Merge "Update existing change on cherry-pick with CommitApi" into stable-3.3

6 files changed, 320 insertions, 57 deletions

diff --git a/java/com/google/gerrit/server/change/ResetCherryPickOp.java b/java/com/google/gerrit/server/change/ResetCherryPickOp.java
new file mode 100644
index 0000000000..d1177d498c
--- /dev/null
+++ b/java/com/google/gerrit/server/change/ResetCherryPickOp.java
@@ -0,0 +1,37 @@
+// 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.change;
+
+import com.google.gerrit.entities.Change;
+import com.google.gerrit.extensions.restapi.RestApiException;
+import com.google.gerrit.server.notedb.ChangeUpdate;
+import com.google.gerrit.server.update.BatchUpdateOp;
+import com.google.gerrit.server.update.ChangeContext;
+
+/** Reset cherryPickOf to an empty value. */
+public class ResetCherryPickOp implements BatchUpdateOp {
+
+  @Override
+  public boolean updateChange(ChangeContext ctx) throws RestApiException {
+    Change change = ctx.getChange();
+    if (change.getCherryPickOf() == null) {
+      return false;
+    }
+
+    ChangeUpdate update = ctx.getUpdate(change.currentPatchSetId());
+    update.resetCherryPickOf();
+    return true;
+  }
+}
diff --git a/java/com/google/gerrit/server/notedb/ChangeNotesParser.java b/java/com/google/gerrit/server/notedb/ChangeNotesParser.java
index 78ba243777..6f9f7e8a30 100644
--- a/java/com/google/gerrit/server/notedb/ChangeNotesParser.java
+++ b/java/com/google/gerrit/server/notedb/ChangeNotesParser.java
@@ -55,6 +55,7 @@ import com.google.common.collect.Table;
 import com.google.common.collect.Tables;
 import com.google.common.flogger.FluentLogger;
 import com.google.common.primitives.Ints;
+import com.google.gerrit.common.Nullable;
 import com.google.gerrit.entities.Account;
 import com.google.gerrit.entities.Address;
 import com.google.gerrit.entities.AttentionSetUpdate;
@@ -153,7 +154,10 @@ class ChangeNotesParser {
   private ReviewerByEmailSet pendingReviewersByEmail;
   private Change.Id revertOf;
   private int updateCount;
-  private PatchSet.Id cherryPickOf;
+  // Null indicates that the field was not parsed (yet).
+  // We only set the value once, based on the latest update (the actual value or Optional.empty() if
+  // the latest record unsets the field).
+  private Optional<PatchSet.Id> cherryPickOf;
 
   ChangeNotesParser(
       Change.Id changeId,
@@ -254,7 +258,7 @@ class ChangeNotesParser {
         firstNonNull(workInProgress, false),
         firstNonNull(hasReviewStarted, true),
         revertOf,
-        cherryPickOf,
+        cherryPickOf != null ? cherryPickOf.orElse(null) : null,
         updateCount);
   }
 
@@ -999,15 +1003,31 @@ class ChangeNotesParser {
     return Change.id(revertOf);
   }
 
-  private PatchSet.Id parseCherryPickOf(ChangeNotesCommit commit) throws ConfigInvalidException {
-    String cherryPickOf = parseOneFooter(commit, FOOTER_CHERRY_PICK_OF);
-    if (cherryPickOf == null) {
+  /**
+   * Parses {@link ChangeNoteUtil#FOOTER_CHERRY_PICK_OF} of the commit.
+   *
+   * @param commit the commit to parse.
+   * @return {@link Optional} value of the parsed footer or {@code null} if the footer is missing in
+   *     this commit.
+   * @throws ConfigInvalidException if the footer value could not be parsed as a valid {@link
+   *     PatchSet.Id}.
+   */
+  @Nullable
+  private Optional<PatchSet.Id> parseCherryPickOf(ChangeNotesCommit commit)
+      throws ConfigInvalidException {
+    String footer = parseOneFooter(commit, FOOTER_CHERRY_PICK_OF);
+    if (footer == null) {
+      // The footer is missing, nothing to parse.
       return null;
-    }
-    try {
-      return PatchSet.Id.parse(cherryPickOf);
-    } catch (IllegalArgumentException e) {
-      throw new ConfigInvalidException("\"" + cherryPickOf + "\" is not a valid patchset", e);
+    } else if (footer.equals("")) {
+      // Empty footer value, cherryPickOf was unset at this commit.
+      return Optional.empty();
+    } else {
+      try {
+        return Optional.of(PatchSet.Id.parse(footer));
+      } catch (IllegalArgumentException e) {
+        throw new ConfigInvalidException("\"" + footer + "\" is not a valid patchset", e);
+      }
     }
   }
 
