {Object=} opt_options
-   * @return {
-   *   Array<{label: string, url: string}>|
-   *   {label: string, url: string}
-   *  }
-   */
-  getChangeWeblinks(repo, commit, opt_options) {
-    const params = {type: GerritNav.WeblinkType.CHANGE, repo, commit};
-    if (opt_options) {
-      params.options = opt_options;
-    }
-    return [].concat(this._generateWeblinks(params));
-  },
-
-  getUserDashboard(user = 'self', sections = DEFAULT_SECTIONS,
-      title = '', config = {}) {
-    const attentionEnabled =
-        config.change && !!config.change.enable_attention_set;
-    const assigneeEnabled =
-        config.change && !!config.change.enable_assignee;
-    sections = sections
-        .filter(section => (attentionEnabled || !section.attentionSetOnly))
-        .filter(section => (assigneeEnabled || !section.assigneeOnly))
-        .filter(section => (user === 'self' || !section.selfOnly))
-        .map(section => {
-          return {...section, name: section.name,
-            query: section.query.replace(USER_PLACEHOLDER_PATTERN, user)};
-        });
-    return {title, sections};
-  },
-};
diff --git a/polygerrit-ui/app/elements/core/gr-navigation/gr-navigation.ts b/polygerrit-ui/app/elements/core/gr-navigation/gr-navigation.ts
new file mode 100644
index 0000000..13b5572
--- /dev/null
+++ b/polygerrit-ui/app/elements/core/gr-navigation/gr-navigation.ts
@@ -0,0 +1,946 @@
+/**
+ * @license
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import {
+  BranchName,
+  ChangeInfo,
+  PatchSetNum,
+  ProjectName,
+  TopicName,
+  RepositoryName,
+  GroupId,
+  DashboardId,
+  NumericChangeId,
+  LegacyChangeId,
+  EditPatchSetNum,
+  ChangeConfigInfo,
+  CommitId,
+  Hashtag,
+  UrlEncodedCommentId,
+} from '../../../types/common';
+
+// Navigation parameters object format:
+//
+// Each object has a `view` property with a value from GerritNav.View. The
+// remaining properties depend on the value used for view.
+//
+//  - GerritNav.View.CHANGE:
+//    - `changeNum`, required, String: the numeric ID of the change.
+//    - `project`, optional, String: the project name.
+//    - `patchNum`, optional, Number: the patch for the right-hand-side of
+//        the diff.
+//    - `basePatchNum`, optional, Number: the patch for the left-hand-side
+//        of the diff. If `basePatchNum` is provided, then `patchNum` must
+//        also be provided.
+//    - `edit`, optional, Boolean: whether or not to load the file list with
+//        edit controls.
+//    - `messageHash`, optional, String: the hash of the change message to
+//        scroll to.
+//
+// - GerritNav.View.SEARCH:
+//    - `query`, optional, String: the literal search query. If provided,
+//        the string will be used as the query, and all other params will be
+//        ignored.
+//    - `owner`, optional, String: the owner name.
+//    - `project`, optional, String: the project name.
+//    - `branch`, optional, String: the branch name.
+//    - `topic`, optional, String: the topic name.
+//    - `hashtag`, optional, String: the hashtag name.
+//    - `statuses`, optional, Array<String>: the list of change statuses to
+//        search for. If more than one is provided, the search will OR them
+//        together.
+//    - `offset`, optional, Number: the offset for the query.
+//
+//  - GerritNav.View.DIFF:
+//    - `changeNum`, required, String: the numeric ID of the change.
+//    - `path`, required, String: the filepath of the diff.
+//    - `patchNum`, required, Number: the patch for the right-hand-side of
+//        the diff.
+//    - `basePatchNum`, optional, Number: the patch for the left-hand-side
+//        of the diff. If `basePatchNum` is provided, then `patchNum` must
+//        also be provided.
+//    - `lineNum`, optional, Number: the line number to be selected on load.
+//    - `leftSide`, optional, Boolean: if a `lineNum` is provided, a value
+//        of true selects the line from base of the patch range. False by
+//        default.
+//
+//  - GerritNav.View.GROUP:
+//    - `groupId`, required, String: the ID of the group.
+//    - `detail`, optional, String: the name of the group detail view.
+//      Takes any value from GerritNav.GroupDetailView.
+//
+//  - GerritNav.View.REPO:
+//    - `repoName`, required, String: the name of the repo
+//    - `detail`, optional, String: the name of the repo detail view.
+//      Takes any value from GerritNav.RepoDetailView.
+//
+//  - GerritNav.View.DASHBOARD
+//    - `repo`, optional, String.
+//    - `sections`, optional, Array of objects with `title` and `query`
+//      strings.
+//    - `user`, optional, String.
+//
+//  - GerritNav.View.ROOT:
+//    - no possible parameters.
+
+const uninitialized = () => {
+  console.warn('Use of uninitialized routing');
+};
+
+const uninitializedNavigate: NavigateCallback = () => {
+  uninitialized();
+  return '';
+};
+
+const uninitializedGenerateUrl: GenerateUrlCallback = () => {
+  uninitialized();
+  return '';
+};
+
+const uninitializedGenerateWebLinks: GenerateWebLinksCallback = () => {
+  uninitialized();
+  return [];
+};
+
+const uninitializedMapCommentLinks: MapCommentLinksCallback = () => {
+  uninitialized();
+  return '';
+};
+
+// TODO(TS): PatchSetNum type express an API type, it is not good to add
+// PARENT into it. Find a better way to add PARENT patchset into our code
+type ParentPatchSetNum = 'PARENT';
+const PARENT_PATCHNUM: ParentPatchSetNum = 'PARENT';
+
+const USER_PLACEHOLDER_PATTERN = /\${user}/g;
+
+export interface DashboardSection {
+  name: string;
+  query: string;
+  suffixForDashboard: string;
+  attentionSetOnly?: boolean;
+  selfOnly?: boolean;
+  hideIfEmpty?: boolean;
+  assigneeOnly?: boolean;
+  isOutgoing?: boolean;
+}
+
+export interface UserDashboardConfig {
+  change?: ChangeConfigInfo;
+}
+
+export interface UserDashboard {
+  title: string;
+  sections: DashboardSection[];
+}
+
+// NOTE: These queries are tested in Java. Any changes made to definitions
+// here require corresponding changes to:
+// javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
+const DEFAULT_SECTIONS: DashboardSection[] = [
+  {
+    // Changes with unpublished draft comments. This section is omitted when
+    // viewing other users, so we don't need to filter anything out.
+    name: 'Has draft comments',
+    query: 'has:draft',
+    selfOnly: true,
+    hideIfEmpty: true,
+    suffixForDashboard: 'limit:10',
+  },
+  {
+    // Changes where the user is in the attention set.
+    name: 'Your Turn',
+    query: 'attention:${user}',
+    hideIfEmpty: false,
+    suffixForDashboard: 'limit:25',
+    attentionSetOnly: true,
+  },
+  {
+    // Changes that are assigned to the viewed user.
+    name: 'Assigned reviews',
+    query:
+      'assignee:${user} (-is:wip OR owner:self OR assignee:self) ' +
+      'is:open -is:ignored',
+    hideIfEmpty: true,
+    suffixForDashboard: 'limit:25',
+    assigneeOnly: true,
+  },
+  {
+    // WIP open changes owned by viewing user. This section is omitted when
+    // viewing other users, so we don't need to filter anything out.
+    name: 'Work in progress',
+    query: 'is:open owner:${user} is:wip',
+    selfOnly: true,
+    hideIfEmpty: true,
+    suffixForDashboard: 'limit:25',
+  },
+  {
+    // Non-WIP open changes owned by viewed user. Filter out changes ignored
+    // by the viewing user.
+    name: 'Outgoing reviews',
+    query: 'is:open owner:${user} -is:wip -is:ignored',
+    isOutgoing: true,
+    suffixForDashboard: 'limit:25',
+  },
+  {
+    // Non-WIP open changes not owned by the viewed user, that the viewed user
+    // is associated with (as either a reviewer or the assignee). Changes
+    // ignored by the viewing user are filtered out.
+    name: 'Incoming reviews',
+    query:
+      'is:open -owner:${user} -is:wip -is:ignored ' +
+      '(reviewer:${user} OR assignee:${user})',
+    suffixForDashboard: 'limit:25',
+  },
+  {
+    // Open changes the viewed user is CCed on. Changes ignored by the viewing
+    // user are filtered out.
+    name: 'CCed on',
+    query: 'is:open -is:ignored cc:${user}',
+    suffixForDashboard: 'limit:10',
+  },
+  {
+    name: 'Recently closed',
+    // Closed changes where viewed user is owner, reviewer, or assignee.
+    // Changes ignored by the viewing user are filtered out, and so are WIP
+    // changes not owned by the viewing user (the one instance of
+    // 'owner:self' is intentional and implements this logic).
+    query:
+      'is:closed -is:ignored (-is:wip OR owner:self) ' +
+      '(owner:${user} OR reviewer:${user} OR assignee:${user} ' +
+      'OR cc:${user})',
+    suffixForDashboard: '-age:4w limit:10',
+  },
+];
+
+export interface GenerateUrlSearchViewParameters {
+  view: GerritView.SEARCH;
+  query?: string;
+  offset?: number;
+  project?: ProjectName;
+  branch?: BranchName;
+  topic?: TopicName;
+  // TODO(TS): Define more precise type (enum?)
+  statuses?: string[];
+  hashtag?: string;
+  host?: string;
+  owner?: string;
+}
+
+export interface GenerateUrlChangeViewParameters {
+  view: GerritView.CHANGE;
+  // TODO(TS): NumericChangeId - not sure about it, may be it can be removeds
+  changeNum: NumericChangeId | LegacyChangeId;
+  project: ProjectName;
+  patchNum?: PatchSetNum;
+  basePatchNum?: PatchSetNum;
+  edit?: boolean;
+  host?: string;
+  messageHash?: string;
+}
+
+export interface GenerateUrlRepoViewParameters {
+  view: GerritView.REPO;
+  repoName: RepositoryName;
+  detail?: RepoDetailView;
+}
+
+export interface GenerateUrlDashboardViewParameters {
+  view: GerritView.DASHBOARD;
+  user?: string;
+  repo?: RepositoryName;
+  dashboard?: DashboardId;
+}
+
+export interface GenerateUrlGroupViewParameters {
+  view: GerritView.GROUP;
+  groupId: GroupId;
+  detail?: GroupDetailView;
+}
+
+export interface GenerateUrlEditViewParameters {
+  view: GerritView.EDIT;
+  changeNum: NumericChangeId | LegacyChangeId;
+  project: ProjectName;
+  path: string;
+  patchNum: PatchSetNum;
+  lineNum?: number;
+}
+
+export interface GenerateUrlRootViewParameters {
+  view: GerritView.ROOT;
+}
+
+export interface GenerateUrlSettingsViewParameters {
+  view: GerritView.SETTINGS;
+}
+
+export interface GenerateUrlDiffViewParameters {
+  view: GerritView.DIFF;
+  changeNum: NumericChangeId | LegacyChangeId;
+  project: ProjectName;
+  path?: string;
+  patchNum?: PatchSetNum;
+  basePatchNum?: PatchSetNum | ParentPatchSetNum;
+  lineNum?: number;
+  leftSide?: boolean;
+  commentId?: UrlEncodedCommentId;
+}
+
+export type GenerateUrlParameters =
+  | GenerateUrlSearchViewParameters
+  | GenerateUrlChangeViewParameters
+  | GenerateUrlRepoViewParameters
+  | GenerateUrlDashboardViewParameters
+  | GenerateUrlGroupViewParameters
+  | GenerateUrlEditViewParameters
+  | GenerateUrlRootViewParameters
+  | GenerateUrlSettingsViewParameters
+  | GenerateUrlDiffViewParameters;
+
+export interface GenerateWebLinksPatchsetParameters {
+  type: WeblinkType.PATCHSET;
+  repo: RepositoryName;
+  commit: CommitId;
+  // TODO(TS): provide better typing
+  options?: unknown;
+}
+export interface GenerateWebLinksFileParameters {
+  type: WeblinkType.FILE;
+  repo: RepositoryName;
+  commit: CommitId;
+  file: string;
+  // TODO(TS): provide better typing
+  options?: unknown;
+}
+export interface GenerateWebLinksChangeParameters {
+  type: WeblinkType.CHANGE;
+  repo: RepositoryName;
+  commit: CommitId;
+  // TODO(TS): provide better typing
+  options?: unknown;
+}
+
+export type GenerateWebLinksParameters =
+  | GenerateWebLinksPatchsetParameters
+  | GenerateWebLinksFileParameters
+  | GenerateWebLinksChangeParameters;
+
+export type NavigateCallback = (target: string, redirect?: boolean) => void;
+export type GenerateUrlCallback = (params: GenerateUrlParameters) => string;
+export type GenerateWebLinksCallback = (
+  params: GenerateWebLinksParameters
+) => WebLink[] | WebLink;
+
+// TODO(TS): type is not clear until more code converted to a typescript.
