diff --git a/Documentation/rest-api-changes.txt b/Documentation/rest-api-changes.txt
index 096b068..3b9320c 100644
--- a/Documentation/rest-api-changes.txt
+++ b/Documentation/rest-api-changes.txt
@@ -6467,6 +6467,8 @@
 Only set if link:#current-revision[the current revision] is requested
 (in which case it will only contain a key for the current revision) or
 if link:#all-revisions[all revisions] are requested.
+|`meta_rev_id`           |optional|
+The SHA1 of the NoteDb meta ref.
 |`tracking_ids`       |optional|
 A list of link:#tracking-id-info[TrackingIdInfo] entities describing
 references to external tracking systems. Only set if
diff --git a/Documentation/rest-api-projects.txt b/Documentation/rest-api-projects.txt
index 677fc6d..49bc7e5 100644
--- a/Documentation/rest-api-projects.txt
+++ b/Documentation/rest-api-projects.txt
@@ -4211,8 +4211,10 @@
 |`branches`                  |optional|
 A list of branches that should be initially created. +
 For the branch names the `refs/heads/` prefix can be omitted. +
-The first entry of the list will be the default branch (ie. the target +
-of the `HEAD` symbolic ref).
+The first entry of the list will be the default branch (ie. the target
+of the `HEAD` symbolic ref). +
+Branches in the Gerrit internal ref space are not allowed, such as
+refs/groups/, refs/changes/, etc...
 |`owners`                    |optional|
 A list of groups that should be assigned as project owner. +
 Each group in the list must be specified as
diff --git a/java/com/google/gerrit/elasticsearch/ElasticChangeIndex.java b/java/com/google/gerrit/elasticsearch/ElasticChangeIndex.java
index 969ffa5..162654d 100644
--- a/java/com/google/gerrit/elasticsearch/ElasticChangeIndex.java
+++ b/java/com/google/gerrit/elasticsearch/ElasticChangeIndex.java
@@ -37,6 +37,7 @@
 import com.google.gerrit.exceptions.StorageException;
 import com.google.gerrit.index.FieldDef;
 import com.google.gerrit.index.QueryOptions;
+import com.google.gerrit.index.RefState;
 import com.google.gerrit.index.Schema;
 import com.google.gerrit.index.query.DataSource;
 import com.google.gerrit.index.query.Predicate;
@@ -354,7 +355,7 @@
 
     // Ref-state.
     if (fields.contains(ChangeField.REF_STATE.getName())) {
-      cd.setRefStates(getByteArray(source, ChangeField.REF_STATE.getName()));
+      cd.setRefStates(RefState.parseStates(getByteArray(source, ChangeField.REF_STATE.getName())));
     }
 
     // Ref-state-pattern.
diff --git a/java/com/google/gerrit/extensions/common/ChangeInfo.java b/java/com/google/gerrit/extensions/common/ChangeInfo.java
index 7ed2f95..528efe3 100644
--- a/java/com/google/gerrit/extensions/common/ChangeInfo.java
+++ b/java/com/google/gerrit/extensions/common/ChangeInfo.java
@@ -70,6 +70,7 @@
   public String submissionId;
   public Integer cherryPickOfChange;
   public Integer cherryPickOfPatchSet;
+  public String metaRevId;
 
   /**
    * Whether the change contains conflicts.
diff --git a/java/com/google/gerrit/extensions/common/FileInfo.java b/java/com/google/gerrit/extensions/common/FileInfo.java
index 32c5bd5..510c2ad 100644
--- a/java/com/google/gerrit/extensions/common/FileInfo.java
+++ b/java/com/google/gerrit/extensions/common/FileInfo.java
@@ -34,8 +34,8 @@
           && Objects.equals(oldPath, fileInfo.oldPath)
           && Objects.equals(linesInserted, fileInfo.linesInserted)
           && Objects.equals(linesDeleted, fileInfo.linesDeleted)
-          && Objects.equals(sizeDelta, fileInfo.sizeDelta)
-          && Objects.equals(size, fileInfo.size);
+          && sizeDelta == fileInfo.sizeDelta
+          && size == fileInfo.size;
     }
     return false;
   }
diff --git a/java/com/google/gerrit/index/RefState.java b/java/com/google/gerrit/index/RefState.java
index 956dcab..ed38de9 100644
--- a/java/com/google/gerrit/index/RefState.java
+++ b/java/com/google/gerrit/index/RefState.java
@@ -20,8 +20,7 @@
 
