Merge "Show quick-approve button even when change is already approved"
diff --git a/Documentation/access-control.txt b/Documentation/access-control.txt
index 529718a..38720fe 100644
--- a/Documentation/access-control.txt
+++ b/Documentation/access-control.txt
@@ -869,6 +869,11 @@
 private changes (even without having the `View Private Changes` access
 right assigned).
 
+**NOTE**: If link:config-gerrit.html#auth.skipFullRefEvaluationIfAllRefsAreVisible[
+auth.skipFullRefEvaluationIfAllRefsAreVisible] is `true` (which is the case by
+default) privates changes and all change edit refs are also visible to users
+that have read access on `refs/*`.
+
 [[category_toggle_work_in_progress_state]]
 === Toggle Work In Progress state
 
diff --git a/Documentation/concept-patch-sets.txt b/Documentation/concept-patch-sets.txt
index 8609afd..274fbb0 100644
--- a/Documentation/concept-patch-sets.txt
+++ b/Documentation/concept-patch-sets.txt
@@ -89,7 +89,7 @@
 set description does not become a part of the project's history.
 
 To add a patch set description, click *Add a patch set description*, located in
-the file list.
+the file list, or provide it link:user-upload.html#patch_set_description[on upload].
 
 GERRIT
 ------
diff --git a/Documentation/config-gerrit.txt b/Documentation/config-gerrit.txt
index e7c0d13..ac5e3b7 100644
--- a/Documentation/config-gerrit.txt
+++ b/Documentation/config-gerrit.txt
@@ -684,8 +684,11 @@
 
 [[auth.skipFullRefEvaluationIfAllRefsAreVisible]]auth.skipFullRefEvaluationIfAllRefsAreVisible::
 +
-Whether to skip the full ref visibility checks as a performance shortcut when all refs are
-visible to a user. Full ref filtering would filter out things like pending edits.
+Whether to skip the full ref visibility checks as a performance shortcut when a
+user has READ permission for all refs.
++
+The full ref filtering would filter out refs for pending edits, private changes
+and auto merge commits.
 +
 By default, true.
 
@@ -742,6 +745,24 @@
 +
 Default is false.
 
+[[cache.openFiles]]cache.openFiles::
++
+The number of file descriptors to add to the limit set by the Gerrit daemon.
++
+Persistent caches are stored on the file system and as such participate in the
+file descriptors utilization. The number of file descriptors can vary depending
+on the cache configuration and the specific backend used.
++
+The additional file descriptors required by the cache should be accounted for
+via this setting, so that the Gerrit daemon can adjust the ulimit accordingly.
++
+If you increase this to a larger setting you may need to also adjust
+the ulimit on file descriptors for the host JVM, as Gerrit needs
+additional file descriptors available for network sockets and other
+repository data manipulation.
++
+Default is 0.
+
 [[cache.name.maxAge]]cache.<name>.maxAge::
 +
 Maximum age to keep an entry in the cache. Entries are removed from
diff --git a/Documentation/dev-plugins.txt b/Documentation/dev-plugins.txt
index b2e1589..1db27d5 100644
--- a/Documentation/dev-plugins.txt
+++ b/Documentation/dev-plugins.txt
@@ -2729,8 +2729,8 @@
 [source, java]
 ----
 import java.util.Optional;
-import com.google.gerrit.common.data.SubmitRecord;
-import com.google.gerrit.common.data.SubmitRecord.Status;
+import com.google.gerrit.entities.SubmitRecord;
+import com.google.gerrit.entities.SubmitRecord.Status;
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.gerrit.server.rules.SubmitRule;
 
diff --git a/Documentation/metrics.txt b/Documentation/metrics.txt
index 3040348..8a95bab 100644
--- a/Documentation/metrics.txt
+++ b/Documentation/metrics.txt
@@ -66,6 +66,11 @@
 * `caches/disk_hit_ratio`: Disk hit ratio for persistent cache.
 * `caches/refresh_count`: The number of refreshes per cache with an indicator if a reload was necessary.
 
+Cache disk metrics are expensive to compute on larger installations and are not
+computed by default. They can be enabled via the
+link:config.gerrit.html#cache.enableDiskStatMetrics[`cache.enableDiskStatMetrics`]
+setting.
+
 === Change
 
 * `change/submit_rule_evaluation`: Latency for evaluating submit rules on a change.
diff --git a/Documentation/user-upload.txt b/Documentation/user-upload.txt
index 926aa71..cdaf155 100644
--- a/Documentation/user-upload.txt
+++ b/Documentation/user-upload.txt
@@ -315,11 +315,11 @@
 preference is set so the default behavior is to create `work-in-progress`
 changes, this can be overridden with the `ready` option.
 
-[[message]]
-==== Message
+[[patch_set_description]]
+==== Patch Set Description
 
-A comment message can be applied to the change by using the `message` (or `m`)
-option:
+A link:concept-patch-sets.html#_description[patch set description] can be
+applied by using the `message` (or `m`) option:
 
 ----
   git push ssh://john.doe@git.example.com:29418/kernel/common HEAD:refs/for/experimental%m=This_is_a_rebase_on_master%21
diff --git a/WORKSPACE b/WORKSPACE
index 3c30026..fff9235 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -51,10 +51,10 @@
 
 http_archive(
     name = "com_google_protobuf",
-    sha256 = "71030a04aedf9f612d2991c1c552317038c3c5a2b578ac4745267a45e7037c29",
-    strip_prefix = "protobuf-3.12.3",
+    sha256 = "d0f5f605d0d656007ce6c8b5a82df3037e1d8fe8b121ed42e536f569dec16113",
+    strip_prefix = "protobuf-3.14.0",
     urls = [
-        "https://github.com/protocolbuffers/protobuf/archive/v3.12.3.tar.gz",
+        "https://github.com/protocolbuffers/protobuf/archive/v3.14.0.tar.gz",
     ],
 )
 
diff --git a/java/com/google/gerrit/entities/RefNames.java b/java/com/google/gerrit/entities/RefNames.java
index 400861c..5595bc7 100644
--- a/java/com/google/gerrit/entities/RefNames.java
+++ b/java/com/google/gerrit/entities/RefNames.java
@@ -288,10 +288,16 @@
    * Whether the ref is managed by Gerrit. Covers all Gerrit-internal refs like refs/cache-automerge
    * and refs/meta as well as refs/changes. Does not cover user-created refs like branches or custom
    * ref namespaces like refs/my-company.
+   *
+   * <p>Any ref for which this method evaluates to true will be served to users who have the {@code
+   * ACCESS_DATABASE} capability.
+   *
+   * <p><b>Caution</b>Any ref not in this list will be served if the user was granted a READ
+   * permission on it using Gerrit's permission model.
    */
   public static boolean isGerritRef(String ref) {
     return ref.startsWith(REFS_CHANGES)
-        || ref.startsWith(REFS_META)
+        || ref.startsWith(REFS_EXTERNAL_IDS)
         || ref.startsWith(REFS_CACHE_AUTOMERGE)
         || ref.startsWith(REFS_DRAFT_COMMENTS)
         || ref.startsWith(REFS_DELETED_GROUPS)
@@ -299,7 +305,8 @@
         || ref.startsWith(REFS_GROUPS)
         || ref.startsWith(REFS_GROUPNAMES)
         || ref.startsWith(REFS_USERS)
-        || ref.startsWith(REFS_STARRED_CHANGES);
+        || ref.startsWith(REFS_STARRED_CHANGES)
+        || ref.startsWith(REFS_REJECT_COMMITS);
   }
 
   static Integer parseShardedRefPart(String name) {
diff --git a/java/com/google/gerrit/server/mail/send/SmtpEmailSender.java b/java/com/google/gerrit/server/mail/send/SmtpEmailSender.java
index af00b20..1ad94be 100644
--- a/java/com/google/gerrit/server/mail/send/SmtpEmailSender.java
+++ b/java/com/google/gerrit/server/mail/send/SmtpEmailSender.java
@@ -391,11 +391,7 @@
   }
 
   private SMTPClient open() throws EmailException {
-    final AuthSMTPClient client = new AuthSMTPClient(UTF_8.name());
-
-    if (smtpEncryption == Encryption.SSL) {
-      client.enableSSL(sslVerify);
-    }
+    final AuthSMTPClient client = new AuthSMTPClient(smtpEncryption == Encryption.SSL, sslVerify);
 
     client.setConnectTimeout(connectTimeout);
     try {
@@ -411,7 +407,7 @@
       }
 
       if (smtpEncryption == Encryption.TLS) {
-        if (!client.startTLS(smtpHost, smtpPort, sslVerify)) {
+        if (!client.execTLS()) {
           throw new EmailException("SMTP server does not support TLS");
         }
         if (!client.login()) {
diff --git a/java/com/google/gerrit/server/permissions/ChangeControl.java b/java/com/google/gerrit/server/permissions/ChangeControl.java
index 0b4828b..37c773a 100644
--- a/java/com/google/gerrit/server/permissions/ChangeControl.java
+++ b/java/com/google/gerrit/server/permissions/ChangeControl.java
@@ -61,11 +61,12 @@
   }
 
   /** Can this user see this change? */
-  private boolean isVisible(ChangeData cd) {
-    if (getChange().isPrivate() && !isPrivateVisible(cd)) {
+  boolean isVisible() {
+    if (getChange().isPrivate() && !isPrivateVisible(changeData)) {
       return false;
     }
-    return refControl.isVisible();
+    // Does the user have READ permission on the destination?
+    return refControl.asForRef().testOrFalse(RefPermission.READ);
   }
 
   /** Can this user abandon this change? */
@@ -201,17 +202,13 @@
 
     private ForChangeImpl() {}
 
-    private ChangeData changeData() {
-      return changeData;
-    }
-
     @Override
     public String resourcePath() {
       if (resourcePath == null) {
         resourcePath =
             String.format(
                 "/projects/%s/+changes/%s",
-                getProjectControl().getProjectState().getName(), changeData().getId().get());
+                getProjectControl().getProjectState().getName(), changeData.getId().get());
       }
       return resourcePath;
     }
@@ -256,7 +253,7 @@
       try {
         switch (perm) {
           case READ:
-            return isVisible(changeData());
+            return isVisible();
           case ABANDON:
             return canAbandon();
           case DELETE:
diff --git a/java/com/google/gerrit/server/permissions/DefaultRefFilter.java b/java/com/google/gerrit/server/permissions/DefaultRefFilter.java
index defec4b..edd3cb1 100644
--- a/java/com/google/gerrit/server/permissions/DefaultRefFilter.java
+++ b/java/com/google/gerrit/server/permissions/DefaultRefFilter.java
@@ -17,10 +17,7 @@
 import static com.google.common.base.Preconditions.checkState;
 import static com.google.common.collect.ImmutableList.toImmutableList;
 import static com.google.common.flogger.LazyArgs.lazy;
-import static com.google.gerrit.entities.RefNames.REFS_CACHE_AUTOMERGE;
 import static com.google.gerrit.entities.RefNames.REFS_CONFIG;
-import static com.google.gerrit.entities.RefNames.REFS_USERS_SELF;
-import static java.util.Objects.requireNonNull;
 import static java.util.stream.Collectors.toCollection;
 
 import com.google.auto.value.AutoValue;
@@ -30,8 +27,6 @@
 import com.google.common.collect.Maps;
 import com.google.common.flogger.FluentLogger;
 import com.google.gerrit.common.Nullable;
-import com.google.gerrit.entities.Account;
-import com.google.gerrit.entities.AccountGroup;
 import com.google.gerrit.entities.BranchNameKey;
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.entities.Project;
@@ -42,13 +37,10 @@
 import com.google.gerrit.metrics.Description;
 import com.google.gerrit.metrics.MetricMaker;
 import com.google.gerrit.server.CurrentUser;
-import com.google.gerrit.server.IdentifiedUser;
-import com.google.gerrit.server.account.GroupCache;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.git.SearchingChangeCacheImpl;
 import com.google.gerrit.server.git.TagCache;
 import com.google.gerrit.server.git.TagMatcher;
-import com.google.gerrit.server.group.InternalGroup;
 import com.google.gerrit.server.logging.TraceContext;
 import com.google.gerrit.server.logging.TraceContext.TraceTimer;
 import com.google.gerrit.server.notedb.ChangeNotes;
@@ -80,8 +72,8 @@
   private final TagCache tagCache;
   private final ChangeNotes.Factory changeNotesFactory;
   @Nullable private final SearchingChangeCacheImpl changeCache;
-  private final GroupCache groupCache;
   private final PermissionBackend permissionBackend;
+  private final RefVisibilityControl refVisibilityControl;
   private final ProjectControl projectControl;
   private final CurrentUser user;
   private final ProjectState projectState;
@@ -97,16 +89,16 @@
       TagCache tagCache,
       ChangeNotes.Factory changeNotesFactory,
       @Nullable SearchingChangeCacheImpl changeCache,
-      GroupCache groupCache,
       PermissionBackend permissionBackend,
+      RefVisibilityControl refVisibilityControl,
       @GerritServerConfig Config config,
       MetricMaker metricMaker,
       @Assisted ProjectControl projectControl) {
     this.tagCache = tagCache;
     this.changeNotesFactory = changeNotesFactory;
     this.changeCache = changeCache;
-    this.groupCache = groupCache;
     this.permissionBackend = permissionBackend;
+    this.refVisibilityControl = refVisibilityControl;
     this.skipFullRefEvaluationIfAllRefsAreVisible =
         config.getBoolean("auth", "skipFullRefEvaluationIfAllRefsAreVisible", true);
     this.projectControl = projectControl;
@@ -227,131 +219,56 @@
     logger.atFinest().log("Doing full ref filtering");
     fullFilterCount.increment();
 
-    boolean viewMetadata;
-    boolean isAdmin;
-    Account.Id userId;
-    IdentifiedUser identifiedUser;
-    PermissionBackend.WithUser withUser = permissionBackend.user(user);
-    if (user.isIdentifiedUser()) {
-      viewMetadata = withUser.testOrFalse(GlobalPermission.ACCESS_DATABASE);
-      isAdmin = withUser.testOrFalse(GlobalPermission.ADMINISTRATE_SERVER);
-      identifiedUser = user.asIdentifiedUser();
-      userId = identifiedUser.getAccountId();
-      logger.atFinest().log(
-          "Account = %d; can view metadata = %s; is admin = %s",
-          userId.get(), viewMetadata, isAdmin);
-    } else {
-      logger.atFinest().log("User is anonymous");
-      viewMetadata = false;
-      isAdmin = false;
-      userId = null;
-      identifiedUser = null;
-    }
-
+    boolean hasAccessDatabase =
+        permissionBackend
+            .user(projectControl.getUser())
+            .testOrFalse(GlobalPermission.ACCESS_DATABASE);
     List<Ref> resultRefs = new ArrayList<>(refs.size());
     List<Ref> deferredTags = new ArrayList<>();
     for (Ref ref : refs) {
-      String name = ref.getName();
+      String refName = ref.getName();
       Change.Id changeId;
-      Account.Id accountId;
-      AccountGroup.UUID accountGroupUuid;
-      if (name.startsWith(REFS_CACHE_AUTOMERGE)) {
-        continue;
-      } else if (opts.filterMeta() && isMetadata(name)) {
-        logger.atFinest().log("Filter out metadata ref %s", name);
-        continue;
-      } else if (RefNames.isRefsEdit(name)) {
-        // Edits are visible only to the owning user, if change is visible.
-        if (viewMetadata || visibleEdit(repo, name)) {
-          logger.atFinest().log("Include edit ref %s", name);
-          resultRefs.add(ref);
-        } else {
-          logger.atFinest().log("Filter out edit ref %s", name);
-        }
-      } else if ((changeId = Change.Id.fromRef(name)) != null) {
-        // Change ref is visible only if the change is visible.
-        if (viewMetadata || visible(repo, changeId)) {
-          logger.atFinest().log("Include change ref %s", name);
-          resultRefs.add(ref);
-        } else {
-          logger.atFinest().log("Filter out change ref %s", name);
-        }
-      } else if ((accountId = Account.Id.fromRef(name)) != null) {
-        // Account ref is visible only to the corresponding account.
-        if (viewMetadata || (accountId.equals(userId) && canReadRef(name))) {
-          logger.atFinest().log("Include user ref %s", name);
-          resultRefs.add(ref);
-        } else {
-          logger.atFinest().log("Filter out user ref %s", name);
-        }
-      } else if ((accountGroupUuid = AccountGroup.UUID.fromRef(name)) != null) {
-        // Group ref is visible only to the corresponding owner group.
-        InternalGroup group = groupCache.get(accountGroupUuid).orElse(null);
-        if (viewMetadata
-            || (group != null
-                && isGroupOwner(group, identifiedUser, isAdmin)
-                && canReadRef(name))) {
-          logger.atFinest().log("Include group ref %s", name);
-          resultRefs.add(ref);
-        } else {
-          logger.atFinest().log("Filter out group ref %s", name);
-        }
+      if (opts.filterMeta() && isMetadata(refName)) {
+        logger.atFinest().log("Filter out metadata ref %s", refName);
       } else if (isTag(ref)) {
         if (hasReadOnRefsStar) {
-          // The user has READ on refs/*. This is the broadest permission one can assign. There is
-          // no way to grant access to (specific) tags in Gerrit, so we have to assume that these
-          // users can see all tags because there could be tags that aren't reachable by any visible
-          // ref while the user can see all non-Gerrit refs. This matches Gerrit's historic
-          // behavior.
+          // The user has READ on refs/* with no effective block permission. This is the broadest
+          // permission one can assign. There is no way to grant access to (specific) tags in
+          // Gerrit,
+          // so we have to assume that these users can see all tags because there could be tags that
+          // aren't reachable by any visible ref while the user can see all non-Gerrit refs. This
+          // matches Gerrit's historic behavior.
           // This makes it so that these users could see commits that they can't see otherwise
           // (e.g. a private change ref) if a tag was attached to it. Tags are meant to be used on
           // the regular Git tree that users interact with, not on any of the Gerrit trees, so this
           // is a negligible risk.
-          logger.atFinest().log("Include tag ref %s because user has read on refs/*", name);
+          logger.atFinest().log("Include tag ref %s because user has read on refs/*", refName);
           resultRefs.add(ref);
         } else {
           // If its a tag, consider it later.
           if (ref.getObjectId() != null) {
-            logger.atFinest().log("Defer tag ref %s", name);
+            logger.atFinest().log("Defer tag ref %s", refName);
             deferredTags.add(ref);
           } else {
-            logger.atFinest().log("Filter out tag ref %s that is not a tag", name);
+            logger.atFinest().log("Filter out tag ref %s that is not a tag", refName);
           }
         }
-      } else if (name.startsWith(RefNames.REFS_SEQUENCES)) {
-        // Sequences are internal database implementation details.
-        if (viewMetadata) {
-          logger.atFinest().log("Include sequence ref %s", name);
+      } else if ((changeId = Change.Id.fromRef(refName)) != null) {
+        // This is a mere performance optimization. RefVisibilityControl could determine the
+        // visibility of these refs just fine. But instead, we use highly-optimized logic that
+        // looks only on the last 10k most recent changes using the change index and a cache.
+        if (hasAccessDatabase) {
           resultRefs.add(ref);
+        } else if (!visible(repo, changeId)) {
+          logger.atFinest().log("Filter out invisible change ref %s", refName);
+        } else if (RefNames.isRefsEdit(refName) && !visibleEdit(repo, refName)) {
+          logger.atFinest().log("Filter out invisible change edit ref %s", refName);
         } else {
-          logger.atFinest().log("Filter out sequence ref %s", name);
-        }
-      } else if (projectState.isAllUsers()
-          && (name.equals(RefNames.REFS_EXTERNAL_IDS) || name.equals(RefNames.REFS_GROUPNAMES))) {
-        // The notes branches with the external IDs / group names must not be exposed to normal
-        // users.
-        if (viewMetadata) {
-          logger.atFinest().log("Include external IDs branch %s", name);
+          // Change is visible
           resultRefs.add(ref);
-        } else {
-          logger.atFinest().log("Filter out external IDs branch %s", name);
         }
-      } else if (canReadRef(ref.getLeaf().getName())) {
-        // Use the leaf to lookup the control data. If the reference is
-        // symbolic we want the control around the final target. If its
-        // not symbolic then getLeaf() is a no-op returning ref itself.
-        logger.atFinest().log(
-            "Include ref %s because its leaf %s is readable", name, ref.getLeaf().getName());
+      } else if (refVisibilityControl.isVisible(projectControl, ref.getLeaf().getName())) {
         resultRefs.add(ref);
-      } else if (isRefsUsersSelf(ref)) {
-        // viewMetadata allows to see all account refs, hence refs/users/self should be included as
-        // well
-        if (viewMetadata) {
-          logger.atFinest().log("Include ref %s", REFS_USERS_SELF);
-          resultRefs.add(ref);
-        }
-      } else {
-        logger.atFinest().log("Filter out ref %s", name);
       }
     }
     Result result = new AutoValue_DefaultRefFilter_Result(resultRefs, deferredTags);
@@ -374,7 +291,8 @@
               r ->
                   !RefNames.isGerritRef(r.getName())
                       && !r.getName().startsWith(RefNames.REFS_TAGS)
-                      && !r.isSymbolic())
+                      && !r.isSymbolic()
+                      && !r.getName().equals(RefNames.REFS_CONFIG))
           // Don't use the default Java Collections.toList() as that is not size-aware and would
           // expand an array list as new elements are added. Instead, provide a list that has the
           // right size. This spares incremental list expansion which is quadratic in complexity.
@@ -520,10 +438,6 @@
     return ref.getLeaf().getName().startsWith(Constants.R_TAGS);
   }
 