+export type MapCommentLinksCallback = (commentLink: unknown) => unknown;
+
+export interface WebLink {
+  label: string;
+  url: string;
+}
+
+export enum GerritView {
+  ADMIN = 'admin',
+  AGREEMENTS = 'agreements',
+  CHANGE = 'change',
+  DASHBOARD = 'dashboard',
+  DIFF = 'diff',
+  DOCUMENTATION_SEARCH = 'documentation-search',
+  EDIT = 'edit',
+  GROUP = 'group',
+  PLUGIN_SCREEN = 'plugin-screen',
+  REPO = 'repo',
+  ROOT = 'root',
+  SEARCH = 'search',
+  SETTINGS = 'settings',
+}
+
+export enum GroupDetailView {
+  MEMBERS = 'members',
+  LOG = 'log',
+}
+
+export enum RepoDetailView {
+  ACCESS = 'access',
+  BRANCHES = 'branches',
+  COMMANDS = 'commands',
+  DASHBOARDS = 'dashboards',
+  TAGS = 'tags',
+}
+
+export enum WeblinkType {
+  CHANGE = 'change',
+  FILE = 'file',
+  PATCHSET = 'patchset',
+}
+
+// TODO(dmfilippov) Convert to class, extract consts, give better name and
+// expose as a service from appContext
+export const GerritNav = {
+  View: GerritView,
+
+  GroupDetailView,
+
+  RepoDetailView,
+
+  WeblinkType,
+
+  _navigate: uninitializedNavigate,
+
+  _generateUrl: uninitializedGenerateUrl,
+
+  _generateWeblinks: uninitializedGenerateWebLinks,
+
+  mapCommentlinks: uninitializedMapCommentLinks,
+
+  _checkPatchRange(
+    patchNum?: PatchSetNum,
+    basePatchNum?: PatchSetNum | ParentPatchSetNum
+  ) {
+    if (basePatchNum && !patchNum) {
+      throw new Error('Cannot use base patch number without patch number.');
+    }
+  },
+
+  /**
+   * Setup router implementation.
+   *
+   * @param navigate the router-abstracted equivalent of
+   *     `window.location.href = ...` or window.location.replace(...). The
+   *     string is a new location and boolean defines is it redirect or not
+   *     (true means redirect, i.e. equivalent of window.location.replace).
+   * @param generateUrl generates a URL given
+   *     navigation parameters, detailed in the file header.
+   * @param generateWeblinks weblinks generator
+   *     function takes single payload parameter with type property that
+   *  determines which
+   *     part of the UI is the consumer of the weblinks. type property can
+   *     be one of file, change, or patchset.
+   *     - For file type, payload will also contain string properties: repo,
+   *         commit, file.
+   *     - For patchset type, payload will also contain string properties:
+   *         repo, commit.
+   *     - For change type, payload will also contain string properties:
+   *         repo, commit. If server provides weblinks, those will be passed
+   *         as options.weblinks property on the main payload object.
+   * @param mapCommentlinks provides an escape
+   *     hatch to modify the commentlinks object, e.g. if it contains any
+   *     relative URLs.
+   */
+  setup(
+    navigate: NavigateCallback,
+    generateUrl: GenerateUrlCallback,
+    generateWeblinks: GenerateWebLinksCallback,
+    mapCommentlinks: MapCommentLinksCallback
+  ) {
+    this._navigate = navigate;
+    this._generateUrl = generateUrl;
+    this._generateWeblinks = generateWeblinks;
+    this.mapCommentlinks = mapCommentlinks;
+  },
+
+  destroy() {
+    this._navigate = uninitializedNavigate;
+    this._generateUrl = uninitializedGenerateUrl;
+    this._generateWeblinks = uninitializedGenerateWebLinks;
+    this.mapCommentlinks = uninitializedMapCommentLinks;
+  },
+
+  /**
+   * Generate a URL for the given route parameters.
+   */
+  _getUrlFor(params: GenerateUrlParameters) {
+    return this._generateUrl(params);
+  },
+
+  getUrlForSearchQuery(query: string, offset?: number) {
+    return this._getUrlFor({
+      view: GerritView.SEARCH,
+      query,
+      offset,
+    });
+  },
+
+  /**
+   * @param openOnly When true, only search open changes in the project.
+   * @param host The host in which to search.
+   */
+  getUrlForProjectChanges(
+    project: ProjectName,
+    openOnly?: boolean,
+    host?: string
+  ) {
+    return this._getUrlFor({
+      view: GerritView.SEARCH,
+      project,
+      statuses: openOnly ? ['open'] : [],
+      host,
+    });
+  },
+
+  /**
+   * @param status The status to search.
+   * @param host The host in which to search.
+   */
+  getUrlForBranch(
+    branch: BranchName,
+    project: ProjectName,
+    status?: string,
+    host?: string
+  ) {
+    return this._getUrlFor({
+      view: GerritView.SEARCH,
+      branch,
+      project,
+      statuses: status ? [status] : undefined,
+      host,
+    });
+  },
+
+  /**
+   * @param topic The name of the topic.
+   * @param host The host in which to search.
+   */
+  getUrlForTopic(topic: TopicName, host?: string) {
+    return this._getUrlFor({
+      view: GerritView.SEARCH,
+      topic,
+      statuses: ['open', 'merged'],
+      host,
+    });
+  },
+
+  /**
+   * @param hashtag The name of the hashtag.
+   */
+  getUrlForHashtag(hashtag: Hashtag) {
+    return this._getUrlFor({
+      view: GerritView.SEARCH,
+      hashtag,
+      statuses: ['open', 'merged'],
+    });
+  },
+
+  /**
+   * Navigate to a search for changes with the given status.
+   */
+  navigateToStatusSearch(status: string) {
+    this._navigate(
+      this._getUrlFor({
+        view: GerritView.SEARCH,
+        statuses: [status],
+      })
+    );
+  },
+
+  /**
+   * Navigate to a search query
+   */
+  navigateToSearchQuery(query: string, offset?: number) {
+    return this._navigate(this.getUrlForSearchQuery(query, offset));
+  },
+
+  /**
+   * Navigate to the user's dashboard
+   */
+  navigateToUserDashboard() {
+    return this._navigate(this.getUrlForUserDashboard('self'));
+  },
+
+  /**
+   * @param basePatchNum The string 'PARENT' can be used for none.
+   */
+  getUrlForChange(
+    change: ChangeInfo,
+    patchNum?: PatchSetNum,
+    basePatchNum?: PatchSetNum | ParentPatchSetNum,
+    isEdit?: boolean,
+    messageHash?: string
+  ) {
+    if (basePatchNum === PARENT_PATCHNUM) {
+      basePatchNum = undefined;
+    }
+
+    this._checkPatchRange(patchNum, basePatchNum);
+    return this._getUrlFor({
+      view: GerritView.CHANGE,
+      changeNum: change._number,
+      project: change.project,
+      patchNum,
+      basePatchNum,
+      edit: isEdit,
+      host: change.internalHost || undefined,
+      messageHash,
+    });
+  },
+
+  getUrlForChangeById(
+    changeNum: NumericChangeId,
+    project: ProjectName,
+    patchNum?: PatchSetNum
+  ) {
+    return this._getUrlFor({
+      view: GerritView.CHANGE,
+      changeNum,
+      project,
+      patchNum,
+    });
+  },
+
+  /**
+   * @param basePatchNum The string 'PARENT' can be used for none.
+   * @param redirect redirect to a change - if true, the current
+   *     location (i.e. page which makes redirect) is not added to a history.
+   *     I.e. back/forward buttons skip current location
+   *
+   */
+  navigateToChange(
+    change: ChangeInfo,
+    patchNum?: PatchSetNum,
+    basePatchNum?: PatchSetNum,
+    isEdit?: boolean,
+    redirect?: boolean
+  ) {
+    this._navigate(
+      this.getUrlForChange(change, patchNum, basePatchNum, isEdit),
+      redirect
+    );
+  },
+
+  /**
+   * @param basePatchNum The string 'PARENT' can be used for none.
+   */
+  getUrlForDiff(
+    change: ChangeInfo,
+    filePath: string,
+    patchNum?: PatchSetNum,
+    basePatchNum?: PatchSetNum | ParentPatchSetNum,
+    lineNum?: number
+  ) {
+    return this.getUrlForDiffById(
+      change._number,
+      change.project,
+      filePath,
+      patchNum,
+      basePatchNum,
+      lineNum
+    );
+  },
+
+  getUrlForComment(
+    changeNum: NumericChangeId | LegacyChangeId,
+    project: ProjectName,
+    commentId: UrlEncodedCommentId
+  ) {
+    return this._getUrlFor({
+      view: GerritView.DIFF,
+      changeNum,
+      project,
+      commentId,
+    });
+  },
+
+  /**
+   * @param basePatchNum The string 'PARENT' can be used for none.
+   */
+  getUrlForDiffById(
+    changeNum: NumericChangeId | LegacyChangeId,
+    project: ProjectName,
+    filePath: string,
+    patchNum?: PatchSetNum,
+    basePatchNum?: PatchSetNum | ParentPatchSetNum,
+    lineNum?: number,
+    leftSide?: boolean
+  ) {
+    if (basePatchNum === PARENT_PATCHNUM) {
+      basePatchNum = undefined;
+    }
+
+    this._checkPatchRange(patchNum, basePatchNum);
+    return this._getUrlFor({
+      view: GerritView.DIFF,
+      changeNum,
+      project,
+      path: filePath,
+      patchNum,
+      basePatchNum,
+      lineNum,
+      leftSide,
+    });
+  },
+
+  getEditUrlForDiff(
+    change: ChangeInfo,
+    filePath: string,
+    patchNum?: PatchSetNum,
+    lineNum?: number
+  ) {
+    return this.getEditUrlForDiffById(
+      change._number,
+      change.project,
+      filePath,
+      patchNum,
+      lineNum
+    );
+  },
+
+  /**
+   * @param patchNum The patchNum the file content should be based on, or
+   *   ${EditPatchSetNum} if left undefined.
