diff --git a/src/applications/transactions/controller/PhabricatorApplicationTransactionDetailController.php b/src/applications/transactions/controller/PhabricatorApplicationTransactionDetailController.php
index 4529c5a23e..5849ae0c5e 100644
--- a/src/applications/transactions/controller/PhabricatorApplicationTransactionDetailController.php
+++ b/src/applications/transactions/controller/PhabricatorApplicationTransactionDetailController.php
@@ -1,32 +1,63 @@
 <?php
 
 final class PhabricatorApplicationTransactionDetailController
   extends PhabricatorApplicationTransactionController {
 
+  private $objectHandle;
+
   public function shouldAllowPublic() {
     return true;
   }
 
   public function handleRequest(AphrontRequest $request) {
+    // Users can end up on this page directly by following links in email,
+    // so we try to make it somewhat reasonable as a standalone page.
+
     $viewer = $this->getViewer();
     $phid = $request->getURIData('phid');
 
     $xaction = id(new PhabricatorObjectQuery())
       ->withPHIDs(array($phid))
       ->setViewer($viewer)
       ->executeOne();
     if (!$xaction) {
       return new Aphront404Response();
     }
 
     $details = $xaction->renderChangeDetails($viewer);
-    $cancel_uri = $this->guessCancelURI($viewer, $xaction);
+
+    $object_phid = $xaction->getObjectPHID();
+    $handles = $viewer->loadHandles(array($object_phid));
+    $handle = $handles[$object_phid];
+    $this->objectHandle = $handle;
+
+    $cancel_uri = $handle->getURI();
+
+    if ($request->isAjax()) {
+      $button_text = pht('Done');
+    } else {
+      $button_text = pht('Continue');
+    }
 
     return $this->newDialog()
       ->setTitle(pht('Change Details'))
       ->setWidth(AphrontDialogView::WIDTH_FORM)
       ->appendChild($details)
-      ->addCancelButton($cancel_uri);
+      ->addCancelButton($cancel_uri, $button_text);
   }
 
+  protected function buildApplicationCrumbs() {
+    $crumbs = parent::buildApplicationCrumbs();
+
+    $handle = $this->objectHandle;
+    if ($handle) {
+      $crumbs->addTextCrumb(
+        $handle->getObjectName(),
+        $handle->getURI());
+    }
+
+    return $crumbs;
+  }
+
+
 }
diff --git a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
index ae58787503..1a4afa2c9f 100644
--- a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
+++ b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
@@ -1,3652 +1,3677 @@
 <?php
 
 /**
  *
  * Publishing and Managing State
  * ======
  *
  * After applying changes, the Editor queues a worker to publish mail, feed,
  * and notifications, and to perform other background work like updating search
  * indexes. This allows it to do this work without impacting performance for
  * users.
  *
  * When work is moved to the daemons, the Editor state is serialized by
  * @{method:getWorkerState}, then reloaded in a daemon process by
  * @{method:loadWorkerState}. **This is fragile.**
  *
  * State is not persisted into the daemons by default, because we can not send
  * arbitrary objects into the queue. This means the default behavior of any
  * state properties is to reset to their defaults without warning prior to
  * publishing.
  *
  * The easiest way to avoid this is to keep Editors stateless: the overwhelming
  * majority of Editors can be written statelessly. If you need to maintain
  * state, you can either:
  *
  *   - not require state to exist during publishing; or
  *   - pass state to the daemons by implementing @{method:getCustomWorkerState}
  *     and @{method:loadCustomWorkerState}.
  *
  * This architecture isn't ideal, and we may eventually split this class into
  * "Editor" and "Publisher" parts to make it more robust. See T6367 for some
  * discussion and context.
  *
  * @task mail Sending Mail
  * @task feed Publishing Feed Stories
  * @task search Search Index
  * @task files Integration with Files
  * @task workers Managing Workers
  */
 abstract class PhabricatorApplicationTransactionEditor
   extends PhabricatorEditor {
 
   private $contentSource;
   private $object;
   private $xactions;
 
   private $isNewObject;
   private $mentionedPHIDs;
   private $continueOnNoEffect;
   private $continueOnMissingFields;
   private $parentMessageID;
   private $heraldAdapter;
   private $heraldTranscript;
   private $subscribers;
   private $unmentionablePHIDMap = array();
   private $applicationEmail;
 
   private $isPreview;
   private $isHeraldEditor;
   private $isInverseEdgeEditor;
   private $actingAsPHID;
   private $disableEmail;
 
   private $heraldEmailPHIDs = array();
   private $heraldForcedEmailPHIDs = array();
   private $heraldHeader;
   private $mailToPHIDs = array();
   private $mailCCPHIDs = array();
   private $feedNotifyPHIDs = array();
   private $feedRelatedPHIDs = array();
 
   const STORAGE_ENCODING_BINARY = 'binary';
 
   /**
    * Get the class name for the application this editor is a part of.
    *
    * Uninstalling the application will disable the editor.
    *
    * @return string Editor's application class name.
    */
   abstract public function getEditorApplicationClass();
 
 
   /**
    * Get a description of the objects this editor edits, like "Differential
    * Revisions".
    *
    * @return string Human readable description of edited objects.
    */
   abstract public function getEditorObjectsDescription();
 
 
   public function setActingAsPHID($acting_as_phid) {
     $this->actingAsPHID = $acting_as_phid;
     return $this;
   }
 
   public function getActingAsPHID() {
     if ($this->actingAsPHID) {
       return $this->actingAsPHID;
     }
     return $this->getActor()->getPHID();
   }
 