 import com.google.auto.value.AutoValue;
 import com.google.common.base.Splitter;
-import com.google.common.collect.MultimapBuilder;
-import com.google.common.collect.SetMultimap;
+import com.google.common.collect.ImmutableSetMultimap;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.entities.Project;
 import com.google.gerrit.git.ObjectIds;
@@ -33,10 +32,10 @@
 
 @AutoValue
 public abstract class RefState {
-  public static SetMultimap<Project.NameKey, RefState> parseStates(Iterable<byte[]> states) {
+  public static ImmutableSetMultimap<Project.NameKey, RefState> parseStates(
+      Iterable<byte[]> states) {
     RefState.check(states != null, null);
-    SetMultimap<Project.NameKey, RefState> result =
-        MultimapBuilder.hashKeys().hashSetValues().build();
+    ImmutableSetMultimap.Builder<Project.NameKey, RefState> result = ImmutableSetMultimap.builder();
     for (byte[] b : states) {
       RefState.check(b != null, null);
       String s = new String(b, UTF_8);
@@ -44,7 +43,7 @@
       RefState.check(parts.size() == 3 && !parts.get(0).isEmpty() && !parts.get(1).isEmpty(), s);
       result.put(Project.nameKey(parts.get(0)), RefState.create(parts.get(1), parts.get(2)));
     }
-    return result;
+    return result.build();
   }
 
   public static RefState create(String ref, String sha) {
diff --git a/java/com/google/gerrit/lucene/LuceneChangeIndex.java b/java/com/google/gerrit/lucene/LuceneChangeIndex.java
index f4b9e69..c3d4440 100644
--- a/java/com/google/gerrit/lucene/LuceneChangeIndex.java
+++ b/java/com/google/gerrit/lucene/LuceneChangeIndex.java
@@ -49,6 +49,7 @@
 import com.google.gerrit.exceptions.StorageException;
 import com.google.gerrit.index.FieldDef;
 import com.google.gerrit.index.QueryOptions;
+import com.google.gerrit.index.RefState;
 import com.google.gerrit.index.Schema;
 import com.google.gerrit.index.query.FieldBundle;
 import com.google.gerrit.index.query.Predicate;
@@ -702,7 +703,7 @@
   }
 
   private void decodeRefStates(ListMultimap<String, IndexableField> doc, ChangeData cd) {
-    cd.setRefStates(copyAsBytes(doc.get(REF_STATE_FIELD)));
+    cd.setRefStates(RefState.parseStates(copyAsBytes(doc.get(REF_STATE_FIELD))));
   }
 
   private void decodeRefStatePatterns(ListMultimap<String, IndexableField> doc, ChangeData cd) {
diff --git a/java/com/google/gerrit/server/change/ChangeJson.java b/java/com/google/gerrit/server/change/ChangeJson.java
index f292245..a461b59 100644
--- a/java/com/google/gerrit/server/change/ChangeJson.java
+++ b/java/com/google/gerrit/server/change/ChangeJson.java
@@ -54,6 +54,7 @@
 import com.google.gerrit.entities.PatchSet;
 import com.google.gerrit.entities.PatchSetApproval;
 import com.google.gerrit.entities.Project;
+import com.google.gerrit.entities.RefNames;
 import com.google.gerrit.entities.SubmitRecord;
 import com.google.gerrit.entities.SubmitRecord.Status;
 import com.google.gerrit.entities.SubmitRequirement;
@@ -75,6 +76,7 @@
 import com.google.gerrit.extensions.common.SubmitRequirementInfo;
 import com.google.gerrit.extensions.common.TrackingIdInfo;
 import com.google.gerrit.extensions.restapi.Url;
+import com.google.gerrit.index.RefState;
 import com.google.gerrit.index.query.QueryResult;
 import com.google.gerrit.metrics.Description;
 import com.google.gerrit.metrics.Description.Units;
@@ -570,6 +572,15 @@
     out.totalCommentCount = cd.totalCommentCount();
     out.unresolvedCommentCount = cd.unresolvedCommentCount();
 
