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diff --git a/java/com/google/gerrit/server/restapi/change/GetRelated.java b/java/com/google/gerrit/server/restapi/change/GetRelated.java
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+++ b/java/com/google/gerrit/server/restapi/change/GetRelated.java
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+// Copyright (C) 2013 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.restapi.change;
+
+import static java.util.stream.Collectors.toSet;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.Lists;
+import com.google.gerrit.common.Nullable;
+import com.google.gerrit.extensions.api.changes.RelatedChangeAndCommitInfo;
+import com.google.gerrit.extensions.api.changes.RelatedChangesInfo;
+import com.google.gerrit.extensions.common.CommitInfo;
+import com.google.gerrit.extensions.restapi.RestReadView;
+import com.google.gerrit.index.IndexConfig;
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.reviewdb.client.Project;
+import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.server.CommonConverters;
+import com.google.gerrit.server.PatchSetUtil;
+import com.google.gerrit.server.change.RevisionResource;
+import com.google.gerrit.server.notedb.ChangeNotes;
+import com.google.gerrit.server.permissions.PermissionBackendException;
+import com.google.gerrit.server.project.NoSuchProjectException;
+import com.google.gerrit.server.query.change.ChangeData;
+import com.google.gerrit.server.query.change.InternalChangeQuery;
+import com.google.gwtorm.server.OrmException;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+import com.google.inject.Singleton;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Set;
+import org.eclipse.jgit.errors.RepositoryNotFoundException;
+import org.eclipse.jgit.revwalk.RevCommit;
+
+@Singleton
+public class GetRelated implements RestReadView<RevisionResource> {
+  private final Provider<ReviewDb> db;
+  private final Provider<InternalChangeQuery> queryProvider;
+  private final PatchSetUtil psUtil;
+  private final RelatedChangesSorter sorter;
+  private final IndexConfig indexConfig;
+
+  @Inject
+  GetRelated(
+      Provider<ReviewDb> db,
+      Provider<InternalChangeQuery> queryProvider,
+      PatchSetUtil psUtil,
+      RelatedChangesSorter sorter,
+      IndexConfig indexConfig) {
+    this.db = db;
+    this.queryProvider = queryProvider;
+    this.psUtil = psUtil;
+    this.sorter = sorter;
+    this.indexConfig = indexConfig;
+  }
+
+  @Override
+  public RelatedChangesInfo apply(RevisionResource rsrc)
+      throws RepositoryNotFoundException, IOException, OrmException, NoSuchProjectException,
+          PermissionBackendException {
+    RelatedChangesInfo relatedChangesInfo = new RelatedChangesInfo();
+    relatedChangesInfo.changes = getRelated(rsrc);
+    return relatedChangesInfo;
+  }
+
+  private List<RelatedChangeAndCommitInfo> getRelated(RevisionResource rsrc)
+      throws OrmException, IOException, PermissionBackendException {
+    Set<String> groups = getAllGroups(rsrc.getNotes(), db.get(), psUtil);
+    if (groups.isEmpty()) {
+      return Collections.emptyList();
+    }
+
+    List<ChangeData> cds =
+        InternalChangeQuery.byProjectGroups(
+            queryProvider, indexConfig, rsrc.getChange().getProject(), groups);
+    if (cds.isEmpty()) {
+      return Collections.emptyList();
+    }
+    if (cds.size() == 1 && cds.get(0).getId().equals(rsrc.getChange().getId())) {
+      return Collections.emptyList();
+    }
+    List<RelatedChangeAndCommitInfo> result = new ArrayList<>(cds.size());
+
+    boolean isEdit = rsrc.getEdit().isPresent();
+    PatchSet basePs = isEdit ? rsrc.getEdit().get().getBasePatchSet() : rsrc.getPatchSet();
+
+    reloadChangeIfStale(cds, basePs);
+
+    for (RelatedChangesSorter.PatchSetData d : sorter.sort(cds, basePs)) {
+      PatchSet ps = d.patchSet();
+      RevCommit commit;
+      if (isEdit && ps.getId().equals(basePs.getId())) {
+        // Replace base of an edit with the edit itself.
+        ps = rsrc.getPatchSet();
+        commit = rsrc.getEdit().get().getEditCommit();
+      } else {
+        commit = d.commit();
+      }
+      result.add(newChangeAndCommit(rsrc.getProject(), d.data().change(), ps, commit));
+    }
+
+    if (result.size() == 1) {
+      RelatedChangeAndCommitInfo r = result.get(0);
+      if (r.commit != null && r.commit.commit.equals(rsrc.getPatchSet().getRevision().get())) {
+        return Collections.emptyList();
+      }
+    }
+    return result;
+  }
+
+  @VisibleForTesting
+  public static Set<String> getAllGroups(ChangeNotes notes, ReviewDb db, PatchSetUtil psUtil)
+      throws OrmException {
+    return psUtil.byChange(db, notes).stream()
+        .flatMap(ps -> ps.getGroups().stream())
+        .collect(toSet());
+  }
+
+  private void reloadChangeIfStale(List<ChangeData> cds, PatchSet wantedPs) throws OrmException {
+    for (ChangeData cd : cds) {
+      if (cd.getId().equals(wantedPs.getId().getParentKey())) {
+        if (cd.patchSet(wantedPs.getId()) == null) {
+          cd.reloadChange();
+        }
+      }
+    }
+  }
+
+  static RelatedChangeAndCommitInfo newChangeAndCommit(
+      Project.NameKey project, @Nullable Change change, @Nullable PatchSet ps, RevCommit c) {
+    RelatedChangeAndCommitInfo info = new RelatedChangeAndCommitInfo();
+    info.project = project.get();
+
+    if (change != null) {
+      info.changeId = change.getKey().get();
+      info._changeNumber = change.getChangeId();
+      info._revisionNumber = ps != null ? ps.getPatchSetId() : null;
+      PatchSet.Id curr = change.currentPatchSetId();
+      info._currentRevisionNumber = curr != null ? curr.get() : null;
+      info.status = change.getStatus().asChangeStatus().toString();
+    }
+
+    info.commit = new CommitInfo();
+    info.commit.commit = c.name();
+    info.commit.parents = Lists.newArrayListWithCapacity(c.getParentCount());
+    for (int i = 0; i < c.getParentCount(); i++) {
+      CommitInfo p = new CommitInfo();
+      p.commit = c.getParent(i).name();
+      info.commit.parents.add(p);
+    }
+    info.commit.author = CommonConverters.toGitPerson(c.getAuthorIdent());
+    info.commit.subject = c.getShortMessage();
+    return info;
+  }
+}