 
   /**
    * When the editor tries to apply transactions that have no effect, should
    * it raise an exception (default) or drop them and continue?
    *
    * Generally, you will set this flag for edits coming from "Edit" interfaces,
    * and leave it cleared for edits coming from "Comment" interfaces, so the
    * user will get a useful error if they try to submit a comment that does
    * nothing (e.g., empty comment with a status change that has already been
    * performed by another user).
    *
    * @param bool  True to drop transactions without effect and continue.
    * @return this
    */
   public function setContinueOnNoEffect($continue) {
     $this->continueOnNoEffect = $continue;
     return $this;
   }
 
   public function getContinueOnNoEffect() {
     return $this->continueOnNoEffect;
   }
 
 
   /**
    * When the editor tries to apply transactions which don't populate all of
    * an object's required fields, should it raise an exception (default) or
    * drop them and continue?
    *
    * For example, if a user adds a new required custom field (like "Severity")
    * to a task, all existing tasks won't have it populated. When users
    * manually edit existing tasks, it's usually desirable to have them provide
    * a severity. However, other operations (like batch editing just the
    * owner of a task) will fail by default.
    *
    * By setting this flag for edit operations which apply to specific fields
    * (like the priority, batch, and merge editors in Maniphest), these
    * operations can continue to function even if an object is outdated.
    *
    * @param bool  True to continue when transactions don't completely satisfy
    *              all required fields.
    * @return this
    */
   public function setContinueOnMissingFields($continue_on_missing_fields) {
     $this->continueOnMissingFields = $continue_on_missing_fields;
     return $this;
   }
 
   public function getContinueOnMissingFields() {
     return $this->continueOnMissingFields;
   }
 
 
   /**
    * Not strictly necessary, but reply handlers ideally set this value to
    * make email threading work better.
    */
   public function setParentMessageID($parent_message_id) {
     $this->parentMessageID = $parent_message_id;
     return $this;
   }
   public function getParentMessageID() {
     return $this->parentMessageID;
   }
 
   public function getIsNewObject() {
     return $this->isNewObject;
   }
 
   protected function getMentionedPHIDs() {
     return $this->mentionedPHIDs;
   }
 
   public function setIsPreview($is_preview) {
     $this->isPreview = $is_preview;
     return $this;
   }
 
   public function getIsPreview() {
     return $this->isPreview;
   }
 
   public function setIsInverseEdgeEditor($is_inverse_edge_editor) {
     $this->isInverseEdgeEditor = $is_inverse_edge_editor;
     return $this;
   }
 
   public function getIsInverseEdgeEditor() {
     return $this->isInverseEdgeEditor;
   }
 
   public function setIsHeraldEditor($is_herald_editor) {
     $this->isHeraldEditor = $is_herald_editor;
     return $this;
   }
 
   public function getIsHeraldEditor() {
     return $this->isHeraldEditor;
   }
 
   /**
    * Prevent this editor from generating email when applying transactions.
    *
    * @param bool  True to disable email.
    * @return this
    */
   public function setDisableEmail($disable_email) {
     $this->disableEmail = $disable_email;
     return $this;
   }
 
   public function getDisableEmail() {
     return $this->disableEmail;
   }
 
   public function setUnmentionablePHIDMap(array $map) {
     $this->unmentionablePHIDMap = $map;
     return $this;
   }
 
   public function getUnmentionablePHIDMap() {
     return $this->unmentionablePHIDMap;
   }
 
   protected function shouldEnableMentions(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return true;
   }
 
   public function setApplicationEmail(
     PhabricatorMetaMTAApplicationEmail $email) {
     $this->applicationEmail = $email;
     return $this;
   }
 
   public function getApplicationEmail() {
     return $this->applicationEmail;
   }
 
   public function getTransactionTypesForObject($object) {
     $old = $this->object;
     try {
       $this->object = $object;
       $result = $this->getTransactionTypes();
       $this->object = $old;
     } catch (Exception $ex) {
       $this->object = $old;
       throw $ex;
     }
     return $result;
   }
 
   public function getTransactionTypes() {
     $types = array();
 
     $types[] = PhabricatorTransactions::TYPE_CREATE;
 
     if ($this->object instanceof PhabricatorSubscribableInterface) {
       $types[] = PhabricatorTransactions::TYPE_SUBSCRIBERS;
     }
 
     if ($this->object instanceof PhabricatorCustomFieldInterface) {
       $types[] = PhabricatorTransactions::TYPE_CUSTOMFIELD;
     }
 
     if ($this->object instanceof HarbormasterBuildableInterface) {
       $types[] = PhabricatorTransactions::TYPE_BUILDABLE;
     }
 
     if ($this->object instanceof PhabricatorTokenReceiverInterface) {
       $types[] = PhabricatorTransactions::TYPE_TOKEN;
     }
 
     if ($this->object instanceof PhabricatorProjectInterface ||
         $this->object instanceof PhabricatorMentionableInterface) {
       $types[] = PhabricatorTransactions::TYPE_EDGE;
     }
 
     if ($this->object instanceof PhabricatorSpacesInterface) {
       $types[] = PhabricatorTransactions::TYPE_SPACE;
     }
 
     return $types;
   }
 
   private function adjustTransactionValues(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     if ($xaction->shouldGenerateOldValue()) {
       $old = $this->getTransactionOldValue($object, $xaction);
       $xaction->setOldValue($old);
     }
 