+    if (cd.getRefStates() != null) {
+      String metaName = RefNames.changeMetaRef(cd.getId());
+      Optional<RefState> metaState =
+          cd.getRefStates().values().stream().filter(r -> r.ref().equals(metaName)).findAny();
+
+      // metaState should always be there, but it doesn't hurt to be extra careful.
+      metaState.ifPresent(rs -> out.metaRevId = rs.id().getName());
+    }
+
     if (user.isIdentifiedUser()) {
       Collection<String> stars = cd.stars(user.getAccountId());
       out.starred = stars.contains(StarredChangesUtil.DEFAULT_LABEL) ? true : null;
diff --git a/java/com/google/gerrit/server/index/change/ChangeField.java b/java/com/google/gerrit/server/index/change/ChangeField.java
index 5f2525e..59600e0 100644
--- a/java/com/google/gerrit/server/index/change/ChangeField.java
+++ b/java/com/google/gerrit/server/index/change/ChangeField.java
@@ -57,7 +57,6 @@
 import com.google.gerrit.entities.converter.PatchSetProtoConverter;
 import com.google.gerrit.entities.converter.ProtoConverter;
 import com.google.gerrit.index.FieldDef;
-import com.google.gerrit.index.RefState;
 import com.google.gerrit.index.SchemaUtil;
 import com.google.gerrit.json.OutputFormat;
 import com.google.gerrit.proto.Protos;
@@ -66,9 +65,7 @@
 import com.google.gerrit.server.StarredChangesUtil;
 import com.google.gerrit.server.config.AllUsersName;
 import com.google.gerrit.server.index.change.StalenessChecker.RefStatePattern;
-import com.google.gerrit.server.notedb.ChangeNotes;
 import com.google.gerrit.server.notedb.ReviewerStateInternal;
-import com.google.gerrit.server.notedb.RobotCommentNotes;
 import com.google.gerrit.server.project.SubmitRuleOptions;
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.gerrit.server.query.change.ChangeQueryBuilder;
@@ -982,27 +979,9 @@
           .buildRepeatable(
               cd -> {
                 List<byte[]> result = new ArrayList<>();
-                Project.NameKey project = cd.change().getProject();
-
-                cd.editRefs()
-                    .values()
-                    .forEach(r -> result.add(RefState.of(r).toByteArray(project)));
-                cd.starRefs()
-                    .values()
-                    .forEach(r -> result.add(RefState.of(r.ref()).toByteArray(allUsers(cd))));
-
-                ChangeNotes notes = cd.notes();
-                result.add(
-                    RefState.create(notes.getRefName(), notes.getMetaId()).toByteArray(project));
-                notes.getRobotComments(); // Force loading robot comments.
-                RobotCommentNotes robotNotes = notes.getRobotCommentNotes();
-                result.add(
-                    RefState.create(robotNotes.getRefName(), robotNotes.getMetaId())
-                        .toByteArray(project));
-                cd.draftRefs()
-                    .values()
-                    .forEach(r -> result.add(RefState.of(r).toByteArray(allUsers(cd))));
-
+                cd.getRefStates()
+                    .entries()
+                    .forEach(e -> result.add(e.getValue().toByteArray(e.getKey())));
                 return result;
               });
 
diff --git a/java/com/google/gerrit/server/index/change/StalenessChecker.java b/java/com/google/gerrit/server/index/change/StalenessChecker.java
index 7e50104..ad5cc2b 100644
--- a/java/com/google/gerrit/server/index/change/StalenessChecker.java
+++ b/java/com/google/gerrit/server/index/change/StalenessChecker.java
@@ -93,7 +93,7 @@
       return StalenessCheckResult.stale("Document %s missing from index", id);
     }
     ChangeData cd = result.get();
-    return check(repoManager, id, parseStates(cd), parsePatterns(cd));
+    return check(repoManager, id, cd.getRefStates(), parsePatterns(cd));
   }
 