-  private static boolean isRefsUsersSelf(Ref ref) {
-    return ref.getName().startsWith(REFS_USERS_SELF);
-  }
-
   private boolean canReadRef(String ref) throws PermissionBackendException {
     try {
       permissionBackendForProject.ref(ref).check(RefPermission.READ);
@@ -544,17 +458,6 @@
     return true;
   }
 
-  private boolean isGroupOwner(
-      InternalGroup group, @Nullable IdentifiedUser user, boolean isAdmin) {
-    requireNonNull(group);
-
-    // Keep this logic in sync with GroupControl#isOwner().
-    boolean isGroupOwner =
-        isAdmin || (user != null && user.getEffectiveGroups().contains(group.getOwnerGroupUUID()));
-    logger.atFinest().log("User is owner of group %s = %s", group.getGroupUUID(), isGroupOwner);
-    return isGroupOwner;
-  }
-
   /**
    * Returns true if the user can see the provided change ref. Uses NoteDb for evaluation, hence
    * does not suffer from the limitations documented in {@link SearchingChangeCacheImpl}.
diff --git a/java/com/google/gerrit/server/permissions/ProjectControl.java b/java/com/google/gerrit/server/permissions/ProjectControl.java
index 724017db..a92fde0 100644
--- a/java/com/google/gerrit/server/permissions/ProjectControl.java
+++ b/java/com/google/gerrit/server/permissions/ProjectControl.java
@@ -36,8 +36,10 @@
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.account.GroupMembership;
+import com.google.gerrit.server.config.AllUsersName;
 import com.google.gerrit.server.config.GitReceivePackGroups;
 import com.google.gerrit.server.config.GitUploadPackGroups;
+import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.group.SystemGroupBackend;
 import com.google.gerrit.server.notedb.ChangeNotes;
 import com.google.gerrit.server.permissions.PermissionBackend.ForChange;
@@ -68,11 +70,14 @@
   private final Set<AccountGroup.UUID> uploadGroups;
   private final Set<AccountGroup.UUID> receiveGroups;
   private final PermissionBackend permissionBackend;
+  private final RefVisibilityControl refVisibilityControl;
+  private final GitRepositoryManager repositoryManager;
   private final CurrentUser user;
   private final ProjectState state;
   private final PermissionCollection.Factory permissionFilter;
   private final DefaultRefFilter.Factory refFilterFactory;
   private final ChangeData.Factory changeDataFactory;
+  private final AllUsersName allUsersName;
 
   private List<SectionMatcher> allSections;
   private Map<String, RefControl> refControls;
@@ -84,16 +89,22 @@
       @GitReceivePackGroups Set<AccountGroup.UUID> receiveGroups,
       PermissionCollection.Factory permissionFilter,
       PermissionBackend permissionBackend,
+      RefVisibilityControl refVisibilityControl,
+      GitRepositoryManager repositoryManager,
       DefaultRefFilter.Factory refFilterFactory,
       ChangeData.Factory changeDataFactory,
+      AllUsersName allUsersName,
       @Assisted CurrentUser who,
       @Assisted ProjectState ps) {
     this.uploadGroups = uploadGroups;
     this.receiveGroups = receiveGroups;
     this.permissionFilter = permissionFilter;
     this.permissionBackend = permissionBackend;
+    this.refVisibilityControl = refVisibilityControl;
+    this.repositoryManager = repositoryManager;
     this.refFilterFactory = refFilterFactory;
     this.changeDataFactory = changeDataFactory;
+    this.allUsersName = allUsersName;
     user = who;
     state = ps;
   }
@@ -117,7 +128,9 @@
     RefControl ctl = refControls.get(refName);
     if (ctl == null) {
       PermissionCollection relevant = permissionFilter.filter(access(), refName, user);
-      ctl = new RefControl(changeDataFactory, this, refName, relevant);
+      ctl =
+          new RefControl(
+              changeDataFactory, refVisibilityControl, this, repositoryManager, refName, relevant);
       refControls.put(refName, ctl);
     }
     return ctl;
@@ -164,7 +177,9 @@
   }
 
   boolean allRefsAreVisible(Set<String> ignore) {
-    return user.isInternalUser() || canPerformOnAllRefs(Permission.READ, ignore);
+    return user.isInternalUser()
+        || (!getProject().getNameKey().equals(allUsersName)
+            && canPerformOnAllRefs(Permission.READ, ignore));
   }
 
   /** Can the user run upload pack? */
@@ -442,7 +457,7 @@
           return canPushToAtLeastOneRef();
 
         case READ_CONFIG:
-          return controlForRef(RefNames.REFS_CONFIG).isVisible();
+          return controlForRef(RefNames.REFS_CONFIG).hasReadPermissionOnRef(false);
 
         case BAN_COMMIT:
         case READ_REFLOG:
diff --git a/java/com/google/gerrit/server/permissions/RefControl.java b/java/com/google/gerrit/server/permissions/RefControl.java
index e704a99..ad4188f 100644
--- a/java/com/google/gerrit/server/permissions/RefControl.java
+++ b/java/com/google/gerrit/server/permissions/RefControl.java
@@ -16,6 +16,7 @@
 
 import static com.google.common.base.Preconditions.checkArgument;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.flogger.FluentLogger;
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.entities.Permission;
@@ -28,6 +29,7 @@
 import com.google.gerrit.extensions.conditions.BooleanCondition;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.server.CurrentUser;
+import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.logging.CallerFinder;
 import com.google.gerrit.server.logging.LoggingContext;
 import com.google.gerrit.server.notedb.ChangeNotes;
@@ -35,17 +37,24 @@
 import com.google.gerrit.server.permissions.PermissionBackend.ForRef;
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.gerrit.server.util.MagicBranch;
+import java.io.IOException;
 import java.util.Collection;
 import java.util.EnumSet;
 import java.util.List;
 import java.util.Set;
+import java.util.concurrent.TimeUnit;
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.lib.Repository;
 
 /** Manages access control for Git references (aka branches, tags). */
 class RefControl {
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
   private final ChangeData.Factory changeDataFactory;
+  private final RefVisibilityControl refVisibilityControl;
   private final ProjectControl projectControl;
+  private final GitRepositoryManager repositoryManager;
   private final String refName;
 
   /** All permissions that apply to this reference. */
@@ -58,15 +67,19 @@
   private Boolean owner;
   private Boolean canForgeAuthor;
   private Boolean canForgeCommitter;
-  private Boolean isVisible;
+  private Boolean hasReadPermissionOnRef;
 
   RefControl(
       ChangeData.Factory changeDataFactory,
+      RefVisibilityControl refVisibilityControl,
       ProjectControl projectControl,
+      GitRepositoryManager repositoryManager,
       String ref,
       PermissionCollection relevant) {
     this.changeDataFactory = changeDataFactory;
+    this.refVisibilityControl = refVisibilityControl;
     this.projectControl = projectControl;
+    this.repositoryManager = repositoryManager;
     this.refName = ref;
     this.relevant = relevant;
     this.callerFinder =
@@ -99,12 +112,27 @@
     return owner;
   }
 
-  /** Can this user see this reference exists? */
-  boolean isVisible() {
-    if (isVisible == null) {
-      isVisible = getUser().isInternalUser() || canPerform(Permission.READ);
+  /**
+   * Returns {@code true} if the user has permission to read the ref. This method evaluates {@link
+   * RefPermission#READ} only. Hence, it is not authoritative. For example, it does not tell if the
+   * user can see NoteDb refs such as {@code refs/meta/external-ids} which requires {@link
+   * GlobalPermission#ACCESS_DATABASE} and deny access in this case.
+   */
+  boolean hasReadPermissionOnRef(boolean allowNoteDbRefs) {
+    // Don't allow checking for NoteDb refs unless instructed otherwise.
+    if (!allowNoteDbRefs
+        && (refName.startsWith(Constants.R_TAGS) || RefNames.isGerritRef(refName))) {
+      logger.atWarning().atMostEvery(30, TimeUnit.SECONDS).log(
+          "%s: Can't determine visibility of %s in RefControl. Denying access. "
+              + "This case should have been handled before.",
+          projectControl.getProject().getName(), refName);
+      return false;
     }
-    return isVisible;
+
+    if (hasReadPermissionOnRef == null) {
+      hasReadPermissionOnRef = getUser().isInternalUser() || canPerform(Permission.READ);
+    }
+    return hasReadPermissionOnRef;
   }
 
   /** @return true if this user can add a new patch set to this ref */
@@ -591,7 +619,10 @@
     private boolean can(RefPermission perm) throws PermissionBackendException {
       switch (perm) {
         case READ:
-          return isVisible();
+          if (refName.startsWith(Constants.R_TAGS)) {
+            return isTagVisible();
+          }
+          return refVisibilityControl.isVisible(projectControl, refName);
         case CREATE:
           // TODO This isn't an accurate test.
           return canPerform(refPermissionName(perm));
@@ -641,6 +672,38 @@
       }
       throw new PermissionBackendException(perm + " unsupported");
     }
+
+    private boolean isTagVisible() throws PermissionBackendException {
+      if (projectControl.asForProject().test(ProjectPermission.READ)) {
+        // The user has READ on refs/* with no effective block permission. This is the broadest
+        // permission one can assign. There is no way to grant access to (specific) tags in Gerrit,
+        // so we have to assume that these users can see all tags because there could be tags that
+        // aren't reachable by any visible ref while the user can see all non-Gerrit refs. This
+        // matches Gerrit's historic behavior.
+        // This makes it so that these users could see commits that they can't see otherwise
+        // (e.g. a private change ref) if a tag was attached to it. Tags are meant to be used on
+        // the regular Git tree that users interact with, not on any of the Gerrit trees, so this
+        // is a negligible risk.
+        return true;
+      }
+
+      try (Repository repo =
+          repositoryManager.openRepository(projectControl.getProject().getNameKey())) {
+        // Tag visibility requires going through RefFilter because it entails loading all taggable
+        // refs and filtering them all by visibility.
+        Ref resolvedRef = repo.getRefDatabase().exactRef(refName);
+        if (resolvedRef == null) {
+          return false;
+        }
+        return projectControl.asForProject()
+            .filter(
+                ImmutableList.of(resolvedRef), repo, PermissionBackend.RefFilterOptions.defaults())
+            .stream()
+            .anyMatch(r -> refName.equals(r.getName()));
+      } catch (IOException e) {
+        throw new PermissionBackendException(e);
+      }
+    }
   }
 
   private static String refPermissionName(RefPermission refPermission) {
diff --git a/java/com/google/gerrit/server/permissions/RefVisibilityControl.java b/java/com/google/gerrit/server/permissions/RefVisibilityControl.java
new file mode 100644
index 0000000..4744037
--- /dev/null
+++ b/java/com/google/gerrit/server/permissions/RefVisibilityControl.java
@@ -0,0 +1,181 @@
+// 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.permissions;
+
+import static com.google.common.base.Preconditions.checkState;
+import static com.google.gerrit.entities.RefNames.REFS_CACHE_AUTOMERGE;
+
+import com.google.common.base.Throwables;
+import com.google.common.flogger.FluentLogger;
+import com.google.gerrit.entities.Account;
+import com.google.gerrit.entities.AccountGroup;
+import com.google.gerrit.entities.Change;
+import com.google.gerrit.entities.RefNames;
+import com.google.gerrit.exceptions.NoSuchGroupException;
+import com.google.gerrit.exceptions.StorageException;
+import com.google.gerrit.extensions.restapi.AuthException;
+import com.google.gerrit.server.CurrentUser;
+import com.google.gerrit.server.account.GroupControl;
+import com.google.gerrit.server.project.NoSuchChangeException;
+import com.google.gerrit.server.query.change.ChangeData;
+import javax.inject.Inject;
+import javax.inject.Singleton;
+import org.eclipse.jgit.lib.Constants;
+
+/**
+ * This class is a component that is internal to {@link DefaultPermissionBackend}. It can
+ * authoritatively tell if a ref is accessible by a user.
+ */
+@Singleton
+class RefVisibilityControl {
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
+
+  private final PermissionBackend permissionBackend;
+  private final GroupControl.GenericFactory groupControlFactory;
+  private final ChangeData.Factory changeDataFactory;
+
+  @Inject
+  RefVisibilityControl(
+      PermissionBackend permissionBackend,
+      GroupControl.GenericFactory groupControlFactory,
+      ChangeData.Factory changeDataFactory) {
+    this.permissionBackend = permissionBackend;
+    this.groupControlFactory = groupControlFactory;
+    this.changeDataFactory = changeDataFactory;
+  }
+
+  /**
+   * Returns an authoritative answer if the ref is visible to the user. Does not have support for
+   * tags and will throw a {@link PermissionBackendException} if asked for tags visibility.
+   */
+  boolean isVisible(ProjectControl projectControl, String refName)
+      throws PermissionBackendException {
+    if (refName.startsWith(Constants.R_TAGS)) {
+      throw new PermissionBackendException(
+          "can't check tags through RefVisibilityControl. Use PermissionBackend#filter instead.");
+    }
+    if (!RefNames.isGerritRef(refName)) {
+      // This is not a special Gerrit ref and not a NoteDb ref. Likely, it's just a ref under
+      // refs/heads or another ref the user created. Apply the regular permissions with inheritance.
+      return projectControl.controlForRef(refName).hasReadPermissionOnRef(false);
+    }
+
+    if (refName.startsWith(REFS_CACHE_AUTOMERGE)) {
+      // Internal cache state that is accessible to no one.
+      return false;
+    }
+
+    boolean hasAccessDatabase =
+        permissionBackend
+            .user(projectControl.getUser())
+            .testOrFalse(GlobalPermission.ACCESS_DATABASE);
+    if (hasAccessDatabase) {
+      return true;
+    }
+
+    // Change and change edit visibility
+    Change.Id changeId;
+    if ((changeId = Change.Id.fromRef(refName)) != null) {
+      // Change ref is visible only if the change is visible.
+      ChangeData cd;
+      try {
+        cd = changeDataFactory.create(projectControl.getProject().getNameKey(), changeId);
+        checkState(cd.change().getId().equals(changeId));
+      } catch (StorageException e) {
+        if (Throwables.getCausalChain(e).stream()
+            .anyMatch(e2 -> e2 instanceof NoSuchChangeException)) {
+          // The change was deleted or is otherwise not accessible anymore.
+          // If the caller can see all refs and is allowed to see private changes on refs/, allow
+          // access. This is an escape hatch for receivers of "ref deleted" events.
+          PermissionBackend.ForProject forProject = projectControl.asForProject();
+          return forProject.test(ProjectPermission.READ)
+              && forProject.ref("refs/").test(RefPermission.READ_PRIVATE_CHANGES);
+        }
+        throw new PermissionBackendException(e);
+      }
+      if (RefNames.isRefsEdit(refName)) {
+        // Edits are visible only to the owning user, if change is visible.
+        return visibleEdit(refName, projectControl, cd);
+      }
+      return projectControl.controlFor(cd).isVisible();
+    }
+
+    // Account visibility
+    CurrentUser user = projectControl.getUser();
+    Account.Id currentUserAccountId = user.isIdentifiedUser() ? user.getAccountId() : null;
+    Account.Id accountId;
+    if ((accountId = Account.Id.fromRef(refName)) != null) {
+      // Account ref is visible only to the corresponding account.
+      if (accountId.equals(currentUserAccountId)
+          && projectControl.controlForRef(refName).hasReadPermissionOnRef(true)) {
+        return true;
+      }
+      return false;
+    }
+
+    // Group visibility
+    AccountGroup.UUID accountGroupUuid;
+    if ((accountGroupUuid = AccountGroup.UUID.fromRef(refName)) != null) {
+      // Group ref is visible only to the corresponding owner group.
+      try {
+        return projectControl.controlForRef(refName).hasReadPermissionOnRef(true)
+            && groupControlFactory.controlFor(user, accountGroupUuid).isOwner();
+      } catch (NoSuchGroupException e) {
+        // The group is broken, but the ref is still around. Pretend the ref is not visible.
+        logger.atWarning().withCause(e).log("Found group ref %s but group isn't parsable", refName);
+        return false;
+      }
+    }
+
+    // We are done checking all cases where we would allow access to Gerrit-managed refs. Deny
+    // access in case we got this far.
+    logger.atFine().log(
+        "Denying access to %s because user doesn't have access to this Gerrit ref", refName);
+    return false;
+  }
+
+  private boolean visibleEdit(String refName, ProjectControl projectControl, ChangeData cd)
+      throws PermissionBackendException {
+    Change.Id id = Change.Id.fromEditRefPart(refName);
+    if (id == null) {
+      throw new IllegalStateException("unable to parse change id from edit ref " + refName);
+    }
+
+    if (!projectControl.controlFor(cd).isVisible()) {
+      // The user can't see the change so they can't see any edits.
+      return false;
+    }
+
+    if (projectControl.getUser().isIdentifiedUser()
+        && refName.startsWith(
+            RefNames.refsEditPrefix(projectControl.getUser().asIdentifiedUser().getAccountId()))) {
+      logger.atFinest().log("Own change edit ref is visible: %s", refName);
+      return true;
+    }
+
+    try {
+      // Default to READ_PRIVATE_CHANGES as there is no special permission for reading edits.
+      projectControl
+          .asForProject()
+          .ref(cd.change().getDest().branch())
+          .check(RefPermission.READ_PRIVATE_CHANGES);
+      logger.atFinest().log("Foreign change edit ref is visible: %s", refName);
+      return true;
+    } catch (AuthException e) {
+      logger.atFinest().log("Foreign change edit ref is not visible: %s", refName);
+      return false;
+    }
+  }
+}
diff --git a/java/com/google/gerrit/util/ssl/BlindSSLSocketFactory.java b/java/com/google/gerrit/util/ssl/BlindSSLSocketFactory.java
index 6dc1006..88845ef 100644
--- a/java/com/google/gerrit/util/ssl/BlindSSLSocketFactory.java
+++ b/java/com/google/gerrit/util/ssl/BlindSSLSocketFactory.java
@@ -20,7 +20,6 @@
 import java.net.UnknownHostException;
 import java.security.GeneralSecurityException;
 import java.security.SecureRandom;
-import java.security.cert.X509Certificate;
 import javax.net.SocketFactory;
 import javax.net.ssl.SSLContext;
 import javax.net.ssl.SSLSocketFactory;
@@ -32,19 +31,7 @@
   private static final BlindSSLSocketFactory INSTANCE;
 