     $new = $this->getTransactionNewValue($object, $xaction);
     $xaction->setNewValue($new);
   }
 
   private function getTransactionOldValue(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_CREATE:
         return null;
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         return array_values($this->subscribers);
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
         if ($this->getIsNewObject()) {
           return null;
         }
         return $object->getViewPolicy();
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
         if ($this->getIsNewObject()) {
           return null;
         }
         return $object->getEditPolicy();
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
         if ($this->getIsNewObject()) {
           return null;
         }
         return $object->getJoinPolicy();
       case PhabricatorTransactions::TYPE_SPACE:
         if ($this->getIsNewObject()) {
           return null;
         }
 
         $space_phid = $object->getSpacePHID();
         if ($space_phid === null) {
           $default_space = PhabricatorSpacesNamespaceQuery::getDefaultSpace();
           if ($default_space) {
             $space_phid = $default_space->getPHID();
           }
         }
 
         return $space_phid;
       case PhabricatorTransactions::TYPE_EDGE:
         $edge_type = $xaction->getMetadataValue('edge:type');
         if (!$edge_type) {
           throw new Exception(
             pht(
               "Edge transaction has no '%s'!",
               'edge:type'));
         }
 
         $old_edges = array();
         if ($object->getPHID()) {
           $edge_src = $object->getPHID();
 
           $old_edges = id(new PhabricatorEdgeQuery())
             ->withSourcePHIDs(array($edge_src))
             ->withEdgeTypes(array($edge_type))
             ->needEdgeData(true)
             ->execute();
 
           $old_edges = $old_edges[$edge_src][$edge_type];
         }
         return $old_edges;
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         // NOTE: Custom fields have their old value pre-populated when they are
         // built by PhabricatorCustomFieldList.
         return $xaction->getOldValue();
       case PhabricatorTransactions::TYPE_COMMENT:
         return null;
       default:
         return $this->getCustomTransactionOldValue($object, $xaction);
     }
   }
 
   private function getTransactionNewValue(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_CREATE:
         return null;
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         return $this->getPHIDTransactionNewValue($xaction);
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
       case PhabricatorTransactions::TYPE_BUILDABLE:
       case PhabricatorTransactions::TYPE_TOKEN:
       case PhabricatorTransactions::TYPE_INLINESTATE:
         return $xaction->getNewValue();
       case PhabricatorTransactions::TYPE_SPACE:
         $space_phid = $xaction->getNewValue();
         if (!strlen($space_phid)) {
           // If an install has no Spaces or the Spaces controls are not visible
           // to the viewer, we might end up with the empty string here instead
           // of a strict `null`, because some controller just used `getStr()`
           // to read the space PHID from the request.
           // Just make this work like callers might reasonably expect so we
           // don't need to handle this specially in every EditController.
           return $this->getActor()->getDefaultSpacePHID();
         } else {
           return $space_phid;
         }
       case PhabricatorTransactions::TYPE_EDGE:
         $new_value = $this->getEdgeTransactionNewValue($xaction);
 
         $edge_type = $xaction->getMetadataValue('edge:type');
         $type_project = PhabricatorProjectObjectHasProjectEdgeType::EDGECONST;
         if ($edge_type == $type_project) {
           $new_value = $this->applyProjectConflictRules($new_value);
         }
 
         return $new_value;
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $field = $this->getCustomFieldForTransaction($object, $xaction);
         return $field->getNewValueFromApplicationTransactions($xaction);
       case PhabricatorTransactions::TYPE_COMMENT:
         return null;
       default:
         return $this->getCustomTransactionNewValue($object, $xaction);
     }
   }
 
   protected function getCustomTransactionOldValue(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     throw new Exception(pht('Capability not supported!'));
   }
 
   protected function getCustomTransactionNewValue(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     throw new Exception(pht('Capability not supported!'));
   }
 
   protected function transactionHasEffect(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_CREATE:
         return true;
       case PhabricatorTransactions::TYPE_COMMENT:
         return $xaction->hasComment();
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $field = $this->getCustomFieldForTransaction($object, $xaction);
         return $field->getApplicationTransactionHasEffect($xaction);
       case PhabricatorTransactions::TYPE_EDGE:
         // A straight value comparison here doesn't always get the right
         // result, because newly added edges aren't fully populated. Instead,
         // compare the changes in a more granular way.
         $old = $xaction->getOldValue();
         $new = $xaction->getNewValue();
 
         $old_dst = array_keys($old);
         $new_dst = array_keys($new);
 
         // NOTE: For now, we don't consider edge reordering to be a change.
         // We have very few order-dependent edges and effectively no order
         // oriented UI. This might change in the future.
         sort($old_dst);
         sort($new_dst);
 
         if ($old_dst !== $new_dst) {
           // We've added or removed edges, so this transaction definitely
           // has an effect.
           return true;
         }
 
