diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/change/WalkSorter.java b/gerrit-server/src/main/java/com/google/gerrit/server/change/WalkSorter.java
new file mode 100644
index 0000000..56d6677
--- /dev/null
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/change/WalkSorter.java
@@ -0,0 +1,203 @@
+// Copyright (C) 2015 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.change;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Function;
+import com.google.common.collect.ArrayListMultimap;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Multimap;
+import com.google.common.collect.Ordering;
+import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.reviewdb.client.Project;
+import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.gerrit.server.query.change.ChangeData;
+import com.google.gwtorm.server.OrmException;
+import com.google.inject.Inject;
+
+import org.eclipse.jgit.errors.IncorrectObjectTypeException;
+import org.eclipse.jgit.errors.MissingObjectException;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevSort;
+import org.eclipse.jgit.revwalk.RevWalk;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Helper to sort {@link ChangeData}s based on {@link RevWalk} ordering.
+ * <p>
+ * Split changes by project, and map each change to a single commit based on the
+ * latest patch set. The set of patch sets considered may be limited by calling
+ * {@link #includePatchSets(Set)}. Perform a standard {@link RevWalk} on each
+ * project repository, and record the order in which each change's commit is
+ * seen.
+ * <p>
+ * Once an order within each project is determined, groups of changes are sorted
+ * based on the project name. This is slightly more stable than sorting on
+ * something like the commit or change timestamp, as it will not unexpectedly
+ * reorder large groups of changes on subsequent calls if one of the changes was
+ * updated.
+ */
+class WalkSorter {
+  private static final Logger log =
+      LoggerFactory.getLogger(WalkSorter.class);
+
+  private static final Ordering<List<PatchSetData>> PROJECT_LIST_SORTER =
+      Ordering.natural().nullsFirst()
+          .onResultOf(
+            new Function<List<PatchSetData>, Project.NameKey>() {
+              @Override
+              public Project.NameKey apply(List<PatchSetData> in) {
+                if (in == null || in.isEmpty()) {
+                  return null;
+                }
+                try {
+                  return in.get(0).data().change().getProject();
+                } catch (OrmException e) {
+                  throw new IllegalStateException(e);
+                }
+              }
+            });
+
+  private final GitRepositoryManager repoManager;
+  private final Set<PatchSet.Id> includePatchSets;
+  private boolean retainBody;
+
+  @Inject
+  WalkSorter(GitRepositoryManager repoManager) {
+    this.repoManager = repoManager;
+    includePatchSets = new HashSet<>();
+  }
+
+  public WalkSorter includePatchSets(Iterable<PatchSet.Id> patchSets) {
+    Iterables.addAll(includePatchSets, patchSets);
+    return this;
+  }
+
+  public WalkSorter setRetainBody(boolean retainBody) {
+    this.retainBody = retainBody;
+    return this;
+  }
+
+  public Iterable<PatchSetData> sort(Iterable<ChangeData> in)
+      throws OrmException, IOException {
+    Multimap<Project.NameKey, ChangeData> byProject =
+        ArrayListMultimap.create();
+    for (ChangeData cd : in) {
+      byProject.put(cd.change().getProject(), cd);
+    }
+
+    List<List<PatchSetData>> sortedByProject =
+        new ArrayList<>(byProject.keySet().size());
+    for (Map.Entry<Project.NameKey, Collection<ChangeData>> e
+        : byProject.asMap().entrySet()) {
+      sortedByProject.add(sortProject(e.getKey(), e.getValue()));
+    }
+    Collections.sort(sortedByProject, PROJECT_LIST_SORTER);
+    return Iterables.concat(sortedByProject);
+  }
+
+  private List<PatchSetData> sortProject(Project.NameKey project,
+      Collection<ChangeData> in) throws OrmException, IOException {
+    try (Repository repo = repoManager.openRepository(project);
+        RevWalk rw = new RevWalk(repo)) {
+      rw.setRetainBody(retainBody);
+      rw.sort(RevSort.TOPO);
+      Multimap<RevCommit, PatchSetData> byCommit = byCommit(rw, in);
+      if (byCommit.isEmpty()) {
+        return ImmutableList.of();
+      }
+
+      // Walk from all patch set SHA-1s, and terminate as soon as we've found
+      // everything we're looking for. This is equivalent to just sorting the
+      // list of commits by the RevWalk's configured order.