+   * @param lineNum The line number to pass to the inline editor.
+   */
+  getEditUrlForDiffById(
+    changeNum: NumericChangeId | LegacyChangeId,
+    project: ProjectName,
+    filePath: string,
+    patchNum?: PatchSetNum,
+    lineNum?: number
+  ) {
+    return this._getUrlFor({
+      view: GerritView.EDIT,
+      changeNum,
+      project,
+      path: filePath,
+      patchNum: patchNum || EditPatchSetNum,
+      lineNum,
+    });
+  },
+
+  /**
+   * @param basePatchNum The string 'PARENT' can be used for none.
+   */
+  navigateToDiff(
+    change: ChangeInfo,
+    filePath: string,
+    patchNum?: PatchSetNum,
+    basePatchNum?: PatchSetNum | ParentPatchSetNum
+  ) {
+    this._navigate(
+      this.getUrlForDiff(change, filePath, patchNum, basePatchNum)
+    );
+  },
+
+  /**
+   * @param owner The name of the owner.
+   */
+  getUrlForOwner(owner: string) {
+    return this._getUrlFor({
+      view: GerritView.SEARCH,
+      owner,
+    });
+  },
+
+  /**
+   * @param user The name of the user.
+   */
+  getUrlForUserDashboard(user: string) {
+    return this._getUrlFor({
+      view: GerritView.DASHBOARD,
+      user,
+    });
+  },
+
+  getUrlForRoot() {
+    return this._getUrlFor({
+      view: GerritView.ROOT,
+    });
+  },
+
+  /**
+   * @param repo The name of the repo.
+   * @param dashboard The ID of the dashboard, in the form of '<ref>:<path>'.
+   */
+  getUrlForRepoDashboard(repo: RepositoryName, dashboard: DashboardId) {
+    return this._getUrlFor({
+      view: GerritView.DASHBOARD,
+      repo,
+      dashboard,
+    });
+  },
+
+  /**
+   * Navigate to an arbitrary relative URL.
+   */
+  navigateToRelativeUrl(relativeUrl: string) {
+    if (!relativeUrl.startsWith('/')) {
+      throw new Error('navigateToRelativeUrl with non-relative URL');
+    }
+    this._navigate(relativeUrl);
+  },
+
+  getUrlForRepo(repoName: RepositoryName) {
+    return this._getUrlFor({
+      view: GerritView.REPO,
+      repoName,
+    });
+  },
+
+  /**
+   * Navigate to a repo settings page.
+   */
+  navigateToRepo(repoName: RepositoryName) {
+    this._navigate(this.getUrlForRepo(repoName));
+  },
+
+  getUrlForRepoTags(repoName: RepositoryName) {
+    return this._getUrlFor({
+      view: GerritView.REPO,
+      repoName,
+      detail: RepoDetailView.TAGS,
+    });
+  },
+
+  getUrlForRepoBranches(repoName: RepositoryName) {
+    return this._getUrlFor({
+      view: GerritView.REPO,
+      repoName,
+      detail: GerritNav.RepoDetailView.BRANCHES,
+    });
+  },
+
+  getUrlForRepoAccess(repoName: RepositoryName) {
+    return this._getUrlFor({
+      view: GerritView.REPO,
+      repoName,
+      detail: GerritNav.RepoDetailView.ACCESS,
+    });
+  },
+
+  getUrlForRepoCommands(repoName: RepositoryName) {
+    return this._getUrlFor({
+      view: GerritView.REPO,
+      repoName,
+      detail: GerritNav.RepoDetailView.COMMANDS,
+    });
+  },
+
+  getUrlForRepoDashboards(repoName: RepositoryName) {
+    return this._getUrlFor({
+      view: GerritView.REPO,
+      repoName,
+      detail: GerritNav.RepoDetailView.DASHBOARDS,
+    });
+  },
+
+  getUrlForGroup(groupId: GroupId) {
+    return this._getUrlFor({
+      view: GerritView.GROUP,
+      groupId,
+    });
+  },
+
+  getUrlForGroupLog(groupId: GroupId) {
+    return this._getUrlFor({
+      view: GerritView.GROUP,
+      groupId,
+      detail: GerritNav.GroupDetailView.LOG,
+    });
+  },
+
+  getUrlForGroupMembers(groupId: GroupId) {
+    return this._getUrlFor({
+      view: GerritView.GROUP,
+      groupId,
+      detail: GroupDetailView.MEMBERS,
+    });
+  },
+
+  getUrlForSettings() {
+    return this._getUrlFor({view: GerritView.SETTINGS});
+  },
+
+  getFileWebLinks(
+    repo: RepositoryName,
+    commit: CommitId,
+    file: string,
+    options?: unknown
+  ): WebLink[] {
+    const params: GenerateWebLinksFileParameters = {
+      type: WeblinkType.FILE,
+      repo,
+      commit,
+      file,
+    };
+    if (options) {
+      params.options = options;
+    }
+    return ([] as WebLink[]).concat(this._generateWeblinks(params));
+  },
+
+  getPatchSetWeblink(
+    repo: RepositoryName,
+    commit: CommitId,
+    options?: unknown
+  ): WebLink {
+    const params: GenerateWebLinksPatchsetParameters = {
+      type: WeblinkType.PATCHSET,
+      repo,
+      commit,
+    };
+    if (options) {
+      params.options = options;
+    }
+    const result = this._generateWeblinks(params);
+    if (Array.isArray(result)) {
+      // TODO(TS): Unclear what to do with empty array.
+      // Either write a comment why result can't be empty or change the return
+      // type or add a check.
+      return result.pop() as WebLink;
+    } else {
+      return result;
+    }
+  },
+
+  getChangeWeblinks(
+    repo: RepositoryName,
+    commit: CommitId,
+    options?: unknown
+  ): WebLink[] {
+    const params: GenerateWebLinksChangeParameters = {
+      type: WeblinkType.CHANGE,
+      repo,
+      commit,
+    };
+    if (options) {
+      params.options = options;
+    }
+    return ([] as WebLink[]).concat(this._generateWeblinks(params));
+  },
+
+  getUserDashboard(
+    user = 'self',
+    sections = DEFAULT_SECTIONS,
+    title = '',
+    config: UserDashboardConfig = {}
+  ): UserDashboard {
+    const attentionEnabled =
+      config.change && !!config.change.enable_attention_set;
+    const assigneeEnabled = config.change && !!config.change.enable_assignee;
+    sections = sections
+      .filter(section => attentionEnabled || !section.attentionSetOnly)
+      .filter(section => assigneeEnabled || !section.assigneeOnly)
+      .filter(section => user === 'self' || !section.selfOnly)
+      .map(section => {
+        return {
+          ...section,
+          name: section.name,
+          query: section.query.replace(USER_PLACEHOLDER_PATTERN, user),
+        };
+      });
+    return {title, sections};
+  },
+};
diff --git a/polygerrit-ui/app/elements/plugins/gr-admin-api/gr-admin-api.js b/polygerrit-ui/app/elements/plugins/gr-admin-api/gr-admin-api.js
deleted file mode 100644
index 2dfb79f..0000000
--- a/polygerrit-ui/app/elements/plugins/gr-admin-api/gr-admin-api.js
+++ /dev/null
@@ -1,35 +0,0 @@
-/**
- * @license
- * Copyright (C) 2018 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-/** @constructor */
-export function GrAdminApi(plugin) {
-  this.plugin = plugin;
-  plugin.on('admin-menu-links', this);
-  this._menuLinks = [];
-}
-
-/**
- * @param {string} text
- * @param {string} url
- */
-GrAdminApi.prototype.addMenuLink = function(text, url, opt_capability) {
-  this._menuLinks.push({text, url, capability: opt_capability || null});
-};
-
-GrAdminApi.prototype.getMenuLinks = function() {
-  return this._menuLinks.slice(0);
-};
diff --git a/polygerrit-ui/app/elements/plugins/gr-admin-api/gr-admin-api.ts b/polygerrit-ui/app/elements/plugins/gr-admin-api/gr-admin-api.ts
new file mode 100644
index 0000000..51ff0ab
--- /dev/null
+++ b/polygerrit-ui/app/elements/plugins/gr-admin-api/gr-admin-api.ts
@@ -0,0 +1,50 @@
+/**
+ * @license
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/** Interface for menu link */
+export interface MenuLink {
+  text: string;
+  url: string;
+  capability: string | null;
+}
+
+// TODO(TS): replace with Plugin once gr-public-js-api migrated
+interface PluginApi {
+  on(eventName: string, adminApi: GrAdminApi): void;
+}
+
+/**
+ * GrAdminApi class.
+ *
+ * Defines common methods to register / retrieve menu links.
