Merge "Add keyboard shortcuts to account dropdown"
diff --git a/Documentation/config-gerrit.txt b/Documentation/config-gerrit.txt
index 94c4552..1f4fd9c 100644
--- a/Documentation/config-gerrit.txt
+++ b/Documentation/config-gerrit.txt
@@ -2242,6 +2242,25 @@
 +
 By default false.
 
+[[gerrit.xframeOption]]gerrit.xframeOption::
++
+Add link:https://tools.ietf.org/html/rfc7034[`X-Frame-Options`] header to all HTTP
+responses. The `X-Frame-Options` HTTP response header can be used to indicate
+whether or not a browser should be allowed to render a page in a
+`<frame>`, `<iframe>`, `<embed>` or `<object>`.
++
+Available values:
++
+1. ALLOW - The page can be displayed in a frame.
+2. SAMEORIGIN - The page can only be displayed in a frame on the same origin as the page itself.
++
+If link:#gerrit.canLoadInIFrame is set to false this option is ignored and the
+`X-Frame-Options` header is always set to `DENY`.
+Setting this option to `ALLOW` will cause the `X-Frame-Options` header to be omitted
+the the page can be displayed in a frame.
++
+By default SAMEORIGIN.
+
 [[gerrit.cdnPath]]gerrit.cdnPath::
 +
 Path prefix for PolyGerrit's static resources if using a CDN.
@@ -2976,7 +2995,7 @@
 [[index.batchThreads]]index.batchThreads::
 +
 Number of threads to use for indexing in background operations, such as
-online schema upgrades.
+online schema upgrades, and also for offline reindexing.
 +
 If not set or set to a zero, defaults to the number of logical CPUs as returned
 by the JVM. If set to a negative value, defaults to a direct executor.
diff --git a/Documentation/config-project-config.txt b/Documentation/config-project-config.txt
index c298ba1..a01df50 100644
--- a/Documentation/config-project-config.txt
+++ b/Documentation/config-project-config.txt
@@ -316,27 +316,35 @@
 The submit section includes configuration of project-specific
 submit settings:
 
-[[content_merge]]
-- 'mergeContent': Defines whether Gerrit will try to
+[[content_merge]]submit.mergeContent::
++
+Defines whether Gerrit will try to
 do a content merge when a path conflict occurs. Valid values are
 'true', 'false', or 'INHERIT'.  Default is 'INHERIT'. This option can
 be modified by any project owner through the project console, `Browse`
 > `Repositories` > my/project > `Allow content merges`.
 
-- 'action': Defines the link:#submit-type[submit type].  Valid
+[[submit.action]]submit.action::
++
+Defines the link:#submit-type[submit type].  Valid
 values are 'fast forward only', 'merge if necessary', 'rebase if necessary',
 'rebase always', 'merge always' and 'cherry pick'.  The default is 'merge if necessary'.
 
-- 'matchAuthorToCommitterDate': Defines whether to the author date will be changed to match the
-submitter date upon submit, so that git log shows when the change was submitted instead of when the
-author last committed. Valid values are 'true', 'false', or 'INHERIT'. The default is 'INHERIT'.
-This option only takes effect in submit strategies which already modify the commit, i.e.
-Cherry Pick, Rebase Always, and (perhaps) Rebase If Necessary.
+[[submit.matchAuthorToCommitterDate]]submit.matchAuthorToCommitterDate::
++
+Defines whether the author date will be changed to match the submitter date upon submit, so that
+git log shows when the change was submitted instead of when the author last committed. Valid
+values are 'true', 'false', or 'INHERIT'. The default is 'INHERIT'. This option only takes effect
+in submit strategies which already modify the commit, i.e. Cherry Pick, Rebase Always, and
+(when rebase is necessary) Rebase If Necessary.
 
-- 'rejectEmptyCommit': Defines whether empty commits should be rejected when a change is merged.
-Changes might not seem empty at first but when attempting to merge, rebasing can lead to an empty
-commit. If this option is set to 'true' the merge would fail. An empty commit is still allowed as
-the initial commit on a branch.
+[[submit.rejectEmptyCommit]]submit.rejectEmptyCommit::
++
+Defines whether empty commits should be rejected when a change is merged. When using
+link:#submit.action[submit action] Cherry Pick, Rebase If Necessary or Rebase Always changes may
+become empty upon submit, since the rebase|cherry-pick can lead to an empty commit. If this option
+is set to 'true' the merge would fail in such a case. An empty commit is still allowed as the
+initial commit on a branch.
 
 [[submit-type]]
 ==== Submit Type
diff --git a/Documentation/note-db.txt b/Documentation/note-db.txt
index 0505dd2..89758a0 100644
--- a/Documentation/note-db.txt
+++ b/Documentation/note-db.txt
@@ -110,6 +110,13 @@
 normally run `gerrit.war daemon` with an `-Xmx` flag, pass that to the migration
 tool as well.
 
