Indicate trivial rebase and commit message update on push

Indication is appended to "Uploaded patch set N" message
in the review history.

For trivial rebase:
  Uploaded patch set 3: Patch set 2 was rebased.

For commit message update:
  Uploaded patch set 3: Commit message was updated.

Change-Id: Ic5e7c45feb2ea5f1b4607f5103153aa70ae6d7da

gerrit-server/src/main/java/com/google/gerrit/server/git/ReceiveCommits.java

@@ -76,6 +76,8 @@ import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.account.AccountCache;
 import com.google.gerrit.server.account.AccountResolver;
 import com.google.gerrit.server.change.ChangeInserter;
+import com.google.gerrit.server.change.ChangeKind;
+import com.google.gerrit.server.change.ChangeKindCache;
 import com.google.gerrit.server.change.ChangesCollection;
 import com.google.gerrit.server.change.MergeabilityChecker;
 import com.google.gerrit.server.change.RevisionResource;
@@ -298,6 +300,7 @@ public class ReceiveCommits {
   private final SshInfo sshInfo;
   private final AllProjectsName allProjectsName;
   private final ReceiveConfig receiveConfig;
+  private final ChangeKindCache changeKindCache;
 
   private final ProjectControl projectControl;
   private final Project project;
@@ -371,6 +374,7 @@ public class ReceiveCommits {
       final SubmoduleOp.Factory subOpFactory,
       final Provider<Submit> submitProvider,
       final MergeQueue mergeQueue,
+      final ChangeKindCache changeKindCache,
       final DynamicMap<ProjectConfigEntry> pluginConfigEntries) throws IOException {
     this.currentUser = (IdentifiedUser) projectControl.getCurrentUser();
     this.db = db;
@@ -404,6 +408,7 @@ public class ReceiveCommits {
     this.sshInfo = sshInfo;
     this.allProjectsName = allProjectsName;
     this.receiveConfig = config;
+    this.changeKindCache = changeKindCache;
 
     this.projectControl = projectControl;
     this.labelTypes = projectControl.getLabelTypes();
@@ -1960,6 +1965,30 @@ public class ReceiveCommits {
       return Futures.makeChecked(future, INSERT_EXCEPTION);
     }
 
+    private ChangeMessage newChangeMessage(ReviewDb db) throws OrmException {
+      msg =
+          new ChangeMessage(new ChangeMessage.Key(change.getId(), ChangeUtil
+              .messageUUID(db)), currentUser.getAccountId(), newPatchSet.getCreatedOn(),
+              newPatchSet.getId());
+      RevCommit priorCommit = revisions.inverse().get(priorPatchSet);
+      ChangeKind changeKind = changeKindCache.getChangeKind(
+          projectControl.getProjectState(), repo, priorCommit, newCommit);
+      String message = "Uploaded patch set " + newPatchSet.getPatchSetId();
+      switch (changeKind) {
+        case TRIVIAL_REBASE:
+          message += ": Patch Set " + priorPatchSet.get() + " was rebased";
+          break;
+        case NO_CODE_CHANGE:
+          message += ": Commit message was updated";
+          break;
+        case REWORK:
+        default:
+          break;
+      }
+      msg.setMessage(message + ".");
+      return msg;
+    }
+
     PatchSet.Id insertPatchSet(ReviewDb db) throws OrmException, IOException {
       final Account.Id me = currentUser.getAccountId();
       final List<FooterLine> footerLines = newCommit.getFooterLines();
@@ -1999,11 +2028,7 @@ public class ReceiveCommits {
             change, changeCtl, approvals);
         recipients.add(oldRecipients);
 
-        msg =
+        cmUtil.addChangeMessage(db, update, newChangeMessage(db));
-            new ChangeMessage(new ChangeMessage.Key(change.getId(), ChangeUtil
-                .messageUUID(db)), me, newPatchSet.getCreatedOn(), newPatchSet.getId());
-        msg.setMessage("Uploaded patch set " + newPatchSet.getPatchSetId() + ".");
-        cmUtil.addChangeMessage(db, update, msg);
 
         if (mergedIntoRef == null) {
           // Change should be new, so it can go through review again.