+ */
+export class GrAdminApi {
+  // TODO(TS): maybe define as enum if its a limited set
+  private menuLinks: MenuLink[] = [];
+
+  constructor(private readonly plugin: PluginApi) {
+    this.plugin.on('admin-menu-links', this);
+  }
+
+  addMenuLink(text: string, url: string, capability?: string) {
+    this.menuLinks.push({text, url, capability: capability || null});
+  }
+
+  getMenuLinks(): MenuLink[] {
+    return this.menuLinks.slice(0);
+  }
+}
diff --git a/polygerrit-ui/app/elements/plugins/gr-popup-interface/gr-plugin-popup.js b/polygerrit-ui/app/elements/plugins/gr-popup-interface/gr-plugin-popup.js
deleted file mode 100644
index eaecd29..0000000
--- a/polygerrit-ui/app/elements/plugins/gr-popup-interface/gr-plugin-popup.js
+++ /dev/null
@@ -1,48 +0,0 @@
-/**
- * @license
- * Copyright (C) 2017 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-import '../../shared/gr-overlay/gr-overlay.js';
-import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners.js';
-import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin.js';
-import {PolymerElement} from '@polymer/polymer/polymer-element.js';
-import {htmlTemplate} from './gr-plugin-popup_html.js';
-
-(function(window) {
-  'use strict';
-
-  /** @extends PolymerElement */
-  class GrPluginPopup extends GestureEventListeners(
-      LegacyElementMixin(
-          PolymerElement)) {
-    static get template() { return htmlTemplate; }
-
-    static get is() { return 'gr-plugin-popup'; }
-
-    get opened() {
-      return this.$.overlay.opened;
-    }
-
-    open() {
-      return this.$.overlay.open();
-    }
-
-    close() {
-      this.$.overlay.close();
-    }
-  }
-
-  customElements.define(GrPluginPopup.is, GrPluginPopup);
-})(window);
diff --git a/polygerrit-ui/app/elements/plugins/gr-popup-interface/gr-plugin-popup.ts b/polygerrit-ui/app/elements/plugins/gr-popup-interface/gr-plugin-popup.ts
new file mode 100644
index 0000000..7c6587a
--- /dev/null
+++ b/polygerrit-ui/app/elements/plugins/gr-popup-interface/gr-plugin-popup.ts
@@ -0,0 +1,55 @@
+/**
+ * @license
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import '../../shared/gr-overlay/gr-overlay';
+import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners';
+import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin';
+import {PolymerElement} from '@polymer/polymer/polymer-element';
+import {htmlTemplate} from './gr-plugin-popup_html';
+import {GrOverlay} from '../../shared/gr-overlay/gr-overlay';
+import {customElement} from '@polymer/decorators';
+
+declare global {
+  interface HTMLElementTagNameMap {
+    'gr-plugin-popup': GrPluginPopup;
+  }
+}
+
+export interface GrPluginPopup {
+  $: {
+    overlay: GrOverlay;
+  };
+}
+@customElement('gr-plugin-popup')
+export class GrPluginPopup extends GestureEventListeners(
+  LegacyElementMixin(PolymerElement)
+) {
+  static get template() {
+    return htmlTemplate;
+  }
+
+  get opened() {
+    return this.$.overlay.opened;
+  }
+
+  open() {
+    return this.$.overlay.open();
+  }
+
+  close() {
+    this.$.overlay.close();
+  }
+}
diff --git a/polygerrit-ui/app/elements/plugins/gr-theme-api/gr-custom-plugin-header.js b/polygerrit-ui/app/elements/plugins/gr-theme-api/gr-custom-plugin-header.js
deleted file mode 100644
index 1e37603..0000000
--- a/polygerrit-ui/app/elements/plugins/gr-theme-api/gr-custom-plugin-header.js
+++ /dev/null
@@ -1,52 +0,0 @@
-/**
- * @license
- * Copyright (C) 2017 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-import {PolymerElement} from '@polymer/polymer/polymer-element.js';
-import {html} from '@polymer/polymer/lib/utils/html-tag.js';
-
-class CustomPluginHeader extends PolymerElement {
-  static get is() {
-    return 'gr-custom-plugin-header';
-  }
-
-  static get properties() {
-    return {
-      logoUrl: String,
-      title: String,
-    };
-  }
-
-  static get template() {
-    return html`
-    <style>
-      img {
-        width: 1em;
-        height: 1em;
-        vertical-align: middle;
-      }
-      .title {
-        margin-left: var(--spacing-xs);
-      }
-    </style>
-    <span>
-      <img src="[[logoUrl]]" hidden\$="[[!logoUrl]]">
-      <span class="title">[[title]]</span>
-    </span>
-`;
-  }
-}
-
-customElements.define(CustomPluginHeader.is, CustomPluginHeader);
\ No newline at end of file
diff --git a/polygerrit-ui/app/elements/plugins/gr-theme-api/gr-custom-plugin-header.ts b/polygerrit-ui/app/elements/plugins/gr-theme-api/gr-custom-plugin-header.ts
new file mode 100644
index 0000000..7d82ff4
--- /dev/null
+++ b/polygerrit-ui/app/elements/plugins/gr-theme-api/gr-custom-plugin-header.ts
@@ -0,0 +1,53 @@
+/**
+ * @license
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import {PolymerElement} from '@polymer/polymer/polymer-element';
+import {html} from '@polymer/polymer/lib/utils/html-tag';
+import {customElement, property} from '@polymer/decorators';
+
+declare global {
+  interface HTMLElementTagNameMap {
+    'gr-custom-plugin-header': GrCustomPluginHeader;
+  }
+}
+
+@customElement('gr-custom-plugin-header')
+export class GrCustomPluginHeader extends PolymerElement {
+  @property({type: String})
+  logoUrl = '';
+
+  @property({type: String})
+  title = '';
+
+  static get template() {
+    return html`
+      <style>
+        img {
+          width: 1em;
+          height: 1em;
+          vertical-align: middle;
+        }
+        .title {
+          margin-left: var(--spacing-xs);
+        }
+      </style>
+      <span>
+        <img src="[[logoUrl]]" hidden$="[[!logoUrl]]" />
+        <span class="title">[[title]]</span>
+      </span>
+    `;
+  }
+}
diff --git a/polygerrit-ui/app/elements/plugins/gr-theme-api/gr-theme-api.js b/polygerrit-ui/app/elements/plugins/gr-theme-api/gr-theme-api.js
deleted file mode 100644
index 48b14d3..0000000
--- a/polygerrit-ui/app/elements/plugins/gr-theme-api/gr-theme-api.js
+++ /dev/null
@@ -1,34 +0,0 @@
-/**
- * @license
- * Copyright (C) 2017 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-import './gr-custom-plugin-header.js';
-
-/** @constructor */
-export function GrThemeApi(plugin) {
-  this.plugin = plugin;
-}
-
-GrThemeApi.prototype.setHeaderLogoAndTitle = function(logoUrl, title) {
-  this.plugin.hook('header-title', {replace: true}).onAttached(
-      element => {
-        const customHeader =
-              document.createElement('gr-custom-plugin-header');
-        customHeader.logoUrl = logoUrl;
-        customHeader.title = title;
-        element.appendChild(customHeader);
-      });
-};
-
diff --git a/polygerrit-ui/app/elements/plugins/gr-theme-api/gr-theme-api.ts b/polygerrit-ui/app/elements/plugins/gr-theme-api/gr-theme-api.ts
new file mode 100644
index 0000000..613bde2
--- /dev/null
+++ b/polygerrit-ui/app/elements/plugins/gr-theme-api/gr-theme-api.ts
@@ -0,0 +1,46 @@
+/**
+ * @license
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import './gr-custom-plugin-header';
+import {GrCustomPluginHeader} from './gr-custom-plugin-header';
+
+// TODO(TS): replace with Plugin once gr-public-js-api migrated
+interface PluginApi {
+  hook(
+    endpointName: string,
+    option: {replace?: boolean}
+  ): {
+    onAttached(callback: (el: Element) => void): void;
+  };
+}
+
+/**
+ * Defines api for theme, can be used to set header logo and title.
+ */
+export class GrThemeApi {
+  constructor(private readonly plugin: PluginApi) {}
+
+  setHeaderLogoAndTitle(logoUrl: string, title: string) {
+    this.plugin.hook('header-title', {replace: true}).onAttached(element => {
+      const customHeader: GrCustomPluginHeader = document.createElement(
+        'gr-custom-plugin-header'
+      );
+      customHeader.logoUrl = logoUrl;
+      customHeader.title = title;
+      element.appendChild(customHeader);
+    });
+  }
+}
diff --git a/polygerrit-ui/app/elements/shared/gr-button/gr-button.ts b/polygerrit-ui/app/elements/shared/gr-button/gr-button.ts
index a0d8d13e..4d75138 100644
--- a/polygerrit-ui/app/elements/shared/gr-button/gr-button.ts
+++ b/polygerrit-ui/app/elements/shared/gr-button/gr-button.ts
@@ -73,7 +73,7 @@
   }
 
   @property({
-    computed: 'computeAriaDisable(disabled, loading)',
+    computed: 'computeAriaDisabled(disabled, loading)',
     reflectToAttribute: true,
     type: Boolean,
   })
diff --git a/polygerrit-ui/app/elements/shared/gr-copy-clipboard/gr-copy-clipboard.js b/polygerrit-ui/app/elements/shared/gr-copy-clipboard/gr-copy-clipboard.js
deleted file mode 100644
index 39c149f..0000000
--- a/polygerrit-ui/app/elements/shared/gr-copy-clipboard/gr-copy-clipboard.js
+++ /dev/null
@@ -1,85 +0,0 @@
-/**
- * @license
- * Copyright (C) 2017 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-import '@polymer/iron-input/iron-input.js';
-import '../../../styles/shared-styles.js';
-import '../gr-button/gr-button.js';
-import '../gr-icons/gr-icons.js';
-import {dom} from '@polymer/polymer/lib/legacy/polymer.dom.js';
-import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners.js';
-import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin.js';
-import {PolymerElement} from '@polymer/polymer/polymer-element.js';
-import {htmlTemplate} from './gr-copy-clipboard_html.js';
-
-const COPY_TIMEOUT_MS = 1000;
-
-/** @extends PolymerElement */
-class GrCopyClipboard extends GestureEventListeners(
-    LegacyElementMixin(
-        PolymerElement)) {
-  static get template() { return htmlTemplate; }
-
-  static get is() { return 'gr-copy-clipboard'; }
-
-  static get properties() {
-    return {
-      text: String,
-      buttonTitle: String,
-      hasTooltip: {
-        type: Boolean,
-        value: false,
-      },
-      hideInput: {
-        type: Boolean,
-        value: false,
-      },
-    };
-  }
-
-  focusOnCopy() {
-    this.$.button.focus();
-  }
-
-  _computeInputClass(hideInput) {
-    return hideInput ? 'hideInput' : '';
-  }
-
-  _handleInputClick(e) {
-    e.preventDefault();
-    dom(e).rootTarget.select();
-  }
-
-  _copyToClipboard(e) {
-    e.preventDefault();
-    e.stopPropagation();
-
-    if (this.hideInput) {
-      this.$.input.style.display = 'block';
-    }
-    this.$.input.focus();
-    this.$.input.select();
-    document.execCommand('copy');
-    if (this.hideInput) {
-      this.$.input.style.display = 'none';
-    }
-    this.$.icon.icon = 'gr-icons:check';
-    this.async(
-        () => this.$.icon.icon = 'gr-icons:content-copy',
-        COPY_TIMEOUT_MS);
-  }
-}
-
-customElements.define(GrCopyClipboard.is, GrCopyClipboard);
diff --git a/polygerrit-ui/app/elements/shared/gr-copy-clipboard/gr-copy-clipboard.ts b/polygerrit-ui/app/elements/shared/gr-copy-clipboard/gr-copy-clipboard.ts
new file mode 100644
index 0000000..47dacc3
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-copy-clipboard/gr-copy-clipboard.ts
@@ -0,0 +1,95 @@
+/**
+ * @license
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import '@polymer/iron-input/iron-input';
+import '../../../styles/shared-styles';
+import '../gr-button/gr-button';
+import '../gr-icons/gr-icons';
+import {dom, EventApi} from '@polymer/polymer/lib/legacy/polymer.dom';
+import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners';
+import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin';
+import {PolymerElement} from '@polymer/polymer/polymer-element';
+import {htmlTemplate} from './gr-copy-clipboard_html';
+import {GrButton} from '../gr-button/gr-button';
+import {customElement, property} from '@polymer/decorators';
+import {IronIconElement} from '@polymer/iron-icon';
+
+const COPY_TIMEOUT_MS = 1000;
+
+declare global {
+  interface HTMLElementTagNameMap {
+    'gr-copy-clipboard': GrCopyClipboard;
+  }
+}
+
+export interface GrCopyClipboard {
+  $: {button: GrButton; icon: IronIconElement; input: HTMLInputElement};
+}
+
+/** @extends PolymerElement */
+@customElement('gr-copy-clipboard')
+export class GrCopyClipboard extends GestureEventListeners(
+  LegacyElementMixin(PolymerElement)
+) {
+  static get template() {
+    return htmlTemplate;
+  }
+
+  @property({type: String})
+  text: string | undefined;
+
+  @property({type: String})
+  buttonTitle: string | undefined;
+
+  @property({type: Boolean})
+  hasTooltip = false;
+
+  @property({type: Boolean})
+  hideInput = false;
+
+  focusOnCopy() {
+    this.$.button.focus();
+  }
+
+  _computeInputClass(hideInput: boolean) {
+    return hideInput ? 'hideInput' : '';
+  }
+
+  _handleInputClick(e: MouseEvent) {
+    e.preventDefault();
+    ((dom(e) as EventApi).rootTarget as HTMLInputElement).select();
+  }
+
+  _copyToClipboard(e: MouseEvent) {
+    e.preventDefault();
+    e.stopPropagation();
+
+    if (this.hideInput) {
+      this.$.input.style.display = 'block';
+    }
+    this.$.input.focus();
+    this.$.input.select();
+    document.execCommand('copy');
+    if (this.hideInput) {
+      this.$.input.style.display = 'none';
+    }
+    this.$.icon.icon = 'gr-icons:check';
+    this.async(
+      () => (this.$.icon.icon = 'gr-icons:content-copy'),
+      COPY_TIMEOUT_MS
+    );
+  }
+}
diff --git a/polygerrit-ui/app/elements/shared/gr-dialog/gr-dialog.js b/polygerrit-ui/app/elements/shared/gr-dialog/gr-dialog.js
deleted file mode 100644
index 2292ae7..0000000
--- a/polygerrit-ui/app/elements/shared/gr-dialog/gr-dialog.js
+++ /dev/null
@@ -1,115 +0,0 @@
-/**
- * @license
- * Copyright (C) 2016 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-import '../gr-button/gr-button.js';
-import '../../../styles/shared-styles.js';
-import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners.js';
-import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin.js';
-import {PolymerElement} from '@polymer/polymer/polymer-element.js';
-import {htmlTemplate} from './gr-dialog_html.js';
-
-/**
- * @extends PolymerElement
- */
-class GrDialog extends GestureEventListeners(
-    LegacyElementMixin(PolymerElement)) {
-  static get template() { return htmlTemplate; }
-
-  static get is() { return 'gr-dialog'; }
-  /**
-   * Fired when the confirm button is pressed.