diff --git a/java/com/google/gerrit/server/notedb/ChangeUpdate.java b/java/com/google/gerrit/server/notedb/ChangeUpdate.java
index 3312d6cfc9..52c551ef0e 100644
--- a/java/com/google/gerrit/server/notedb/ChangeUpdate.java
+++ b/java/com/google/gerrit/server/notedb/ChangeUpdate.java
@@ -152,7 +152,9 @@ public class ChangeUpdate extends AbstractChangeUpdate {
   private Boolean isPrivate;
   private Boolean workInProgress;
   private Integer revertOf;
-  private String cherryPickOf;
+  // If null, the update does not modify the field. Otherwise, it updates the field with the
+  // new value or resets if cherryPickOf == Optional.empty().
+  private Optional<String> cherryPickOf;
 
   private ChangeDraftUpdate draftUpdate;
   private RobotCommentUpdate robotCommentUpdate;
@@ -473,7 +475,12 @@ public class ChangeUpdate extends AbstractChangeUpdate {
   }
 
   public void setCherryPickOf(String cherryPickOf) {
-    this.cherryPickOf = cherryPickOf;
+    checkArgument(cherryPickOf != null, "use resetCherryPickOf");
+    this.cherryPickOf = Optional.of(cherryPickOf);
+  }
+
+  public void resetCherryPickOf() {
+    this.cherryPickOf = Optional.empty();
   }
 
   /** @return the tree id for the updated tree */
@@ -753,7 +760,12 @@ public class ChangeUpdate extends AbstractChangeUpdate {
     }
 
     if (cherryPickOf != null) {
-      addFooter(msg, FOOTER_CHERRY_PICK_OF, cherryPickOf);
+      if (cherryPickOf.isPresent()) {
+        addFooter(msg, FOOTER_CHERRY_PICK_OF, cherryPickOf.get());
+      } else {
+        // Update cherryPickOf with an empty value.
+        addFooter(msg, FOOTER_CHERRY_PICK_OF).append('\n');
+      }
     }
 
     if (plannedAttentionSetUpdates != null) {
diff --git a/java/com/google/gerrit/server/restapi/change/CherryPickChange.java b/java/com/google/gerrit/server/restapi/change/CherryPickChange.java
index fdac552edf..6ee3284c5d 100644
--- a/java/com/google/gerrit/server/restapi/change/CherryPickChange.java
+++ b/java/com/google/gerrit/server/restapi/change/CherryPickChange.java
@@ -42,6 +42,7 @@ import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.change.ChangeInserter;
 import com.google.gerrit.server.change.NotifyResolver;
 import com.google.gerrit.server.change.PatchSetInserter;
+import com.google.gerrit.server.change.ResetCherryPickOp;
 import com.google.gerrit.server.change.SetCherryPickOp;
 import com.google.gerrit.server.config.UrlFormatter;
 import com.google.gerrit.server.git.CodeReviewCommit;
@@ -371,7 +372,7 @@ public class CherryPickChange {
                     git,
                     destChanges.get(0).notes(),
                     cherryPickCommit,
-                    sourceChange.currentPatchSetId(),
+                    sourceChange,
                     newTopic,
                     workInProgress);
           } else {
@@ -456,7 +457,7 @@ public class CherryPickChange {
       Repository git,
       ChangeNotes destNotes,
       CodeReviewCommit cherryPickCommit,
-      PatchSet.Id sourcePatchSetId,
+      @Nullable Change sourceChange,
       String topic,
       @Nullable Boolean workInProgress)
       throws IOException {
@@ -469,7 +470,11 @@ public class CherryPickChange {
       inserter.setWorkInProgress(workInProgress);
     }
     bu.addOp(destChange.getId(), inserter);
-    if (destChange.getCherryPickOf() == null
+    PatchSet.Id sourcePatchSetId = sourceChange == null ? null : sourceChange.currentPatchSetId();
+    // If sourceChange is not provided, reset cherryPickOf to avoid stale value.
+    if (sourcePatchSetId == null) {
+      bu.addOp(destChange.getId(), new ResetCherryPickOp());
+    } else if (destChange.getCherryPickOf() == null
         || !destChange.getCherryPickOf().equals(sourcePatchSetId)) {
       SetCherryPickOp cherryPickOfUpdater = setCherryPickOfFactory.create(sourcePatchSetId);
       bu.addOp(destChange.getId(), cherryPickOfUpdater);
diff --git a/javatests/com/google/gerrit/acceptance/api/project/CommitIT.java b/javatests/com/google/gerrit/acceptance/api/project/CommitIT.java
index 23563275b8..3b5ac78b26 100644
--- a/javatests/com/google/gerrit/acceptance/api/project/CommitIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/project/CommitIT.java
@@ -24,6 +24,7 @@ import static org.eclipse.jgit.lib.Constants.R_TAGS;
 