   /**
@@ -127,10 +127,6 @@
     return StalenessCheckResult.notStale();
   }
 
-  private SetMultimap<Project.NameKey, RefState> parseStates(ChangeData cd) {
-    return RefState.parseStates(cd.getRefStates());
-  }
-
   private ListMultimap<Project.NameKey, RefStatePattern> parsePatterns(ChangeData cd) {
     return parsePatterns(cd.getRefStatePatterns());
   }
diff --git a/java/com/google/gerrit/server/query/change/ChangeData.java b/java/com/google/gerrit/server/query/change/ChangeData.java
index 6de263e..05ecc61 100644
--- a/java/com/google/gerrit/server/query/change/ChangeData.java
+++ b/java/com/google/gerrit/server/query/change/ChangeData.java
@@ -26,13 +26,16 @@
 import com.google.common.collect.ImmutableListMultimap;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.ImmutableSetMultimap;
 import com.google.common.collect.ImmutableSortedSet;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.ListMultimap;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
+import com.google.common.collect.SetMultimap;
 import com.google.common.primitives.Ints;
 import com.google.gerrit.common.Nullable;
+import com.google.gerrit.common.UsedAt;
 import com.google.gerrit.entities.Account;
 import com.google.gerrit.entities.AttentionSetUpdate;
 import com.google.gerrit.entities.Change;
@@ -43,6 +46,7 @@
 import com.google.gerrit.entities.PatchSet;
 import com.google.gerrit.entities.PatchSetApproval;
 import com.google.gerrit.entities.Project;
+import com.google.gerrit.entities.Project.NameKey;
 import com.google.gerrit.entities.RefNames;
 import com.google.gerrit.entities.RobotComment;
 import com.google.gerrit.entities.SubmitRecord;
@@ -50,6 +54,7 @@
 import com.google.gerrit.exceptions.StorageException;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.ResourceConflictException;
+import com.google.gerrit.index.RefState;
 import com.google.gerrit.server.ApprovalsUtil;
 import com.google.gerrit.server.ChangeMessagesUtil;
 import com.google.gerrit.server.CommentsUtil;
@@ -69,6 +74,7 @@
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.git.MergeUtil;
 import com.google.gerrit.server.notedb.ChangeNotes;
+import com.google.gerrit.server.notedb.RobotCommentNotes;
 import com.google.gerrit.server.patch.DiffSummary;
 import com.google.gerrit.server.patch.DiffSummaryKey;
 import com.google.gerrit.server.patch.PatchListCache;
@@ -308,7 +314,7 @@
   private Integer totalCommentCount;
   private LabelTypes labelTypes;
   private Optional<Timestamp> mergedOn;
-  private ImmutableList<byte[]> refStates;
+  private ImmutableSetMultimap<NameKey, RefState> refStates;
   private ImmutableList<byte[]> refStatePatterns;
 
   @Inject
@@ -1169,12 +1175,38 @@
     }
   }
 
-  public ImmutableList<byte[]> getRefStates() {
+  public SetMultimap<NameKey, RefState> getRefStates() {
+    if (refStates == null) {
+      if (!lazyLoad) {
+        return ImmutableSetMultimap.of();
+      }
+
+      ImmutableSetMultimap.Builder<NameKey, RefState> result = ImmutableSetMultimap.builder();
+      editRefs().values().forEach(r -> result.put(project, RefState.of(r)));
+      starRefs().values().forEach(r -> result.put(allUsersName, RefState.of(r.ref())));
+
+      // TODO: instantiating the notes is too much. We don't want to parse NoteDb, we just want the
+      // refs.
+      result.put(project, RefState.create(notes().getRefName(), notes().getMetaId()));
+      notes().getRobotComments(); // Force loading robot comments.
+      RobotCommentNotes robotNotes = notes().getRobotCommentNotes();
+      result.put(project, RefState.create(robotNotes.getRefName(), robotNotes.getMetaId()));
+      draftRefs().values().forEach(r -> result.put(allUsersName, RefState.of(r)));
+
+      refStates = result.build();
+    }
+
     return refStates;
   }
 