-   *
-   * @event confirm
-   */
-
-  /**
-   * Fired when the cancel button is pressed.
-   *
-   * @event cancel
-   */
-
-  static get properties() {
-    return {
-      confirmLabel: {
-        type: String,
-        value: 'Confirm',
-      },
-      // Supplying an empty cancel label will hide the button completely.
-      cancelLabel: {
-        type: String,
-        value: 'Cancel',
-      },
-      disabled: {
-        type: Boolean,
-        value: false,
-      },
-      confirmOnEnter: {
-        type: Boolean,
-        value: false,
-      },
-      confirmTooltip: {
-        type: String,
-        observer: '_handleConfirmTooltipUpdate',
-      },
-    };
-  }
-
-  /** @override */
-  ready() {
-    super.ready();
-    this._ensureAttribute('role', 'dialog');
-  }
-
-  _handleConfirmTooltipUpdate(confirmTooltip) {
-    if (confirmTooltip) {
-      this.$.confirm.setAttribute('has-tooltip', true);
-    } else {
-      this.$.confirm.removeAttribute('has-tooltip');
-    }
-  }
-
-  _handleConfirm(e) {
-    if (this.disabled) { return; }
-
-    e.preventDefault();
-    e.stopPropagation();
-    this.dispatchEvent(new CustomEvent('confirm', {
-      composed: true, bubbles: false,
-    }));
-  }
-
-  _handleCancelTap(e) {
-    e.preventDefault();
-    e.stopPropagation();
-    this.dispatchEvent(new CustomEvent('cancel', {
-      composed: true, bubbles: false,
-    }));
-  }
-
-  _handleKeydown(e) {
-    if (this.confirmOnEnter && e.keyCode === 13) { this._handleConfirm(e); }
-  }
-
-  resetFocus() {
-    this.$.confirm.focus();
-  }
-
-  _computeCancelClass(cancelLabel) {
-    return cancelLabel.length ? '' : 'hidden';
-  }
-}
-
-customElements.define(GrDialog.is, GrDialog);
diff --git a/polygerrit-ui/app/elements/shared/gr-dialog/gr-dialog.ts b/polygerrit-ui/app/elements/shared/gr-dialog/gr-dialog.ts
new file mode 100644
index 0000000..fa6403a
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-dialog/gr-dialog.ts
@@ -0,0 +1,128 @@
+/**
+ * @license
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import '../gr-button/gr-button';
+import '../../../styles/shared-styles';
+import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners';
+import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin';
+import {PolymerElement} from '@polymer/polymer/polymer-element';
+import {htmlTemplate} from './gr-dialog_html';
+import {customElement, property, observe} from '@polymer/decorators';
+import {GrButton} from '../gr-button/gr-button';
+
+declare global {
+  interface HTMLElementTagNameMap {
+    'gr-dialog': GrDialog;
+  }
+}
+
+export interface GrDialog {
+  $: {
+    confirm: GrButton;
+  };
+}
+
+@customElement('gr-dialog')
+export class GrDialog extends GestureEventListeners(
+  LegacyElementMixin(PolymerElement)
+) {
+  static get template() {
+    return htmlTemplate;
+  }
+
+  /**
+   * Fired when the confirm button is pressed.
+   *
+   * @event confirm
+   */
+
+  /**
+   * Fired when the cancel button is pressed.
+   *
+   * @event cancel
+   */
+
+  @property({type: String})
+  confirmLabel = 'Confirm';
+
+  // Supplying an empty cancel label will hide the button completely.
+  @property({type: String})
+  cancelLabel = 'Cancel';
+
+  @property({type: Boolean})
+  disabled = false;
+
+  @property({type: Boolean})
+  confirmOnEnter = false;
+
+  @property({type: String})
+  confirmTooltip?: string;
+
+  /** @override */
+  ready() {
+    super.ready();
+    this._ensureAttribute('role', 'dialog');
+  }
+
+  @observe('confirmTooltip')
+  _handleConfirmTooltipUpdate(confirmTooltip?: string) {
+    if (confirmTooltip) {
+      this.$.confirm.setAttribute('has-tooltip', 'true');
+    } else {
+      this.$.confirm.removeAttribute('has-tooltip');
+    }
+  }
+
+  _handleConfirm(e: KeyboardEvent) {
+    if (this.disabled) {
+      return;
+    }
+
+    e.preventDefault();
+    e.stopPropagation();
+    this.dispatchEvent(
+      new CustomEvent('confirm', {
+        composed: true,
+        bubbles: false,
+      })
+    );
+  }
+
+  _handleCancelTap(e: MouseEvent) {
+    e.preventDefault();
+    e.stopPropagation();
+    this.dispatchEvent(
+      new CustomEvent('cancel', {
+        composed: true,
+        bubbles: false,
+      })
+    );
+  }
+
+  _handleKeydown(e: KeyboardEvent) {
+    if (this.confirmOnEnter && e.keyCode === 13) {
+      this._handleConfirm(e);
+    }
+  }
+
+  resetFocus() {
+    this.$.confirm.focus();
+  }
+
+  _computeCancelClass(cancelLabel: string) {
+    return cancelLabel.length ? '' : 'hidden';
+  }
+}
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils.js b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils.js
deleted file mode 100644
index 9bef3a2..0000000
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils.js
+++ /dev/null
@@ -1,103 +0,0 @@
-/**
- * @license
- * Copyright (C) 2019 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-import {getBaseUrl} from '../../../utils/url-util.js';
-
-export const PRELOADED_PROTOCOL = 'preloaded:';
-export const PLUGIN_LOADING_TIMEOUT_MS = 10000;
-
-let _restAPI;
-export function getRestAPI() {
-  if (!_restAPI) {
-    _restAPI = document.createElement('gr-rest-api-interface');
-  }
-  return _restAPI;
-}
-
-/**
- * Retrieves the name of the plugin base on the url.
- *
- * @param {string|URL} url
- */
-export function getPluginNameFromUrl(url) {
-  if (!(url instanceof URL)) {
-    try {
-      url = new URL(url);
-    } catch (e) {
-      console.warn(e);
-      return null;
-    }
-  }
-  if (url.protocol === PRELOADED_PROTOCOL) {
-    return url.pathname;
-  }
-  const base = getBaseUrl();
-  let pathname = url.pathname.replace(base, '');
-  // Load from ASSETS_PATH
-  if (window.ASSETS_PATH && url.href.includes(window.ASSETS_PATH)) {
-    pathname = url.href.replace(window.ASSETS_PATH, '');
-  }
-  // Site theme is server from predefined path.
-  if ([
-    '/static/gerrit-theme.html',
-    '/static/gerrit-theme.js',
-  ].includes(pathname)) {
-    return 'gerrit-theme';
-  } else if (!pathname.startsWith('/plugins')) {
-    console.warn('Plugin not being loaded from /plugins base path:',
-        url.href, '— Unable to determine name.');
-    return null;
-  }
-
-  // Pathname should normally look like this:
-  // /plugins/PLUGINNAME/static/SCRIPTNAME.html
-  // Or, for app/samples:
-  // /plugins/PLUGINNAME.html
-  // TODO(taoalpha): guard with a regex
-  return pathname.split('/')[2].split('.')[0];
-}
-
-// TODO(taoalpha): to be deprecated.
-export function send(method, url, opt_callback, opt_payload) {
-  return getRestAPI().send(method, url, opt_payload)
-      .then(response => {
-        if (response.status < 200 || response.status >= 300) {
-          return response.text().then(text => {
-            if (text) {
-              return Promise.reject(new Error(text));
-            } else {
-              return Promise.reject(new Error(response.status));
-            }
-          });
-        } else {
-          return getRestAPI().getResponseObject(response);
-        }
-      })
-      .then(response => {
-        if (opt_callback) {
-          opt_callback(response);
-        }
-        return response;
-      });
-}
-
-// TEST only methods / properties
-
-export function testOnly_resetInternalState() {
-  _restAPI = undefined;
-}
-
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils.ts b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils.ts
new file mode 100644
index 0000000..2b60e94
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils.ts
@@ -0,0 +1,113 @@
+/**
+ * @license
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {getBaseUrl} from '../../../utils/url-util';
+import {RestApiService} from '../../../services/services/gr-rest-api/gr-rest-api';
+
+export const PRELOADED_PROTOCOL = 'preloaded:';
+export const PLUGIN_LOADING_TIMEOUT_MS = 10000;
+
+let _restAPI: RestApiService | undefined;
+export function getRestAPI() {
+  if (!_restAPI) {
+    _restAPI = (document.createElement(
+      'gr-rest-api-interface'
+    ) as unknown) as RestApiService;
+  }
+  return _restAPI;
+}
+
+/**
+ * Retrieves the name of the plugin base on the url.
+ *
+ * @param {string|URL} url
+ */
+export function getPluginNameFromUrl(url: URL | string) {
+  if (!(url instanceof URL)) {
+    try {
+      url = new URL(url);
+    } catch (e) {
+      console.warn(e);
+      return null;
+    }
+  }
+  if (url.protocol === PRELOADED_PROTOCOL) {
+    return url.pathname;
+  }
+  const base = getBaseUrl();
+  let pathname = url.pathname.replace(base, '');
+  // Load from ASSETS_PATH
+  if (window.ASSETS_PATH && url.href.includes(window.ASSETS_PATH)) {
+    pathname = url.href.replace(window.ASSETS_PATH, '');
+  }
+  // Site theme is server from predefined path.