         // We haven't added or removed edges, but we might have changed
         // edge data.
         foreach ($old as $key => $old_value) {
           $new_value = $new[$key];
           if ($old_value['data'] !== $new_value['data']) {
             return true;
           }
         }
 
         return false;
     }
 
     return ($xaction->getOldValue() !== $xaction->getNewValue());
   }
 
   protected function shouldApplyInitialEffects(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return false;
   }
 
   protected function applyInitialEffects(
     PhabricatorLiskDAO $object,
     array $xactions) {
     throw new PhutilMethodNotImplementedException();
   }
 
   private function applyInternalEffects(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $field = $this->getCustomFieldForTransaction($object, $xaction);
         return $field->applyApplicationTransactionInternalEffects($xaction);
       case PhabricatorTransactions::TYPE_CREATE:
       case PhabricatorTransactions::TYPE_BUILDABLE:
       case PhabricatorTransactions::TYPE_TOKEN:
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
       case PhabricatorTransactions::TYPE_INLINESTATE:
       case PhabricatorTransactions::TYPE_EDGE:
       case PhabricatorTransactions::TYPE_SPACE:
       case PhabricatorTransactions::TYPE_COMMENT:
         return $this->applyBuiltinInternalTransaction($object, $xaction);
     }
 
     return $this->applyCustomInternalTransaction($object, $xaction);
   }
 
   private function applyExternalEffects(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         $subeditor = id(new PhabricatorSubscriptionsEditor())
           ->setObject($object)
           ->setActor($this->requireActor());
 
         $old_map = array_fuse($xaction->getOldValue());
         $new_map = array_fuse($xaction->getNewValue());
 
         $subeditor->unsubscribe(
           array_keys(
             array_diff_key($old_map, $new_map)));
 
         $subeditor->subscribeExplicit(
           array_keys(
             array_diff_key($new_map, $old_map)));
 
         $subeditor->save();
 
         // for the rest of these edits, subscribers should include those just
         // added as well as those just removed.
         $subscribers = array_unique(array_merge(
           $this->subscribers,
           $xaction->getOldValue(),
           $xaction->getNewValue()));
         $this->subscribers = $subscribers;
         return $this->applyBuiltinExternalTransaction($object, $xaction);
 
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $field = $this->getCustomFieldForTransaction($object, $xaction);
         return $field->applyApplicationTransactionExternalEffects($xaction);
       case PhabricatorTransactions::TYPE_CREATE:
       case PhabricatorTransactions::TYPE_EDGE:
       case PhabricatorTransactions::TYPE_BUILDABLE:
       case PhabricatorTransactions::TYPE_TOKEN:
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
       case PhabricatorTransactions::TYPE_INLINESTATE:
       case PhabricatorTransactions::TYPE_SPACE:
       case PhabricatorTransactions::TYPE_COMMENT:
         return $this->applyBuiltinExternalTransaction($object, $xaction);
     }
 
     return $this->applyCustomExternalTransaction($object, $xaction);
   }
 
   protected function applyCustomInternalTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     $type = $xaction->getTransactionType();
     throw new Exception(
       pht(
         "Transaction type '%s' is missing an internal apply implementation!",
         $type));
   }
 
   protected function applyCustomExternalTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     $type = $xaction->getTransactionType();
     throw new Exception(
       pht(
         "Transaction type '%s' is missing an external apply implementation!",
         $type));
   }
 
   /**
    * @{class:PhabricatorTransactions} provides many built-in transactions
    * which should not require much - if any - code in specific applications.
    *
    * This method is a hook for the exceedingly-rare cases where you may need
    * to do **additional** work for built-in transactions. Developers should
    * extend this method, making sure to return the parent implementation
    * regardless of handling any transactions.
    *
    * See also @{method:applyBuiltinExternalTransaction}.
    */
   protected function applyBuiltinInternalTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
         $object->setViewPolicy($xaction->getNewValue());
         break;
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
         $object->setEditPolicy($xaction->getNewValue());
         break;
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
         $object->setJoinPolicy($xaction->getNewValue());
         break;
       case PhabricatorTransactions::TYPE_SPACE:
         $object->setSpacePHID($xaction->getNewValue());
         break;
     }
   }
 
   /**
    * See @{method::applyBuiltinInternalTransaction}.
    */
   protected function applyBuiltinExternalTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_EDGE:
         if ($this->getIsInverseEdgeEditor()) {
           // If we're writing an inverse edge transaction, don't actually
           // do anything. The initiating editor on the other side of the
           // transaction will take care of the edge writes.
           break;
         }
 
         $old = $xaction->getOldValue();
         $new = $xaction->getNewValue();
         $src = $object->getPHID();
         $const = $xaction->getMetadataValue('edge:type');
 
         $type = PhabricatorEdgeType::getByConstant($const);
         if ($type->shouldWriteInverseTransactions()) {
           $this->applyInverseEdgeTransactions(
             $object,
             $xaction,
             $type->getInverseEdgeConstant());
         }
 
         foreach ($new as $dst_phid => $edge) {
           $new[$dst_phid]['src'] = $src;
         }
 
         $editor = new PhabricatorEdgeEditor();
 
         foreach ($old as $dst_phid => $edge) {
           if (!empty($new[$dst_phid])) {
             if ($old[$dst_phid]['data'] === $new[$dst_phid]['data']) {
               continue;
             }
           }
           $editor->removeEdge($src, $const, $dst_phid);
         }
 
         foreach ($new as $dst_phid => $edge) {
           if (!empty($old[$dst_phid])) {
             if ($old[$dst_phid]['data'] === $new[$dst_phid]['data']) {
               continue;
             }
           }
 
           $data = array(
             'data' => $edge['data'],
           );
 
           $editor->addEdge($src, $const, $dst_phid, $data);
         }
 
         $editor->save();
 
         $this->updateWorkboardColumns($object, $const, $old, $new);
         break;
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
       case PhabricatorTransactions::TYPE_SPACE:
         $this->scrambleFileSecrets($object);
         break;
     }
   }
 