   static {
-    final X509TrustManager dummyTrustManager =
-        new X509TrustManager() {
-          @Override
-          public X509Certificate[] getAcceptedIssuers() {
-            return null;
-          }
-
-          @Override
-          public void checkClientTrusted(X509Certificate[] chain, String authType) {}
-
-          @Override
-          public void checkServerTrusted(X509Certificate[] chain, String authType) {}
-        };
+    final X509TrustManager dummyTrustManager = new BlindTrustManager();
 
     try {
       final SSLContext context = SSLContext.getInstance("SSL");
diff --git a/java/com/google/gerrit/util/ssl/BlindTrustManager.java b/java/com/google/gerrit/util/ssl/BlindTrustManager.java
new file mode 100644
index 0000000..2db091a
--- /dev/null
+++ b/java/com/google/gerrit/util/ssl/BlindTrustManager.java
@@ -0,0 +1,33 @@
+// 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.util.ssl;
+
+import java.security.cert.X509Certificate;
+import javax.net.ssl.X509TrustManager;
+
+/** TrustManager implementation that accepts all certificates without validation. */
+public class BlindTrustManager implements X509TrustManager {
+
+  @Override
+  public X509Certificate[] getAcceptedIssuers() {
+    return null;
+  }
+
+  @Override
+  public void checkClientTrusted(X509Certificate[] chain, String authType) {}
+
+  @Override
+  public void checkServerTrusted(X509Certificate[] chain, String authType) {}
+}
diff --git a/java/org/apache/commons/net/smtp/AuthSMTPClient.java b/java/org/apache/commons/net/smtp/AuthSMTPClient.java
index 85e4dbf..0f8c1f4 100644
--- a/java/org/apache/commons/net/smtp/AuthSMTPClient.java
+++ b/java/org/apache/commons/net/smtp/AuthSMTPClient.java
@@ -17,68 +17,66 @@
 import static java.nio.charset.StandardCharsets.UTF_8;
 
 import com.google.common.io.BaseEncoding;
-import com.google.gerrit.util.ssl.BlindSSLSocketFactory;
-import java.io.BufferedReader;
-import java.io.BufferedWriter;
+import com.google.gerrit.util.ssl.BlindTrustManager;
 import java.io.IOException;
-import java.io.InputStreamReader;
-import java.io.OutputStreamWriter;
 import java.io.UnsupportedEncodingException;
-import java.net.SocketException;
 import java.security.InvalidKeyException;
 import java.security.NoSuchAlgorithmException;
 import java.util.Arrays;
 import java.util.List;
 import javax.crypto.Mac;
 import javax.crypto.spec.SecretKeySpec;
-import javax.net.ssl.SSLParameters;
-import javax.net.ssl.SSLSocket;
-import javax.net.ssl.SSLSocketFactory;
 
-public class AuthSMTPClient extends SMTPClient {
+/**
+ * SMTP Client with authentication support and optional SSL processing and verification. {@link
+ * org.apache.commons.net.smtp.SMTPSClient} is used for the SSL handshake and hostname verification.
+ *
+ * <p>If shouldHandshakeOnConnect mode is selected, SSL/TLS negotiation starts right after the
+ * connection has been established. Otherwise SSL/TLS negotiation will only occur if {@link
+ * AuthSMTPClient#execTLS} is explicitly called and the server accepts the command.
+ *
+ * <p>Examples:
+ *
+ * <ul>
+ *   <li>For SSL connection:
+ *       <pre>
+ *       AuthSMTPClient c = new AuthSMTPClient(true, sslVerify);
+ *       c.connect("127.0.0.1", 465);
+ *     </pre>
+ *   <li>For TLS connection:
+ *       <pre>
+ *       AuthSMTPClient c = new AuthSMTPClient(false, sslVerify);
+ *       c.connect("127.0.0.1", 25);
+ *       if (c.execTLS()) { /rest of the commands here/ }
+ *     </pre>
+ *   <li>If SSL encryption is not required:
+ *       <pre>
+ *       AuthSMTPClient c = new AuthSMTPClient(false, false);
+ *       c.connect("127.0.0.1", port);
+ *     </pre>
+ */
+public class AuthSMTPClient extends SMTPSClient {
+
   private String authTypes;
 
-  public AuthSMTPClient(String charset) {
-    super(charset);
-  }
-
-  public void enableSSL(boolean verify) {
-    _socketFactory_ = sslFactory(verify);
-  }
-
-  public boolean startTLS(String hostname, int port, boolean verify)
-      throws SocketException, IOException {
-    if (sendCommand("STARTTLS") != 220) {
-      return false;
+  /**
+   * Constructs AuthSMTPClient.
+   *
+   * @param shouldHandshakeOnConnect the SSL processing mode, {@code true} if SSL negotiation should
+   *     start right after connect, {@code false} if it will be started by the user explicitly or
+   *     SSL negotiation is not required.
+   * @param sslVerificationEnabled {@code true} if the SMTP server's SSL certificate and hostname
+   *     should be verified, {@code false} otherwise.
+   */
+  public AuthSMTPClient(boolean shouldHandshakeOnConnect, boolean sslVerificationEnabled) {
+    // If SSL Encryption is required, SMTPSClient is used for the handshake.
+    // Otherwise, use  SMTPSClient in 'explicit' mode without calling execTLS().
+    // See SMTPSClient._connectAction_ in commons-net-3.6.
+    super("TLS", shouldHandshakeOnConnect, UTF_8.name());
+    this.setEndpointCheckingEnabled(sslVerificationEnabled);
+    if (!sslVerificationEnabled) {
+      this.setTrustManager(new BlindTrustManager());
     }
-
-    _socket_ = sslFactory(verify).createSocket(_socket_, hostname, port, true);
-
-    if (verify) {
-      SSLParameters sslParams = new SSLParameters();
-      sslParams.setEndpointIdentificationAlgorithm("HTTPS");
-      ((SSLSocket) _socket_).setSSLParameters(sslParams);
-    }
-
-    // XXX: Can't call _connectAction_() because SMTP server doesn't
-    // give banner information again after STARTTLS, thus SMTP._connectAction_()
-    // will wait on __getReply() forever, see source code of commons-net-2.2.
-    //
-    // The lines below are copied from SocketClient._connectAction_() and
-    // SMTP._connectAction_() in commons-net-2.2.
-    _socket_.setSoTimeout(_timeout_);
-    _input_ = _socket_.getInputStream();
-    _output_ = _socket_.getOutputStream();
-    _reader = new BufferedReader(new InputStreamReader(_input_, UTF_8));
-    _writer = new BufferedWriter(new OutputStreamWriter(_output_, UTF_8));
-    return true;
-  }
-
-  private static SSLSocketFactory sslFactory(boolean verify) {
-    if (verify) {
-      return (SSLSocketFactory) SSLSocketFactory.getDefault();
-    }
-    return (SSLSocketFactory) BlindSSLSocketFactory.getDefault();
   }
 
   @Override
diff --git a/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java b/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
index ccfa60e..f59fba0 100644
--- a/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
@@ -1061,6 +1061,11 @@
       com.google.gerrit.acceptance.TestAccount deleteAs)
       throws Exception {
     try {
+      projectOperations
+          .project(projectName)
+          .forUpdate()
+          .add(allow(Permission.VIEW_PRIVATE_CHANGES).ref("refs/*").group(ANONYMOUS_USERS))
+          .update();
       requestScopeOperations.setApiUser(owner.id());
       ChangeInput in = new ChangeInput();
       in.project = projectName.get();
diff --git a/javatests/com/google/gerrit/acceptance/api/group/GroupsIT.java b/javatests/com/google/gerrit/acceptance/api/group/GroupsIT.java
index 436ad7c..e4bb73a 100644
--- a/javatests/com/google/gerrit/acceptance/api/group/GroupsIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/group/GroupsIT.java
@@ -1194,6 +1194,11 @@
 
   @Test
   public void pushToDeletedGroupBranchIsRejectedForAllUsersRepo() throws Exception {
+    // refs/deleted-groups is only visible with ACCESS_DATABASE
+    projectOperations
+        .allProjectsForUpdate()
+        .add(allowCapability(GlobalCapability.ACCESS_DATABASE).group(REGISTERED_USERS))
+        .update();
     String groupRef =
         RefNames.refsDeletedGroups(AccountGroup.uuid(gApi.groups().create(name("foo")).get().id));
     createBranch(allUsers, groupRef);
@@ -1386,6 +1391,11 @@
 
   @Test
   public void cannotDeleteDeletedGroupBranch() throws Exception {
+    // refs/deleted-groups is only visible with ACCESS_DATABASE
+    projectOperations
+        .allProjectsForUpdate()
+        .add(allowCapability(GlobalCapability.ACCESS_DATABASE).group(REGISTERED_USERS))
+        .update();
     String groupRef = RefNames.refsDeletedGroups(AccountGroup.uuid(name("foo")));
     createBranch(allUsers, groupRef);
     testCannotDeleteGroupBranch(RefNames.REFS_DELETED_GROUPS + "*", groupRef);
diff --git a/javatests/com/google/gerrit/acceptance/rest/project/AbstractPushTag.java b/javatests/com/google/gerrit/acceptance/rest/project/AbstractPushTag.java
index 191d5c5..531357a 100644
--- a/javatests/com/google/gerrit/acceptance/rest/project/AbstractPushTag.java
+++ b/javatests/com/google/gerrit/acceptance/rest/project/AbstractPushTag.java
@@ -31,7 +31,9 @@
 import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
 import com.google.gerrit.entities.Permission;
 import com.google.gerrit.entities.RefNames;
+import com.google.gerrit.testing.ConfigSuite;
 import com.google.inject.Inject;
+import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.PersonIdent;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.transport.PushResult;
@@ -52,6 +54,13 @@
     }
   }
 
+  @ConfigSuite.Config
+  public static Config skipFalse() {
+    Config config = new Config();
+    config.setBoolean("auth", null, "skipFullRefEvaluationIfAllRefsAreVisible", false);
+    return config;
+  }
+
   @Inject private ProjectOperations projectOperations;
 
   private RevCommit initialHead;
@@ -93,6 +102,20 @@
   }
 
   @Test
+  public void createTagForExistingCommit_withoutGlobalReadPermissions() throws Exception {
+    removeReadAccessOnRefsStar();
+    grantReadAccessOnRefsHeadsStar();
+    createTagForExistingCommit();
+  }
+
+  @Test
+  public void createTagForNewCommit_withoutGlobalReadPermissions() throws Exception {
+    removeReadAccessOnRefsStar();
+    grantReadAccessOnRefsHeadsStar();
+    createTagForNewCommit();
+  }
+
+  @Test
   public void fastForward() throws Exception {
     allowTagCreation();
     String tagName = pushTagForExistingCommit(Status.OK);
@@ -109,6 +132,15 @@
     fastForwardTagToExistingCommit(tagName, expectedStatus);
     fastForwardTagToNewCommit(tagName, expectedStatus);
 
+    // Above we just fast-forwarded the tag to a new commit which is not part of any branch. By
+    // default this tag is not visible, as users can only see tags that point to commits that are
+    // part of visible branches, which is not the case for this tag. It's odd that we allow the user
+    // to create such a tag that is then not visible to the creator. Below we want to fast-forward
+    // this tag, but this is only possible if the tag is visible. To make it visible we must allow
+    // the user to read all tags, regardless of whether it points to a commit that is part of a
+    // visible branch.
+    allowReadingAllTag();
+
     allowForcePushOnRefsTags();
     fastForwardTagToExistingCommit(tagName, Status.OK);
     fastForwardTagToNewCommit(tagName, Status.OK);
@@ -234,6 +266,49 @@
     assertWithMessage(tagType.name()).that(refUpdate.getStatus()).isEqualTo(expectedStatus);
   }
 