+[NOTE]
+Note that by appending `--reindex false` to the above command, you can skip the
+lengthy, implicit reindexing step of the migration. This is useful if you plan
+to perform further Gerrit upgrades while the server is offline and have to
+reindex later anyway (E.g.: a follow-up upgrade to Gerrit 3.2 or newer, which
+requires to reindex changes anyway).
+
 *Advantages*
 
 * Much faster than online; can use all available CPUs, since no live traffic
diff --git a/Documentation/rest-api-changes.txt b/Documentation/rest-api-changes.txt
index 4006d1d..de6d6be 100644
--- a/Documentation/rest-api-changes.txt
+++ b/Documentation/rest-api-changes.txt
@@ -4471,7 +4471,7 @@
 .Request
 ----
   POST /changes/myProject~master~I8473b95934b5732ac55d26311a706c9c2bde9940/revisions/current/test.submit_type HTTP/1.0
-  Content-Type: text/plain; charset-UTF-8
+  Content-Type: text/plain; charset=UTF-8
 
   submit_type(cherry_pick).
 ----
@@ -4502,7 +4502,7 @@
 .Request
 ----
   POST /changes/myProject~master~I8473b95934b5732ac55d26311a706c9c2bde9940/revisions/current/test.submit_rule?filters=SKIP HTTP/1.0
-  Content-Type: text/plain; charset-UTF-8
+  Content-Type: text/plain; charset=UTF-8
 
   submit_rule(submit(R)) :-
     R = label('Any-Label-Name', reject(_)).
@@ -6191,7 +6191,7 @@
 Notify handling that defines to whom email notifications should be sent
 after the cherry-pick. +
 Allowed values are `NONE`, `OWNER`, `OWNER_REVIEWERS` and `ALL`. +
-If not set, the default is `NONE`.
+If not set, the default is `ALL`.
 |`notify_details`   |optional|
 Additional information about whom to notify about the update as a map
 of recipient type to link:#notify-info[NotifyInfo] entity.
diff --git a/java/com/google/gerrit/extensions/api/changes/CherryPickInput.java b/java/com/google/gerrit/extensions/api/changes/CherryPickInput.java
index 69c1790..fb03bc5 100644
--- a/java/com/google/gerrit/extensions/api/changes/CherryPickInput.java
+++ b/java/com/google/gerrit/extensions/api/changes/CherryPickInput.java
@@ -24,7 +24,7 @@
   public String base;
   public Integer parent;
 
-  public NotifyHandling notify = NotifyHandling.NONE;
+  public NotifyHandling notify = NotifyHandling.ALL;
   public Map<RecipientType, NotifyInfo> notifyDetails;
 
   public boolean keepReviewers;
diff --git a/java/com/google/gerrit/httpd/AllRequestFilter.java b/java/com/google/gerrit/httpd/AllRequestFilter.java
index 9d171d5..1c3cafe 100644
--- a/java/com/google/gerrit/httpd/AllRequestFilter.java
+++ b/java/com/google/gerrit/httpd/AllRequestFilter.java
@@ -18,6 +18,8 @@
 import com.google.gerrit.server.plugins.Plugin;
 import com.google.gerrit.server.plugins.StopPluginListener;
 import com.google.inject.Inject;
+import com.google.inject.Module;
+import com.google.inject.Scopes;
 import com.google.inject.Singleton;
 import com.google.inject.internal.UniqueAnnotations;
 import com.google.inject.servlet.ServletModule;
@@ -32,11 +34,15 @@
 
 /** Filters all HTTP requests passing through the server. */
 public abstract class AllRequestFilter implements Filter {
-  public static ServletModule module() {
+  public static Module module() {
     return new ServletModule() {
       @Override
       protected void configureServlets() {
         DynamicSet.setOf(binder(), AllRequestFilter.class);
+        DynamicSet.bind(binder(), AllRequestFilter.class)
+            .to(AllowRenderInFrameFilter.class)
+            .in(Scopes.SINGLETON);
+
         filter("/*").through(FilterProxy.class);
 
         bind(StopPluginListener.class)
diff --git a/java/com/google/gerrit/httpd/AllowRenderInFrameFilter.java b/java/com/google/gerrit/httpd/AllowRenderInFrameFilter.java
new file mode 100644
index 0000000..b414aad
--- /dev/null
+++ b/java/com/google/gerrit/httpd/AllowRenderInFrameFilter.java
@@ -0,0 +1,59 @@
+// 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.httpd;
+
+import com.google.gerrit.server.config.GerritServerConfig;
+import com.google.inject.Inject;
+import java.io.IOException;
+import javax.servlet.FilterChain;
+import javax.servlet.ServletException;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
+import javax.servlet.http.HttpServletResponse;
+import org.eclipse.jgit.lib.Config;
+
+public class AllowRenderInFrameFilter extends AllRequestFilter {
+  static final String X_FRAME_OPTIONS_HEADER_NAME = "X-Frame-Options";
+
+  public static enum XFrameOption {
+    ALLOW,
+    SAMEORIGIN;
+  }
+
+  private final String xframeOptionString;
+  private final boolean skipXFrameOption;
+
+  @Inject
+  public AllowRenderInFrameFilter(@GerritServerConfig Config cfg) {
+    XFrameOption xframeOption =
+        cfg.getEnum("gerrit", null, "xframeOption", XFrameOption.SAMEORIGIN);
+    boolean canLoadInIFrame = cfg.getBoolean("gerrit", "canLoadInIFrame", false);
+    xframeOptionString = canLoadInIFrame ? xframeOption.name() : "DENY";
+
+    skipXFrameOption = xframeOption.equals(XFrameOption.ALLOW) && canLoadInIFrame;
+  }
+
+  @Override
+  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
+      throws IOException, ServletException {
+    if (skipXFrameOption) {
+      chain.doFilter(request, response);
+    } else {
+      HttpServletResponse httpResponse = (HttpServletResponse) response;
+      httpResponse.addHeader(X_FRAME_OPTIONS_HEADER_NAME, xframeOptionString);
+      chain.doFilter(request, httpResponse);
+    }
+  }
+}
diff --git a/java/com/google/gerrit/httpd/raw/IndexHtmlUtil.java b/java/com/google/gerrit/httpd/raw/IndexHtmlUtil.java
index 41d2f83..cddaea4 100644
--- a/java/com/google/gerrit/httpd/raw/IndexHtmlUtil.java
+++ b/java/com/google/gerrit/httpd/raw/IndexHtmlUtil.java
@@ -153,8 +153,7 @@
           serializeObject(GSON, accountApi.getEditPreferences()));
       data.put("userIsAuthenticated", true);
     } catch (AuthException e) {
-      logger.atFine().withCause(e).log(
-          "Can't inline account-related data because user is unauthenticated");
+      logger.atFine().log("Can't inline account-related data because user is unauthenticated");
       // Don't render data
     }
 