+      for (RevCommit c : byCommit.keySet()) {
+        rw.markStart(c);
+      }
+
+      int expected = byCommit.keySet().size();
+      int found = 0;
+      RevCommit c;
+      List<PatchSetData> result = new ArrayList<>(expected);
+      while (found < expected && (c = rw.next()) != null) {
+        Collection<PatchSetData> psds = byCommit.get(c);
+        if (!psds.isEmpty()) {
+          found++;
+          for (PatchSetData psd : psds) {
+            result.add(psd);
+          }
+        }
+      }
+      return result;
+    }
+  }
+
+  private Multimap<RevCommit, PatchSetData> byCommit(RevWalk rw,
+      Collection<ChangeData> in) throws OrmException, IOException {
+    Multimap<RevCommit, PatchSetData> byCommit =
+        ArrayListMultimap.create(in.size(), 1);
+    for (ChangeData cd : in) {
+      PatchSet maxPs = null;
+      for (PatchSet ps : cd.patchSets()) {
+        if (shouldInclude(ps)
+            && (maxPs == null || ps.getId().get() > maxPs.getId().get())) {
+          maxPs = ps;
+        }
+      }
+      if (maxPs == null) {
+       continue; // No patch sets matched.
+      }
+      ObjectId id = ObjectId.fromString(maxPs.getRevision().get());
+      try {
+        RevCommit c = rw.parseCommit(id);
+        byCommit.put(c, PatchSetData.create(cd, maxPs, c));
+      } catch (MissingObjectException | IncorrectObjectTypeException e) {
+        log.warn(
+            "missing commit " + id.name() + " for patch set " + maxPs.getId(),
+            e);
+      }
+    }
+    return byCommit;
+  }
+
+  private boolean shouldInclude(PatchSet ps) {
+    return includePatchSets.isEmpty() || includePatchSets.contains(ps.getId());
+  }
+
+  @AutoValue
+  static abstract class PatchSetData {
+    @VisibleForTesting
+    static PatchSetData create(ChangeData cd, PatchSet ps, RevCommit commit) {
+      return new AutoValue_WalkSorter_PatchSetData(cd, ps, commit);
+    }
+
+    abstract ChangeData data();
+    abstract PatchSet patchSet();
+    abstract RevCommit commit();
+  }
+}
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeData.java b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeData.java
index d94921e..5c023e2 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeData.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeData.java
@@ -172,12 +172,13 @@
   /**
    * Create an instance for testing only.
    * <p>
-   * Attempting to lazy load data will fail with NPEs.
+   * Attempting to lazy load data will fail with NPEs. Callers may consider
+   * manually setting fields that can be set.
    *
    * @param id change ID
    * @return instance for testing.
    */
-  static ChangeData createForTest(Change.Id id, int currentPatchSetId) {
+  public static ChangeData createForTest(Change.Id id, int currentPatchSetId) {
     ChangeData cd = new ChangeData(null, null, null, null, null, null, null,
         null, null, null, null, null, null, id);
     cd.currentPatchSet = new PatchSet(new PatchSet.Id(id, currentPatchSetId));
diff --git a/gerrit-server/src/test/java/com/google/gerrit/server/change/WalkSorterTest.java b/gerrit-server/src/test/java/com/google/gerrit/server/change/WalkSorterTest.java
new file mode 100644
index 0000000..7b7983c
--- /dev/null
+++ b/gerrit-server/src/test/java/com/google/gerrit/server/change/WalkSorterTest.java
@@ -0,0 +1,267 @@
+// Copyright (C) 2015 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.change;
+
+import static com.google.common.collect.Collections2.permutations;
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
+import com.google.gerrit.reviewdb.client.Account;
+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.client.RevId;
+import com.google.gerrit.server.change.WalkSorter.PatchSetData;
+import com.google.gerrit.server.query.change.ChangeData;
+import com.google.gerrit.testutil.InMemoryRepositoryManager;
+import com.google.gerrit.testutil.InMemoryRepositoryManager.Repo;
+import com.google.gerrit.testutil.TestChanges;
+import com.google.gwtorm.client.KeyUtil;
+import com.google.gwtorm.server.StandardKeyEncoder;
+
+import org.eclipse.jgit.junit.TestRepository;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevWalk;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class WalkSorterTest {
+  static {
+    KeyUtil.setEncoderImpl(new StandardKeyEncoder());
+  }
+
+  private Account.Id userId;
+  private InMemoryRepositoryManager repoManager;
+
+  @Before
+  public void setUp() {
+    userId = new Account.Id(1);
+    repoManager = new InMemoryRepositoryManager();
+  }
+
+  @Test
+  public void seriesOfChanges() throws Exception {
+    TestRepository<Repo> p = newRepo("p");
+    RevCommit c1_1 = p.commit().create();
+    RevCommit c2_1 = p.commit().parent(c1_1).create();
+    RevCommit c3_1 = p.commit().parent(c2_1).create();
+
+    ChangeData cd1 = newChange(p, c1_1);
+    ChangeData cd2 = newChange(p, c2_1);
+    ChangeData cd3 = newChange(p, c3_1);
+
+    List<ChangeData> changes = ImmutableList.of(cd1, cd2, cd3);
+    WalkSorter sorter = new WalkSorter(repoManager);
+
+    assertSorted(sorter, changes, ImmutableList.of(
+        patchSetData(cd3, c3_1),
+        patchSetData(cd2, c2_1),
+        patchSetData(cd1, c1_1)));
+
+    // Add new patch sets whose commits are in reverse order, so output is in
+    // reverse order.
