public function updateTransactionMailBody(PhabricatorMetaMTAMailBody $body, PhabricatorApplicationTransactionEditor $editor, array $xactions)
 {
     if ($editor->getIsNewObject()) {
         return;
     }
     if ($editor->getIsCloseByCommit()) {
         return;
     }
     $xaction = $editor->getDiffUpdateTransaction($xactions);
     if (!$xaction) {
         return;
     }
     $original = id(new DifferentialDiffQuery())->setViewer($this->getViewer())->withPHIDs(array($xaction->getOldValue()))->executeOne();
     if (!$original) {
         return;
     }
     $revision = $this->getObject();
     $current = $revision->getActiveDiff();
     $old_id = $original->getID();
     $new_id = $current->getID();
     $uri = '/' . $revision->getMonogram() . '?vs=' . $old_id . '&id=' . $new_id;
     $uri = PhabricatorEnv::getProductionURI($uri);
     $body->addTextSection(pht('CHANGES SINCE LAST UPDATE'), $uri);
 }