diff --git a/java/com/google/gerrit/httpd/restapi/RestApiServlet.java b/java/com/google/gerrit/httpd/restapi/RestApiServlet.java
index 89ebdc1..f743578 100644
--- a/java/com/google/gerrit/httpd/restapi/RestApiServlet.java
+++ b/java/com/google/gerrit/httpd/restapi/RestApiServlet.java
@@ -601,6 +601,7 @@
         }
       } catch (MalformedJsonException | JsonParseException e) {
         cause = Optional.of(e);
+        logger.atFine().withCause(e).log("REST call failed on JSON parsing");
         responseBytes =
             replyError(
                 req, res, statusCode = SC_BAD_REQUEST, "Invalid " + JSON_TYPE + " in request", e);
diff --git a/java/com/google/gerrit/index/Schema.java b/java/com/google/gerrit/index/Schema.java
index 0aa374b..3aa9de0 100644
--- a/java/com/google/gerrit/index/Schema.java
+++ b/java/com/google/gerrit/index/Schema.java
@@ -22,6 +22,7 @@
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.flogger.FluentLogger;
+import com.google.gerrit.exceptions.StorageException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -176,6 +177,33 @@
     return true;
   }
 
+  private Values<T> fieldValues(T obj, FieldDef<T, ?> f, ImmutableSet<String> skipFields) {
+    if (skipFields.contains(f.getName())) {
+      return null;
+    }
+
+    Object v;
+    try {
+      v = f.get(obj);
+    } catch (StorageException e) {
+      // StorageException is thrown when the object is not found. On this case,
+      // it is pointless to make further attempts for each field, so propagate
+      // the exception to return an empty list.
+      logger.atSevere().withCause(e).log("error getting field %s of %s", f.getName(), obj);
+      throw e;
+    } catch (RuntimeException e) {
+      logger.atSevere().withCause(e).log("error getting field %s of %s", f.getName(), obj);
+      return null;
+    }
+    if (v == null) {
+      return null;
+    } else if (f.isRepeatable()) {
+      return new Values<>(f, (Iterable<?>) v);
+    } else {
+      return new Values<>(f, Collections.singleton(v));
+    }
+  }
+
   /**
    * Build all fields in the schema from an input object.
    *
@@ -186,31 +214,14 @@
    * @return all non-null field values from the object.
    */
   public final Iterable<Values<T>> buildFields(T obj, ImmutableSet<String> skipFields) {
-    return fields.values().stream()
-        .map(
-            f -> {
-              if (skipFields.contains(f.getName())) {
-                return null;
-              }
-
-              Object v;
-              try {
-                v = f.get(obj);
-              } catch (RuntimeException e) {
-                logger.atSevere().withCause(e).log(
-                    "error getting field %s of %s", f.getName(), obj);
-                return null;
-              }
-              if (v == null) {
-                return null;
-              } else if (f.isRepeatable()) {
-                return new Values<>(f, (Iterable<?>) v);
-              } else {
-                return new Values<>(f, Collections.singleton(v));
-              }
-            })
-        .filter(Objects::nonNull)
-        .collect(toImmutableList());
+    try {
+      return fields.values().stream()
+          .map(f -> fieldValues(obj, f, skipFields))
+          .filter(Objects::nonNull)
+          .collect(toImmutableList());
+    } catch (StorageException e) {
+      return ImmutableList.of();
+    }
   }
 
   @Override
diff --git a/java/com/google/gerrit/index/SiteIndexer.java b/java/com/google/gerrit/index/SiteIndexer.java
index ecfc7bd..32b4b21 100644
--- a/java/com/google/gerrit/index/SiteIndexer.java
+++ b/java/com/google/gerrit/index/SiteIndexer.java
@@ -83,7 +83,7 @@
   }
 
   protected PrintWriter newPrintWriter(OutputStream out) {
-    return new PrintWriter(new OutputStreamWriter(out, UTF_8));
+    return new PrintWriter(new OutputStreamWriter(out, UTF_8), true);
   }
 
   private static class ErrorListener implements Runnable {
diff --git a/java/com/google/gerrit/pgm/Reindex.java b/java/com/google/gerrit/pgm/Reindex.java
index 2e526bb..966801f 100644
--- a/java/com/google/gerrit/pgm/Reindex.java
+++ b/java/com/google/gerrit/pgm/Reindex.java
@@ -202,6 +202,9 @@
     if (result.success()) {
       index.markReady(true);
     }
+    System.out.format(
+        "Index %s in version %d is %sready\n",
+        def.getName(), index.getSchema().getVersion(), result.success() ? "" : "NOT ");
     return result.success();
   }
 }
diff --git a/java/com/google/gerrit/server/index/change/AllChangesIndexer.java b/java/com/google/gerrit/server/index/change/AllChangesIndexer.java
index 2a8a5ba..e9349c4 100644
--- a/java/com/google/gerrit/server/index/change/AllChangesIndexer.java
+++ b/java/com/google/gerrit/server/index/change/AllChangesIndexer.java
@@ -21,7 +21,6 @@
 import static com.google.gerrit.server.git.QueueProvider.QueueType.BATCH;
 