+    RevCommit c3_2 = p.commit().create();
+    RevCommit c2_2 = p.commit().parent(c3_2).create();
+    RevCommit c1_2 = p.commit().parent(c2_2).create();
+
+    addPatchSet(cd1, c1_2);
+    addPatchSet(cd2, c2_2);
+    addPatchSet(cd3, c3_2);
+
+    assertSorted(sorter, changes, ImmutableList.of(
+        patchSetData(cd1, c1_2),
+        patchSetData(cd2, c2_2),
+        patchSetData(cd3, c3_2)));
+  }
+
+  @Test
+  public void seriesOfChangesAtSameTimestamp() throws Exception {
+    TestRepository<Repo> p = newRepo("p");
+    RevCommit c1 = p.commit().tick(0).create();
+    RevCommit c2 = p.commit().tick(0).parent(c1).create();
+    RevCommit c3 = p.commit().tick(0).parent(c2).create();
+    RevCommit c4 = p.commit().tick(0).parent(c3).create();
+
+    RevWalk rw = p.getRevWalk();
+    rw.parseCommit(c1);
+    assertThat(rw.parseCommit(c2).getCommitTime())
+        .isEqualTo(c1.getCommitTime());
+    assertThat(rw.parseCommit(c3).getCommitTime())
+        .isEqualTo(c1.getCommitTime());
+    assertThat(rw.parseCommit(c4).getCommitTime())
+        .isEqualTo(c1.getCommitTime());
+
+    ChangeData cd1 = newChange(p, c1);
+    ChangeData cd2 = newChange(p, c2);
+    ChangeData cd3 = newChange(p, c3);
+    ChangeData cd4 = newChange(p, c4);
+
+    List<ChangeData> changes = ImmutableList.of(cd1, cd2, cd3, cd4);
+    WalkSorter sorter = new WalkSorter(repoManager);
+
+    assertSorted(sorter, changes, ImmutableList.of(
+        patchSetData(cd4, c4),
+        patchSetData(cd3, c3),
+        patchSetData(cd2, c2),
+        patchSetData(cd1, c1)));
+  }
+
+  @Test
+  public void projectsSortedByName() throws Exception {
+    TestRepository<Repo> pa = newRepo("a");
+    TestRepository<Repo> pb = newRepo("b");
+    RevCommit c1 = pa.commit().create();
+    RevCommit c2 = pb.commit().create();
+    RevCommit c3 = pa.commit().parent(c1).create();
+    RevCommit c4 = pb.commit().parent(c2).create();
+
+    ChangeData cd1 = newChange(pa, c1);
+    ChangeData cd2 = newChange(pb, c2);
+    ChangeData cd3 = newChange(pa, c3);
+    ChangeData cd4 = newChange(pb, c4);
+
+    assertSorted(
+        new WalkSorter(repoManager),
+        ImmutableList.of(cd1, cd2, cd3, cd4),
+        ImmutableList.of(
+            patchSetData(cd3, c3),
+            patchSetData(cd1, c1),
+            patchSetData(cd4, c4),
+            patchSetData(cd2, c2)));
+  }
+
+  @Test
+  public void restrictToPatchSets() throws Exception {
+    TestRepository<Repo> p = newRepo("p");
+    RevCommit c1_1 = p.commit().create();
+    RevCommit c2_1 = p.commit().parent(c1_1).create();
+
+    ChangeData cd1 = newChange(p, c1_1);
+    ChangeData cd2 = newChange(p, c2_1);
+
+    // Add new patch sets whose commits are in reverse order.