+  @UsedAt(UsedAt.Project.GOOGLE)
   public void setRefStates(Iterable<byte[]> refStates) {
-    this.refStates = ImmutableList.copyOf(refStates);
+    // TODO(hanwen): remove Google use, and drop this method.
+    setRefStates(RefState.parseStates(refStates));
+  }
+
+  public void setRefStates(ImmutableSetMultimap<Project.NameKey, RefState> refStates) {
+    this.refStates = refStates;
   }
 
   public ImmutableList<byte[]> getRefStatePatterns() {
diff --git a/java/com/google/gerrit/server/restapi/project/CreateProject.java b/java/com/google/gerrit/server/restapi/project/CreateProject.java
index a5a0034..faab241 100644
--- a/java/com/google/gerrit/server/restapi/project/CreateProject.java
+++ b/java/com/google/gerrit/server/restapi/project/CreateProject.java
@@ -208,4 +208,18 @@
     }
     return normalizedBranches;
   }
+
+  static class ValidBranchListener implements ProjectCreationValidationListener {
+    @Override
+    public void validateNewProject(CreateProjectArgs args) throws ValidationException {
+      for (String branch : args.branch) {
+        if (RefNames.isGerritRef(branch)) {
+          throw new ValidationException(
+              String.format(
+                  "Cannot create a project with branch %s. Branches in the Gerrit internal refs namespace are not allowed",
+                  branch));
+        }
+      }
+    }
+  }
 }
diff --git a/java/com/google/gerrit/server/restapi/project/Module.java b/java/com/google/gerrit/server/restapi/project/Module.java
index 517b888..9217077 100644
--- a/java/com/google/gerrit/server/restapi/project/Module.java
+++ b/java/com/google/gerrit/server/restapi/project/Module.java
@@ -29,6 +29,7 @@
 import com.google.gerrit.server.config.GerritConfigListener;
 import com.google.gerrit.server.project.RefValidationHelper;
 import com.google.gerrit.server.restapi.change.CherryPickCommit;
+import com.google.gerrit.server.validators.ProjectCreationValidationListener;
 
 public class Module extends RestApiModule {
 
@@ -47,6 +48,8 @@
     DynamicMap.mapOf(binder(), LABEL_KIND);
 
     DynamicSet.bind(binder(), GerritConfigListener.class).to(SetParent.class);
+    DynamicSet.bind(binder(), ProjectCreationValidationListener.class)
+        .to(CreateProject.ValidBranchListener.class);
 