 import com.google.common.base.Stopwatch;
-import com.google.common.collect.ComparisonChain;
 import com.google.common.flogger.FluentLogger;
 import com.google.common.primitives.Ints;
 import com.google.common.util.concurrent.ListenableFuture;
@@ -43,10 +42,9 @@
 import com.google.inject.Inject;
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
-import java.util.SortedSet;
-import java.util.TreeSet;
 import java.util.concurrent.Callable;
 import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -62,6 +60,7 @@
  */
 public class AllChangesIndexer extends SiteIndexer<Change.Id, ChangeData, ChangeIndex> {
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
+  private static final int PROJECT_SLICE_MAX_REFS = 1000;
 
   private final ChangeData.Factory changeDataFactory;
   private final GitRepositoryManager repoManager;
@@ -86,22 +85,27 @@
     this.projectCache = projectCache;
   }
 
-  private static class ProjectHolder implements Comparable<ProjectHolder> {
-    final Project.NameKey name;
-    private final long size;
+  private static class ProjectSlice {
+    private final Project.NameKey name;
+    private final int slice;
+    private final int slices;
 
-    ProjectHolder(Project.NameKey name, long size) {
+    ProjectSlice(Project.NameKey name, int slice, int slices) {
       this.name = name;
-      this.size = size;
+      this.slice = slice;
+      this.slices = slices;
     }
 
-    @Override
-    public int compareTo(ProjectHolder other) {
-      // Sort projects based on size first to maximize utilization of threads early on.
-      return ComparisonChain.start()
-          .compare(other.size, size)
-          .compare(other.name.get(), name.get())
-          .result();
+    public Project.NameKey getName() {
+      return name;
+    }
+
+    public int getSlice() {
+      return slice;
+    }
+
+    public int getSlices() {
+      return slices;
     }
   }
 
@@ -109,19 +113,39 @@
   public Result indexAll(ChangeIndex index) {
     ProgressMonitor pm = new TextProgressMonitor();
     pm.beginTask("Collecting projects", ProgressMonitor.UNKNOWN);
-    SortedSet<ProjectHolder> projects = new TreeSet<>();
+    List<ProjectSlice> projectSlices = new ArrayList<>();
     int changeCount = 0;
     Stopwatch sw = Stopwatch.createStarted();
     int projectsFailed = 0;
     for (Project.NameKey name : projectCache.all()) {
       try (Repository repo = repoManager.openRepository(name)) {
+        // The simplest approach to distribute indexing would be to let each thread grab a project
+        // and index it fully. But if a site has one big project and 100s of small projects, then
+        // in the beginning all CPUs would be busy reindexing projects. But soon enough all small
+        // projects have been reindexed, and only the thread that reindexes the big project is
+        // still working. The other threads would idle. Reindexing the big project on a single
+        // thread becomes the critical path. Bringing in more CPUs would not speed up things.
+        //
+        // To avoid such situations, we split big repos into smaller parts and let
+        // the thread pool index these smaller parts. This splitting introduces an overhead in the
+        // workload setup and there might be additional slow-downs from multiple threads
+        // concurrently working on different parts of the same project. But for Wikimedia's Gerrit,
+        // which had 2 big projects, many middle sized ones, and lots of smaller ones, the
+        // splitting of repos into smaller parts reduced indexing time from 1.5 hours to 55 minutes
+        // in 2020.
         int size = estimateSize(repo);
         changeCount += size;
-        projects.add(new ProjectHolder(name, size));
+        int slices = 1 + size / PROJECT_SLICE_MAX_REFS;
+        if (slices > 1) {
+          verboseWriter.println("Submitting " + name + " for indexing in " + slices + " slices");
+        }
+        for (int slice = 0; slice < slices; slice++) {
+          projectSlices.add(new ProjectSlice(name, slice, slices));
+        }
       } catch (IOException e) {
         logger.atSevere().withCause(e).log("Error collecting project %s", name);
         projectsFailed++;
-        if (projectsFailed > projects.size() / 2) {
+        if (projectsFailed > projectCache.all().size() / 2) {
           logger.atSevere().log("Over 50%% of the projects could not be collected: aborted");
           return Result.create(sw, false, 0, 0);
         }
@@ -130,7 +154,15 @@
     }
     pm.endTask();
     setTotalWork(changeCount);
-    return indexAll(index, projects);
+
+    // projectSlices are currently grouped by projects. First all slices for project1, followed
+    // by all slices for project2, and so on. As workers pick tasks sequentially, multiple threads
+    // would typically work concurrently on different slices of the same project. While this is not
+    // a big issue, shuffling the list beforehand helps with ungrouping the project slices, so
+    // different slices are less likely to be worked on concurrently.
+    // This shuffling gave a 6% runtime reduction for Wikimedia's Gerrit in 2020.
+    Collections.shuffle(projectSlices);
+    return indexAll(index, projectSlices);
   }
 
   private int estimateSize(Repository repo) throws IOException {
@@ -146,10 +178,10 @@
     return Ints.saturatedCast(size);
   }
 