   /**
    * Fill in a transaction's common values, like author and content source.
    */
   protected function populateTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     $actor = $this->getActor();
 
     // TODO: This needs to be more sophisticated once we have meta-policies.
     $xaction->setViewPolicy(PhabricatorPolicies::POLICY_PUBLIC);
 
     if ($actor->isOmnipotent()) {
       $xaction->setEditPolicy(PhabricatorPolicies::POLICY_NOONE);
     } else {
       $xaction->setEditPolicy($this->getActingAsPHID());
     }
 
     // If the transaction already has an explicit author PHID, allow it to
     // stand. This is used by applications like Owners that hook into the
     // post-apply change pipeline.
     if (!$xaction->getAuthorPHID()) {
       $xaction->setAuthorPHID($this->getActingAsPHID());
     }
 
     $xaction->setContentSource($this->getContentSource());
     $xaction->attachViewer($actor);
     $xaction->attachObject($object);
 
     if ($object->getPHID()) {
       $xaction->setObjectPHID($object->getPHID());
     }
 
     return $xaction;
   }
 
   protected function didApplyInternalEffects(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return $xactions;
   }
 
   protected function applyFinalEffects(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return $xactions;
   }
 
   public function setContentSource(PhabricatorContentSource $content_source) {
     $this->contentSource = $content_source;
     return $this;
   }
 
   public function setContentSourceFromRequest(AphrontRequest $request) {
     return $this->setContentSource(
       PhabricatorContentSource::newFromRequest($request));
   }
 
   public function getContentSource() {
     return $this->contentSource;
   }
 
   final public function applyTransactions(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $this->object = $object;
     $this->xactions = $xactions;
     $this->isNewObject = ($object->getPHID() === null);
 
     $this->validateEditParameters($object, $xactions);
 
     $actor = $this->requireActor();
 
     // NOTE: Some transaction expansion requires that the edited object be
     // attached.
     foreach ($xactions as $xaction) {
       $xaction->attachObject($object);
       $xaction->attachViewer($actor);
     }
 
     $xactions = $this->expandTransactions($object, $xactions);
     $xactions = $this->expandSupportTransactions($object, $xactions);
     $xactions = $this->combineTransactions($xactions);
 
     foreach ($xactions as $xaction) {
       $xaction = $this->populateTransaction($object, $xaction);
     }
 
     $is_preview = $this->getIsPreview();
     $read_locking = false;
     $transaction_open = false;
 
     if (!$is_preview) {
       $errors = array();
       $type_map = mgroup($xactions, 'getTransactionType');
       foreach ($this->getTransactionTypes() as $type) {
         $type_xactions = idx($type_map, $type, array());
         $errors[] = $this->validateTransaction($object, $type, $type_xactions);
       }
 
       $errors[] = $this->validateAllTransactions($object, $xactions);
       $errors = array_mergev($errors);
 
       $continue_on_missing = $this->getContinueOnMissingFields();
       foreach ($errors as $key => $error) {
         if ($continue_on_missing && $error->getIsMissingFieldError()) {
           unset($errors[$key]);
         }
       }
 
       if ($errors) {
         throw new PhabricatorApplicationTransactionValidationException($errors);
       }
 
       if ($object->getID()) {
         foreach ($xactions as $xaction) {
 
           // If any of the transactions require a read lock, hold one and
           // reload the object. We need to do this fairly early so that the
           // call to `adjustTransactionValues()` (which populates old values)
           // is based on the synchronized state of the object, which may differ
           // from the state when it was originally loaded.
 
           if ($this->shouldReadLock($object, $xaction)) {
             $object->openTransaction();
             $object->beginReadLocking();
             $transaction_open = true;
             $read_locking = true;
             $object->reload();
             break;
           }
         }
       }
 
       if ($this->shouldApplyInitialEffects($object, $xactions)) {
         if (!$transaction_open) {
           $object->openTransaction();
           $transaction_open = true;
         }
       }
     }
 
     if ($this->shouldApplyInitialEffects($object, $xactions)) {
       $this->applyInitialEffects($object, $xactions);
     }
 
     foreach ($xactions as $xaction) {
       $this->adjustTransactionValues($object, $xaction);
     }
 
     try {
       $xactions = $this->filterTransactions($object, $xactions);
     } catch (Exception $ex) {
       if ($read_locking) {
         $object->endReadLocking();
       }
       if ($transaction_open) {
         $object->killTransaction();
       }
       throw $ex;
     }
 
     // TODO: Once everything is on EditEngine, just use getIsNewObject() to
     // figure this out instead.
     $mark_as_create = false;
     $create_type = PhabricatorTransactions::TYPE_CREATE;
     foreach ($xactions as $xaction) {
       if ($xaction->getTransactionType() == $create_type) {
         $mark_as_create = true;
       }
     }
 
     if ($mark_as_create) {
       foreach ($xactions as $xaction) {
         $xaction->setIsCreateTransaction(true);
       }
     }
 
     // Now that we've merged, filtered, and combined transactions, check for
     // required capabilities.
     foreach ($xactions as $xaction) {
       $this->requireCapabilities($object, $xaction);
     }
 
     $xactions = $this->sortTransactions($xactions);
     $file_phids = $this->extractFilePHIDs($object, $xactions);
 
     if ($is_preview) {
       $this->loadHandles($xactions);
       return $xactions;
     }
 