+  if (
+    ['/static/gerrit-theme.html', '/static/gerrit-theme.js'].includes(pathname)
+  ) {
+    return 'gerrit-theme';
+  } else if (!pathname.startsWith('/plugins')) {
+    console.warn(
+      'Plugin not being loaded from /plugins base path:',
+      url.href,
+      '— Unable to determine name.'
+    );
+    return null;
+  }
+
+  // Pathname should normally look like this:
+  // /plugins/PLUGINNAME/static/SCRIPTNAME.html
+  // Or, for app/samples:
+  // /plugins/PLUGINNAME.html
+  // TODO(taoalpha): guard with a regex
+  return pathname.split('/')[2].split('.')[0];
+}
+
+// TODO(taoalpha): to be deprecated.
+export function send(
+  method: string,
+  url: string,
+  opt_callback?: (response: unknown) => void,
+  opt_payload?: unknown
+) {
+  return getRestAPI()
+    .send(method, url, opt_payload)
+    .then(response => {
+      if (response.status < 200 || response.status >= 300) {
+        return response.text().then((text: string | undefined) => {
+          if (text) {
+            return Promise.reject(new Error(text));
+          } else {
+            return Promise.reject(new Error(`${response.status}`));
+          }
+        });
+      } else {
+        return getRestAPI().getResponseObject(response);
+      }
+    })
+    .then(response => {
+      if (opt_callback) {
+        opt_callback(response);
+      }
+      return response;
+    });
+}
+
+// TEST only methods / properties
+
+export function testOnly_resetInternalState() {
+  _restAPI = undefined;
+}
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-rest-api.js b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-rest-api.js
deleted file mode 100644
index 31ff8ee..0000000
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-rest-api.js
+++ /dev/null
@@ -1,151 +0,0 @@
-/**
- * @license
- * Copyright (C) 2017 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-let restApi;
-
-export function _testOnlyResetRestApi() {
-  restApi = null;
-}
-
-function getRestApi() {
-  if (!restApi) {
-    restApi = document.createElement('gr-rest-api-interface');
-  }
-  return restApi;
-}
-
-export function GrPluginRestApi(opt_prefix) {
-  this.opt_prefix = opt_prefix || '';
-}
-
-GrPluginRestApi.prototype.getLoggedIn = function() {
-  return getRestApi().getLoggedIn();
-};
-
-GrPluginRestApi.prototype.getVersion = function() {
-  return getRestApi().getVersion();
-};
-
-GrPluginRestApi.prototype.getConfig = function() {
-  return getRestApi().getConfig();
-};
-
-GrPluginRestApi.prototype.invalidateReposCache = function() {
-  getRestApi().invalidateReposCache();
-};
-
-GrPluginRestApi.prototype.getAccount = function() {
-  return getRestApi().getAccount();
-};
-
-GrPluginRestApi.prototype.getAccountCapabilities = function(capabilities) {
-  return getRestApi().getAccountCapabilities(capabilities);
-};
-
-GrPluginRestApi.prototype.getRepos =
-  function(filter, reposPerPage, opt_offset) {
-    return getRestApi().getRepos(filter, reposPerPage, opt_offset);
-  };
-
-/**
- * Fetch and return native browser REST API Response.
- *
- * @param {string} method HTTP Method (GET, POST, etc)
- * @param {string} url URL without base path or plugin prefix
- * @param {Object=} payload Respected for POST and PUT only.
- * @param {?function(?Response, string=)=} opt_errFn
- *    passed as null sometimes.
- * @return {!Promise}
- */
-GrPluginRestApi.prototype.fetch = function(method, url, opt_payload,
-    opt_errFn, opt_contentType) {
-  return getRestApi().send(method, this.opt_prefix + url, opt_payload,
-      opt_errFn, opt_contentType);
-};
-
-/**
- * Fetch and parse REST API response, if request succeeds.
- *
- * @param {string} method HTTP Method (GET, POST, etc)
- * @param {string} url URL without base path or plugin prefix
- * @param {Object=} payload Respected for POST and PUT only.
- * @param {?function(?Response, string=)=} opt_errFn
- *    passed as null sometimes.
- * @return {!Promise} resolves on success, rejects on error.
- */
-GrPluginRestApi.prototype.send = function(method, url, opt_payload,
-    opt_errFn, opt_contentType) {
-  return this.fetch(method, url, opt_payload, opt_errFn, opt_contentType)
-      .then(response => {
-        if (response.status < 200 || response.status >= 300) {
-          return response.text().then(text => {
-            if (text) {
-              return Promise.reject(new Error(text));
-            } else {
-              return Promise.reject(new Error(response.status));
-            }
-          });
-        } else {
-          return getRestApi().getResponseObject(response);
-        }
-      });
-};
-
-/**
- * @param {string} url URL without base path or plugin prefix
- * @return {!Promise} resolves on success, rejects on error.
- */
-GrPluginRestApi.prototype.get = function(url) {
-  return this.send('GET', url);
-};
-
-/**
- * @param {string} url URL without base path or plugin prefix
- * @return {!Promise} resolves on success, rejects on error.
- */
-GrPluginRestApi.prototype.post = function(url, opt_payload, opt_errFn,
-    opt_contentType) {
-  return this.send('POST', url, opt_payload, opt_errFn, opt_contentType);
-};
-
-/**
- * @param {string} url URL without base path or plugin prefix
- * @return {!Promise} resolves on success, rejects on error.
- */
-GrPluginRestApi.prototype.put = function(url, opt_payload, opt_errFn,
-    opt_contentType) {
-  return this.send('PUT', url, opt_payload, opt_errFn, opt_contentType);
-};
-
-/**
- * @param {string} url URL without base path or plugin prefix
- * @return {!Promise} resolves on 204, rejects on error.
- */
-GrPluginRestApi.prototype.delete = function(url) {
-  return this.fetch('DELETE', url).then(response => {
-    if (response.status !== 204) {
-      return response.text().then(text => {
-        if (text) {
-          return Promise.reject(new Error(text));
-        } else {
-          return Promise.reject(new Error(response.status));
-        }
-      });
-    }
-    return response;
-  });
-};
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-rest-api.ts b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-rest-api.ts
new file mode 100644
index 0000000..a82e90c
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-rest-api.ts
@@ -0,0 +1,161 @@
+/**
+ * @license
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import {
+  ErrorCallback,
+  RestApiService,
+} from '../../../services/services/gr-rest-api/gr-rest-api';
+
+/**
+ * Enum for all http methods used in Gerrit.
+ * TODO(TS): might move to common later.
+ */
+export enum HttpMethod {
+  POST = 'POST',
+  GET = 'GET',
+  DELETE = 'DELETE',
+  PUT = 'PUT',
+}
+
+let restApi: RestApiService | null = null;
+
+export function _testOnlyResetRestApi() {
+  restApi = null;
+}
+
+function getRestApi(): RestApiService {
+  if (!restApi) {
+    restApi = (document.createElement(
+      'gr-rest-api-interface'
+    ) as unknown) as RestApiService;
+  }
+  return restApi;
+}
+
+export class GrPluginRestApi {
+  constructor(private readonly prefix = '') {}
+
+  getLoggedIn() {
+    return getRestApi().getLoggedIn();
+  }
+
+  getVersion() {
+    return getRestApi().getVersion();
+  }
+
+  getConfig() {
+    return getRestApi().getConfig();
+  }
+
+  invalidateReposCache() {
+    getRestApi().invalidateReposCache();
+  }
+
+  getAccount() {
+    return getRestApi().getAccount();
+  }
+
+  getAccountCapabilities(capabilities: string[]) {
+    return getRestApi().getAccountCapabilities(capabilities);
+  }
+
+  getRepos(filter: string, reposPerPage: number, offset?: number) {
+    return getRestApi().getRepos(filter, reposPerPage, offset);
+  }
+
+  /**
+   * Fetch and return native browser REST API Response.
+   */
+  fetch(
+    method: HttpMethod,
+    url: string,
+    payload?: unknown,
+    errFn?: ErrorCallback,
+    contentType?: string
+  ): Promise<Response> {
+    return getRestApi().send(
+      method,
+      this.prefix + url,
+      payload,
+      errFn,
+      contentType
+    );
+  }
+
+  /**
+   * Fetch and parse REST API response, if request succeeds.
+   */
+  send(
+    method: HttpMethod,
+    url: string,
+    payload?: unknown,
+    errFn?: ErrorCallback,
+    contentType?: string
+  ) {
+    return this.fetch(method, url, payload, errFn, contentType).then(
+      response => {
+        if (response.status < 200 || response.status >= 300) {
+          return response.text().then(text => {
+            if (text) {
+              return Promise.reject(new Error(text));
+            } else {
+              return Promise.reject(new Error(`${response.status}`));
+            }
+          });
+        } else {
+          return getRestApi().getResponseObject(response);
+        }
+      }
+    );
+  }
+
+  get(url: string) {
+    return this.send(HttpMethod.GET, url);
+  }
+
+  post(
+    url: string,
+    payload?: unknown,
+    errFn?: ErrorCallback,
+    contentType?: string
+  ) {
+    return this.send(HttpMethod.POST, url, payload, errFn, contentType);
+  }
+
+  put(
+    url: string,
+    payload?: unknown,
+    errFn?: ErrorCallback,
+    contentType?: string
+  ) {
+    return this.send(HttpMethod.PUT, url, payload, errFn, contentType);
+  }
+
+  delete(url: string) {
+    return this.fetch(HttpMethod.DELETE, url).then(response => {
+      if (response.status !== 204) {
+        return response.text().then(text => {
+          if (text) {
+            return Promise.reject(new Error(text));
+          } else {
+            return Promise.reject(new Error(`${response.status}`));
+          }
+        });
+      }
+      return response;
+    });
+  }
+}
diff --git a/polygerrit-ui/app/elements/shared/gr-overlay/gr-overlay.js b/polygerrit-ui/app/elements/shared/gr-overlay/gr-overlay.js
deleted file mode 100644
index 083b802..0000000
--- a/polygerrit-ui/app/elements/shared/gr-overlay/gr-overlay.js
+++ /dev/null
@@ -1,130 +0,0 @@
-/**
- * @license
- * Copyright (C) 2016 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-import {IronOverlayBehaviorImpl} from '@polymer/iron-overlay-behavior/iron-overlay-behavior.js';
-import '../../../styles/shared-styles.js';
-import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners.js';
-import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin.js';
-import {PolymerElement} from '@polymer/polymer/polymer-element.js';
-import {htmlTemplate} from './gr-overlay_html.js';
-import {IronOverlayMixin} from '../../../mixins/iron-overlay-mixin/iron-overlay-mixin.js';
-
-const AWAIT_MAX_ITERS = 10;
-const AWAIT_STEP = 5;
-const BREAKPOINT_FULLSCREEN_OVERLAY = '50em';
-
-/**
- * @extends PolymerElement
- */
-class GrOverlay extends IronOverlayMixin(GestureEventListeners(
-    LegacyElementMixin(PolymerElement))) {
-  static get template() { return htmlTemplate; }
-
-  static get is() { return 'gr-overlay'; }
-  /**
-   * Fired when a fullscreen overlay is closed
-   *
-   * @event fullscreen-overlay-closed
-   */
-
-  /**
-   * Fired when an overlay is opened in full screen mode
-   *
-   * @event fullscreen-overlay-opened
-   */
-
-  static get properties() {
-    return {
-      _fullScreenOpen: {
-        type: Boolean,
-        value: false,
-      },
-    };
-  }
-
-  /** @override */
-  created() {
-    this._boundHandleClose = () => this.close();
-    super.created();
-    this.addEventListener('iron-overlay-closed',
-        () => this._overlayClosed());
-    this.addEventListener('iron-overlay-cancelled',
-        () => this._overlayClosed());
-  }
-
-  open(...args) {
-    window.addEventListener('popstate', this._boundHandleClose);
-    return new Promise((resolve, reject) => {
-      IronOverlayBehaviorImpl.open.apply(this, args);
-      if (this._isMobile()) {
-        this.dispatchEvent(new CustomEvent('fullscreen-overlay-opened', {
-          composed: true, bubbles: true,
-        }));
-        this._fullScreenOpen = true;
-      }
-      this._awaitOpen(resolve, reject);
-    });
-  }
-
-  _isMobile() {
-    return window.matchMedia(`(max-width: ${BREAKPOINT_FULLSCREEN_OVERLAY})`);
-  }
-
-  // called after iron-overlay is closed. Does not actually close the overlay
-  _overlayClosed() {
-    window.removeEventListener('popstate', this._boundHandleClose);
-    if (this._fullScreenOpen) {
-      this.dispatchEvent(new CustomEvent('fullscreen-overlay-closed', {
-        composed: true, bubbles: true,
-      }));
-      this._fullScreenOpen = false;
-    }
-  }
-
-  /**
-   * Override the focus stops that iron-overlay-behavior tries to find.