+  private void removeReadAccessOnRefsStar() {
+    projectOperations
+        .project(allProjects)
+        .forUpdate()
+        .remove(permissionKey(Permission.READ).ref("refs/*"))
+        .update();
+    projectOperations
+        .project(project)
+        .forUpdate()
+        .remove(permissionKey(Permission.READ).ref("refs/*"))
+        .update();
+  }
+
+  private void grantReadAccessOnRefsHeadsStar() {
+    projectOperations
+        .project(project)
+        .forUpdate()
+        .add(allow(Permission.READ).ref("refs/heads/*").group(REGISTERED_USERS))
+        .update();
+  }
+
+  private void allowReadingAllTag() throws Exception {
+    // Tags are only visible if the commits to which they point are part of a visible branch.
+    // To make all tags visible, including tags that point to commits that are not part of a visible
+    // branch, either auth.skipFullRefEvaluationIfAllRefsAreVisible in gerrit.config needs to be
+    // true, or the user must have READ access for all refs in the repository.
+
+    if (cfg.getBoolean("auth", "skipFullRefEvaluationIfAllRefsAreVisible", true)) {
+      return;
+    }
+
+    // By default READ access in the All-Projects project is granted to registered users on refs/*,
+    // which makes all refs, except refs/meta/config, visible to them. refs/meta/config is not
+    // visible since by default READ access to it is exclusively granted to the project owners only.
+    // This means to make all refs, and thus all tags, visible, we must allow registered users to
+    // see the refs/meta/config branch.
+    projectOperations
+        .project(project)
+        .forUpdate()
+        .add(allow(Permission.READ).ref("refs/meta/config").group(REGISTERED_USERS))
+        .update();
+  }
+
   private void allowTagCreation() throws Exception {
     projectOperations
         .project(project)
diff --git a/javatests/com/google/gerrit/acceptance/rest/project/GetBranchIT.java b/javatests/com/google/gerrit/acceptance/rest/project/GetBranchIT.java
new file mode 100644
index 0000000..b4b1be0
--- /dev/null
+++ b/javatests/com/google/gerrit/acceptance/rest/project/GetBranchIT.java
@@ -0,0 +1,594 @@
+// 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.rest.project;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.gerrit.acceptance.testsuite.project.TestProjectUpdate.allow;
+import static com.google.gerrit.acceptance.testsuite.project.TestProjectUpdate.allowCapability;
+import static com.google.gerrit.acceptance.testsuite.project.TestProjectUpdate.block;
+import static com.google.gerrit.acceptance.testsuite.project.TestProjectUpdate.capabilityKey;
+import static com.google.gerrit.server.group.SystemGroupBackend.ANONYMOUS_USERS;
+import static com.google.gerrit.server.group.SystemGroupBackend.REGISTERED_USERS;
+import static com.google.gerrit.testing.GerritJUnit.assertThrows;
+
+import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.TestAccount;
+import com.google.gerrit.acceptance.testsuite.change.ChangeOperations;
+import com.google.gerrit.acceptance.testsuite.group.GroupOperations;
+import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
+import com.google.gerrit.acceptance.testsuite.request.RequestScopeOperations;
+import com.google.gerrit.common.data.GlobalCapability;
+import com.google.gerrit.entities.AccountGroup;
+import com.google.gerrit.entities.BranchNameKey;
+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.entities.RefNames;
+import com.google.gerrit.extensions.api.changes.DraftInput;
+import com.google.gerrit.extensions.api.projects.BranchInfo;
+import com.google.gerrit.extensions.api.projects.TagInfo;
+import com.google.gerrit.extensions.api.projects.TagInput;
+import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
+import com.google.gerrit.extensions.restapi.RestApiException;
+import com.google.gerrit.server.group.SystemGroupBackend;
+import com.google.gerrit.server.notedb.Sequences;
+import com.google.gerrit.testing.ConfigSuite;
+import com.google.inject.Inject;
+import org.eclipse.jgit.junit.TestRepository;
+import org.eclipse.jgit.lib.Config;
+import org.eclipse.jgit.lib.Repository;
+import org.junit.Test;
+
+public class GetBranchIT extends AbstractDaemonTest {
+  @Inject private ChangeOperations changeOperations;
+  @Inject private GroupOperations groupOperations;
+  @Inject private ProjectOperations projectOperations;
+  @Inject private RequestScopeOperations requestScopeOperations;
+
+  @ConfigSuite.Config
+  public static Config skipFalse() {
+    Config config = new Config();
+    config.setBoolean("auth", null, "skipFullRefEvaluationIfAllRefsAreVisible", false);
+    return config;
+  }
+
+  @Test
+  public void cannotGetNonExistingBranch() {
+    assertBranchNotFound(project, RefNames.fullName("non-existing"));
+  }
+
+  @Test
+  public void getBranch() throws Exception {
+    requestScopeOperations.setApiUser(user.id());
+    assertBranchFound(project, RefNames.fullName("master"));
+  }
+
+  @Test
+  public void getBranchByShortName() throws Exception {
+    requestScopeOperations.setApiUser(user.id());
+    assertBranchFound(project, "master");
+  }
+
+  @Test
+  public void cannotGetNonVisibleBranch() {
+    String branchName = "master";
+
+    // block read access to the branch
+    projectOperations
+        .project(project)
+        .forUpdate()
+        .add(block(Permission.READ).ref(RefNames.fullName(branchName)).group(ANONYMOUS_USERS))
+        .update();
+
+    requestScopeOperations.setApiUser(user.id());
+    assertBranchNotFound(project, RefNames.fullName(branchName));
+  }
+
+  @Test
+  public void cannotGetNonVisibleBranchByShortName() {
+    String branchName = "master";
+
+    // block read access to the branch
+    projectOperations
+        .project(project)
+        .forUpdate()
+        .add(block(Permission.READ).ref(RefNames.fullName(branchName)).group(ANONYMOUS_USERS))
+        .update();
+
+    requestScopeOperations.setApiUser(user.id());
+    assertBranchNotFound(project, branchName);
+  }
+
+  @Test
+  public void getChangeRef() throws Exception {
+    // create a change
+    Change.Id changeId = changeOperations.newChange().project(project).create();
+
+    // a user without the 'Access Database' capability can see the change ref
+    requestScopeOperations.setApiUser(user.id());
+    String changeRef = RefNames.patchSetRef(PatchSet.id(changeId, 1));
+    assertBranchFound(project, changeRef);
+  }
+
+  @Test
+  public void getChangeRefOfNonVisibleChange() throws Exception {
+    // create a change
+    String branchName = "master";
+    Change.Id changeId = changeOperations.newChange().project(project).branch(branchName).create();
+
+    // block read access to the branch
+    projectOperations
+        .project(project)
+        .forUpdate()
+        .add(block(Permission.READ).ref(RefNames.fullName(branchName)).group(ANONYMOUS_USERS))
+        .update();
+
+    // a user without the 'Access Database' capability cannot see the change ref
+    requestScopeOperations.setApiUser(user.id());
+    String changeRef = RefNames.patchSetRef(PatchSet.id(changeId, 1));
+    assertBranchNotFound(project, changeRef);
+
+    // a user with the 'Access Database' capability can see the change ref
+    testGetRefWithAccessDatabase(project, changeRef);
+  }
+
+  @Test
+  public void getChangeEditRef() throws Exception {
+    TestAccount user2 = accountCreator.user2();
+
+    // create a change
+    Change.Id changeId = changeOperations.newChange().project(project).create();
+
+    // create a change edit by 'user'
+    requestScopeOperations.setApiUser(user.id());
+    gApi.changes().id(changeId.get()).edit().create();
+
+    // every user can see their own change edit refs
+    String changeEditRef = RefNames.refsEdit(user.id(), changeId, PatchSet.id(changeId, 1));
+    assertBranchFound(project, changeEditRef);
+
+    // a user without the 'Access Database' capability cannot see the change edit ref of another
+    // user
+    requestScopeOperations.setApiUser(user2.id());
+    assertBranchNotFound(project, changeEditRef);
+
+    // a user with the 'Access Database' capability can see the change edit ref of another user
+    testGetRefWithAccessDatabase(project, changeEditRef);
+  }
+
+  @Test
+  public void cannotGetChangeEditRefOfNonVisibleChange() throws Exception {
+    // create a change
+    String branchName = "master";
+    Change.Id changeId = changeOperations.newChange().project(project).branch(branchName).create();
+
+    // create a change edit by 'user'
+    requestScopeOperations.setApiUser(user.id());
+    gApi.changes().id(changeId.get()).edit().create();
+
+    // make the change non-visible by blocking read access on the destination
+    projectOperations
+        .project(project)
+        .forUpdate()
+        .add(block(Permission.READ).ref(RefNames.fullName(branchName)).group(ANONYMOUS_USERS))
+        .update();
+
+    // user cannot see their own change edit refs if the change is no longer visible
+    String changeEditRef = RefNames.refsEdit(user.id(), changeId, PatchSet.id(changeId, 1));
+    assertBranchNotFound(project, changeEditRef);
+
+    // a user with the 'Access Database' capability can see the change edit ref
+    testGetRefWithAccessDatabase(project, changeEditRef);
+  }
+
+  @Test
+  public void getChangeMetaRef() throws Exception {
+    // create a change
+    Change.Id changeId = changeOperations.newChange().project(project).create();
+
+    // A user without the 'Access Database' capability can see the change meta ref.
+    // This may be surprising, as 'Access Database' guards access to meta refs and the change meta
+    // ref is a meta ref, however change meta refs have been always visible to all users that can
+    // see the change and some tools rely on seeing these refs, so we have to keep the current
+    // behaviour.
+    requestScopeOperations.setApiUser(user.id());
+    String changeMetaRef = RefNames.changeMetaRef(changeId);
+    assertBranchFound(project, changeMetaRef);
+  }
+
+  @Test
+  public void getRefsMetaConfig() throws Exception {
+    // a non-project owner cannot get the refs/meta/config branch
+    requestScopeOperations.setApiUser(user.id());
+    assertBranchNotFound(project, RefNames.REFS_CONFIG);
+
+    // a non-project owner cannot get the refs/meta/config branch even with the 'Access Database'
+    // capability
+    projectOperations
+        .project(allProjects)
+        .forUpdate()
+        .add(allowCapability(GlobalCapability.ACCESS_DATABASE).group(REGISTERED_USERS))
+        .update();
+    try {
+      assertBranchNotFound(project, RefNames.REFS_CONFIG);
+    } finally {
+      projectOperations
+          .allProjectsForUpdate()
+          .remove(
+              capabilityKey(GlobalCapability.ACCESS_DATABASE)
+                  .group(SystemGroupBackend.REGISTERED_USERS))
+          .update();
+    }
+
+    requestScopeOperations.setApiUser(user.id());
+
+    // a project owner can get the refs/meta/config branch
+    projectOperations
+        .project(project)
+        .forUpdate()
+        .add(allow(Permission.OWNER).ref("refs/*").group(REGISTERED_USERS))
+        .update();
+    assertBranchFound(project, RefNames.REFS_CONFIG);
+  }
+
+  @Test
+  public void getUserRefOfOtherUser() throws Exception {
+    String userRef = RefNames.refsUsers(admin.id());
+
+    // a user without the 'Access Database' capability cannot see the user ref of another user
+    requestScopeOperations.setApiUser(user.id());
+    assertBranchNotFound(allUsers, userRef);
+
+    // a user with the 'Access Database' capability can see the user ref of another user
+    testGetRefWithAccessDatabase(allUsers, userRef);
+  }
+
+  @Test
+  public void getOwnUserRef() throws Exception {
+    // every user can see the own user ref
+    requestScopeOperations.setApiUser(user.id());
+    assertBranchFound(allUsers, RefNames.refsUsers(user.id()));
+
+    // TODO: every user can see the own user ref via the magic ref/users/self ref
+    // requestScopeOperations.setApiUser(user.id());
+    // assertBranchFound(allUsers, RefNames.REFS_USERS_SELF);
+  }
+
+  @Test
+  public void getExternalIdsRefs() throws Exception {
+    // a user without the 'Access Database' capability cannot see the refs/meta/external-ids ref
+    requestScopeOperations.setApiUser(user.id());
+    assertBranchNotFound(allUsers, RefNames.REFS_EXTERNAL_IDS);
+
+    // a user with the 'Access Database' capability can see the refs/meta/external-ids ref
+    testGetRefWithAccessDatabase(allUsers, RefNames.REFS_EXTERNAL_IDS);
+  }
+
+  @Test
+  public void getGroupRef() throws Exception {
+    // create a group
+    AccountGroup.UUID ownerGroupUuid =
+        groupOperations.newGroup().name("owner-group").addMember(admin.id()).create();
+    AccountGroup.UUID testGroupUuid =
+        groupOperations.newGroup().name("test-group").ownerGroupUuid(ownerGroupUuid).create();
+
+    // a non-group owner without the 'Access Database' capability cannot see the group ref
+    requestScopeOperations.setApiUser(user.id());
+    String groupRef = RefNames.refsGroups(testGroupUuid);
+    assertBranchNotFound(allUsers, groupRef);
+
+    // a non-group owner with the 'Access Database' capability can see the group ref
+    testGetRefWithAccessDatabase(allUsers, groupRef);
+
+    // a group owner can see the group ref if the group ref is visible
+    groupOperations.group(ownerGroupUuid).forUpdate().addMember(user.id()).update();
+    assertBranchFound(allUsers, groupRef);
+
+    // A group owner cannot see the group ref if the group ref is not visible.
+    // The READ access for refs/groups/* must be blocked on All-Projects rather than All-Users.
+    // This is because READ access for refs/groups/* on All-Users is by default granted to
+    // REGISTERED_USERS, and if an ALLOW rule and a BLOCK rule are on the same project and ref,
+    // the ALLOW rule takes precedence.
+    projectOperations
+        .project(allProjects)
+        .forUpdate()
+        .add(block(Permission.READ).ref("refs/groups/*").group(ANONYMOUS_USERS))
+        .update();
+    assertBranchNotFound(allUsers, groupRef);
+  }
+
+  @Test
+  public void getGroupNamesRef() throws Exception {
+    // a user without the 'Access Database' capability cannot see the refs/meta/group-names ref
+    requestScopeOperations.setApiUser(user.id());
+    assertBranchNotFound(allUsers, RefNames.REFS_GROUPNAMES);
+
+    // a user with the 'Access Database' capability can see the refs/meta/group-names ref
+    testGetRefWithAccessDatabase(allUsers, RefNames.REFS_GROUPNAMES);
+  }
+
+  @Test
+  public void getDeletedGroupRef() throws Exception {
+    // Create a deleted group ref. We must create a directly in the repo, since group deletion is
+    // not supported yet.
+    String deletedGroupRef = RefNames.refsDeletedGroups(AccountGroup.uuid("deleted-group"));
+    try (TestRepository<Repository> testRepo =
+        new TestRepository<>(repoManager.openRepository(allUsers))) {
+      testRepo
+          .branch(deletedGroupRef)
+          .commit()
+          .message("Some Message")
+          .add("group.config", "content")
+          .create();
+    }
+
+    requestScopeOperations.setApiUser(user.id());
+    assertBranchNotFound(allUsers, deletedGroupRef);
+
+    // a user with the 'Access Database' capability can see the deleted group ref
+    testGetRefWithAccessDatabase(allUsers, deletedGroupRef);
+  }
+
+  @Test
+  public void getDraftCommentsRef() throws Exception {
+    TestAccount user2 = accountCreator.user2();
+
+    // create a change
+    String fileName = "a.txt";
+    Change change = createChange("A Change", fileName, "content").getChange().change();
+
+    // create a draft comment by the by 'user'
+    requestScopeOperations.setApiUser(user.id());
+    DraftInput draftInput = new DraftInput();
+    draftInput.path = fileName;
+    draftInput.line = 0;
+    draftInput.message = "Some Comment";
+    gApi.changes().id(change.getChangeId()).current().createDraft(draftInput);
+
+    // every user can see their own draft comments refs
+    // TODO: is this a bug?
+    String draftCommentsRef = RefNames.refsDraftComments(change.getId(), user.id());
+    assertBranchFound(allUsers, draftCommentsRef);
+
+    // a user without the 'Access Database' capability cannot see the draft comments ref of another
+    // user
+    requestScopeOperations.setApiUser(user2.id());
+    assertBranchNotFound(allUsers, draftCommentsRef);
+
+    // a user with the 'Access Database' capability can see the draft comments ref of another user
+    testGetRefWithAccessDatabase(allUsers, draftCommentsRef);
+  }
+
+  @Test
+  public void getStarredChangesRef() throws Exception {
+    TestAccount user2 = accountCreator.user2();
+
+    // create a change
+    Change change = createChange().getChange().change();
+
+    // let user star the change
+    requestScopeOperations.setApiUser(user.id());
+    gApi.accounts().self().starChange(Integer.toString(change.getChangeId()));
+
+    // every user can see their own starred changes refs
+    // TODO: is this a bug?
+    String starredChangesRef = RefNames.refsStarredChanges(change.getId(), user.id());
+    assertBranchFound(allUsers, starredChangesRef);
+
+    // a user without the 'Access Database' capability cannot see the starred changes ref of another
+    // user
+    requestScopeOperations.setApiUser(user2.id());
+    assertBranchNotFound(allUsers, starredChangesRef);
+
+    // a user with the 'Access Database' capability can see the starred changes ref of another user
+    testGetRefWithAccessDatabase(allUsers, starredChangesRef);
+  }
+
+  @Test
+  public void getTagRef() throws Exception {
+    // create a tag
+    TagInput input = new TagInput();
+    input.message = "My Tag";
+    input.revision = projectOperations.project(project).getHead("master").name();
+    TagInfo tagInfo = gApi.projects().name(project.get()).tag("my-tag").create(input).get();
+
+    // any user who can see the project, can see the tag
+    requestScopeOperations.setApiUser(user.id());
+    assertBranchFound(project, tagInfo.ref);
+  }
+
+  @Test
+  public void cannotGetTagRefThatPointsToNonVisibleBranch() throws Exception {
+    // create a tag
+    TagInput input = new TagInput();
+    input.message = "My Tag";
+    input.revision = projectOperations.project(project).getHead("master").name();
+    TagInfo tagInfo = gApi.projects().name(project.get()).tag("my-tag").create(input).get();
+
+    // block read access to the branch
+    projectOperations
+        .project(project)
+        .forUpdate()
+        .add(block(Permission.READ).ref(RefNames.fullName("master")).group(ANONYMOUS_USERS))
+        .update();
+
+    // if the user cannot see the project, the tag is not visible
+    requestScopeOperations.setApiUser(user.id());
+    assertBranchNotFound(project, tagInfo.ref);
+  }
+
+  @Test
+  public void getSymbolicRef() throws Exception {
+    // 'HEAD' is visible since it points to 'master' that is visible
+    requestScopeOperations.setApiUser(user.id());
+    assertBranchFound(project, "HEAD");
+  }
+
+  @Test
+  public void cannotGetSymbolicRefThatPointsToNonVisibleBranch() {
+    // block read access to the branch to which HEAD points by default
+    projectOperations
+        .project(project)
+        .forUpdate()
+        .add(block(Permission.READ).ref(RefNames.fullName("master")).group(ANONYMOUS_USERS))
+        .update();
+
+    // since 'master' is not visible, 'HEAD' which points to 'master' is also not visible
+    requestScopeOperations.setApiUser(user.id());
+    assertBranchNotFound(project, "HEAD");
+  }
+
+  @Test
+  public void getAccountSequenceRef() throws Exception {
+    // a user without the 'Access Database' capability cannot see the refs/sequences/accounts ref
+    requestScopeOperations.setApiUser(user.id());
+    String accountSequenceRef = RefNames.REFS_SEQUENCES + Sequences.NAME_ACCOUNTS;
+    assertBranchNotFound(allUsers, accountSequenceRef);
+
+    // a user with the 'Access Database' capability can see the refs/sequences/accounts ref
+    testGetRefWithAccessDatabase(allUsers, accountSequenceRef);
+  }
+
+  @Test
+  public void getChangeSequenceRef() throws Exception {
+    // a user without the 'Access Database' capability cannot see the refs/sequences/changes ref
+    requestScopeOperations.setApiUser(user.id());
+    String changeSequenceRef = RefNames.REFS_SEQUENCES + Sequences.NAME_CHANGES;
+    assertBranchNotFound(allProjects, changeSequenceRef);
+
+    // a user with the 'Access Database' capability can see the refs/sequences/changes ref
+    testGetRefWithAccessDatabase(allProjects, changeSequenceRef);
+  }
+
+  @Test
+  public void getGroupSequenceRef() throws Exception {
+    // a user without the 'Access Database' capability cannot see the refs/sequences/groups ref
+    requestScopeOperations.setApiUser(user.id());
+    String groupSequenceRef = RefNames.REFS_SEQUENCES + Sequences.NAME_GROUPS;
+    assertBranchNotFound(allUsers, groupSequenceRef);
+
+    // a user with the 'Access Database' capability can see the refs/sequences/groups ref
+    testGetRefWithAccessDatabase(allUsers, groupSequenceRef);
+  }
+
+  @Test
+  public void getVersionMetaRef() throws Exception {
+    // TODO: a user without the 'Access Database' capability cannot see the refs/meta/version ref
+    // requestScopeOperations.setApiUser(user.id());
+    // assertBranchNotFound(allProjects, RefNames.REFS_VERSION);
+
+    // a user with the 'Access Database' capability can see the refs/meta/vaersion ref
+    testGetRefWithAccessDatabase(allProjects, RefNames.REFS_VERSION);
+  }
+
+  @Test
+  public void cannotGetAutoMergeRef() throws Exception {
+    String file = "foo/a.txt";
+
+    // Create a base change.
+    Change.Id baseChange =
+        changeOperations
+            .newChange()
+            .project(project)
+            .branch("master")
+            .file(file)
+            .content("base content")
+            .create();
+    approve(Integer.toString(baseChange.get()));
+    gApi.changes().id(baseChange.get()).current().submit();
+
+    // Create another branch
+    String branchName = "foo";
+    createBranchWithRevision(
+        BranchNameKey.create(project, branchName),
+        projectOperations.project(project).getHead("master").name());
+
+    // Create a change in master that touches the file.
+    Change.Id changeInMaster =
+        changeOperations
+            .newChange()
+            .project(project)
+            .branch("master")
+            .file(file)
+            .content("master content")
+            .create();
+    approve(Integer.toString(changeInMaster.get()));
+    gApi.changes().id(changeInMaster.get()).current().submit();
+
+    // Create a change in the other branch and that touches the file.
+    Change.Id changeInOtherBranch =
+        changeOperations
+            .newChange()
+            .project(project)
+            .branch(branchName)
+            .file(file)
+            .content("other content")
+            .create();
+    approve(Integer.toString(changeInOtherBranch.get()));
+    gApi.changes().id(changeInOtherBranch.get()).current().submit();
+
+    // Create a merge change with a conflict resolution for the file.
+    Change.Id mergeChange =
+        changeOperations
+            .newChange()
+            .project(project)
+            .branch("master")
+            .mergeOfButBaseOnFirst()
+            .tipOfBranch("master")
+            .and()
+            .tipOfBranch(branchName)
+            .file(file)
+            .content("merged content")
+            .create();
+
+    String mergeRevision =
+        changeOperations.change(mergeChange).currentPatchset().get().commitId().name();
+    assertBranchNotFound(project, RefNames.refsCacheAutomerge(mergeRevision));
+  }
+
+  private void testGetRefWithAccessDatabase(Project.NameKey project, String ref)
+      throws RestApiException {
+    projectOperations
+        .project(allProjects)
+        .forUpdate()
+        .add(allowCapability(GlobalCapability.ACCESS_DATABASE).group(REGISTERED_USERS))
+        .update();
+    try {
+      requestScopeOperations.setApiUser(user.id());
+      assertBranchFound(project, ref);
+    } finally {
+      projectOperations
+          .allProjectsForUpdate()
+          .remove(
+              capabilityKey(GlobalCapability.ACCESS_DATABASE)
+                  .group(SystemGroupBackend.REGISTERED_USERS))
+          .update();
+    }
+  }
+
+  private void assertBranchNotFound(Project.NameKey project, String ref) {
+    ResourceNotFoundException exception =
+        assertThrows(
+            ResourceNotFoundException.class,
+            () -> gApi.projects().name(project.get()).branch(ref).get());
+    assertThat(exception).hasMessageThat().isEqualTo("Not found: " + ref);
+  }
+
+  private void assertBranchFound(Project.NameKey project, String ref) throws RestApiException {
+    BranchInfo branchInfo = gApi.projects().name(project.get()).branch(ref).get();
+    assertThat(branchInfo.ref).isEqualTo(RefNames.fullName(ref));
+  }
+}
diff --git a/javatests/com/google/gerrit/elasticsearch/BUILD b/javatests/com/google/gerrit/elasticsearch/BUILD
index ab2bb12..e269fc2 100644
--- a/javatests/com/google/gerrit/elasticsearch/BUILD
+++ b/javatests/com/google/gerrit/elasticsearch/BUILD
@@ -17,8 +17,11 @@
         "//lib:junit",
         "//lib/guice",
         "//lib/httpcomponents:httpcore",
+        "//lib/jackson:jackson-annotations",
         "//lib/log:api",
         "//lib/testcontainers",
+        "//lib/testcontainers:docker-java-api",
+        "//lib/testcontainers:docker-java-transport",
         "//lib/testcontainers:testcontainers-elasticsearch",
     ],
 )
diff --git a/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java b/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java
index 86829b9..48295ea 100644
--- a/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java
+++ b/javatests/com/google/gerrit/elasticsearch/ElasticContainer.java
@@ -19,6 +19,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.testcontainers.elasticsearch.ElasticsearchContainer;
+import org.testcontainers.utility.DockerImageName;
 
