Merge "Fix auto-merge detection in new diff cache"

java/com/google/gerrit/server/patch/filediff/FileDiffCacheImpl.java

diff --git a/java/com/google/gerrit/server/patch/filediff/FileDiffCacheImpl.java b/java/com/google/gerrit/server/patch/filediff/FileDiffCacheImpl.java
index 1bb407d..8163b19 100644
--- a/java/com/google/gerrit/server/patch/filediff/FileDiffCacheImpl.java
+++ b/java/com/google/gerrit/server/patch/filediff/FileDiffCacheImpl.java
@@ -93,7 +93,7 @@
         persist(DIFF, FileDiffCacheKey.class, FileDiffOutput.class)
             .maximumWeight(10 << 20)
             .weigher(FileDiffWeigher.class)
-            .version(2)
+            .version(3)
             .keySerializer(FileDiffCacheKey.Serializer.INSTANCE)
             .valueSerializer(FileDiffOutput.Serializer.INSTANCE)
             .loader(FileDiffLoader.class);
@@ -203,9 +203,8 @@
       // COMMIT_MSG and MERGE_LIST evaluations outside of the diff cache. For more details, see
       // discussion in
       // https://gerrit-review.googlesource.com/c/gerrit/+/280519/6..18/java/com/google/gerrit/server/patch/FileDiffCache.java#b540
-      Text oldCommitMsgTxt = Text.forCommit(reader, oldCommit);
-      if (oldCommitMsgTxt.size() > 0
-          && oldCommitMsgTxt.getString(0).startsWith(AutoMerger.AUTO_MERGE_MSG_PREFIX)) {
+      String oldCommitMsgTxt = new String(Text.forCommit(reader, oldCommit).getContent(), UTF_8);
+      if (oldCommitMsgTxt.contains(AutoMerger.AUTO_MERGE_MSG_PREFIX)) {
         return ComparisonType.againstAutoMerge();
       }
       return ComparisonType.againstOtherPatchSet();

javatests/com/google/gerrit/acceptance/api/revision/RevisionDiffIT.java

diff --git a/javatests/com/google/gerrit/acceptance/api/revision/RevisionDiffIT.java b/javatests/com/google/gerrit/acceptance/api/revision/RevisionDiffIT.java
index ec59674..f443238 100644
--- a/javatests/com/google/gerrit/acceptance/api/revision/RevisionDiffIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/revision/RevisionDiffIT.java
@@ -519,6 +519,32 @@
   }
 
   @Test
+  public void diffAgainstAutoMergeCanBeRetrievedForCommitMessageAndMergeList() throws Exception {
+    PushOneCommit.Result result = createMergeCommitChange("refs/for/master", "my_file.txt");
+    String changeId = result.getChangeId();
+    addModifiedPatchSet(changeId, "my_file.txt", content -> content.concat("Line I\nLine II\n"));
+
+    DiffInfo commitMessageDiffInfo =
+        getDiffRequest(changeId, CURRENT, COMMIT_MSG)
+            .get(); // diff latest PS against base (auto-merge)
+    DiffInfo mergeListDiffInfo =
+        getDiffRequest(changeId, CURRENT, MERGE_LIST)
+            .get(); // diff latest PS against base (auto-merge)
+
+    assertThat(commitMessageDiffInfo).changeType().isEqualTo(ChangeType.ADDED);
+    assertThat(commitMessageDiffInfo).content().hasSize(1);
+
+    assertThat(mergeListDiffInfo).changeType().isEqualTo(ChangeType.ADDED);
+    assertThat(mergeListDiffInfo).content().hasSize(1);
+    assertThat(mergeListDiffInfo)
+        .content()
+        .element(0)
+        .linesOfB()
+        .element(0)
+        .isEqualTo("Merge List:");
+  }
+
+  @Test
   public void diffOfUnmodifiedFileMarksAllLinesAsCommon() throws Exception {
     String filePath = "a_new_file.txt";
     String fileContent = "Line 1\nLine 2\nLine 3\n";