     $comment_editor = id(new PhabricatorApplicationTransactionCommentEditor())
       ->setActor($actor)
       ->setActingAsPHID($this->getActingAsPHID())
       ->setContentSource($this->getContentSource());
 
     if (!$transaction_open) {
       $object->openTransaction();
     }
 
       foreach ($xactions as $xaction) {
         $this->applyInternalEffects($object, $xaction);
       }
 
       $xactions = $this->didApplyInternalEffects($object, $xactions);
 
       try {
         $object->save();
       } catch (AphrontDuplicateKeyQueryException $ex) {
         $object->killTransaction();
 
         // This callback has an opportunity to throw a better exception,
         // so execution may end here.
         $this->didCatchDuplicateKeyException($object, $xactions, $ex);
 
         throw $ex;
       }
 
       foreach ($xactions as $xaction) {
         $xaction->setObjectPHID($object->getPHID());
         if ($xaction->getComment()) {
           $xaction->setPHID($xaction->generatePHID());
           $comment_editor->applyEdit($xaction, $xaction->getComment());
         } else {
           $xaction->save();
         }
       }
 
       if ($file_phids) {
         $this->attachFiles($object, $file_phids);
       }
 
       foreach ($xactions as $xaction) {
         $this->applyExternalEffects($object, $xaction);
       }
 
       $xactions = $this->applyFinalEffects($object, $xactions);
       if ($read_locking) {
         $object->endReadLocking();
         $read_locking = false;
       }
 
     $object->saveTransaction();
 
     // Now that we've completely applied the core transaction set, try to apply
     // Herald rules. Herald rules are allowed to either take direct actions on
     // the database (like writing flags), or take indirect actions (like saving
     // some targets for CC when we generate mail a little later), or return
     // transactions which we'll apply normally using another Editor.
 
     // First, check if *this* is a sub-editor which is itself applying Herald
     // rules: if it is, stop working and return so we don't descend into
     // madness.
 
     // Otherwise, we're not a Herald editor, so process Herald rules (possibly
     // using a Herald editor to apply resulting transactions) and then send out
     // mail, notifications, and feed updates about everything.
 
     if ($this->getIsHeraldEditor()) {
       // We are the Herald editor, so stop work here and return the updated
       // transactions.
       return $xactions;
     } else if ($this->getIsInverseEdgeEditor()) {
       // If we're applying inverse edge transactions, don't trigger Herald.
       // From a product perspective, the current set of inverse edges (most
       // often, mentions) aren't things users would expect to trigger Herald.
       // From a technical perspective, objects loaded by the inverse editor may
       // not have enough data to execute rules. At least for now, just stop
       // Herald from executing when applying inverse edges.
     } else if ($this->shouldApplyHeraldRules($object, $xactions)) {
       // We are not the Herald editor, so try to apply Herald rules.
       $herald_xactions = $this->applyHeraldRules($object, $xactions);
 
       if ($herald_xactions) {
         $xscript_id = $this->getHeraldTranscript()->getID();
         foreach ($herald_xactions as $herald_xaction) {
           // Don't set a transcript ID if this is a transaction from another
           // application or source, like Owners.
           if ($herald_xaction->getAuthorPHID()) {
             continue;
           }
 
           $herald_xaction->setMetadataValue('herald:transcriptID', $xscript_id);
         }
 
         // NOTE: We're acting as the omnipotent user because rules deal with
         // their own policy issues. We use a synthetic author PHID (the
         // Herald application) as the author of record, so that transactions
         // will render in a reasonable way ("Herald assigned this task ...").
         $herald_actor = PhabricatorUser::getOmnipotentUser();
         $herald_phid = id(new PhabricatorHeraldApplication())->getPHID();
 
         // TODO: It would be nice to give transactions a more specific source
         // which points at the rule which generated them. You can figure this
         // out from transcripts, but it would be cleaner if you didn't have to.
 
         $herald_source = PhabricatorContentSource::newForSource(
           PhabricatorHeraldContentSource::SOURCECONST);
 
         $herald_editor = newv(get_class($this), array())
           ->setContinueOnNoEffect(true)
           ->setContinueOnMissingFields(true)
           ->setParentMessageID($this->getParentMessageID())
           ->setIsHeraldEditor(true)
           ->setActor($herald_actor)
           ->setActingAsPHID($herald_phid)
           ->setContentSource($herald_source);
 
         $herald_xactions = $herald_editor->applyTransactions(
           $object,
           $herald_xactions);
 
         // Merge the new transactions into the transaction list: we want to
         // send email and publish feed stories about them, too.
         $xactions = array_merge($xactions, $herald_xactions);
       }
 
       // If Herald did not generate transactions, we may still need to handle
       // "Send an Email" rules.
       $adapter = $this->getHeraldAdapter();
       $this->heraldEmailPHIDs = $adapter->getEmailPHIDs();
       $this->heraldForcedEmailPHIDs = $adapter->getForcedEmailPHIDs();
     }
 
     $this->didApplyTransactions($xactions);
 
     if ($object instanceof PhabricatorCustomFieldInterface) {
       // Maybe this makes more sense to move into the search index itself? For
       // now I'm putting it here since I think we might end up with things that
       // need it to be up to date once the next page loads, but if we don't go
       // there we could move it into search once search moves to the daemons.
 
       // It now happens in the search indexer as well, but the search indexer is
       // always daemonized, so the logic above still potentially holds. We could
       // possibly get rid of this. The major motivation for putting it in the
       // indexer was to enable reindexing to work.
 