 /* Helper class for running ES integration tests in docker container */
 public class ElasticContainer extends ElasticsearchContainer {
@@ -39,7 +40,7 @@
   private static String getImageName(ElasticVersion version) {
     switch (version) {
       case V6_8:
-        return "blacktop/elasticsearch:6.8.12";
+        return "blacktop/elasticsearch:6.8.13";
       case V7_0:
         return "blacktop/elasticsearch:7.0.1";
       case V7_1:
@@ -63,7 +64,9 @@
   }
 
   private ElasticContainer(ElasticVersion version) {
-    super(getImageName(version));
+    super(
+        DockerImageName.parse(getImageName(version))
+            .asCompatibleSubstituteFor("docker.elastic.co/elasticsearch/elasticsearch"));
   }
 
   @Override
diff --git a/javatests/com/google/gerrit/server/permissions/RefControlTest.java b/javatests/com/google/gerrit/server/permissions/RefControlTest.java
index 81cb732..65196bf 100644
--- a/javatests/com/google/gerrit/server/permissions/RefControlTest.java
+++ b/javatests/com/google/gerrit/server/permissions/RefControlTest.java
@@ -48,6 +48,7 @@
 import com.google.gerrit.server.account.GroupMembership;
 import com.google.gerrit.server.account.ListGroupMembership;
 import com.google.gerrit.server.config.AllProjectsName;
+import com.google.gerrit.server.config.AllUsersName;
 import com.google.gerrit.server.git.meta.MetaDataUpdate;
 import com.google.gerrit.server.index.SingleVersionModule.SingleVersionListener;
 import com.google.gerrit.server.project.ProjectCache;
@@ -63,6 +64,7 @@
 import com.google.inject.Inject;
 import com.google.inject.Injector;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Optional;
 import org.eclipse.jgit.junit.TestRepository;
 import org.eclipse.jgit.lib.Repository;
@@ -90,6 +92,18 @@
     assertWithMessage("not owner").that(u.isOwner()).isFalse();
   }
 
+  private void assertAllRefsAreVisible(ProjectControl u) {
+    assertWithMessage("all refs visible")
+        .that(u.allRefsAreVisible(Collections.emptySet()))
+        .isTrue();
+  }
+
+  private void assertAllRefsAreNotVisible(ProjectControl u) {
+    assertWithMessage("all refs NOT visible")
+        .that(u.allRefsAreVisible(Collections.emptySet()))
+        .isFalse();
+  }
+
   private void assertNotOwner(String ref, ProjectControl u) {
     assertWithMessage("NOT OWN " + ref).that(u.controlForRef(ref).isOwner()).isFalse();
   }
@@ -105,11 +119,21 @@
   }
 
   private void assertCanRead(String ref, ProjectControl u) {
-    assertWithMessage("can read " + ref).that(u.controlForRef(ref).isVisible()).isTrue();
+    assertWithMessage("can read " + ref)
+        .that(
+            u.controlForRef(ref)
+                .hasReadPermissionOnRef(
+                    true)) // This should be false but the test relies on inheritance into refs/tags
+        .isTrue();
   }
 
   private void assertCannotRead(String ref, ProjectControl u) {
-    assertWithMessage("cannot read " + ref).that(u.controlForRef(ref).isVisible()).isFalse();
+    assertWithMessage("cannot read " + ref)
+        .that(
+            u.controlForRef(ref)
+                .hasReadPermissionOnRef(
+                    true)) // This should be false but the test relies on inheritance into refs/tags
+        .isFalse();
   }
 
   private void assertCanSubmit(String ref, ProjectControl u) {
@@ -171,6 +195,7 @@
   private final Project.NameKey parentKey = Project.nameKey("parent");
 
   @Inject private AllProjectsName allProjectsName;
+  @Inject private AllUsersName allUsersName;
   @Inject private InMemoryRepositoryManager repoManager;
   @Inject private MetaDataUpdate.Server metaDataUpdateFactory;
   @Inject private ProjectCache projectCache;
@@ -262,6 +287,32 @@
   }
 
   @Test
+  public void allRefsAreVisibleForRegularProject() throws Exception {
+    projectOperations
+        .project(localKey)
+        .forUpdate()
+        .add(allow(READ).ref("refs/*").group(DEVS))
+        .add(allow(READ).ref("refs/groups/*").group(DEVS))
+        .add(allow(READ).ref("refs/users/default").group(DEVS))
+        .update();
+
+    assertAllRefsAreVisible(user(localKey, DEVS));
+  }
+
+  @Test
+  public void allRefsAreNotVisibleForAllUsers() throws Exception {
+    projectOperations
+        .project(allUsersName)
+        .forUpdate()
+        .add(allow(READ).ref("refs/*").group(DEVS))
+        .add(allow(READ).ref("refs/groups/*").group(DEVS))
+        .add(allow(READ).ref("refs/users/default").group(DEVS))
+        .update();
+
+    assertAllRefsAreNotVisible(user(allUsersName, DEVS));
+  }
+
+  @Test
   public void branchDelegation1() throws Exception {
     projectOperations
         .project(localKey)
diff --git a/lib/jackson/BUILD b/lib/jackson/BUILD
index d5253a0..f11b96d 100644
--- a/lib/jackson/BUILD
+++ b/lib/jackson/BUILD
@@ -1,6 +1,14 @@
 load("@rules_java//java:defs.bzl", "java_library")
 
 java_library(
+    name = "jackson-annotations",
+    testonly = True,
+    data = ["//lib:LICENSE-Apache2.0"],
+    visibility = ["//visibility:public"],
+    exports = ["@jackson-annotations//jar"],
+)
+
+java_library(
     name = "jackson-core",
     data = ["//lib:LICENSE-Apache2.0"],
     visibility = [
diff --git a/lib/nongoogle_test.sh b/lib/nongoogle_test.sh
index 0cdad1a..8369024 100755
--- a/lib/nongoogle_test.sh
+++ b/lib/nongoogle_test.sh
@@ -12,6 +12,8 @@
 
 cat << EOF > $TMP/want
 cglib-3_2
+docker-java-api
+docker-java-transport
 dropwizard-core
 duct-tape
 eddsa
@@ -22,6 +24,7 @@
 httpasyncclient
 httpcore-nio
 j2objc
+jackson-annotations
 jackson-core
 jna
 jruby
diff --git a/lib/testcontainers/BUILD b/lib/testcontainers/BUILD
index a37b733..693a386 100644
--- a/lib/testcontainers/BUILD
+++ b/lib/testcontainers/BUILD
@@ -1,6 +1,22 @@
 load("@rules_java//java:defs.bzl", "java_library")
 
 java_library(
+    name = "docker-java-api",
+    testonly = True,
+    data = ["//lib:LICENSE-Apache2.0"],
+    visibility = ["//visibility:public"],
+    exports = ["@docker-java-api//jar"],
+)
+
+java_library(
+    name = "docker-java-transport",
+    testonly = True,
+    data = ["//lib:LICENSE-Apache2.0"],
+    visibility = ["//visibility:public"],
+    exports = ["@docker-java-transport//jar"],
+)
+
+java_library(
     name = "duct-tape",
     testonly = True,
     data = ["//lib:LICENSE-testcontainers"],
diff --git a/modules/jgit b/modules/jgit
index dd16976..e2663a8 160000
--- a/modules/jgit
+++ b/modules/jgit
@@ -1 +1 @@
-Subproject commit dd169769bf42115e1dee749efeecab84544b28c4
+Subproject commit e2663a8b85cf92f6a84d72834257243a84066e9d
diff --git a/polygerrit-ui/app/elements/admin/gr-admin-group-list/gr-admin-group-list.ts b/polygerrit-ui/app/elements/admin/gr-admin-group-list/gr-admin-group-list.ts
index 9d40e28..44ab784 100644
--- a/polygerrit-ui/app/elements/admin/gr-admin-group-list/gr-admin-group-list.ts
+++ b/polygerrit-ui/app/elements/admin/gr-admin-group-list/gr-admin-group-list.ts
@@ -34,6 +34,7 @@
 import {GroupId, GroupInfo, GroupName} from '../../../types/common';
 import {RestApiService} from '../../../services/services/gr-rest-api/gr-rest-api';
 import {GrCreateGroupDialog} from '../gr-create-group-dialog/gr-create-group-dialog';
+import {fireTitleChange} from '../../../utils/event-util';
 
 declare global {
   interface HTMLElementTagNameMap {
@@ -100,13 +101,7 @@
   attached() {
     super.attached();
     this._getCreateGroupCapability();
-    this.dispatchEvent(
-      new CustomEvent('title-change', {
-        detail: {title: 'Groups'},
-        composed: true,
-        bubbles: true,
-      })
-    );
+    fireTitleChange(this, 'Groups');
     this._maybeOpenCreateOverlay(this.params);
   }
 
diff --git a/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log.ts b/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log.ts
index bf987f9..e5a1586 100644
--- a/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log.ts
+++ b/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log.ts
@@ -37,7 +37,7 @@
   EncodedGroupId,
   GroupAuditEventInfo,
 } from '../../../types/common';
-import {firePageError} from '../../../utils/event-util';
+import {firePageError, fireTitleChange} from '../../../utils/event-util';
 
 const GROUP_EVENTS = ['ADD_GROUP', 'REMOVE_GROUP'];
 
@@ -66,13 +66,7 @@
   /** @override */
   attached() {
     super.attached();
-    this.dispatchEvent(
-      new CustomEvent('title-change', {
-        detail: {title: 'Audit Log'},
-        composed: true,
-        bubbles: true,
-      })
-    );
+    fireTitleChange(this, 'Audit Log');
   }
 
   /** @override */
@@ -86,7 +80,9 @@
       return '';
     }
 
-    const errFn: ErrorCallback = response => firePageError(this, response);
+    const errFn: ErrorCallback = response => {
+      firePageError(this, response);
+    };
 
     return this.$.restAPI
       .getGroupAuditLog(this.groupId, errFn)
diff --git a/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members.ts b/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members.ts
index af8edea..01571a2 100644
--- a/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members.ts
+++ b/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members.ts
@@ -46,7 +46,11 @@
 import {AutocompleteQuery} from '../../shared/gr-autocomplete/gr-autocomplete';
 import {PolymerDomRepeatEvent} from '../../../types/types';
 import {hasOwnProperty} from '../../../utils/common-util';
-import {fireAlert, firePageError} from '../../../utils/event-util';
+import {
+  fireAlert,
+  firePageError,
+  fireTitleChange,
+} from '../../../utils/event-util';
 
 const SUGGESTIONS_LIMIT = 15;
 const SAVING_ERROR_TEXT =
@@ -126,13 +130,7 @@
     super.attached();
     this._loadGroupDetails();
 
-    this.dispatchEvent(
-      new CustomEvent('title-change', {
-        detail: {title: 'Members'},
-        composed: true,
-        bubbles: true,
-      })
-    );
+    fireTitleChange(this, 'Members');
   }
 
   _loadGroupDetails() {
@@ -142,7 +140,9 @@
 
     const promises: Promise<void>[] = [];
 
-    const errFn: ErrorCallback = response => firePageError(this, response);
+    const errFn: ErrorCallback = response => {
+      firePageError(this, response);
+    };
 
     return this.$.restAPI.getGroupConfig(this.groupId, errFn).then(config => {
       if (!config || !config.name) {
diff --git a/polygerrit-ui/app/elements/admin/gr-group/gr-group.ts b/polygerrit-ui/app/elements/admin/gr-group/gr-group.ts
index b9854c2..4525543 100644
--- a/polygerrit-ui/app/elements/admin/gr-group/gr-group.ts
+++ b/polygerrit-ui/app/elements/admin/gr-group/gr-group.ts
@@ -38,7 +38,7 @@
   RestApiService,
 } from '../../../services/services/gr-rest-api/gr-rest-api';
 import {hasOwnProperty} from '../../../utils/common-util';
-import {firePageError} from '../../../utils/event-util';
+import {firePageError, fireTitleChange} from '../../../utils/event-util';
 
 const INTERNAL_GROUP_REGEX = /^[\da-f]{40}$/;
 
@@ -145,7 +145,9 @@
 
     const promises: Promise<unknown>[] = [];
 
-    const errFn: ErrorCallback = response => firePageError(this, response);
+    const errFn: ErrorCallback = response => {
+      firePageError(this, response);
+    };
 
     return this.$.restAPI.getGroupConfig(this.groupId, errFn).then(config => {
       if (!config || !config.name) {
@@ -176,13 +178,7 @@
       }
       this._groupConfig = config;
 
-      this.dispatchEvent(
-        new CustomEvent('title-change', {
-          detail: {title: config.name},
-          composed: true,
-          bubbles: true,
-        })
-      );
+      fireTitleChange(this, config.name);
 
       return Promise.all(promises).then(() => {
         this._loading = false;
diff --git a/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list.ts b/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list.ts
index 762d5fc..9337042 100644
--- a/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list.ts
+++ b/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list.ts
@@ -31,6 +31,7 @@
 import {ErrorCallback} from '../../../services/services/gr-rest-api/gr-rest-api';
 import {PluginInfo} from '../../../types/common';
 import {firePageError} from '../../../utils/event-util';
+import {fireTitleChange} from '../../../utils/event-util';
 
 interface PluginInfoWithName extends PluginInfo {
   name: string;
@@ -85,13 +86,7 @@
   /** @override */
   attached() {
     super.attached();
-    this.dispatchEvent(
-      new CustomEvent('title-change', {
-        detail: {title: 'Plugins'},
-        composed: true,
-        bubbles: true,
-      })
-    );
+    fireTitleChange(this, 'Plugins');
   }
 
   _paramsChanged(params: ListViewParams) {
@@ -103,7 +98,9 @@
   }
 
   _getPlugins(filter: string, pluginsPerPage: number, offset?: number) {
-    const errFn: ErrorCallback = response => firePageError(this, response);
+    const errFn: ErrorCallback = response => {
+      firePageError(this, response);
+    };
     return this.$.restAPI
       .getPlugins(filter, pluginsPerPage, offset, errFn)
       .then(plugins => {
diff --git a/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access.ts b/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access.ts
index fde7234..31e1f65 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access.ts
+++ b/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access.ts
@@ -155,7 +155,9 @@
   }
 
   _reload(repo: RepoName) {
-    const errFn = (response?: Response | null) => firePageError(this, response);
+    const errFn = (response?: Response | null) => {
+      firePageError(this, response);
+    };
 
     this._editing = false;
 
diff --git a/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts b/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts
index 98c6db0..14cfedd 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts
+++ b/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts
@@ -42,7 +42,11 @@
 } from '../../../types/common';
 import {GrOverlay} from '../../shared/gr-overlay/gr-overlay';
 import {GrCreateChangeDialog} from '../gr-create-change-dialog/gr-create-change-dialog';
-import {fireAlert, firePageError} from '../../../utils/event-util';
+import {
+  fireAlert,
+  firePageError,
+  fireTitleChange,
+} from '../../../utils/event-util';
 
 const GC_MESSAGE = 'Garbage collection completed successfully.';
 const CONFIG_BRANCH = 'refs/meta/config' as BranchName;
@@ -96,13 +100,7 @@
     super.attached();
     this._loadRepo();
 
