Pass the constructed message to the TYPE_DIFF_DIDBUILDMESSAGE event.

Summary: We want to use TYPE_DIFF_DIDBUILDMESSAGE to abort arc diff when a message doesn't fit some

Test Plan: Created an EventListener subscribed to TYPE_DIFF_DIDBUILDMESSAGE, validated the 'message' field was filled in

Reviewers: vrana, epriestley

Reviewed By: epriestley

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D4361

src/workflow/ArcanistDiffWorkflow.php

@@ -428,7 +428,10 @@ EOTEXT
 
     $this->dispatchEvent(
       ArcanistEventType::TYPE_DIFF_DIDBUILDMESSAGE,
-      array());
+      array(
+        'message' => $commit_message
+      )
+    );
 
     if (!$this->shouldOnlyCreateDiff()) {
       $revision = $this->buildRevisionFromCommitMessage($commit_message);