       $fields = PhabricatorCustomField::getObjectFields(
         $object,
         PhabricatorCustomField::ROLE_APPLICATIONSEARCH);
       $fields->readFieldsFromStorage($object);
       $fields->rebuildIndexes($object);
     }
 
     $herald_xscript = $this->getHeraldTranscript();
     if ($herald_xscript) {
       $herald_header = $herald_xscript->getXHeraldRulesHeader();
       $herald_header = HeraldTranscript::saveXHeraldRulesHeader(
         $object->getPHID(),
         $herald_header);
     } else {
       $herald_header = HeraldTranscript::loadXHeraldRulesHeader(
         $object->getPHID());
     }
     $this->heraldHeader = $herald_header;
 
     // We're going to compute some of the data we'll use to publish these
     // transactions here, before queueing a worker.
     //
     // Primarily, this is more correct: we want to publish the object as it
     // exists right now. The worker may not execute for some time, and we want
     // to use the current To/CC list, not respect any changes which may occur
     // between now and when the worker executes.
     //
     // As a secondary benefit, this tends to reduce the amount of state that
     // Editors need to pass into workers.
     $object = $this->willPublish($object, $xactions);
 
     if (!$this->getDisableEmail()) {
       if ($this->shouldSendMail($object, $xactions)) {
         $this->mailToPHIDs = $this->getMailTo($object);
         $this->mailCCPHIDs = $this->getMailCC($object);
       }
     }
 
     if ($this->shouldPublishFeedStory($object, $xactions)) {
       $this->feedRelatedPHIDs = $this->getFeedRelatedPHIDs($object, $xactions);
       $this->feedNotifyPHIDs = $this->getFeedNotifyPHIDs($object, $xactions);
     }
 
     PhabricatorWorker::scheduleTask(
       'PhabricatorApplicationTransactionPublishWorker',
       array(
         'objectPHID' => $object->getPHID(),
         'actorPHID' => $this->getActingAsPHID(),
         'xactionPHIDs' => mpull($xactions, 'getPHID'),
         'state' => $this->getWorkerState(),
       ),
       array(
         'objectPHID' => $object->getPHID(),
         'priority' => PhabricatorWorker::PRIORITY_ALERTS,
       ));
 
     return $xactions;
   }
 
   protected function didCatchDuplicateKeyException(
     PhabricatorLiskDAO $object,
     array $xactions,
     Exception $ex) {
     return;
   }
 
   public function publishTransactions(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     // Hook for edges or other properties that may need (re-)loading
     $object = $this->willPublish($object, $xactions);
 
     $messages = array();
     if (!$this->getDisableEmail()) {
       if ($this->shouldSendMail($object, $xactions)) {
         $messages = $this->buildMail($object, $xactions);
       }
     }
 
     if ($this->supportsSearch()) {
       PhabricatorSearchWorker::queueDocumentForIndexing(
         $object->getPHID(),
         array(
           'transactionPHIDs' => mpull($xactions, 'getPHID'),
         ));
     }
 
     if ($this->shouldPublishFeedStory($object, $xactions)) {
 
       $mailed = array();
       foreach ($messages as $mail) {
         foreach ($mail->buildRecipientList() as $phid) {
           $mailed[$phid] = $phid;
         }
       }
 
       $this->publishFeedStory($object, $xactions, $mailed);
     }
 
     // NOTE: This actually sends the mail. We do this last to reduce the chance
     // that we send some mail, hit an exception, then send the mail again when
     // retrying.
     foreach ($messages as $mail) {
       $mail->save();
     }
 
     return $xactions;
   }
 
   protected function didApplyTransactions(array $xactions) {
     // Hook for subclasses.
     return;
   }
 
 
   /**
    * Determine if the editor should hold a read lock on the object while
    * applying a transaction.
    *
    * If the editor does not hold a lock, two editors may read an object at the
    * same time, then apply their changes without any synchronization. For most
    * transactions, this does not matter much. However, it is important for some
    * transactions. For example, if an object has a transaction count on it, both
    * editors may read the object with `count = 23`, then independently update it
    * and save the object with `count = 24` twice. This will produce the wrong
    * state: the object really has 25 transactions, but the count is only 24.
    *
    * Generally, transactions fall into one of four buckets:
    *
    *   - Append operations: Actions like adding a comment to an object purely
    *     add information to its state, and do not depend on the current object
    *     state in any way. These transactions never need to hold locks.
    *   - Overwrite operations: Actions like changing the title or description
    *     of an object replace the current value with a new value, so the end
    *     state is consistent without a lock. We currently do not lock these
    *     transactions, although we may in the future.
    *   - Edge operations: Edge and subscription operations have internal
    *     synchronization which limits the damage race conditions can cause.
    *     We do not currently lock these transactions, although we may in the
    *     future.
    *   - Update operations: Actions like incrementing a count on an object.
    *     These operations generally should use locks, unless it is not
    *     important that the state remain consistent in the presence of races.
    *
    * @param   PhabricatorLiskDAO  Object being updated.
    * @param   PhabricatorApplicationTransaction Transaction being applied.
    * @return  bool                True to synchronize the edit with a lock.
    */
   protected function shouldReadLock(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     return false;
   }
 