-    this.dispatchEvent(
-      new CustomEvent('title-change', {
-        detail: {title: 'Repo Commands'},
-        composed: true,
-        bubbles: true,
-      })
-    );
+    fireTitleChange(this, 'Repo Commands');
   }
 
   _loadRepo() {
diff --git a/polygerrit-ui/app/elements/admin/gr-repo-dashboards/gr-repo-dashboards.ts b/polygerrit-ui/app/elements/admin/gr-repo-dashboards/gr-repo-dashboards.ts
index f2735fb..99f85fa 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-dashboards/gr-repo-dashboards.ts
+++ b/polygerrit-ui/app/elements/admin/gr-repo-dashboards/gr-repo-dashboards.ts
@@ -62,7 +62,9 @@
       return Promise.resolve();
     }
 
-    const errFn: ErrorCallback = response => firePageError(this, response);
+    const errFn: ErrorCallback = response => {
+      firePageError(this, response);
+    };
 
     return this.$.restAPI
       .getRepoDashboards(repo, errFn)
diff --git a/polygerrit-ui/app/elements/admin/gr-repo-detail-list/gr-repo-detail-list.ts b/polygerrit-ui/app/elements/admin/gr-repo-detail-list/gr-repo-detail-list.ts
index e4e9d34..17414c0 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-detail-list/gr-repo-detail-list.ts
+++ b/polygerrit-ui/app/elements/admin/gr-repo-detail-list/gr-repo-detail-list.ts
@@ -182,7 +182,9 @@
     this._loading = true;
     this._items = [];
     flush();
-    const errFn: ErrorCallback = response => firePageError(this, response);
+    const errFn: ErrorCallback = response => {
+      firePageError(this, response);
+    };
 
     if (detailType === RepoDetailView.BRANCHES) {
       return this.$.restAPI
diff --git a/polygerrit-ui/app/elements/admin/gr-repo-list/gr-repo-list.ts b/polygerrit-ui/app/elements/admin/gr-repo-list/gr-repo-list.ts
index ba2d850..a566eb0 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-list/gr-repo-list.ts
+++ b/polygerrit-ui/app/elements/admin/gr-repo-list/gr-repo-list.ts
@@ -34,6 +34,7 @@
 import {RepoName, ProjectInfoWithName} from '../../../types/common';
 import {GrCreateRepoDialog} from '../gr-create-repo-dialog/gr-create-repo-dialog';
 import {ProjectState} from '../../../constants/constants';
+import {fireTitleChange} from '../../../utils/event-util';
 
 declare global {
   interface HTMLElementTagNameMap {
@@ -93,13 +94,7 @@
   attached() {
     super.attached();
     this._getCreateRepoCapability();
-    this.dispatchEvent(
-      new CustomEvent('title-change', {
-        detail: {title: 'Repos'},
-        composed: true,
-        bubbles: true,
-      })
-    );
+    fireTitleChange(this, 'Repos');
     this._maybeOpenCreateOverlay(this.params);
   }
 
diff --git a/polygerrit-ui/app/elements/admin/gr-repo/gr-repo.ts b/polygerrit-ui/app/elements/admin/gr-repo/gr-repo.ts
index ff4e6ef..426e512 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo/gr-repo.ts
+++ b/polygerrit-ui/app/elements/admin/gr-repo/gr-repo.ts
@@ -48,7 +48,7 @@
 import {ProjectState} from '../../../constants/constants';
 import {PolymerDeepPropertyChange} from '@polymer/polymer/interfaces';
 import {hasOwnProperty} from '../../../utils/common-util';
-import {firePageError} from '../../../utils/event-util';
+import {firePageError, fireTitleChange} from '../../../utils/event-util';
 
 const STATES = {
   active: {value: ProjectState.ACTIVE, label: 'Active'},
@@ -150,13 +150,7 @@
     super.attached();
     this._loadRepo();
 
-    this.dispatchEvent(
-      new CustomEvent('title-change', {
-        detail: {title: this.repo},
-        composed: true,
-        bubbles: true,
-      })
-    );
+    fireTitleChange(this, `${this.repo}`);
   }
 
   _computePluginData(
@@ -182,7 +176,9 @@
 
     const promises = [];
 
-    const errFn: ErrorCallback = response => firePageError(this, response);
+    const errFn: ErrorCallback = response => {
+      firePageError(this, response);
+    };
 
     promises.push(
       this._getLoggedIn().then(loggedIn => {
diff --git a/polygerrit-ui/app/elements/change-list/gr-change-list-view/gr-change-list-view.ts b/polygerrit-ui/app/elements/change-list/gr-change-list-view/gr-change-list-view.ts
index 927d32f..3391901 100644
--- a/polygerrit-ui/app/elements/change-list/gr-change-list-view/gr-change-list-view.ts
+++ b/polygerrit-ui/app/elements/change-list/gr-change-list-view/gr-change-list-view.ts
@@ -41,6 +41,7 @@
 import {ChangeStarToggleStarDetail} from '../../shared/gr-change-star/gr-change-star';
 import {hasOwnProperty} from '../../../utils/common-util';
 import {ChangeListViewState} from '../../../types/types';
+import {fireTitleChange} from '../../../utils/event-util';
 
 const LookupQueryPatterns = {
   CHANGE_ID: /^\s*i?[0-9a-f]{7,40}\s*$/i,
@@ -143,15 +144,7 @@
 
     // NOTE: This method may be called before attachment. Fire title-change
     // in an async so that attachment to the DOM can take place first.
-    this.async(() =>
-      this.dispatchEvent(
-        new CustomEvent('title-change', {
-          detail: {title: this._query},
-          composed: true,
-          bubbles: true,
-        })
-      )
-    );
+    this.async(() => fireTitleChange(this, this._query));
 
     this.$.restAPI
       .getPreferences()
diff --git a/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view.ts b/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view.ts
index 5f90169..ce3a811 100644
--- a/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view.ts
+++ b/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view.ts
@@ -58,7 +58,7 @@
 import {ChangeListToggleReviewedDetail} from '../gr-change-list-item/gr-change-list-item';
 import {ChangeStarToggleStarDetail} from '../../shared/gr-change-star/gr-change-star';
 import {DashboardViewState} from '../../../types/types';
-import {firePageError} from '../../../utils/event-util';
+import {firePageError, fireTitleChange} from '../../../utils/event-util';
 
 const PROJECT_PLACEHOLDER_PATTERN = /\$\{project\}/g;
 
@@ -150,7 +150,9 @@
     project: RepoName,
     dashboard: DashboardId
   ): Promise<UserDashboard | undefined> {
-    const errFn = (response?: Response | null) => firePageError(this, response);
+    const errFn = (response?: Response | null) => {
+      firePageError(this, response);
+    };
     return this.$.restAPI
       .getDashboard(project, dashboard, errFn)
       .then(response => {
@@ -221,13 +223,7 @@
     return dashboardPromise
       .then(res => {
         if (res && res.title) {
-          this.dispatchEvent(
-            new CustomEvent('title-change', {
-              detail: {title: res.title},
-              composed: true,
-              bubbles: true,
-            })
-          );
+          fireTitleChange(this, res.title);
         }
         return this._fetchDashboardChanges(res, checkForNewUser);
       })
@@ -236,15 +232,7 @@
         this.reporting.dashboardDisplayed();
       })
       .catch(err => {
-        this.dispatchEvent(
-          new CustomEvent('title-change', {
-            detail: {
-              title: title || this._computeTitle(user),
-            },
-            composed: true,
-            bubbles: true,
-          })
-        );
+        fireTitleChange(this, title || this._computeTitle(user));
         console.warn(err);
       })
       .then(() => {
diff --git a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.ts b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.ts
index f8a5940..6b04153 100644
--- a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.ts
@@ -76,6 +76,13 @@
 import {RestApiService} from '../../../services/services/gr-rest-api/gr-rest-api';
 import {GrEditableLabel} from '../../shared/gr-editable-label/gr-editable-label';
 import {GrLinkedChip} from '../../shared/gr-linked-chip/gr-linked-chip';
+import {appContext} from '../../../services/app-context';
+import {KnownExperimentId} from '../../../services/flags/flags';
+import {
+  Metadata,
+  isSectionSet,
+  DisplayRules,
+} from '../../../utils/change-metadata-util';
 
 const HASHTAG_ADD_MESSAGE = 'Add Hashtag';
 
@@ -194,6 +201,25 @@
   @property({type: Object})
   _CHANGE_ROLE = ChangeRole;
 
+  @property({type: Object})
+  _SECTION = Metadata;
+
+  @property({type: Boolean})
+  _showAllSections = false;
+
+  @property({type: Boolean})
+  _isNewChangeSummaryUiEnabled = false;
+
+  flagsService = appContext.flagsService;
+
+  /** @override */
+  ready() {
+    super.ready();
+    this._isNewChangeSummaryUiEnabled = this.flagsService.isEnabled(
+      KnownExperimentId.NEW_CHANGE_SUMMARY_UI
+    );
+  }
+
   @observe('change.labels')
   _labelsChanged(labels?: LabelNameToInfoMap) {
     this.labels = {...labels} || null;
@@ -566,6 +592,35 @@
     return this._getNonOwnerRole(change, role) ? '' : 'hideDisplay';
   }
 
+  _computeDisplayState(
+    showAllSections: boolean,
+    change: ParsedChangeInfo | undefined,
+    section: Metadata
+  ) {
+    if (
+      !this._isNewChangeSummaryUiEnabled ||
+      showAllSections ||
+      DisplayRules.ALWAYS_SHOW.includes(section) ||
+      (DisplayRules.SHOW_IF_SET.includes(section) &&
+        isSectionSet(section, change))
+    ) {
+      return '';
+    }
+    return 'hideDisplay';
+  }
+
+  _computeShowAllLabelText(showAllSections: boolean) {
+    if (showAllSections) {
+      return 'Show less';
+    } else {
+      return 'Show all';
+    }
+  }
+
+  _onShowAllClick() {
+    this._showAllSections = !this._showAllSections;
+  }
+
   /**
    * Get the user with the specified role on the change. Returns null if the
    * user with that role is the same as the owner.
diff --git a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata_html.ts b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata_html.ts
index f1d1127..88f7351 100644
--- a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata_html.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata_html.ts
@@ -94,9 +94,31 @@
       --account-max-length: 120px;
       max-width: 285px;
     }
+    .metadata-title {
+      font-weight: var(--font-weight-bold);
+      color: var(--deemphasized-text-color);
+      padding-left: var(--metadata-horizontal-padding);
+    }
+    .metadata-header {
+      display: flex;
+      justify-content: space-between;
+    }
   </style>
   <gr-external-style id="externalStyle" name="change-metadata">
-    <section>
+    <template is="dom-if" if="[[_isNewChangeSummaryUiEnabled]]">
+      <div class="metadata-header">
+        <h3 class="metadata-title">Change Info</h3>
+        <gr-button
+          class="show-all-button"
+          on-click="_onShowAllClick"
+          no-uppercase=""
+          >[[_computeShowAllLabelText(_showAllSections)]]</gr-button
+        >
+      </div>
+    </template>
+    <section
+      class$="[[_computeDisplayState(_showAllSections, change, _SECTION.UPDATED)]]"
+    >
       <span class="title">Updated</span>
       <span class="value">
         <gr-date-formatter
@@ -105,7 +127,9 @@
         ></gr-date-formatter>
       </span>
     </section>
-    <section>
+    <section
+      class$="[[_computeDisplayState(_showAllSections, change, _SECTION.OWNER)]]"
+    >
       <span class="title">Owner</span>
       <span class="value">
         <gr-account-chip
@@ -156,7 +180,9 @@
       </span>
     </section>
     <template is="dom-if" if="[[_isAssigneeEnabled(serverConfig)]]">
-      <section class="assignee">
+      <section
+        class$="assignee [[_computeDisplayState(_showAllSections, change, _SECTION.ASSIGNEE)]]"
+      >
         <span class="title">Assignee</span>
         <span class="value">
           <gr-account-list
@@ -172,7 +198,9 @@
         </span>
       </section>
     </template>
-    <section>
+    <section
+      class$="[[_computeDisplayState(_showAllSections, change, _SECTION.REVIEWERS)]]"
+    >
       <span class="title">Reviewers</span>
       <span class="value">
         <gr-reviewer-list
@@ -183,7 +211,9 @@
         ></gr-reviewer-list>
       </span>
     </section>
-    <section>
+    <section
+      class$="[[_computeDisplayState(_showAllSections, change, _SECTION.CC)]]"
+    >
       <span class="title">CC</span>
       <span class="value">
         <gr-reviewer-list
@@ -198,7 +228,9 @@
       is="dom-if"
       if="[[_computeShowRepoBranchTogether(change.project, change.branch)]]"
     >
-      <section>
+      <section
+        class$="[[_computeDisplayState(_showAllSections, change, _SECTION.REPO_BRANCH)]]"
+      >
         <span class="title">Repo | Branch</span>
         <span class="value">
           <a href$="[[_computeProjectUrl(change.project)]]"
@@ -215,7 +247,9 @@
       is="dom-if"
       if="[[!_computeShowRepoBranchTogether(change.project, change.branch)]]"
     >
-      <section>
+      <section
+        class$="[[_computeDisplayState(_showAllSections, change, _SECTION.REPO_BRANCH)]]"
+      >
         <span class="title">Repo</span>
         <span class="value">
           <a href$="[[_computeProjectUrl(change.project)]]">
@@ -226,7 +260,9 @@
           </a>
         </span>
       </section>
-      <section>
+      <section
+        class$="[[_computeDisplayState(_showAllSections, change, _SECTION.REPO_BRANCH)]]"
+      >
         <span class="title">Branch</span>
         <span class="value">
           <a href$="[[_computeBranchUrl(change.project, change.branch)]]">
@@ -238,7 +274,9 @@
         </span>
       </section>
     </template>
-    <section>
+    <section
+      class$="[[_computeDisplayState(_showAllSections, change, _SECTION.PARENT)]]"
+    >
       <span class="title">[[_computeParentsLabel(_currentParents)]]</span>
       <span class="value">
         <ol
@@ -262,7 +300,9 @@
         </ol>
       </span>
     </section>
-    <section class="topic">
+    <section
+      class$="topic [[_computeDisplayState(_showAllSections, change, _SECTION.TOPIC)]]"
+    >
       <span class="title">Topic</span>
       <span class="value">
         <template is="dom-if" if="[[_showTopicChip(change.*, _settingTopic)]]">
@@ -288,7 +328,9 @@
       </span>
     </section>
     <template is="dom-if" if="[[_showCherryPickOf(change.*)]]">
-      <section>
+      <section
+        class$="[[_computeDisplayState(_showAllSections, change, _SECTION.CHERRY_PICK_OF)]]"
+      >
         <span class="title">Cherry pick of</span>
         <span class="value">
           <a
@@ -304,14 +346,16 @@
       </section>
     </template>
     <section
-      class="strategy"
+      class$="strategy [[_computeDisplayState(_showAllSections, change, _SECTION.STRATEGY)]]"
       hidden$="[[_computeHideStrategy(change)]]"
       hidden=""
     >
       <span class="title">Strategy</span>
       <span class="value">[[_computeStrategy(change)]]</span>
     </section>
-    <section class="hashtag">
+    <section
+      class$="hashtag [[_computeDisplayState(_showAllSections, change, _SECTION.HASHTAGS)]]"
+    >
       <span class="title">Hashtags</span>
       <span class="value">
         <template is="dom-repeat" items="[[change.hashtags]]">
diff --git a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts
index c763aef..24841fc 100644
--- a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts
@@ -146,7 +146,6 @@
   CustomKeyboardEvent,
   EditableContentSaveEvent,
   OpenFixPreviewEvent,
-  ShowAlertEventDetail,
   SwitchTabEvent,
 } from '../../../types/events';
 import {GrButton} from '../../shared/gr-button/gr-button';
@@ -155,6 +154,7 @@
 import {PORTING_COMMENTS_CHANGE_LATENCY_LABEL} from '../../../services/gr-reporting/gr-reporting';
 import {fireAlert, firePageError} from '../../../utils/event-util';
 import {KnownExperimentId} from '../../../services/flags/flags';
+import {fireTitleChange} from '../../../utils/event-util';
 
 const CHANGE_ID_ERROR = {
   MISMATCH: 'mismatch',
@@ -1489,13 +1489,7 @@
     this.set('_patchRange.basePatchNum', parent);
 
     const title = change.subject + ' (' + change.change_id.substr(0, 9) + ')';
-    this.dispatchEvent(
-      new CustomEvent('title-change', {
-        detail: {title},
-        composed: true,
-        bubbles: true,
-      })
-    );
+    fireTitleChange(this, title);
   }
 
   /**
@@ -1698,16 +1692,7 @@
       throw new Error('missing required _patchRange property');
     const latestPatchNum = computeLatestPatchNum(this._allPatchSets);
     if (patchNumEquals(this._patchRange.patchNum, latestPatchNum)) {
-      const detail: ShowAlertEventDetail = {
-        message: 'Latest is already selected.',
-      };
-      this.dispatchEvent(
-        new CustomEvent('show-alert', {
-          detail,
-          composed: true,
-          bubbles: true,
-        })
-      );
+      fireAlert(this, 'Latest is already selected.');
       return;
     }
     GerritNav.navigateToChange(
diff --git a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts
index 108f9ed..7759b7b 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts
+++ b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts
@@ -1558,7 +1558,7 @@
             'changeComments, patchRange and diffPrefs must be set'
           );
         }
-        diffElem.comments = this.changeComments.getCommentsBySideForFile(
+        diffElem.threads = this.changeComments.getThreadsBySideForFile(
           file,
           this.patchRange,
           this.projectConfig
diff --git a/polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager.ts b/polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager.ts
index 7a56d1c..4f3d7ce6 100644
--- a/polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager.ts
+++ b/polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager.ts
@@ -39,6 +39,7 @@
 import {FetchRequest} from '../../shared/gr-rest-api-interface/gr-rest-apis/gr-rest-api-helper';
 import {ErrorType, FixIronA11yAnnouncer} from '../../../types/types';
 import {AccountId} from '../../../types/common';
+import {EventType} from '../../../utils/event-util';
 
 const HIDE_ALERT_TIMEOUT_MS = 5000;
 const CHECK_SIGN_IN_INTERVAL_MS = 60 * 1000;
@@ -129,7 +130,7 @@
     super.attached();
     this.listen(document, 'server-error', '_handleServerError');
     this.listen(document, 'network-error', '_handleNetworkError');
-    this.listen(document, 'show-alert', '_handleShowAlert');
+    this.listen(document, EventType.SHOW_ALERT, '_handleShowAlert');
     this.listen(document, 'hide-alert', '_hideAlert');
     this.listen(document, 'show-error', '_handleShowErrorDialog');
     this.listen(document, 'visibilitychange', '_handleVisibilityChange');
@@ -151,7 +152,7 @@
     this._clearHideAlertHandle();
     this.unlisten(document, 'server-error', '_handleServerError');
     this.unlisten(document, 'network-error', '_handleNetworkError');
-    this.unlisten(document, 'show-alert', '_handleShowAlert');
+    this.unlisten(document, EventType.SHOW_ALERT, '_handleShowAlert');
     this.unlisten(document, 'hide-alert', '_hideAlert');
     this.unlisten(document, 'show-error', '_handleShowErrorDialog');
     this.unlisten(document, 'visibilitychange', '_handleVisibilityChange');
diff --git a/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api.ts b/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api.ts
index b01a110..683d887 100644
--- a/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api.ts
+++ b/polygerrit-ui/app/elements/diff/gr-comment-api/gr-comment-api.ts
@@ -38,7 +38,7 @@
   RevisionId,
 } from '../../../types/common';
 import {hasOwnProperty} from '../../../utils/common-util';
-import {CommentSide} from '../../../constants/constants';
+import {CommentSide, Side} from '../../../constants/constants';
 import {RestApiService} from '../../../services/services/gr-rest-api/gr-rest-api';
 import {
   Comment,
@@ -313,6 +313,30 @@
     return allDrafts;
   }
 