-   */
-  setFocusStops(stops) {
-    this.__firstFocusableNode = stops.start;
-    this.__lastFocusableNode = stops.end;
-  }
-
-  /**
-   * NOTE: (wyatta) Slightly hacky way to listen to the overlay actually
-   * opening. Eventually replace with a direct way to listen to the overlay.
-   */
-  _awaitOpen(fn, reject) {
-    let iters = 0;
-    const step = () => {
-      this.async(() => {
-        if (this.style.display !== 'none') {
-          fn.call(this);
-        } else if (iters++ < AWAIT_MAX_ITERS) {
-          step.call(this);
-        } else {
-          reject(new Error('gr-overlay _awaitOpen failed to resolve'));
-        }
-      }, AWAIT_STEP);
-    };
-    step.call(this);
-  }
-
-  _id() {
-    return this.getAttribute('id') || 'global';
-  }
-}
-
-customElements.define(GrOverlay.is, GrOverlay);
diff --git a/polygerrit-ui/app/elements/shared/gr-overlay/gr-overlay.ts b/polygerrit-ui/app/elements/shared/gr-overlay/gr-overlay.ts
new file mode 100644
index 0000000..aabbac1
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-overlay/gr-overlay.ts
@@ -0,0 +1,148 @@
+/**
+ * @license
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import '../../../styles/shared-styles';
+import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners';
+import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin';
+import {PolymerElement} from '@polymer/polymer/polymer-element';
+import {htmlTemplate} from './gr-overlay_html';
+import {IronOverlayMixin} from '../../../mixins/iron-overlay-mixin/iron-overlay-mixin';
+import {customElement, property} from '@polymer/decorators';
+
+const AWAIT_MAX_ITERS = 10;
+const AWAIT_STEP = 5;
+const BREAKPOINT_FULLSCREEN_OVERLAY = '50em';
+
+declare global {
+  interface HTMLElementTagNameMap {
+    'gr-overlay': GrOverlay;
+  }
+}
+
+@customElement('gr-overlay')
+export class GrOverlay extends IronOverlayMixin(
+  GestureEventListeners(LegacyElementMixin(PolymerElement))
+) {
+  static get template() {
+    return htmlTemplate;
+  }
+
+  /**
+   * Fired when a fullscreen overlay is closed
+   *
+   * @event fullscreen-overlay-closed
+   */
+
+  /**
+   * Fired when an overlay is opened in full screen mode
+   *
+   * @event fullscreen-overlay-opened
+   */
+
+  @property({type: Boolean})
+  private _fullScreenOpen = false;
+
+  private _boundHandleClose: () => void = () => super.close();
+
+  private focusableNodes: Node[] | undefined;
+
+  get _focusableNodes() {
+    if (this.focusableNodes) {
+      return this.focusableNodes;
+    }
+    return super._focusableNodes;
+  }
+
+  /** @override */
+  created() {
+    super.created();
+    this.addEventListener('iron-overlay-closed', () => this._overlayClosed());
+    this.addEventListener('iron-overlay-cancelled', () =>
+      this._overlayClosed()
+    );
+  }
+
+  open() {
+    window.addEventListener('popstate', this._boundHandleClose);
+    return new Promise((resolve, reject) => {
+      super.open.apply(this);
+      if (this._isMobile()) {
+        this.dispatchEvent(
+          new CustomEvent('fullscreen-overlay-opened', {
+            composed: true,
+            bubbles: true,
+          })
+        );
+        this._fullScreenOpen = true;
+      }
+      this._awaitOpen(resolve, reject);
+    });
+  }
+
+  _isMobile() {
+    return window.matchMedia(`(max-width: ${BREAKPOINT_FULLSCREEN_OVERLAY})`);
+  }
+
+  // called after iron-overlay is closed. Does not actually close the overlay
+  _overlayClosed() {
+    window.removeEventListener('popstate', this._boundHandleClose);
+    if (this._fullScreenOpen) {
+      this.dispatchEvent(
+        new CustomEvent('fullscreen-overlay-closed', {
+          composed: true,
+          bubbles: true,
+        })
+      );
+      this._fullScreenOpen = false;
+    }
+  }
+
+  /**
+   * Override the focus stops that iron-overlay-behavior tries to find.
+   */
+  setFocusStops(stops: GrOverlayStops) {
+    this.focusableNodes = [stops.start, stops.end];
+  }
+
+  /**
+   * NOTE: (wyatta) Slightly hacky way to listen to the overlay actually
+   * opening. Eventually replace with a direct way to listen to the overlay.
+   */
+  _awaitOpen(fn: (this: GrOverlay) => void, reject: (error: Error) => void) {
+    let iters = 0;
+    const step = () => {
+      this.async(() => {
+        if (this.style.display !== 'none') {
+          fn.call(this);
+        } else if (iters++ < AWAIT_MAX_ITERS) {
+          step.call(this);
+        } else {
+          reject(new Error('gr-overlay _awaitOpen failed to resolve'));
+        }
+      }, AWAIT_STEP);
+    };
+    step.call(this);
+  }
+
+  _id() {
+    return this.getAttribute('id') || 'global';
+  }
+}
+
+export interface GrOverlayStops {
+  start: Node;
+  end: Node;
+}
diff --git a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-etag-decorator.js b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-etag-decorator.js
deleted file mode 100644
index b364caf..0000000
--- a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-etag-decorator.js
+++ /dev/null
@@ -1,97 +0,0 @@
-/**
- * @license
- * Copyright (C) 2017 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-// Limit cache size because /change/detail responses may be large.
-const MAX_CACHE_SIZE = 30;
-
-/** @constructor */
-export function GrEtagDecorator() {
-  this._etags = new Map();
-  this._payloadCache = new Map();
-}
-
-/**
- * Get or upgrade fetch options to include an ETag in a request.
- *
- * @param {string} url The URL being fetched.
- * @param {!Object=} opt_options Optional options object in which to include
- *     the ETag request header. If omitted, the result will be a fresh option
- *     set.
- * @return {!Object}
- */
-GrEtagDecorator.prototype.getOptions = function(url, opt_options) {
-  const etag = this._etags.get(url);
-  if (!etag) {
-    return opt_options;
-  }
-  const options = {...opt_options};
-  options.headers = options.headers || new Headers();
-  options.headers.set('If-None-Match', this._etags.get(url));
-  return options;
-};
-
-/**
- * Handle a response to a request with ETag headers, potentially incorporating
- * its result in the payload cache.
- *
- * @param {string} url The URL of the request.
- * @param {!Response} response The response object.
- * @param {string} payload The raw, unparsed JSON contained in the response
- *     body. Note: because response.text() cannot be read twice, this must be
- *     provided separately.
- */
-GrEtagDecorator.prototype.collect = function(url, response, payload) {
-  if (!response ||
-      !response.ok ||
-      response.status !== 200 ||
-      response.status === 304) {
-    // 304 Not Modified means etag is still valid.
-    return;
-  }
-  this._payloadCache.set(url, payload);
-  const etag = response.headers && response.headers.get('etag');
-  if (!etag) {
-    this._etags.delete(url);
-  } else {
-    this._etags.set(url, etag);
-    this._truncateCache();
-  }
-};
-
-/**
- * Get the cached payload for a given URL.
- *
- * @param {string} url
- * @return {string|undefined} Returns the unparsed JSON payload from the
- *     cache.
- */
-GrEtagDecorator.prototype.getCachedPayload = function(url) {
-  return this._payloadCache.get(url);
-};
-
-/**
- * Limit the cache size to MAX_CACHE_SIZE.
- */
-GrEtagDecorator.prototype._truncateCache = function() {
-  for (const url of this._etags.keys()) {
-    if (this._etags.size <= MAX_CACHE_SIZE) {
-      break;
-    }
-    this._etags.delete(url);
-    this._payloadCache.delete(url);
-  }
-};
diff --git a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-etag-decorator.ts b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-etag-decorator.ts
new file mode 100644
index 0000000..2c1ba70
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-etag-decorator.ts
@@ -0,0 +1,98 @@
+/**
+ * @license
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Limit cache size because /change/detail responses may be large.
+const MAX_CACHE_SIZE = 30;
+
+/**
+ * Option to send with etag requests.
+ */
+export interface ETagOption {
+  headers?: Headers;
+}
+
+/**
+ * GrTagDecorator class.
+ *
+ * Defines common methods to help cache and build ETag into a request header.
+ */
+export class GrEtagDecorator {
+  _etags = new Map<string, string | null>();
+
+  _payloadCache = new Map<string, string>();
+
+  /**
+   * Get or upgrade fetch options to include an ETag in a request.
+   *
+   */
+  getOptions(url: string, options?: ETagOption) {
+    const etag = this._etags.get(url);
+    if (!etag) {
+      return options;
+    }
+    const optionsCopy: ETagOption = {...options};
+    optionsCopy.headers = optionsCopy.headers || new Headers();
+    optionsCopy.headers.set('If-None-Match', etag);
+    return optionsCopy;
+  }
+
+  /**
+   * Handle a response to a request with ETag headers, potentially incorporating
+   * its result in the payload cache.
+   *
+   *
+   * @param url The URL of the request.
+   * @param response The response object.
+   * @param payload The raw, unparsed JSON contained in the response
+   *     body. Note: because response.text() cannot be read twice, this must be
+   *     provided separately.