 import com.google.gerrit.acceptance.AbstractDaemonTest;
 import com.google.gerrit.acceptance.NoHttpd;
+import com.google.gerrit.acceptance.PushOneCommit;
 import com.google.gerrit.acceptance.PushOneCommit.Result;
 import com.google.gerrit.acceptance.TestAccount;
 import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
@@ -147,77 +148,237 @@ public class CommitIT extends AbstractDaemonTest {
   }
 
   @Test
-  public void cherryPickWithoutMessage() throws Exception {
-    String branch = "foo";
+  public void cherryPickWithoutMessageSameBranch() throws Exception {
+    String destBranch = "master";
 
     // Create change to cherry-pick
-    RevCommit revCommit = createChange().getCommit();
-
-    // Create target branch to cherry-pick to.
-    gApi.projects().name(project.get()).branch(branch).create(new BranchInput());
+    PushOneCommit.Result r = createChange();
+    ChangeInfo changeToCherryPick = info(r.getChangeId());
+    RevCommit commitToCherryPick = r.getCommit();
 
     // Cherry-pick without message.
     CherryPickInput input = new CherryPickInput();
-    input.destination = branch;
-    String changeId =
-        gApi.projects().name(project.get()).commit(revCommit.name()).cherryPick(input).get().id;
+    input.destination = destBranch;
+    ChangeInfo cherryPickResult =
+        gApi.projects()
+            .name(project.get())
+            .commit(commitToCherryPick.name())
+            .cherryPick(input)
+            .get();
+
+    // Expect that the Change-Id of the cherry-picked commit was used for the cherry-pick change.
+    // New patch-set to existing change was uploaded.
+    assertThat(cherryPickResult._number).isEqualTo(changeToCherryPick._number);
+    assertThat(cherryPickResult.revisions).hasSize(2);
+    assertThat(cherryPickResult.changeId).isEqualTo(changeToCherryPick.changeId);
+    assertThat(cherryPickResult.messages).hasSize(2);
+
+    // Cherry-pick of is not set, because the source change was not provided.
+    assertThat(cherryPickResult.cherryPickOfChange).isNull();
+    assertThat(cherryPickResult.cherryPickOfPatchSet).isNull();
+    // Expect that the message of the cherry-picked commit was used for the cherry-pick change.
+    RevisionInfo revInfo = cherryPickResult.revisions.get(cherryPickResult.currentRevision);
+    assertThat(revInfo).isNotNull();
+    assertThat(revInfo.commit.message).isEqualTo(commitToCherryPick.getFullMessage());
+  }
 
+  @Test
+  public void cherryPickWithoutMessageOtherBranch() throws Exception {
+    String destBranch = "foo";
+    createBranch(BranchNameKey.create(project, destBranch));
+
+    // Create change to cherry-pick
+    PushOneCommit.Result r = createChange();
+    ChangeInfo changeToCherryPick = info(r.getChangeId());
+    RevCommit commitToCherryPick = r.getCommit();
+
+    // Cherry-pick without message.
+    CherryPickInput input = new CherryPickInput();
+    input.destination = destBranch;
+    ChangeInfo cherryPickResult =
+        gApi.projects()
+            .name(project.get())
+            .commit(commitToCherryPick.name())
+            .cherryPick(input)
+            .get();
+
+    // Expect that the Change-Id of the cherry-picked commit was used for the cherry-pick change.
+    // New change in destination branch was created.
+    assertThat(cherryPickResult._number).isGreaterThan(changeToCherryPick._number);
+    assertThat(cherryPickResult.revisions).hasSize(1);
+    assertThat(cherryPickResult.changeId).isEqualTo(changeToCherryPick.changeId);
+    assertThat(cherryPickResult.messages).hasSize(1);
+
+    // Cherry-pick of is not set, because the source change was not provided.
+    assertThat(cherryPickResult.cherryPickOfChange).isNull();
+    assertThat(cherryPickResult.cherryPickOfPatchSet).isNull();
     // Expect that the message of the cherry-picked commit was used for the cherry-pick change.
-    ChangeInfo changeInfo = gApi.changes().id(changeId).get();
-    RevisionInfo revInfo = changeInfo.revisions.get(changeInfo.currentRevision);
+    RevisionInfo revInfo = cherryPickResult.revisions.get(cherryPickResult.currentRevision);
     assertThat(revInfo).isNotNull();
-    assertThat(revInfo.commit.message).isEqualTo(revCommit.getFullMessage());
+    assertThat(revInfo.commit.message).isEqualTo(commitToCherryPick.getFullMessage());
   }
 