+  _addCommentSide(comments: TwoSidesComments) {
+    const allComments = [];
+    for (const side of [Side.LEFT, Side.RIGHT]) {
+      // This is needed by the threading.
+      for (const comment of comments[side]) {
+        comment.__commentSide = side;
+      }
+      allComments.push(...comments[side]);
+    }
+    return allComments;
+  }
+
+  getThreadsBySideForPath(
+    path: string,
+    patchRange: PatchRange,
+    projectConfig?: ConfigInfo
+  ): CommentThread[] {
+    return createCommentThreads(
+      this._addCommentSide(
+        this.getCommentsBySideForPath(path, patchRange, projectConfig)
+      )
+    );
+  }
+
   /**
    * Get the comments (with drafts and robot comments) for a path and
    * patch-range. Returns an object with left and right properties mapping to
@@ -371,6 +395,18 @@
     };
   }
 
+  getThreadsBySideForFile(
+    file: PatchSetFile,
+    patchRange: PatchRange,
+    projectConfig?: ConfigInfo
+  ): CommentThread[] {
+    return createCommentThreads(
+      this._addCommentSide(
+        this.getCommentsBySideForFile(file, patchRange, projectConfig)
+      )
+    );
+  }
+
   /**
    * Get the comments (with drafts and robot comments) for a file and
    * patch-range. Returns an object with left and right properties mapping to
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor.ts b/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor.ts
index 684a58a..43ed77f 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor.ts
@@ -226,9 +226,10 @@
             bubbles: true,
           })
         );
+      } else {
+        this.lastDisplayedNavigateToNextFileToast = Date.now();
+        fireAlert(this, 'Press n again to navigate to next unreviewed file');
       }
-      this.lastDisplayedNavigateToNextFileToast = Date.now();
-      fireAlert(this, 'Press n again to navigate to next unreviewed file');
     }
 
     this._fixSide();
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.ts b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.ts
index 8c08084..4b4f429 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.ts
@@ -31,14 +31,7 @@
   isMergeParent,
   isNumber,
 } from '../../../utils/patch-set-util';
-import {
-  Comment,
-  isDraft,
-  UIComment,
-  CommentThread,
-  createCommentThreads,
-} from '../../../utils/comment-util';
-import {TwoSidesComments} from '../gr-comment-api/gr-comment-api';
+import {CommentThread} from '../../../utils/comment-util';
 import {customElement, observe, property} from '@polymer/decorators';
 import {
   CommitRange,
@@ -198,8 +191,8 @@
   @property({type: Boolean})
   noRenderOnPrefsChange = false;
 
-  @property({type: Object, observer: '_commentsChanged'})
-  comments?: TwoSidesComments;
+  @property({type: Object, observer: '_threadsChanged'})
+  threads?: CommentThread[];
 
   @property({type: Boolean})
   lineWrapping = false;
@@ -276,11 +269,12 @@
       'create-comment',
       e => this._handleCreateComment(e)
     );
-    this.addEventListener('comment-discard', e =>
-      this._handleCommentDiscard(e)
+    this.addEventListener('comment-discard', () =>
+      this._handleCommentSaveOrDiscard()
     );
-    this.addEventListener('comment-update', e => this._handleCommentUpdate(e));
-    this.addEventListener('comment-save', e => this._handleCommentSave(e));
+    this.addEventListener('comment-save', () =>
+      this._handleCommentSaveOrDiscard()
+    );
     this.addEventListener('render-start', () => this._handleRenderStart());
     this.addEventListener('render-content', () => this._handleRenderContent());
     this.addEventListener('normalize-range', event =>
@@ -679,21 +673,12 @@
     return isImageDiff(diff);
   }
 
-  _commentsChanged(newComments: TwoSidesComments) {
-    const allComments = [];
-    for (const side of [Side.LEFT, Side.RIGHT]) {
-      // This is needed by the threading.
-      for (const comment of newComments[side]) {
-        comment.__commentSide = side;
-      }
-      allComments.push(...newComments[side]);
-    }
+  _threadsChanged(threads: CommentThread[]) {
     // Currently, the only way this is ever changed here is when the initial
-    // comments are loaded, so it's okay performance wise to clear the threads
+    // threads are loaded, so it's okay performance wise to clear the threads
     // and recreate them. If this changes in future, we might want to reuse
     // some DOM nodes here.
     this._clearThreads();
-    const threads = createCommentThreads(allComments);
     for (const thread of threads) {
       const threadEl = this._createThreadElement(thread);
       this._attachThreadElement(threadEl);
@@ -932,79 +917,12 @@
       : null;
   }
 
-  _handleCommentSave(e: CustomEvent) {
-    const comment = e.detail.comment;
-    const side = e.detail.comment.__commentSide;
-    const idx = this._findDraftIndex(comment, side);
-    this.set(['comments', side, idx], comment);
-    this._handleCommentSaveOrDiscard();
-  }
-
-  _handleCommentDiscard(e: CustomEvent) {
-    const comment = e.detail.comment;
-    this._removeComment(comment);
-    this._handleCommentSaveOrDiscard();
-  }
-
-  _handleCommentUpdate(e: CustomEvent) {
-    const comment = e.detail.comment;
-    const side = e.detail.comment.__commentSide;
-    let idx = this._findCommentIndex(comment, side);
-    if (idx === -1) {
-      idx = this._findDraftIndex(comment, side);
-    }
-    if (idx !== -1) {
-      // Update draft or comment.
-      this.set(['comments', side, idx], comment);
-    } else {
-      // Create new draft.
-      this.push(['comments', side], comment);
-    }
-  }
-
   _handleCommentSaveOrDiscard() {
     this.dispatchEvent(
       new CustomEvent('diff-comments-modified', {bubbles: true, composed: true})
     );
   }
 
-  _removeComment(comment: UIComment) {
-    const side = comment.__commentSide;
-    if (!side) throw new Error('Missing required "side" in comment.');
-    this._removeCommentFromSide(comment, side);
-  }
-
-  _removeCommentFromSide(comment: Comment, side: Side) {
-    let idx = this._findCommentIndex(comment, side);
-    if (idx === -1) {
-      idx = this._findDraftIndex(comment, side);
-    }
-    if (idx !== -1) {
-      this.splice('comments.' + side, idx, 1);
-    }
-  }
-
-  _findCommentIndex(comment: Comment, side: Side) {
-    if (!comment.id || !this.comments || !this.comments[side]) {
-      return -1;
-    }
-    return this.comments[side].findIndex(item => item.id === comment.id);
-  }
-
-  _findDraftIndex(comment: Comment, side: Side) {
-    if (
-      !isDraft(comment) ||
-      !comment.__draftID ||
-      !this.comments ||
-      !this.comments[side]
-    ) {
-      return -1;
-    }
-    return this.comments[side].findIndex(
-      item => isDraft(item) && item.__draftID === comment.__draftID
-    );
-  }
-
   _isSyntaxHighlightingEnabled(
     preferenceChangeRecord?: PolymerDeepPropertyChange<
       DiffPreferencesInfo,
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js
index bf4d912..402cb52 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js
@@ -62,198 +62,6 @@
     });
   });
 
-  suite('handle comment-update', () => {
-    setup(() => {
-      sinon.stub(element, '_commentsChanged');
-      element.comments = {
-        meta: {
-          changeNum: '42',
-          patchRange: {
-            basePatchNum: 'PARENT',
-            patchNum: 3,
-          },
-          path: '/path/to/foo',
-          projectConfig: {foo: 'bar'},
-        },
-        left: [
-          {id: 'bc1', side: 'PARENT', __commentSide: 'left'},
-          {id: 'bc2', side: 'PARENT', __commentSide: 'left'},
-          {id: 'bd1', __draft: true, side: 'PARENT', __commentSide: 'left'},
-          {id: 'bd2', __draft: true, side: 'PARENT', __commentSide: 'left'},
-        ],
-        right: [
-          {id: 'c1', __commentSide: 'right'},
-          {id: 'c2', __commentSide: 'right'},
-          {id: 'd1', __draft: true, __commentSide: 'right'},
-          {id: 'd2', __draft: true, __commentSide: 'right'},
-        ],
-      };
-    });
-
-    test('creating a draft', () => {
-      const comment = {__draft: true, __draftID: 'tempID', side: 'PARENT',
-        __commentSide: 'left'};
-      element.dispatchEvent(
-          new CustomEvent('comment-update', {
-            detail: {comment},
-            composed: true, bubbles: true,
-          }));
-      assert.include(element.comments.left, comment);
-    });
-
-    test('discarding a draft', () => {
-      const draftID = 'tempID';
-      const id = 'savedID';
-      const comment = {
-        __draft: true,
-        __draftID: draftID,
-        side: 'PARENT',
-        __commentSide: 'left',
-      };
-      const diffCommentsModifiedStub = sinon.stub();
-      element.addEventListener('diff-comments-modified',
-          diffCommentsModifiedStub);
-      element.comments.left.push(comment);
-      comment.id = id;
-      element.dispatchEvent(
-          new CustomEvent('comment-discard', {
-            detail: {comment},
-            composed: true, bubbles: true,
-          }));
-      const drafts = element.comments.left
-          .filter(item => item.__draftID === draftID);
-      assert.equal(drafts.length, 0);
-      assert.isTrue(diffCommentsModifiedStub.called);
-    });
-
-    test('saving a draft', () => {
-      const draftID = 'tempID';
-      const id = 'savedID';
-      const comment = {
-        __draft: true,
-        __draftID: draftID,
-        side: 'PARENT',
-        __commentSide: 'left',
-      };
-      const diffCommentsModifiedStub = sinon.stub();
-      element.addEventListener('diff-comments-modified',
-          diffCommentsModifiedStub);
-      element.comments.left.push(comment);
-      comment.id = id;
-      element.dispatchEvent(
-          new CustomEvent('comment-save', {
-            detail: {comment},
-            composed: true, bubbles: true,
-          }));
-      const drafts = element.comments.left
-          .filter(item => item.__draftID === draftID);
-      assert.equal(drafts.length, 1);
-      assert.equal(drafts[0].id, id);
-      assert.isTrue(diffCommentsModifiedStub.called);
-    });
-  });
-
-  test('remove comment', () => {
-    sinon.stub(element, '_commentsChanged');
-    element.comments = {
-      meta: {
-        changeNum: '42',
-        patchRange: {
-          basePatchNum: 'PARENT',
-          patchNum: 3,
-        },
-        path: '/path/to/foo',
-        projectConfig: {foo: 'bar'},
-      },
-      left: [
-        {id: 'bc1', side: 'PARENT', __commentSide: 'left'},
-        {id: 'bc2', side: 'PARENT', __commentSide: 'left'},
-        {id: 'bd1', __draft: true, side: 'PARENT', __commentSide: 'left'},
-        {id: 'bd2', __draft: true, side: 'PARENT', __commentSide: 'left'},
-      ],
-      right: [
-        {id: 'c1', __commentSide: 'right'},
-        {id: 'c2', __commentSide: 'right'},
-        {id: 'd1', __draft: true, __commentSide: 'right'},
-        {id: 'd2', __draft: true, __commentSide: 'right'},
-      ],
-    };
-
-    // Using JSON.stringify because Safari 9.1 (11601.5.17.1) doesn’t seem
-    // to believe that one object deepEquals another even when they do :-/.
-    assert.equal(JSON.stringify(element.comments), JSON.stringify({
-      meta: {
-        changeNum: '42',
-        patchRange: {
-          basePatchNum: 'PARENT',
-          patchNum: 3,
-        },
-        path: '/path/to/foo',
-        projectConfig: {foo: 'bar'},
-      },
-      left: [
-        {id: 'bc1', side: 'PARENT', __commentSide: 'left'},
-        {id: 'bc2', side: 'PARENT', __commentSide: 'left'},
-        {id: 'bd1', __draft: true, side: 'PARENT', __commentSide: 'left'},
-        {id: 'bd2', __draft: true, side: 'PARENT', __commentSide: 'left'},
-      ],
-      right: [
-        {id: 'c1', __commentSide: 'right'},
-        {id: 'c2', __commentSide: 'right'},
-        {id: 'd1', __draft: true, __commentSide: 'right'},
-        {id: 'd2', __draft: true, __commentSide: 'right'},
-      ],
-    }));
-
-    element._removeComment({id: 'bc2', side: 'PARENT',
-      __commentSide: 'left'});
-    assert.deepEqual(element.comments, {
-      meta: {
-        changeNum: '42',
-        patchRange: {
-          basePatchNum: 'PARENT',
-          patchNum: 3,
-        },
-        path: '/path/to/foo',
-        projectConfig: {foo: 'bar'},
-      },
-      left: [
-        {id: 'bc1', side: 'PARENT', __commentSide: 'left'},
-        {id: 'bd1', __draft: true, side: 'PARENT', __commentSide: 'left'},
-        {id: 'bd2', __draft: true, side: 'PARENT', __commentSide: 'left'},
-      ],
-      right: [
-        {id: 'c1', __commentSide: 'right'},
-        {id: 'c2', __commentSide: 'right'},
-        {id: 'd1', __draft: true, __commentSide: 'right'},
-        {id: 'd2', __draft: true, __commentSide: 'right'},
-      ],
-    });
-
-    element._removeComment({id: 'd2', __commentSide: 'right'});
-    assert.deepEqual(element.comments, {
-      meta: {
-        changeNum: '42',
-        patchRange: {
-          basePatchNum: 'PARENT',
-          patchNum: 3,
-        },
-        path: '/path/to/foo',
-        projectConfig: {foo: 'bar'},
-      },
-      left: [
-        {id: 'bc1', side: 'PARENT', __commentSide: 'left'},
-        {id: 'bd1', __draft: true, side: 'PARENT', __commentSide: 'left'},
-        {id: 'bd2', __draft: true, side: 'PARENT', __commentSide: 'left'},
-      ],
-      right: [
-        {id: 'c1', __commentSide: 'right'},
-        {id: 'c2', __commentSide: 'right'},
-        {id: 'd1', __draft: true, __commentSide: 'right'},
-      ],
-    });
-  });
-
   test('thread-discard handling', () => {
     const threads = createCommentThreads([
       {
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts
index e1780f8..bb0ed61 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts
@@ -65,11 +65,7 @@
   GrDropdownList,
 } from '../../shared/gr-dropdown-list/gr-dropdown-list';
 import {GrOverlay} from '../../shared/gr-overlay/gr-overlay';
-import {
-  ChangeComments,
-  GrCommentApi,
-  TwoSidesComments,
-} from '../gr-comment-api/gr-comment-api';
+import {ChangeComments, GrCommentApi} from '../gr-comment-api/gr-comment-api';
 import {GrDiffModeSelector} from '../gr-diff-mode-selector/gr-diff-mode-selector';
 import {
   ChangeInfo,
@@ -101,7 +97,7 @@
 import {AppElementParams} from '../../gr-app-types';
 import {CustomKeyboardEvent, OpenFixPreviewEvent} from '../../../types/events';
 import {PORTING_COMMENTS_DIFF_LATENCY_LABEL} from '../../../services/gr-reporting/gr-reporting';
-import {fireAlert} from '../../../utils/event-util';
+import {fireAlert, fireTitleChange} from '../../../utils/event-util';
 
 const ERR_REVIEW_STATUS = 'Couldn’t change file review status.';
 const MSG_LOADING_BLAME = 'Loading blame...';
@@ -240,9 +236,6 @@
   @property({type: Object})
   _commentMap?: CommentMap;
 
-  @property({type: Object})
-  _commentsForDiff?: TwoSidesComments;
-
   @property({
     type: Object,
     computed: '_computeCommentSkips(_commentMap, _fileList, _path)',
@@ -1013,12 +1006,6 @@
     }
 
     this._commentMap = this._getPaths(this._patchRange);
-
-    this._commentsForDiff = this._getCommentsForPath(
-      this._path,
-      this._patchRange,
-      this._projectConfig
-    );
   }
 
   _isFileUnchanged(diff: DiffInfo) {
@@ -1087,7 +1074,13 @@
         this._loading = false;
         this._initPatchRange();
         this._initCommitRange();
-        this.$.diffHost.comments = this._commentsForDiff;
+        if (this._changeComments && this._path && this._patchRange) {
+          this.$.diffHost.threads = this._changeComments.getThreadsBySideForPath(
+            this._path,
+            this._patchRange,
+            this._projectConfig
+          );
+        }
         portedCommentsPromise.then(() => {
           this.reporting.timeEnd(PORTING_COMMENTS_DIFF_LATENCY_LABEL);
         });
@@ -1223,13 +1216,7 @@
 
   _pathChanged(path: string) {
     if (path) {
-      this.dispatchEvent(
-        new CustomEvent('title-change', {
-          detail: {title: computeTruncatedPath(path)},
-          composed: true,
-          bubbles: true,
-        })
-      );
+      fireTitleChange(this, computeTruncatedPath(path));
     }
 
     if (!this._fileList || this._fileList.length === 0) return;
@@ -1581,13 +1568,11 @@
 
     const file = files[path];
     if (file && file.old_path) {
-      this._commentsForDiff = this._changeComments.getCommentsBySideForFile(
+      this.$.diffHost.threads = this._changeComments.getThreadsBySideForFile(
         {path, basePath: file.old_path},
         patchRange,
         projectConfig
       );
-
-      this.$.diffHost.comments = this._commentsForDiff;
     }
   }
 
