public function saveDiff(DifferentialDiff $diff)
 {
     $actor = $this->requireActor();
     // Generate a PHID first, so the transcript will point at the object if
     // we deicde to preserve it.
     $phid = $diff->generatePHID();
     $diff->setPHID($phid);
     $adapter = id(new HeraldDifferentialDiffAdapter())->setDiff($diff);
     $adapter->setContentSource($this->getContentSource());
     $adapter->setIsNewObject(true);
     $engine = new HeraldEngine();
     $rules = $engine->loadRulesForAdapter($adapter);
     $rules = mpull($rules, null, 'getID');
     $effects = $engine->applyRules($rules, $adapter);
     $blocking_effect = null;
     foreach ($effects as $effect) {
         if ($effect->getAction() == HeraldAdapter::ACTION_BLOCK) {
             $blocking_effect = $effect;
             break;
         }
     }
     if ($blocking_effect) {
         $rule = idx($rules, $effect->getRuleID());
         if ($rule && strlen($rule->getName())) {
             $rule_name = $rule->getName();
         } else {
             $rule_name = pht('Unnamed Herald Rule');
         }
         $message = $effect->getTarget();
         if (!strlen($message)) {
             $message = pht('(None.)');
         }
         throw new DifferentialDiffCreationRejectException(pht("Creation of this diff was rejected by Herald rule %s.\n" . "  Rule: %s\n" . "Reason: %s", 'H' . $effect->getRuleID(), $rule_name, $message));
     }
     $diff->save();
     // NOTE: We only save the transcript if we didn't block the diff.
     // Otherwise, we might save some of the diff's content in the transcript
     // table, which would defeat the purpose of allowing rules to block
     // storage of key material.
     $engine->applyEffects($effects, $adapter, $rules);
     $xscript = $engine->getTranscript();
 }