Implement MatchAuthorToCommitterDate for applicable strategies

Bug: https://crbug.com/732968
Change-Id: I0408d3c871d9120855c180d849cafc791f872b23

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

@@ -248,6 +248,7 @@ public class MergeUtil {
       mergeCommit.setAuthor(originalCommit.getAuthorIdent());
       mergeCommit.setCommitter(cherryPickCommitterIdent);
       mergeCommit.setMessage(commitMsg);
+      matchAuthorToCommitterDate(project, mergeCommit);
       return rw.parseCommit(inserter.insert(mergeCommit));
     }
     throw new MergeConflictException("merge conflict");
@@ -857,4 +858,14 @@ public class MergeUtil {
       throw new ResourceNotFoundException(e.getMessage());
     }
   }
+
+  private static void matchAuthorToCommitterDate(ProjectState project, CommitBuilder commit) {
+    if (project.isMatchAuthorToCommitterDate()) {
+      commit.setAuthor(
+          new PersonIdent(
+              commit.getAuthor(),
+              commit.getCommitter().getWhen(),
+              commit.getCommitter().getTimeZone()));
+    }
+  }
 }

gerrit-server/src/main/java/com/google/gerrit/server/git/strategy/MergeOneOp.java

@@ -28,7 +28,8 @@ class MergeOneOp extends SubmitStrategyOp {
   @Override
   public void updateRepoImpl(RepoContext ctx) throws IntegrationException, IOException {
     PersonIdent caller =
-        ctx.getIdentifiedUser().newCommitterIdent(ctx.getWhen(), ctx.getTimeZone());
+        ctx.getIdentifiedUser()
+            .newCommitterIdent(args.serverIdent.getWhen(), args.serverIdent.getTimeZone());
     if (args.mergeTip.getCurrentTip() == null) {
       throw new IllegalStateException(
           "cannot merge commit "

gerrit-server/src/main/java/com/google/gerrit/server/git/strategy/RebaseSubmitStrategy.java

@@ -179,7 +179,8 @@ public class RebaseSubmitStrategy extends SubmitStrategy {
                 .setDetailedCommitMessage(rebaseAlways)
                 // Do not post message after inserting new patchset because there
                 // will be one about change being merged already.
-                .setPostMessage(false);
+                .setPostMessage(false)
+                .setMatchAuthorToCommitterDate(args.project.isMatchAuthorToCommitterDate());
         try {
           rebaseOp.updateRepo(ctx);
         } catch (MergeConflictException | NoSuchChangeException e) {