   @Test
-  public void cherryPickCommitWithoutChangeId() throws Exception {
+  public void cherryPickCommitWithoutChangeIdCreateNewChange() throws Exception {
+    String destBranch = "foo";
+    createBranch(BranchNameKey.create(project, destBranch));
+
     CherryPickInput input = new CherryPickInput();
-    input.destination = "foo";
+    input.destination = destBranch;
     input.message = "it goes to foo branch";
-    gApi.projects().name(project.get()).branch(input.destination).create(new BranchInput());
-
-    RevCommit revCommit = createNewCommitWithoutChangeId("refs/heads/master", "a.txt", "content");
-    ChangeInfo changeInfo =
-        gApi.projects().name(project.get()).commit(revCommit.getName()).cherryPick(input).get();
 
-    assertThat(changeInfo.messages).hasSize(1);
-    Iterator<ChangeMessageInfo> messageIterator = changeInfo.messages.iterator();
+    RevCommit commitToCherryPick =
+        createNewCommitWithoutChangeId("refs/heads/master", "a.txt", "content");
+    ChangeInfo cherryPickResult =
+        gApi.projects()
+            .name(project.get())
+            .commit(commitToCherryPick.getName())
+            .cherryPick(input)
+            .get();
+
+    assertThat(cherryPickResult.messages).hasSize(1);
+    Iterator<ChangeMessageInfo> messageIterator = cherryPickResult.messages.iterator();
     String expectedMessage =
-        String.format("Patch Set 1: Cherry Picked from commit %s.", revCommit.getName());
+        String.format("Patch Set 1: Cherry Picked from commit %s.", commitToCherryPick.getName());
     assertThat(messageIterator.next().message).isEqualTo(expectedMessage);
 
-    RevisionInfo revInfo = changeInfo.revisions.get(changeInfo.currentRevision);
+    RevisionInfo revInfo = cherryPickResult.revisions.get(cherryPickResult.currentRevision);
     assertThat(revInfo).isNotNull();
     CommitInfo commitInfo = revInfo.commit;
     assertThat(commitInfo.message)
-        .isEqualTo(input.message + "\n\nChange-Id: " + changeInfo.changeId + "\n");
+        .isEqualTo(input.message + "\n\nChange-Id: " + cherryPickResult.changeId + "\n");
   }
 
   @Test
-  public void cherryPickCommitWithChangeId() throws Exception {
-    CherryPickInput input = new CherryPickInput();
-    input.destination = "foo";
-
-    RevCommit revCommit = createChange().getCommit();
-    List<String> footers = revCommit.getFooterLines("Change-Id");
+  public void cherryPickCommitWithChangeIdCreateNewChange() throws Exception {
+    String destBranch = "foo";
+    createBranch(BranchNameKey.create(project, destBranch));
+
+    PushOneCommit.Result r = createChange();
+    ChangeInfo changeToCherryPick = info(r.getChangeId());
+    RevCommit commitToCherryPick = r.getCommit();
+    List<String> footers = commitToCherryPick.getFooterLines("Change-Id");
     assertThat(footers).hasSize(1);
     String changeId = footers.get(0);
 