-  private SiteIndexer.Result indexAll(ChangeIndex index, SortedSet<ProjectHolder> projects) {
+  private SiteIndexer.Result indexAll(ChangeIndex index, List<ProjectSlice> projectSlices) {
     Stopwatch sw = Stopwatch.createStarted();
     MultiProgressMonitor mpm = new MultiProgressMonitor(progressOut, "Reindexing changes");
-    Task projTask = mpm.beginSubTask("projects", projects.size());
+    Task projTask = mpm.beginSubTask("project-slices", projectSlices.size());
     checkState(totalWork >= 0);
     Task doneTask = mpm.beginSubTask(null, totalWork);
     Task failedTask = mpm.beginSubTask("failed", MultiProgressMonitor.UNKNOWN);
@@ -157,12 +189,21 @@
     List<ListenableFuture<?>> futures = new ArrayList<>();
     AtomicBoolean ok = new AtomicBoolean(true);
 
-    for (ProjectHolder project : projects) {
+    for (ProjectSlice projectSlice : projectSlices) {
+      Project.NameKey name = projectSlice.getName();
+      int slice = projectSlice.getSlice();
+      int slices = projectSlice.getSlices();
       ListenableFuture<?> future =
           executor.submit(
               reindexProject(
-                  indexerFactory.create(executor, index), project.name, doneTask, failedTask));
-      addErrorListener(future, "project " + project.name, projTask, ok);
+                  indexerFactory.create(executor, index),
+                  name,
+                  slice,
+                  slices,
+                  doneTask,
+                  failedTask));
+      String description = "project " + name + " (" + slice + "/" + slices + ")";
+      addErrorListener(future, description, projTask, ok);
       futures.add(future);
     }
 
@@ -197,22 +238,38 @@
 
   public Callable<Void> reindexProject(
       ChangeIndexer indexer, Project.NameKey project, Task done, Task failed) {
-    return new ProjectIndexer(indexer, project, done, failed);
+    return reindexProject(indexer, project, 0, 1, done, failed);
+  }
+
+  public Callable<Void> reindexProject(
+      ChangeIndexer indexer,
+      Project.NameKey project,
+      int slice,
+      int slices,
+      Task done,
+      Task failed) {
+    return new ProjectIndexer(indexer, project, slice, slices, done, failed);
   }
 
   private class ProjectIndexer implements Callable<Void> {
     private final ChangeIndexer indexer;
     private final Project.NameKey project;
+    private final int slice;
+    private final int slices;
     private final ProgressMonitor done;
     private final ProgressMonitor failed;
 
     private ProjectIndexer(
         ChangeIndexer indexer,
         Project.NameKey project,
+        int slice,
+        int slices,
         ProgressMonitor done,
         ProgressMonitor failed) {
       this.indexer = indexer;
       this.project = project;
+      this.slice = slice;
+      this.slices = slices;
       this.done = done;
       this.failed = failed;
     }
@@ -227,7 +284,7 @@
         // It does mean that reindexing after invalidating the DiffSummary cache will be expensive,
         // but the goal is to invalidate that cache as infrequently as we possibly can. And besides,
         // we don't have concrete proof that improving packfile locality would help.
-        notesFactory.scan(repo, project).forEach(r -> index(r));
+        notesFactory.scan(repo, project, id -> (id.get() % slices) == slice).forEach(r -> index(r));
       } catch (RepositoryNotFoundException rnfe) {
         logger.atSevere().log(rnfe.getMessage());
       } finally {
@@ -244,7 +301,8 @@
       try {
         indexer.index(changeDataFactory.create(r.notes()));
         done.update(1);
-        verboseWriter.println("Reindexed change " + r.id());
+        verboseWriter.format(
+            "Reindexed change %d (project: %s)\n", r.id().get(), r.notes().getProjectName().get());
       } catch (RejectedExecutionException e) {
         // Server shutdown, don't spam the logs.
         failSilently();
diff --git a/java/com/google/gerrit/server/notedb/ChangeNotes.java b/java/com/google/gerrit/server/notedb/ChangeNotes.java
index 0a71fa1..36a61cc0 100644
--- a/java/com/google/gerrit/server/notedb/ChangeNotes.java
+++ b/java/com/google/gerrit/server/notedb/ChangeNotes.java
@@ -207,9 +207,19 @@
 
     public Stream<ChangeNotesResult> scan(Repository repo, Project.NameKey project)
         throws IOException {
+      return scan(repo, project, null);
+    }
+
+    public Stream<ChangeNotesResult> scan(
+        Repository repo, Project.NameKey project, Predicate<Change.Id> changeIdPredicate)
+        throws IOException {
       ScanResult sr = scanChangeIds(repo);
 
-      return sr.all().stream().map(id -> scanOneChange(project, sr, id)).filter(Objects::nonNull);
+      Stream<Change.Id> idStream = sr.all().stream();
+      if (changeIdPredicate != null) {
+        idStream = idStream.filter(changeIdPredicate);
+      }
+      return idStream.map(id -> scanOneChange(project, sr, id)).filter(Objects::nonNull);
     }
 