+    RevCommit c2_2 = p.commit().create();
+    RevCommit c1_2 = p.commit().parent(c2_2).create();
+
+    addPatchSet(cd1, c1_2);
+    addPatchSet(cd2, c2_2);
+
+    List<ChangeData> changes = ImmutableList.of(cd1, cd2);
+    WalkSorter sorter = new WalkSorter(repoManager);
+
+    assertSorted(sorter, changes, ImmutableList.of(
+        patchSetData(cd1, c1_2),
+        patchSetData(cd2, c2_2)));
+
+    // If we restrict to PS1 of each change, the sorter uses that commit.
+    sorter.includePatchSets(ImmutableSet.of(
+        new PatchSet.Id(cd1.getId(), 1),
+        new PatchSet.Id(cd2.getId(), 1)));
+    assertSorted(sorter, changes, ImmutableList.of(
+        patchSetData(cd2, 1, c2_1),
+        patchSetData(cd1, 1, c1_1)));
+  }
+
+  @Test
+  public void restrictToPatchSetsOmittingWholeProject() throws Exception {
+    TestRepository<Repo> pa = newRepo("a");
+    TestRepository<Repo> pb = newRepo("b");
+    RevCommit c1 = pa.commit().create();
+    RevCommit c2 = pa.commit().create();
+
+    ChangeData cd1 = newChange(pa, c1);
+    ChangeData cd2 = newChange(pb, c2);
+
+    List<ChangeData> changes = ImmutableList.of(cd1, cd2);
+    WalkSorter sorter = new WalkSorter(repoManager)
+        .includePatchSets(ImmutableSet.of(cd1.currentPatchSet().getId()));
+
+    assertSorted(sorter, changes, ImmutableList.of(patchSetData(cd1, c1)));
+  }
+
+  @Test
+  public void retainBody() throws Exception {
+    TestRepository<Repo> p = newRepo("p");
+    RevCommit c = p.commit().message("message").create();
+    ChangeData cd = newChange(p, c);
+
+    List<ChangeData> changes = ImmutableList.of(cd);
+    RevCommit actual = new WalkSorter(repoManager)
+        .setRetainBody(true)
+        .sort(changes)
+        .iterator().next()
+        .commit();
+    assertThat(actual.getRawBuffer()).isNotNull();
+    assertThat(actual.getShortMessage()).isEqualTo("message");
+
+    actual = new WalkSorter(repoManager)
+        .setRetainBody(false)
+        .sort(changes)
+        .iterator().next()
+        .commit();
+    assertThat(actual.getRawBuffer()).isNull();
+  }
+
+  private ChangeData newChange(TestRepository<Repo> tr, ObjectId id)
+      throws Exception {
+    Project.NameKey project = tr.getRepository().getDescription().getProject();
+    Change c = TestChanges.newChange(project, userId);
+    ChangeData cd = ChangeData.createForTest(c.getId(), 1);
+    cd.setChange(c);
+    cd.currentPatchSet().setRevision(new RevId(id.name()));
+    cd.setPatchSets(ImmutableList.of(cd.currentPatchSet()));
+    return cd;
+  }
+
+  private PatchSet addPatchSet(ChangeData cd, ObjectId id) throws Exception {
+    TestChanges.incrementPatchSet(cd.change());
+    PatchSet ps = new PatchSet(cd.change().currentPatchSetId());
+    ps.setRevision(new RevId(id.name()));
+    List<PatchSet> patchSets = new ArrayList<>(cd.patchSets());
+    patchSets.add(ps);
+    cd.setPatchSets(patchSets);
+    return ps;
+  }
+
+  private TestRepository<Repo> newRepo(String name)
+      throws Exception {
+    return new TestRepository<>(
+        repoManager.createRepository(new Project.NameKey(name)));
+  }
+
+  private static PatchSetData patchSetData(ChangeData cd, RevCommit commit)
+      throws Exception {
+    return PatchSetData.create(cd, cd.currentPatchSet(), commit);
+  }
+
+  private static PatchSetData patchSetData(ChangeData cd, int psId,
+      RevCommit commit) throws Exception {
+    return PatchSetData.create(
+        cd, cd.patchSet(new PatchSet.Id(cd.getId(), psId)), commit);
+  }
+
+  private static void assertSorted(WalkSorter sorter, List<ChangeData> changes,
+      List<PatchSetData> expected) throws Exception {
+    for (List<ChangeData> list : permutations(changes)) {
+      assertThat(sorter.sort(list))
+          .containsExactlyElementsIn(expected).inOrder();
+    }
+  }
+}