Separate revision updates into two separate comments

Summary:
Ref T2222. Instead of writing one comment which performs both a diff update and adds a comment, write two comments, one for each action. These will translate directly into ApplicationTransactions writes.

This has a small impact on the UX: these updates now render in two rows, instead of one. After T2222, they'll automerge back together.

{F111909}

Test Plan: Updated a revision.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8200

src/applications/differential/editor/DifferentialRevisionEditor.php

@@ -786,21 +786,29 @@ final class DifferentialRevisionEditor extends PhabricatorEditor {
 
 
   private function createComment() {
-    $comment = id(new DifferentialComment())
+    $template = id(new DifferentialComment())
       ->setAuthorPHID($this->getActorPHID())
-      ->setRevision($this->revision)
-      ->setContent($this->getComments())
+      ->setRevision($this->revision);
+    if ($this->contentSource) {
+      $template->setContentSource($this->contentSource);
+    }
+
+    // Write the "update active diff" transaction.
+    id(clone $template)
       ->setAction(DifferentialAction::ACTION_UPDATE)
       ->setMetadata(
         array(
           DifferentialComment::METADATA_DIFF_ID => $this->getDiff()->getID(),
-        ));
+        ))
+      ->save();
 
-    if ($this->contentSource) {
-      $comment->setContentSource($this->contentSource);
+    // If we have a comment, write the "add a comment" transaction.
+    if (strlen($this->getComments())) {
+      id(clone $template)
+        ->setAction(DifferentialAction::ACTION_COMMENT)
+        ->setContent($this->getComments())
+        ->save();
     }
-
-    $comment->save();
   }
 
   private function updateAuxiliaryFields() {

src/applications/differential/storage/DifferentialComment.php

@@ -127,6 +127,7 @@ final class DifferentialComment extends DifferentialDAO
     $this->openTransaction();
       $result = parent::save();
 
+      if (strlen($this->getContent())) {
         $content_source = PhabricatorContentSource::newForSource(
           PhabricatorContentSource::SOURCE_LEGACY,
           array());
@@ -145,6 +146,8 @@ final class DifferentialComment extends DifferentialDAO
           ->setLegacyCommentID($this->getID())
           ->setTransactionPHID($xaction_phid)
           ->save();
+      }
+
     $this->saveTransaction();
 
     return $result;