     @Nullable
diff --git a/java/com/google/gerrit/server/project/ProjectJson.java b/java/com/google/gerrit/server/project/ProjectJson.java
index f2254d6..f00df53 100644
--- a/java/com/google/gerrit/server/project/ProjectJson.java
+++ b/java/com/google/gerrit/server/project/ProjectJson.java
@@ -18,6 +18,7 @@
 
 import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableList;
+import com.google.common.flogger.FluentLogger;
 import com.google.gerrit.common.data.LabelType;
 import com.google.gerrit.common.data.LabelValue;
 import com.google.gerrit.entities.Project;
@@ -34,6 +35,7 @@
 /** Collection of routines to populate {@link ProjectInfo}. */
 @Singleton
 public class ProjectJson {
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
   private final AllProjectsName allProjects;
   private final WebLinks webLinks;
@@ -50,7 +52,17 @@
     for (LabelType t : projectState.getLabelTypes().getLabelTypes()) {
       LabelTypeInfo labelInfo = new LabelTypeInfo();
       labelInfo.values =
-          t.getValues().stream().collect(toMap(LabelValue::formatValue, LabelValue::getText));
+          t.getValues().stream()
+              .collect(
+                  toMap(
+                      LabelValue::formatValue,
+                      LabelValue::getText,
+                      (v1, v2) -> {
+                        logger.atSevere().log(
+                            "Duplicate values for project: %s, label: %s found: '%s':'%s'",
+                            projectState.getName(), t.getName(), v1, v2);
+                        return v1;
+                      }));
       labelInfo.defaultValue = t.getDefaultValue();
       info.labels.put(t.getName(), labelInfo);
     }
diff --git a/java/com/google/gerrit/server/rules/PrologOptions.java b/java/com/google/gerrit/server/rules/PrologOptions.java
index da9b3ab..a176f04 100644
--- a/java/com/google/gerrit/server/rules/PrologOptions.java
+++ b/java/com/google/gerrit/server/rules/PrologOptions.java
@@ -15,18 +15,21 @@
 package com.google.gerrit.server.rules;
 
 import com.google.auto.value.AutoValue;
+import com.google.common.flogger.FluentLogger;
 import com.google.gerrit.common.Nullable;
 import java.util.Optional;
 
 @AutoValue
 public abstract class PrologOptions {
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
+
   public static PrologOptions defaultOptions() {
     return new AutoValue_PrologOptions.Builder().logErrors(true).skipFilters(false).build();
   }
 