+   */
+  collect(url: string, response: Response, payload: string) {
+    if (!response || !response.ok || response.status !== 200) {
+      // 304 Not Modified means etag is still valid.
+      return;
+    }
+    this._payloadCache.set(url, payload);
+    const etag = response.headers && response.headers.get('etag');
+    if (!etag) {
+      this._etags.delete(url);
+    } else {
+      this._etags.set(url, etag);
+      this._truncateCache();
+    }
+  }
+
+  /**
+   * Get the cached payload for a given URL.
+   */
+  getCachedPayload(url: string) {
+    return this._payloadCache.get(url);
+  }
+
+  /**
+   * Limit the cache size to MAX_CACHE_SIZE.
+   */
+  _truncateCache() {
+    for (const url of this._etags.keys()) {
+      if (this._etags.size <= MAX_CACHE_SIZE) {
+        break;
+      }
+      this._etags.delete(url);
+      this._payloadCache.delete(url);
+    }
+  }
+}
diff --git a/polygerrit-ui/app/elements/shared/gr-shell-command/gr-shell-command.js b/polygerrit-ui/app/elements/shared/gr-shell-command/gr-shell-command.js
deleted file mode 100644
index a5212fc..0000000
--- a/polygerrit-ui/app/elements/shared/gr-shell-command/gr-shell-command.js
+++ /dev/null
@@ -1,44 +0,0 @@
-/**
- * @license
- * Copyright (C) 2018 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-import '../../../styles/shared-styles.js';
-import '../gr-copy-clipboard/gr-copy-clipboard.js';
-import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners.js';
-import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin.js';
-import {PolymerElement} from '@polymer/polymer/polymer-element.js';
-import {htmlTemplate} from './gr-shell-command_html.js';
-
-/** @extends PolymerElement */
-class GrShellCommand extends GestureEventListeners(
-    LegacyElementMixin(
-        PolymerElement)) {
-  static get template() { return htmlTemplate; }
-
-  static get is() { return 'gr-shell-command'; }
-
-  static get properties() {
-    return {
-      command: String,
-      label: String,
-    };
-  }
-
-  focusOnCopy() {
-    this.shadowRoot.querySelector('gr-copy-clipboard').focusOnCopy();
-  }
-}
-
-customElements.define(GrShellCommand.is, GrShellCommand);
diff --git a/polygerrit-ui/app/elements/shared/gr-shell-command/gr-shell-command.ts b/polygerrit-ui/app/elements/shared/gr-shell-command/gr-shell-command.ts
new file mode 100644
index 0000000..27f4069
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-shell-command/gr-shell-command.ts
@@ -0,0 +1,53 @@
+/**
+ * @license
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import '../../../styles/shared-styles';
+import '../gr-copy-clipboard/gr-copy-clipboard';
+import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners';
+import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin';
+import {PolymerElement} from '@polymer/polymer/polymer-element';
+import {htmlTemplate} from './gr-shell-command_html';
+import {customElement, property} from '@polymer/decorators';
+
+declare global {
+  interface HTMLElementTagNameMap {
+    'gr-shell-command': GrShellCommand;
+  }
+}
+
+@customElement('gr-shell-command')
+class GrShellCommand extends GestureEventListeners(
+  LegacyElementMixin(PolymerElement)
+) {
+  static get template() {
+    return htmlTemplate;
+  }
+
+  @property({type: String})
+  command: string | undefined;
+
+  @property({type: String})
+  label: string | undefined;
+
+  focusOnCopy() {
+    if (this.shadowRoot !== null) {
+      const copyClipboard = this.shadowRoot.querySelector('gr-copy-clipboard');
+      if (copyClipboard !== null) {
+        copyClipboard.focusOnCopy();
+      }
+    }
+  }
+}
diff --git a/polygerrit-ui/app/mixins/gr-tooltip-mixin/gr-tooltip-mixin.ts b/polygerrit-ui/app/mixins/gr-tooltip-mixin/gr-tooltip-mixin.ts
index 516877e..5ef17e2 100644
--- a/polygerrit-ui/app/mixins/gr-tooltip-mixin/gr-tooltip-mixin.ts
+++ b/polygerrit-ui/app/mixins/gr-tooltip-mixin/gr-tooltip-mixin.ts
@@ -101,7 +101,7 @@
       @observe('hasTooltip')
       _setupTooltipListeners() {
         if (!this.mouseenterHandler) {
-          this.mouseenterHandler = () => this._handleShowTooltip();
+          this.mouseenterHandler = this.showHandler;
         }
 
         if (!this.hasTooltip) {
@@ -151,7 +151,7 @@
 
         this._tooltip = tooltip;
         window.addEventListener('scroll', this.windowScrollHandler);
-        this.addEventListener('mouseleave', this.showHandler);
+        this.addEventListener('mouseleave', this.hideHandler);
         this.addEventListener('click', this.hideHandler);
       }
 
diff --git a/polygerrit-ui/app/services/services/gr-rest-api/gr-rest-api.ts b/polygerrit-ui/app/services/services/gr-rest-api/gr-rest-api.ts
index 8038764..e1f0ffc 100644
--- a/polygerrit-ui/app/services/services/gr-rest-api/gr-rest-api.ts
+++ b/polygerrit-ui/app/services/services/gr-rest-api/gr-rest-api.ts
@@ -16,10 +16,13 @@
  */
 
 import {
+  AccountDetailInfo,
   AccountInfo,
+  CapabilityInfo,
   GroupBaseInfo,
   NumericChangeId,
   ServerInfo,
+  ProjectInfo,
 } from '../../../types/common';
 
 export type ErrorCallback = (response?: Response, err?: Error) => void;
@@ -62,6 +65,26 @@
 export interface RestApiService {
   getConfig(): Promise<ServerInfo>;
   getLoggedIn(): Promise<boolean>;
+  getVersion(): Promise<string>;
+  invalidateReposCache(): void;
+  getAccount(): Promise<AccountDetailInfo>;
+  getAccountCapabilities(params?: string[]): Promise<CapabilityInfo>;
+  getRepos(
+    filter: string,
+    reposPerPage: number,
+    offset?: number
+  ): Promise<ProjectInfo>;
+  send(
+    method: string,
+    url: string,
+    body?: unknown,
+    errFn?: ErrorCallback,
+    contentType?: string,
+    headers?: unknown
+  ): Promise<Response>;
+
+  getResponseObject(response: Response): null | unknown;
+
   getChangeSuggestedReviewers(
     changeNum: NumericChangeId,
     input: string,
diff --git a/polygerrit-ui/app/types/common.ts b/polygerrit-ui/app/types/common.ts
index ed89a42..bc8c28c 100644
--- a/polygerrit-ui/app/types/common.ts
+++ b/polygerrit-ui/app/types/common.ts
@@ -21,6 +21,7 @@
   FileInfoStatus,
   GpgKeyInfoStatus,
   ProblemInfoStatus,
+  ProjectState,
   RequirementStatus,
   ReviewerState,
   RevisionKind,
@@ -30,11 +31,14 @@
   {[__brand in BrandName]: never};
 
 export type PatchSetNum = BrandType<'edit' | number, '_patchSet'>;
+export const EditPatchSetNum = 'edit' as PatchSetNum;
+
 export type ChangeId = BrandType<string, '_changeId'>;
 export type ChangeMessageId = BrandType<string, '_changeMessageId'>;
 export type LegacyChangeId = BrandType<number, '_legacyChangeId'>;
 export type NumericChangeId = BrandType<number, '_numericChangeId'>;
 export type ProjectName = BrandType<string, '_projectName'>;
+export type UrlEncodedProjectName = BrandType<string, '_urlEncodedProjectName'>;
 export type TopicName = BrandType<string, '_topicName'>;
 export type AccountId = BrandType<number, '_accountId'>;
 export type HttpMethod = BrandType<string, '_httpMethod'>;
@@ -42,6 +46,13 @@
 export type RequirementType = BrandType<string, '_requirementType'>;
 export type TrackingId = BrandType<string, '_trackingId'>;
 export type ReviewInputTag = BrandType<string, '_reviewInputTag'>;
+export type RepositoryName = BrandType<string, '_repositoryName'>;
+
+// The URL encoded UUID of the comment
+export type UrlEncodedCommentId = BrandType<string, '_urlEncodedCommentId'>;
+
+// The ID of the dashboard, in the form of '<ref>:<path>'
+export type DashboardId = BrandType<string, '_dahsboardId'>;
 
 // The 8-char hex GPG key ID.
 export type GpgKeyId = BrandType<string, '_gpgKeyId'>;
@@ -166,6 +177,7 @@
   cherry_pick_of_change?: NumericChangeId;
   cherry_pick_of_patch_set?: PatchSetNum;
   contains_git_conflicts?: boolean;
+  internalHost?: string; // TODO(TS): provide an explanation what is its
 }
 
 /**
@@ -186,6 +198,14 @@
 }
 
 /**
+ * The AccountDetailInfo entity contains detailed information about an account.
+ * https://gerrit-review.googlesource.com/Documentation/rest-api-accounts.html#account-detail-info
+ */
+export interface AccountDetailInfo extends AccountInfo {
+  registered_on: Timestamp;
+}
+
+/**
  * The GroupAuditEventInfo entity contains information about an auditevent of a group.
  * https://gerrit-review.googlesource.com/Documentation/rest-api-groups.html
  */
@@ -211,7 +231,7 @@
  * https://gerrit-review.googlesource.com/Documentation/rest-api-groups.html
  */
 export interface GroupInfo {
-  id: string;
+  id: GroupId;
   name: string;
   url?: string;
   options?: GroupOptionsInfo;
@@ -920,7 +940,7 @@
  */
 export interface CommentInfo {
   patch_set?: PatchSetNum;
-  id: string;
+  id: UrlEncodedCommentId;
   path?: string;
   side?: string;
   parent?: string;
@@ -946,3 +966,33 @@
   end_line: string;
   end_character: string;
 }
+
+/**
+ * The ProjectInfo entity contains information about a project
+ * https://gerrit-review.googlesource.com/Documentation/rest-api-projects.html#project-info
+ */
+export interface ProjectInfo {
+  id: UrlEncodedProjectName;
+  // name is not set if returned in a map where the project name is used as
+  // map key
+  name?: ProjectName;
+  // ?-<n> if the parent project is not visible (<n> is a number which
+  // is increased for each non-visible project).
+  parent?: ProjectName;
+  description?: string;
+  state?: ProjectState;
+  branches?: {[branchName: string]: CommitId};
+  // labels is filled for Create Project and Get Project calls.
+  labels?: {[labelName: string]: LabelTypeInfo};
+  // Links to the project in external sites
+  web_links?: WebLinkInfo[];
+}
+
+/**
+ * The LabelTypeInfo entity contains metadata about the labels that a project
+ * has.
+ */
+export interface LabelTypeInfo {
+  values: {[value: string]: string};
+  default_value: number;
+}
diff --git a/polygerrit-ui/app/types/globals.ts b/polygerrit-ui/app/types/globals.ts
index 81db291..c15cee6 100644
--- a/polygerrit-ui/app/types/globals.ts
+++ b/polygerrit-ui/app/types/globals.ts
@@ -27,6 +27,7 @@
       text: string,
       options: {callback: (text: string, href?: string) => void}
     ): void;
+    ASSETS_PATH?: string;
   }
 
   interface Performance {