-    input.message = "it goes to foo branch\n\nChange-Id: " + changeId;
-    gApi.projects().name(project.get()).branch(input.destination).create(new BranchInput());
-
-    ChangeInfo changeInfo =
-        gApi.projects().name(project.get()).commit(revCommit.getName()).cherryPick(input).get();
-
-    assertThat(changeInfo.messages).hasSize(1);
-    Iterator<ChangeMessageInfo> messageIterator = changeInfo.messages.iterator();
+    CherryPickInput input = new CherryPickInput();
+    input.destination = destBranch;
+    input.message =
+        String.format(
+            "it goes to foo branch\n\nChange-Id: Ideadbeefdeadbeefdeadbeefdeadbeefdeadbeef\n\nChange-Id: %s\n",
+            changeId);
+
+    ChangeInfo cherryPickResult =
+        gApi.projects()
+            .name(project.get())
+            .commit(commitToCherryPick.getName())
+            .cherryPick(input)
+            .get();
+
+    // No change was found in destination branch with the provided Change-Id.
+    assertThat(cherryPickResult._number).isGreaterThan(changeToCherryPick._number);
+    assertThat(cherryPickResult.changeId).isEqualTo(changeId);
+    assertThat(cherryPickResult.revisions).hasSize(1);
+    assertThat(cherryPickResult.messages).hasSize(1);
+    Iterator<ChangeMessageInfo> messageIterator = cherryPickResult.messages.iterator();
     String expectedMessage =
-        String.format("Patch Set 1: Cherry Picked from commit %s.", revCommit.getName());
+        String.format("Patch Set 1: Cherry Picked from commit %s.", commitToCherryPick.getName());
     assertThat(messageIterator.next().message).isEqualTo(expectedMessage);
 
-    RevisionInfo revInfo = changeInfo.revisions.get(changeInfo.currentRevision);
+    // Cherry-pick of is not set, because the source change was not provided.
+    assertThat(cherryPickResult.cherryPickOfChange).isNull();
+    assertThat(cherryPickResult.cherryPickOfPatchSet).isNull();
+    RevisionInfo revInfo = cherryPickResult.revisions.get(cherryPickResult.currentRevision);
+    assertThat(revInfo).isNotNull();
+    assertThat(revInfo.commit.message).isEqualTo(input.message);
+  }
+
+  @Test
+  public void cherryPickCommitToExistingChange() throws Exception {
+    String destBranch = "foo";
+    createBranch(BranchNameKey.create(project, destBranch));
+
+    PushOneCommit.Result r = createChange("refs/for/" + destBranch);
+    ChangeInfo existingDestChange = info(r.getChangeId());
+
+    String commitToCherryPick = createChange().getCommit().getName();
+
+    CherryPickInput input = new CherryPickInput();
+    input.destination = destBranch;
+    input.message =
+        String.format(
+            "it goes to foo branch\n\nChange-Id: Ideadbeefdeadbeefdeadbeefdeadbeefdeadbeef\n\nChange-Id: %s\n",
+            existingDestChange.changeId);
+    input.allowConflicts = true;
+    input.allowEmpty = true;
+
+    ChangeInfo cherryPickResult =
+        gApi.projects().name(project.get()).commit(commitToCherryPick).cherryPick(input).get();
+
+    // New patch-set to existing change was uploaded.
+    assertThat(cherryPickResult._number).isEqualTo(existingDestChange._number);
+    assertThat(cherryPickResult.changeId).isEqualTo(existingDestChange.changeId);
+    assertThat(cherryPickResult.messages).hasSize(2);
+    assertThat(cherryPickResult.revisions).hasSize(2);
+    Iterator<ChangeMessageInfo> messageIterator = cherryPickResult.messages.iterator();
+
+    assertThat(messageIterator.next().message).isEqualTo("Uploaded patch set 1.");
+    assertThat(messageIterator.next().message).isEqualTo("Uploaded patch set 2.");
+    // Cherry-pick of is not set, because the source change was not provided.
+    assertThat(cherryPickResult.cherryPickOfChange).isNull();
+    assertThat(cherryPickResult.cherryPickOfPatchSet).isNull();
+    RevisionInfo revInfo = cherryPickResult.revisions.get(cherryPickResult.currentRevision);
+    assertThat(revInfo).isNotNull();
+    assertThat(revInfo.commit.message).isEqualTo(input.message);
+  }
+
+  @Test
+  public void cherryPickCommitToExistingCherryPickedChange() throws Exception {
+    String destBranch = "foo";
+    createBranch(BranchNameKey.create(project, destBranch));
+
+    PushOneCommit.Result r = createChange("refs/for/" + destBranch);
+    ChangeInfo existingDestChange = info(r.getChangeId());
+
+    r = createChange();
+    ChangeInfo changeToCherryPick = info(r.getChangeId());
+    RevCommit commitToCherryPick = r.getCommit();
+
+    CherryPickInput input = new CherryPickInput();
+    input.destination = destBranch;
+    input.message =
+        String.format("it goes to foo branch\n\nChange-Id: %s\n", existingDestChange.changeId);
+    input.allowConflicts = true;
+    input.allowEmpty = true;
+    // Use RevisionAPI to submit initial cherryPick.
+    ChangeInfo cherryPickResult =
+        gApi.changes().id(changeToCherryPick.changeId).current().cherryPick(input).get();
+    assertThat(cherryPickResult.changeId).isEqualTo(existingDestChange.changeId);
+    // Cherry-pick was set.
+    assertThat(cherryPickResult.cherryPickOfChange).isEqualTo(changeToCherryPick._number);
+    assertThat(cherryPickResult.cherryPickOfPatchSet).isEqualTo(1);
+    RevisionInfo revInfo = cherryPickResult.revisions.get(cherryPickResult.currentRevision);
     assertThat(revInfo).isNotNull();
-    assertThat(revInfo.commit.message).isEqualTo(input.message + "\n");
+    assertThat(revInfo.commit.message).isEqualTo(input.message);
+    // Use CommitApi to update the cherryPick change.
+    cherryPickResult =
+        gApi.projects()
+            .name(project.get())
+            .commit(commitToCherryPick.getName())
+            .cherryPick(input)
+            .get();
+
+    assertThat(cherryPickResult.changeId).isEqualTo(existingDestChange.changeId);
+    assertThat(cherryPickResult.messages).hasSize(3);
+    Iterator<ChangeMessageInfo> messageIterator = cherryPickResult.messages.iterator();
+
+    assertThat(messageIterator.next().message).isEqualTo("Uploaded patch set 1.");
+    assertThat(messageIterator.next().message).isEqualTo("Uploaded patch set 2.");
+    assertThat(messageIterator.next().message).isEqualTo("Uploaded patch set 3.");
+    // Cherry-pick was reset to empty value.
+    assertThat(cherryPickResult._number).isEqualTo(existingDestChange._number);
+    assertThat(cherryPickResult.cherryPickOfChange).isNull();
+    assertThat(cherryPickResult.cherryPickOfPatchSet).isNull();
   }
 