   public static PrologOptions dryRunOptions(String ruleToTest, boolean skipFilters) {
     return new AutoValue_PrologOptions.Builder()
-        .logErrors(false)
+        .logErrors(logger.atFine().isEnabled())
         .skipFilters(skipFilters)
         .rule(ruleToTest)
         .build();
diff --git a/javatests/com/google/gerrit/httpd/AllowRenderInFrameFilterTest.java b/javatests/com/google/gerrit/httpd/AllowRenderInFrameFilterTest.java
new file mode 100644
index 0000000..2679829
--- /dev/null
+++ b/javatests/com/google/gerrit/httpd/AllowRenderInFrameFilterTest.java
@@ -0,0 +1,136 @@
+// 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.httpd;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.gerrit.httpd.AllowRenderInFrameFilter.X_FRAME_OPTIONS_HEADER_NAME;
+import static com.google.gerrit.testing.GerritJUnit.assertThrows;
+import static org.mockito.Mockito.anyString;
+import static org.mockito.Mockito.eq;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+import com.google.gerrit.httpd.AllowRenderInFrameFilter.XFrameOption;
+import java.io.IOException;
+import javax.servlet.FilterChain;
+import javax.servlet.ServletException;
+import javax.servlet.ServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import org.eclipse.jgit.lib.Config;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
+
+@RunWith(MockitoJUnitRunner.class)
+public class AllowRenderInFrameFilterTest {
+
+  private Config cfg = new Config();
+  @Mock ServletRequest request;
+  @Mock HttpServletResponse response;
+  @Mock FilterChain filterChain;
+
+  @Test
+  public void shouldDenyInFrameRenderingWhenCanRenderInFrameIsFalse()
+      throws IOException, ServletException {
+    cfg.setBoolean("gerrit", null, "canLoadInIFrame", false);
+
+    AllowRenderInFrameFilter objectUnderTest = new AllowRenderInFrameFilter(cfg);
+    objectUnderTest.doFilter(request, response, filterChain);
+
+    verify(response, times(1)).addHeader(X_FRAME_OPTIONS_HEADER_NAME, "DENY");
+  }
+
+  @Test
+  public void shouldDenyInFrameRenderingWhenCanRenderInFrameIsFalseAndXFormOptionIsSAMEORIGIN()
+      throws IOException, ServletException {
+    cfg.setBoolean("gerrit", null, "canLoadInIFrame", false);
+    cfg.setEnum("gerrit", null, "xframeOption", XFrameOption.SAMEORIGIN);
+
+    AllowRenderInFrameFilter objectUnderTest = new AllowRenderInFrameFilter(cfg);
+    objectUnderTest.doFilter(request, response, filterChain);
+
+    verify(response, times(1)).addHeader(X_FRAME_OPTIONS_HEADER_NAME, "DENY");
+  }
+
+  @Test
+  public void shouldDenyInFrameRenderingWhenCanRenderInFrameIsFalseAndXFormOptionIsALLOW()
+      throws IOException, ServletException {
+    cfg.setBoolean("gerrit", null, "canLoadInIFrame", false);
+    cfg.setEnum("gerrit", null, "xframeOption", XFrameOption.ALLOW);
+
+    AllowRenderInFrameFilter objectUnderTest = new AllowRenderInFrameFilter(cfg);
+    objectUnderTest.doFilter(request, response, filterChain);
+
+    verify(response, times(1)).addHeader(X_FRAME_OPTIONS_HEADER_NAME, "DENY");
+  }
+
+  @Test
+  public void shouldRestrictAccessToSAMEORIGINWhenCanRenderInFrameIsTrue()
+      throws IOException, ServletException {
+    cfg.setBoolean("gerrit", null, "canLoadInIFrame", true);
+
+    AllowRenderInFrameFilter objectUnderTest = new AllowRenderInFrameFilter(cfg);
+    objectUnderTest.doFilter(request, response, filterChain);
+
+    verify(response, times(1)).addHeader(X_FRAME_OPTIONS_HEADER_NAME, "SAMEORIGIN");
+  }
+
+  @Test
+  public void shouldSkipHeaderWhenCanRenderInFrameIsTrueAndXFormOptionIsALLOW()
+      throws IOException, ServletException {
+    cfg.setBoolean("gerrit", null, "canLoadInIFrame", true);
+    cfg.setEnum("gerrit", null, "xframeOption", XFrameOption.ALLOW);
+
+    AllowRenderInFrameFilter objectUnderTest = new AllowRenderInFrameFilter(cfg);
+    objectUnderTest.doFilter(request, response, filterChain);
+
+    verify(response, never()).addHeader(eq(X_FRAME_OPTIONS_HEADER_NAME), anyString());
+  }
+
+  @Test
+  public void shouldRestrictAccessToSAMEORIGINWhenCanRenderInFrameIsTrueAndXFormOptionIsSAMEORIGIN()
+      throws IOException, ServletException {
+    cfg.setBoolean("gerrit", null, "canLoadInIFrame", true);
+    cfg.setEnum("gerrit", null, "xframeOption", XFrameOption.SAMEORIGIN);
+
+    AllowRenderInFrameFilter objectUnderTest = new AllowRenderInFrameFilter(cfg);
+    objectUnderTest.doFilter(request, response, filterChain);
+
+    verify(response, times(1)).addHeader(X_FRAME_OPTIONS_HEADER_NAME, "SAMEORIGIN");
+  }
+
+  @Test
+  public void shouldIgnoreXFrameOriginCaseSensitivity() throws IOException, ServletException {
+    cfg.setBoolean("gerrit", null, "canLoadInIFrame", true);
+    cfg.setString("gerrit", null, "xframeOption", "sameOrigin");
+
+    AllowRenderInFrameFilter objectUnderTest = new AllowRenderInFrameFilter(cfg);
+    objectUnderTest.doFilter(request, response, filterChain);
+
+    verify(response, times(1)).addHeader(X_FRAME_OPTIONS_HEADER_NAME, "SAMEORIGIN");
+  }
+
+  @Test
+  public void shouldThrowExceptionWhenUnknownXFormOptionValue() {
+    cfg.setBoolean("gerrit", null, "canLoadInIFrame", true);
+    cfg.setString("gerrit", null, "xframeOption", "unsupported value");
+
+    IllegalArgumentException e =
+        assertThrows(IllegalArgumentException.class, () -> new AllowRenderInFrameFilter(cfg));
+    assertThat(e).hasMessageThat().contains("gerrit.xframeOption=unsupported value");
+  }
+}
diff --git a/modules/jgit b/modules/jgit
index 8a44216..8e79d5a 160000
--- a/modules/jgit
+++ b/modules/jgit
@@ -1 +1 @@
-Subproject commit 8a44216e8bdad1a13ce637b1395467600870849a
+Subproject commit 8e79d5a290843b929f073a536a0d678fc74382ca
diff --git a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list_html.js b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list_html.js
index df7cb00..a2714d9 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list_html.js
+++ b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list_html.js
@@ -329,6 +329,12 @@
           as="headerEndpoint"
         >
           <gr-endpoint-decorator name$="[[headerEndpoint]]" role="columnheader">
+            <gr-endpoint-param
+              name="change"
+              value="[[change]]"
+            ></gr-endpoint-param>
+            <gr-endpoint-param name="patchRange" value="[[patchRange]]">
+            </gr-endpoint-param>
           </gr-endpoint-decorator>
         </template>
       </template>
@@ -381,6 +387,8 @@
               as="contentEndpoint"
             >
               <gr-endpoint-decorator name="[[contentEndpoint]]" role="gridcell">
+                <gr-endpoint-param name="change" value="[[change]]">
+                </gr-endpoint-param>
                 <gr-endpoint-param name="changeNum" value="[[changeNum]]">
                 </gr-endpoint-param>
                 <gr-endpoint-param name="patchRange" value="[[patchRange]]">
@@ -439,7 +447,7 @@
             <div class="comments desktop">
               <span class="drafts"
                 ><!-- This comments ensure that span is empty when the function
-                returns empty string.                
+                returns empty string.
               -->[[_computeDraftsString(changeComments, patchRange,
                 file.__path)]]<!-- This comments ensure that span is empty when
                 the function returns empty string.
@@ -458,7 +466,7 @@
               Without this span, screen readers don't navigate correctly inside
               table, because empty div doesn't rendered. For example, VoiceOver
               jumps back to the whole table.
-              We can use &nbsp instead, but it sounds worse.                            
+              We can use &nbsp instead, but it sounds worse.
               -->
                 No comments
               </span>
@@ -553,6 +561,8 @@
             >
               <div class$="[[_computeClass('', file.__path)]]" role="gridcell">
                 <gr-endpoint-decorator name="[[contentEndpoint]]">
+                  <gr-endpoint-param name="change" value="[[change]]">
+                  </gr-endpoint-param>
                   <gr-endpoint-param name="changeNum" value="[[changeNum]]">
                   </gr-endpoint-param>
                   <gr-endpoint-param name="patchRange" value="[[patchRange]]">
@@ -575,7 +585,7 @@
             >
             <!-- Do not use input type="checkbox" with hidden input and
                   visible label here. Screen readers don't read/interract
-                  correctly with such input. 
+                  correctly with such input.
               -->
             <span
               class="reviewedSwitch"
@@ -611,7 +621,7 @@
           <div class="show-hide" role="gridcell">
             <!-- Do not use input type="checkbox" with hidden input and
                 visible label here. Screen readers don't read/interract
-                correctly with such input. 
+                correctly with such input.
             -->
             <span
               class="show-hide"
@@ -683,6 +693,12 @@
         as="summaryEndpoint"
       >
         <gr-endpoint-decorator name="[[summaryEndpoint]]">
+          <gr-endpoint-param
+            name="change"
+            value="[[change]]"
+          ></gr-endpoint-param>
+          <gr-endpoint-param name="patchRange" value="[[patchRange]]">
+          </gr-endpoint-param>
         </gr-endpoint-decorator>
       </template>
     </template>
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.js b/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.js
index c2279e2..1cabd82 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.js
@@ -318,6 +318,7 @@
     // Both td and button need a number of classes/attributes for various
     // selectors to work.
     this._decorateLineEl(td, number, side);
+    td.classList.add('lineNum');
 