     create(PROJECT_KIND).to(CreateProject.class);
     put(PROJECT_KIND).to(PutProject.class);
diff --git a/javatests/com/google/gerrit/acceptance/rest/change/ChangeMetaIT.java b/javatests/com/google/gerrit/acceptance/rest/change/ChangeMetaIT.java
new file mode 100644
index 0000000..3787a35
--- /dev/null
+++ b/javatests/com/google/gerrit/acceptance/rest/change/ChangeMetaIT.java
@@ -0,0 +1,58 @@
+// 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.
+
+package com.google.gerrit.acceptance.rest.change;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.gerrit.entities.RefNames.changeMetaRef;
+
+import com.google.common.collect.Iterables;
+import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.PushOneCommit;
+import com.google.gerrit.entities.Change;
+import com.google.gerrit.extensions.common.ChangeInfo;
+import org.eclipse.jgit.lib.Repository;
+import org.junit.Test;
+
+/** Test handling of the NoteDb commit hash in the GetChange endpoint */
+public class ChangeMetaIT extends AbstractDaemonTest {
+  @Test
+  public void metaSha1_fromIndex() throws Exception {
+    PushOneCommit.Result result = createChange();
+    String changeId = result.getChangeId();
+
+    try (AutoCloseable ignored = disableNoteDb()) {
+      ChangeInfo change =
+          Iterables.getOnlyElement(gApi.changes().query().withQuery("change:" + changeId).get());
+
+      try (Repository repo = repoManager.openRepository(project)) {
+        assertThat(change.metaRevId)
+            .isEqualTo(
+                repo.exactRef(changeMetaRef(Change.id(change._number))).getObjectId().getName());
+      }
+    }
+  }
+
+  @Test
+  public void metaSha1_fromNoteDb() throws Exception {
+    PushOneCommit.Result result = createChange();
+    String changeId = result.getChangeId();
+    ChangeInfo before = gApi.changes().id(changeId).get();
+    try (Repository repo = repoManager.openRepository(project)) {
+      assertThat(before.metaRevId)
+          .isEqualTo(
+              repo.exactRef(changeMetaRef(Change.id(before._number))).getObjectId().getName());
+    }
+  }
+}
diff --git a/javatests/com/google/gerrit/acceptance/rest/project/CreateProjectIT.java b/javatests/com/google/gerrit/acceptance/rest/project/CreateProjectIT.java
index 10fd65f..e5c5952 100644
--- a/javatests/com/google/gerrit/acceptance/rest/project/CreateProjectIT.java
+++ b/javatests/com/google/gerrit/acceptance/rest/project/CreateProjectIT.java
@@ -53,6 +53,7 @@
 import com.google.gerrit.extensions.restapi.Url;
 import com.google.gerrit.server.group.SystemGroupBackend;
 import com.google.gerrit.server.project.ProjectState;
+import com.google.gerrit.server.validators.ValidationException;
 import com.google.inject.Inject;
 import java.util.Collections;
 import java.util.Optional;
@@ -328,6 +329,21 @@
   }
 
   @Test
+  public void createProjectWithInvalidBranch() throws Exception {
+    String newProjectName = name("newProject");
+    ProjectInput in = new ProjectInput();
+    in.name = newProjectName;
+    in.createEmptyCommit = true;
+    in.branches = ImmutableList.of("refs/heads/test", "refs/changes/34/1234");
+    Throwable thrown =
+        assertThrows(ResourceConflictException.class, () -> gApi.projects().create(in));
+    assertThat(thrown).hasCauseThat().isInstanceOf(ValidationException.class);
+    assertThat(thrown)
+        .hasMessageThat()
+        .contains("Cannot create a project with branch refs/changes/34/1234");
+  }
+
+  @Test
   public void createProjectWithCapability() throws Exception {
     projectOperations
         .allProjectsForUpdate()
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-submit-dialog/gr-confirm-submit-dialog_html.ts b/polygerrit-ui/app/elements/change/gr-confirm-submit-dialog/gr-confirm-submit-dialog_html.ts
index fae920d..99094d2 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-submit-dialog/gr-confirm-submit-dialog_html.ts
+++ b/polygerrit-ui/app/elements/change/gr-confirm-submit-dialog/gr-confirm-submit-dialog_html.ts
@@ -53,7 +53,7 @@
           <template is="dom-if" if="[[change.is_private]]">
             <p>
               <iron-icon
-                icon="gr-icons:error"
+                icon="gr-icons:warning"
                 class="warningBeforeSubmit"
               ></iron-icon>
               <strong>Heads Up!</strong>
@@ -63,7 +63,7 @@
           <template is="dom-if" if="[[change.unresolved_comment_count]]">
             <p>
               <iron-icon
-                icon="gr-icons:error"
+                icon="gr-icons:warning"
                 class="warningBeforeSubmit"
               ></iron-icon>
               [[_computeUnresolvedCommentsWarning(change)]]
@@ -80,7 +80,7 @@
           </template>
           <template is="dom-if" if="[[_computeHasChangeEdit(change)]]">
             <iron-icon
-              icon="gr-icons:error"
+              icon="gr-icons:warning"
               class="warningBeforeSubmit"
             ></iron-icon>
             Your unpublished edit will not be submitted. Did you forget to click