When creating a new revision, include the summary in the initial email

Summary: This got dropped in the ApplicationTransactions stuff.

Test Plan: Created a new revision.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: aran, epriestley

Differential Revision: https://secure.phabricator.com/D8495

src/applications/differential/editor/DifferentialTransactionEditor.php

@@ -999,6 +999,12 @@ final class DifferentialTransactionEditor
 
     $body = parent::buildMailBody($object, $xactions);
 
+    if ($this->getIsNewObject()) {
+      $body->addTextSection(
+        pht('REVISION SUMMARY'),
+        $object->getSummary());
+    }
+
     $type_inline = DifferentialTransaction::TYPE_INLINE;
 
     $inlines = array();