     if (this._prefs.show_file_comment_button === false && number === 'FILE') {
       return td;
@@ -328,7 +329,6 @@
     button.tabIndex = -1;
     this._decorateLineEl(button, number, side);
 
-    td.classList.add('lineNum');
     button.classList.add('lineNumButton');
 
     button.textContent = number === 'FILE' ? 'File' : number;
diff --git a/polygerrit-ui/app/elements/diff/gr-patch-range-select/gr-patch-range-select.js b/polygerrit-ui/app/elements/diff/gr-patch-range-select/gr-patch-range-select.js
index 3bf3697..c00c0fb 100644
--- a/polygerrit-ui/app/elements/diff/gr-patch-range-select/gr-patch-range-select.js
+++ b/polygerrit-ui/app/elements/diff/gr-patch-range-select/gr-patch-range-select.js
@@ -25,6 +25,7 @@
 import {htmlTemplate} from './gr-patch-range-select_html.js';
 import {PatchSetBehavior} from '../../../behaviors/gr-patch-set-behavior/gr-patch-set-behavior.js';
 import {GrCountStringFormatter} from '../../shared/gr-count-string-formatter/gr-count-string-formatter.js';
+import {appContext} from '../../../services/app-context.js';
 
 // Maximum length for patch set descriptions.
 const PATCH_DESC_MAX_LENGTH = 500;
@@ -78,6 +79,11 @@
     ];
   }
 
+  constructor() {
+    super();
+    this.reporting = appContext.reportingService;
+  }
+
   _getShaForPatch(patch) {
     return patch.sha.substring(0, 10);
   }
@@ -285,8 +291,14 @@
     const target = dom(e).localTarget;
 
     if (target === this.$.patchNumDropdown) {
+      if (detail.patchNum === e.detail.value) return;
+      this.reporting.reportInteraction('right-patchset-changed',
+          {previous: detail.patchNum, current: e.detail.value});
       detail.patchNum = e.detail.value;
     } else {
+      if (detail.basePatchNum === e.detail.value) return;
+      this.reporting.reportInteraction('left-patchset-changed',
+          {previous: detail.basePatchNum, current: e.detail.value});
       detail.basePatchNum = e.detail.value;
     }
 
diff --git a/resources/com/google/gerrit/httpd/raw/HostPage.html b/resources/com/google/gerrit/httpd/raw/HostPage.html
deleted file mode 100644
index c0d8446..0000000
--- a/resources/com/google/gerrit/httpd/raw/HostPage.html
+++ /dev/null
@@ -1,26 +0,0 @@
-<html>
-  <head>
-    <title>Gerrit Code Review</title>
-    <meta name="gwt:property" content="locale=en_US" />
-    <script id="gerrit_hostpagedata"></script>
-    <style id="gerrit_sitecss" type="text/css"></style>
-    <link rel="shortcut icon" type="image/x-icon" href="favicon.ico" />
-  </head>
-  <body>
-    <div id="gerrit_topmenu"></div>
-    <div id="gerrit_header"></div>
-    <div id="gerrit_startinggerrit" style="margin-left: 10px;">
-      <p>Loading <a href="https://www.gerritcodereview.com/" target="_blank">Gerrit Code Review</a> ...</p>
-      <noscript>
-        <p>Gerrit requires a JavaScript enabled browser.</p>
-      </noscript>
-    </div>
-    <div id="gerrit_body"></div>
-    <div style="clear: both">
-      <div id="gerrit_footer"></div>
-      <div id="gerrit_btmmenu"></div>
-    </div>
-    <iframe src="javascript:''" id="__gwt_historyFrame" tabIndex='-1' style="position:absolute;width:0;height:0;border:0"></iframe>
-    <script id="gerrit_module"></script>
-  </body>
-</html>