   @Test
diff --git a/javatests/com/google/gerrit/server/notedb/ChangeNotesTest.java b/javatests/com/google/gerrit/server/notedb/ChangeNotesTest.java
index 938fffc443..6b9859f4e3 100644
--- a/javatests/com/google/gerrit/server/notedb/ChangeNotesTest.java
+++ b/javatests/com/google/gerrit/server/notedb/ChangeNotesTest.java
@@ -3146,6 +3146,34 @@ public class ChangeNotesTest extends AbstractChangeNotesTest {
   }
 
   @Test
+  public void resetCherryPickOf() throws Exception {
+    Change destinationChange = newChange();
+    Change cherryPickChange = newChange();
+    assertThat(newNotes(destinationChange).getChange().getCherryPickOf()).isNull();
+
+    ChangeUpdate update = newUpdate(destinationChange, changeOwner);
+    update.setCherryPickOf(
+        cherryPickChange.currentPatchSetId().getCommaSeparatedChangeAndPatchSetId());
+    update.commit();
+    assertThat(newNotes(destinationChange).getChange().getCherryPickOf())
+        .isEqualTo(cherryPickChange.currentPatchSetId());
+
+    update = newUpdate(destinationChange, changeOwner);
+    update.resetCherryPickOf();
+    update.commit();
+    assertThat(newNotes(destinationChange).getChange().getCherryPickOf()).isNull();
+
+    // Can set again after reset.
+    cherryPickChange = newChange();
+    update = newUpdate(destinationChange, changeOwner);
+    update.setCherryPickOf(
+        cherryPickChange.currentPatchSetId().getCommaSeparatedChangeAndPatchSetId());
+    update.commit();
+    assertThat(newNotes(destinationChange).getChange().getCherryPickOf())
+        .isEqualTo(cherryPickChange.currentPatchSetId());
+  }
+
+  @Test
   public void updateCount() throws Exception {
     Change c = newChange();
     assertThat(newNotes(c).getUpdateCount()).isEqualTo(1);