@@ -1596,22 +1581,6 @@
     return this._changeComments.getPaths(patchRange);
   }
 
-  _getCommentsForPath(
-    path?: string,
-    patchRange?: PatchRange,
-    projectConfig?: ConfigInfo
-  ) {
-    if (!path) return undefined;
-    if (!patchRange) return undefined;
-    if (!this._changeComments) return undefined;
-
-    return this._changeComments.getCommentsBySideForPath(
-      path,
-      patchRange,
-      projectConfig
-    );
-  }
-
   _getDiffDrafts() {
     if (!this._changeNum) throw new Error('Missing this._changeNum');
 
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_test.js b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_test.js
index 7ef75ed..8e1e5c1 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_test.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_test.js
@@ -151,8 +151,10 @@
         computeCommentThreadCount: () => {},
         computeUnresolvedNum: () => {},
         getPaths: () => {},
-        getCommentsBySideForPath: () => {},
+        getThreadsBySideForPath: () => {},
+        getThreadsBySideForFile: () => {},
         findCommentById: _testOnly_findCommentById,
+
       }));
       await element._loadComments();
       await flush();
@@ -200,11 +202,6 @@
         commentLink: true,
         commentId: 'c1',
       };
-      sinon.stub(element.$.diffHost, '_commentsChanged');
-      sinon.stub(element, '_getCommentsForPath').returns({
-        left: [{id: 'c1', __commentSide: 'left', line: 10}],
-        right: [{id: 'c2', __commentSide: 'right', line: 11}],
-      });
       element._change = {
         ...createChange(),
         revisions: createRevisions(11),
@@ -263,7 +260,6 @@
             commentLink: true,
             commentId: 'c1',
           };
-          sinon.stub(element.$.diffHost, '_commentsChanged');
           element._change = {
             ...createChange(),
             revisions: createRevisions(11),
@@ -293,7 +289,6 @@
             commentLink: true,
             commentId: 'c3',
           };
-          sinon.stub(element.$.diffHost, '_commentsChanged');
           element._change = {
             ...createChange(),
             revisions: createRevisions(11),
@@ -1455,7 +1450,6 @@
         await flush();
       });
       test('empty', () => {
-        sinon.stub(element, '_getCommentsForPath');
         sinon.stub(element, '_getPaths').returns(new Map());
         element._initPatchRange();
         assert.equal(Object.keys(element._commentMap).length, 0);
@@ -1467,7 +1461,6 @@
           'path/to/file/one.cpp': [{patch_set: 3, message: 'lorem'}],
           'path-to/file/two.py': [{patch_set: 5, message: 'ipsum'}],
         });
-        sinon.stub(element, '_getCommentsForPath').returns({meta: {}});
         element._changeNum = '42';
         element._patchRange = {
           basePatchNum: 3,
diff --git a/polygerrit-ui/app/elements/documentation/gr-documentation-search/gr-documentation-search.ts b/polygerrit-ui/app/elements/documentation/gr-documentation-search/gr-documentation-search.ts
index 5967b03..79c4359 100644
--- a/polygerrit-ui/app/elements/documentation/gr-documentation-search/gr-documentation-search.ts
+++ b/polygerrit-ui/app/elements/documentation/gr-documentation-search/gr-documentation-search.ts
@@ -30,6 +30,7 @@
 import {customElement, property} from '@polymer/decorators';
 import {RestApiService} from '../../../services/services/gr-rest-api/gr-rest-api';
 import {DocResult} from '../../../types/common';
+import {fireTitleChange} from '../../../utils/event-util';
 
 export interface GrDocumentationSearch {
   $: {
@@ -62,9 +63,7 @@
   /** @override */
   attached() {
     super.attached();
-    this.dispatchEvent(
-      new CustomEvent('title-change', {detail: {title: 'Documentation Search'}})
-    );
+    fireTitleChange(this, 'Documentation Search');
   }
 
   _paramsChanged(params: ListViewParams) {
diff --git a/polygerrit-ui/app/elements/edit/gr-editor-view/gr-editor-view.ts b/polygerrit-ui/app/elements/edit/gr-editor-view/gr-editor-view.ts
index 5863ee3..60944d0 100644
--- a/polygerrit-ui/app/elements/edit/gr-editor-view/gr-editor-view.ts
+++ b/polygerrit-ui/app/elements/edit/gr-editor-view/gr-editor-view.ts
@@ -47,7 +47,7 @@
 } from '../../../types/common';
 import {GrStorage} from '../../shared/gr-storage/gr-storage';
 import {HttpMethod, NotifyType} from '../../../constants/constants';
-import {fireAlert} from '../../../utils/event-util';
+import {fireAlert, fireTitleChange} from '../../../utils/event-util';
 
 const RESTORED_MESSAGE = 'Content restored from a previous edit.';
 const SAVING_MESSAGE = 'Saving changes...';
@@ -177,13 +177,7 @@
     // has been queued, the event can bubble up to the handler in gr-app.
     this.async(() => {
       const title = `Editing ${computeTruncatedPath(value.path)}`;
-      this.dispatchEvent(
-        new CustomEvent('title-change', {
-          detail: {title},
-          composed: true,
-          bubbles: true,
-        })
-      );
+      fireTitleChange(this, title);
     });
 
     const promises = [];
diff --git a/polygerrit-ui/app/elements/gr-app-element.ts b/polygerrit-ui/app/elements/gr-app-element.ts
index c2fb124..2915acd 100644
--- a/polygerrit-ui/app/elements/gr-app-element.ts
+++ b/polygerrit-ui/app/elements/gr-app-element.ts
@@ -79,6 +79,7 @@
   TitleChangeEventDetail,
 } from '../types/events';
 import {ViewState} from '../types/types';
+import {EventType} from '../utils/event-util';
 
 interface ErrorInfo {
   text: string;
@@ -209,8 +210,12 @@
   created() {
     super.created();
     this._bindKeyboardShortcuts();
-    this.addEventListener('page-error', e => this._handlePageError(e));
-    this.addEventListener('title-change', e => this._handleTitleChange(e));
+    this.addEventListener(EventType.PAGE_ERROR, e => {
+      this._handlePageError(e);
+    });
+    this.addEventListener(EventType.TITLE_CHANGE, e => {
+      this._handleTitleChange(e);
+    });
     this.addEventListener('location-change', e =>
       this._handleLocationChange(e)
     );
diff --git a/polygerrit-ui/app/elements/settings/gr-cla-view/gr-cla-view.ts b/polygerrit-ui/app/elements/settings/gr-cla-view/gr-cla-view.ts
index 092c5de..891fdf6 100644
--- a/polygerrit-ui/app/elements/settings/gr-cla-view/gr-cla-view.ts
+++ b/polygerrit-ui/app/elements/settings/gr-cla-view/gr-cla-view.ts
@@ -32,7 +32,7 @@
   GroupInfo,
   ContributorAgreementInfo,
 } from '../../../types/common';
-import {fireAlert} from '../../../utils/event-util';
+import {fireAlert, fireTitleChange} from '../../../utils/event-util';
 
 export interface GrClaView {
   $: {
@@ -80,13 +80,7 @@
     super.attached();
     this.loadData();
 
-    this.dispatchEvent(
-      new CustomEvent('title-change', {
-        detail: {title: 'New Contributor Agreement'},
-        composed: true,
-        bubbles: true,
-      })
-    );
+    fireTitleChange(this, 'New Contributor Agreement');
   }
 
   loadData() {
diff --git a/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view.ts b/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view.ts
index 84bdf78..4293a83 100644
--- a/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view.ts
+++ b/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view.ts
@@ -68,7 +68,7 @@
 import {GerritView} from '../../core/gr-navigation/gr-navigation';
 import {GrEmailEditor} from '../gr-email-editor/gr-email-editor';
 import {CustomKeyboardEvent} from '../../../types/events';
-import {fireAlert} from '../../../utils/event-util';
+import {fireAlert, fireTitleChange} from '../../../utils/event-util';
 
 const PREFS_SECTION_FIELDS: Array<keyof PreferencesInput> = [
   'changes_per_page',
@@ -220,13 +220,7 @@
     // Polymer 2: anchor tag won't work on shadow DOM
     // we need to manually calling scrollIntoView when hash changed
     this.listen(window, 'location-change', '_handleLocationChange');
-    this.dispatchEvent(
-      new CustomEvent('title-change', {
-        detail: {title: 'Settings'},
-        composed: true,
-        bubbles: true,
-      })
-    );
+    fireTitleChange(this, 'Settings');
 
     this._isDark = !!window.localStorage.getItem('dark-theme');
 
diff --git a/polygerrit-ui/app/elements/shared/gr-textarea/gr-textarea.ts b/polygerrit-ui/app/elements/shared/gr-textarea/gr-textarea.ts
index b3c0a85..b0b40dd 100644
--- a/polygerrit-ui/app/elements/shared/gr-textarea/gr-textarea.ts
+++ b/polygerrit-ui/app/elements/shared/gr-textarea/gr-textarea.ts
@@ -38,32 +38,23 @@
   {value: '😊', match: 'smile :)'},
   {value: '👍', match: 'thumbs up'},
   {value: '😄', match: 'laugh :D'},
-  {value: '🎉', match: 'party'},
-  {value: '😞', match: 'sad :('},
+  {value: '❤️', match: 'heart <3'},
   {value: '😂', match: "tears :')"},
-  {value: '🙏', match: 'pray'},
+  {value: '🎉', match: 'party'},
+  {value: '😎', match: 'cool |;)'},
+  {value: '😞', match: 'sad :('},
   {value: '😐', match: 'neutral :|'},
   {value: '😮', match: 'shock :O'},
-  {value: '👎', match: 'thumbs down'},
-  {value: '😎', match: 'cool |;)'},
+  {value: '🙏', match: 'pray'},
   {value: '😕', match: 'confused'},
   {value: '👌', match: 'ok'},
   {value: '🔥', match: 'fire'},
-  {value: '👊', match: 'fistbump'},
   {value: '💯', match: '100'},
-  {value: '💔', match: 'broken heart'},
-  {value: '🍺', match: 'beer'},
   {value: '✔', match: 'check'},
   {value: '😋', match: 'tongue'},
   {value: '😭', match: "crying :'("},
-  {value: '🐨', match: 'koala'},
   {value: '🤓', match: 'glasses'},
-  {value: '😆', match: 'grin'},
-  {value: '💩', match: 'poop'},
   {value: '😢', match: 'tear'},
-  {value: '😒', match: 'unamused'},
-  {value: '😉', match: 'wink ;)'},
-  {value: '🍷', match: 'wine'},
   {value: '😜', match: 'winking tongue ;)'},
 ];
 
diff --git a/polygerrit-ui/app/services/flags/flags.ts b/polygerrit-ui/app/services/flags/flags.ts
index e40412d..ba33954 100644
--- a/polygerrit-ui/app/services/flags/flags.ts
+++ b/polygerrit-ui/app/services/flags/flags.ts
@@ -27,4 +27,5 @@
   PATCHSET_COMMENTS = 'UiFeature__patchset_comments',
   NEW_CONTEXT_CONTROLS = 'UiFeature__new_context_controls',
   CI_REBOOT_CHECKS = 'UiFeature__ci_reboot_checks',
+  NEW_CHANGE_SUMMARY_UI = 'UiFeature__new_change_summary_ui',
 }
diff --git a/polygerrit-ui/app/utils/change-metadata-util.ts b/polygerrit-ui/app/utils/change-metadata-util.ts
new file mode 100644
index 0000000..6ce1483
--- /dev/null
+++ b/polygerrit-ui/app/utils/change-metadata-util.ts
@@ -0,0 +1,75 @@
+/**
+ * @license
+ * 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.
+ */
+
+import {ParsedChangeInfo} from '../elements/shared/gr-rest-api-interface/gr-reviewer-updates-parser';
+
+export enum Metadata {
+  OWNER = 'Owner',
+  REVIEWERS = 'Reviewers',
+  REPO_BRANCH = 'Repo | Branch',
+  SUBMITTED = 'Submitted',
+  PARENT = 'Parent',
+  STRATEGY = 'Strategy',
+  UPDATED = 'Updated',
+  CC = 'CC',
+  HASHTAGS = 'Hashtags',
+  TOPIC = 'Topic',
+  UPLOADER = 'Uploader',
+  AUTHOR = 'Author',
+  COMMITTER = 'Committer',
+  ASSIGNEE = 'Assignee',
+  CHERRY_PICK_OF = 'Cherry pick of',
+}
+
+export const DisplayRules = {
+  ALWAYS_SHOW: [
+    Metadata.OWNER,
+    Metadata.REVIEWERS,
+    Metadata.REPO_BRANCH,
+    Metadata.SUBMITTED,
+  ],
+  SHOW_IF_SET: [
+    Metadata.CC,
+    Metadata.HASHTAGS,
+    Metadata.TOPIC,
+    Metadata.UPLOADER,
+    Metadata.AUTHOR,
+    Metadata.COMMITTER,
+    Metadata.ASSIGNEE,
+    Metadata.CHERRY_PICK_OF,
+  ],
+  ALWAYS_HIDE: [Metadata.PARENT, Metadata.STRATEGY, Metadata.UPDATED],
+};
+
+export function isSectionSet(section: Metadata, change?: ParsedChangeInfo) {
+  switch (section) {
+    case Metadata.CC:
+      return !!change?.reviewers?.CC?.length;
+    case Metadata.HASHTAGS:
+      return !!change?.hashtags?.length;
+    case Metadata.TOPIC:
+      return !!change?.topic;
+    case Metadata.UPLOADER:
+    case Metadata.AUTHOR:
+    case Metadata.COMMITTER:
+    case Metadata.ASSIGNEE:
+      return false;
+    case Metadata.CHERRY_PICK_OF:
+      return !!change?.cherry_pick_of_change;
+  }
+  return true;
+}
diff --git a/polygerrit-ui/app/utils/event-util.ts b/polygerrit-ui/app/utils/event-util.ts
index 6587dfa..0af8fe2 100644
--- a/polygerrit-ui/app/utils/event-util.ts
+++ b/polygerrit-ui/app/utils/event-util.ts
@@ -18,6 +18,7 @@
 export enum EventType {
   SHOW_ALERT = 'show-alert',
   PAGE_ERROR = 'page-error',
+  TITLE_CHANGE = 'title-change',
 }
 
 export function fireAlert(target: EventTarget, message: string) {
@@ -39,3 +40,13 @@
     })
   );
 }
+
+export function fireTitleChange(target: EventTarget, title: string) {
+  target.dispatchEvent(
+    new CustomEvent(EventType.TITLE_CHANGE, {
+      detail: {title},
+      composed: true,
+      bubbles: true,
+    })
+  );
+}
diff --git a/resources/com/google/gerrit/pgm/init/gerrit.sh b/resources/com/google/gerrit/pgm/init/gerrit.sh
index ce858d5..87a6c05 100755
--- a/resources/com/google/gerrit/pgm/init/gerrit.sh
+++ b/resources/com/google/gerrit/pgm/init/gerrit.sh
@@ -296,6 +296,11 @@
 GERRIT_FDS=`expr $FDS_MULTIPLIER \* $GERRIT_FDS`
 test $GERRIT_FDS -lt 1024 && GERRIT_FDS=1024
 
+CACHE_FDS=`get_config --get cache.openFiles`
+if test -n "$CACHE_FDS"; then
+  GERRIT_FDS=`expr $CACHE_FDS \+ $GERRIT_FDS`
+fi
+
 GERRIT_STARTUP_TIMEOUT=`get_config --get container.startupTimeout`
 test -z "$GERRIT_STARTUP_TIMEOUT" && GERRIT_STARTUP_TIMEOUT=90  # seconds
 
diff --git a/tools/nongoogle.bzl b/tools/nongoogle.bzl
index a3cc66e..459143d 100644
--- a/tools/nongoogle.bzl
+++ b/tools/nongoogle.bzl
@@ -23,8 +23,8 @@
 
     maven_jar(
         name = "dropwizard-core",
-        artifact = "io.dropwizard.metrics:metrics-core:4.1.14",
-        sha1 = "14cf9dd67619a0390812dddb232df339e3383d35",
+        artifact = "io.dropwizard.metrics:metrics-core:4.1.12.1",
+        sha1 = "cb2f351bf4463751201f43bb99865235d5ba07ca",
     )
 
     SSHD_VERS = "2.4.0"
@@ -143,18 +143,40 @@
         sha1 = "dc13ae4faca6df981fc7aeb5a522d9db446d5d50",
     )
 
-    TESTCONTAINERS_VERSION = "1.14.3"
+    DOCKER_JAVA_VERS = "3.2.5"
+
+    maven_jar(
+        name = "docker-java-api",
+        artifact = "com.github.docker-java:docker-java-api:" + DOCKER_JAVA_VERS,
+        sha1 = "8fe5c5e39f940ce58620e77cedc0a2a52d76f9d8",
+    )
+
+    maven_jar(
+        name = "docker-java-transport",
+        artifact = "com.github.docker-java:docker-java-transport:" + DOCKER_JAVA_VERS,
+        sha1 = "27af0ee7ebc2f5672e23ea64769497b5d55ce3ac",
+    )
+
+    # https://github.com/docker-java/docker-java/blob/3.2.5/pom.xml#L61
+    # <=> DOCKER_JAVA_VERS
+    maven_jar(
+        name = "jackson-annotations",
+        artifact = "com.fasterxml.jackson.core:jackson-annotations:2.10.3",
+        sha1 = "0f63b3b1da563767d04d2e4d3fc1ae0cdeffebe7",
+    )
+
+    TESTCONTAINERS_VERSION = "1.15.0"
 
     maven_jar(
         name = "testcontainers",
         artifact = "org.testcontainers:testcontainers:" + TESTCONTAINERS_VERSION,
-        sha1 = "071fc82ba663f469447a19434e7db90f3a872753",
+        sha1 = "b627535b444d88e7b14953bb953d80d9b7b3bd76",
     )
 
     maven_jar(
         name = "testcontainers-elasticsearch",
         artifact = "org.testcontainers:elasticsearch:" + TESTCONTAINERS_VERSION,
-        sha1 = "3709e2ebb0b6aa4e2ba2b6ca92ffdd3bf637a86c",
+        sha1 = "2bd79fd915e5c7bcf9b5d86cd8e0b7a0fff4b8ce",
     )
 
     maven_jar(