   private function loadHandles(array $xactions) {
     $phids = array();
     foreach ($xactions as $key => $xaction) {
       $phids[$key] = $xaction->getRequiredHandlePHIDs();
     }
     $handles = array();
     $merged = array_mergev($phids);
     if ($merged) {
       $handles = id(new PhabricatorHandleQuery())
         ->setViewer($this->requireActor())
         ->withPHIDs($merged)
         ->execute();
     }
     foreach ($xactions as $key => $xaction) {
       $xaction->setHandles(array_select_keys($handles, $phids[$key]));
     }
   }
 
   private function loadSubscribers(PhabricatorLiskDAO $object) {
     if ($object->getPHID() &&
         ($object instanceof PhabricatorSubscribableInterface)) {
       $subs = PhabricatorSubscribersQuery::loadSubscribersForPHID(
         $object->getPHID());
       $this->subscribers = array_fuse($subs);
     } else {
       $this->subscribers = array();
     }
   }
 
   private function validateEditParameters(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     if (!$this->getContentSource()) {
       throw new PhutilInvalidStateException('setContentSource');
     }
 
     // Do a bunch of sanity checks that the incoming transactions are fresh.
     // They should be unsaved and have only "transactionType" and "newValue"
     // set.
 
     $types = array_fill_keys($this->getTransactionTypes(), true);
 
     assert_instances_of($xactions, 'PhabricatorApplicationTransaction');
     foreach ($xactions as $xaction) {
       if ($xaction->getPHID() || $xaction->getID()) {
         throw new PhabricatorApplicationTransactionStructureException(
           $xaction,
           pht('You can not apply transactions which already have IDs/PHIDs!'));
       }
 
       if ($xaction->getObjectPHID()) {
         throw new PhabricatorApplicationTransactionStructureException(
           $xaction,
           pht(
             'You can not apply transactions which already have %s!',
             'objectPHIDs'));
       }
 
       if ($xaction->getCommentPHID()) {
         throw new PhabricatorApplicationTransactionStructureException(
           $xaction,
           pht(
             'You can not apply transactions which already have %s!',
             'commentPHIDs'));
       }
 
       if ($xaction->getCommentVersion() !== 0) {
         throw new PhabricatorApplicationTransactionStructureException(
           $xaction,
           pht(
             'You can not apply transactions which already have '.
             'commentVersions!'));
       }
 
       $expect_value = !$xaction->shouldGenerateOldValue();
       $has_value = $xaction->hasOldValue();
 
       if ($expect_value && !$has_value) {
         throw new PhabricatorApplicationTransactionStructureException(
           $xaction,
           pht(
             'This transaction is supposed to have an %s set, but it does not!',
             'oldValue'));
       }
 
       if ($has_value && !$expect_value) {
         throw new PhabricatorApplicationTransactionStructureException(
           $xaction,
           pht(
             'This transaction should generate its %s automatically, '.
             'but has already had one set!',
             'oldValue'));
       }
 
       $type = $xaction->getTransactionType();
       if (empty($types[$type])) {
         throw new PhabricatorApplicationTransactionStructureException(
           $xaction,
           pht(
             'Transaction has type "%s", but that transaction type is not '.
             'supported by this editor (%s).',
             $type,
             get_class($this)));
       }
     }
   }
 
   protected function requireCapabilities(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     if ($this->getIsNewObject()) {
       return;
     }
 
     $actor = $this->requireActor();
     switch ($xaction->getTransactionType()) {
       case PhabricatorTransactions::TYPE_COMMENT:
         PhabricatorPolicyFilter::requireCapability(
           $actor,
           $object,
           PhabricatorPolicyCapability::CAN_VIEW);
         break;
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
       case PhabricatorTransactions::TYPE_SPACE:
         PhabricatorPolicyFilter::requireCapability(
           $actor,
           $object,
           PhabricatorPolicyCapability::CAN_EDIT);
         break;
     }
   }
 
   private function buildSubscribeTransaction(
     PhabricatorLiskDAO $object,
     array $xactions,
     array $blocks) {
 
     if (!($object instanceof PhabricatorSubscribableInterface)) {
       return null;
     }
 
     if ($this->shouldEnableMentions($object, $xactions)) {
       $texts = array_mergev($blocks);
       $phids = PhabricatorMarkupEngine::extractPHIDsFromMentions(
         $this->getActor(),
         $texts);
     } else {
       $phids = array();
     }
 
     $this->mentionedPHIDs = $phids;
 
     if ($object->getPHID()) {
       // Don't try to subscribe already-subscribed mentions: we want to generate
       // a dialog about an action having no effect if the user explicitly adds
       // existing CCs, but not if they merely mention existing subscribers.
       $phids = array_diff($phids, $this->subscribers);
     }
 
     if ($phids) {
       $users = id(new PhabricatorPeopleQuery())
         ->setViewer($this->getActor())
         ->withPHIDs($phids)
         ->execute();
       $users = mpull($users, null, 'getPHID');
 
       foreach ($phids as $key => $phid) {
         // Do not subscribe mentioned users
         // who do not have VIEW Permissions
         if ($object instanceof PhabricatorPolicyInterface
           && !PhabricatorPolicyFilter::hasCapability(
           $users[$phid],
           $object,
           PhabricatorPolicyCapability::CAN_VIEW)
         ) {
           unset($phids[$key]);
         } else {
           if ($object->isAutomaticallySubscribed($phid)) {
             unset($phids[$key]);
           }
         }
       }
       $phids = array_values($phids);
     }
     // No else here to properly return null should we unset all subscriber
     if (!$phids) {
       return null;
     }
 
     $xaction = newv(get_class(head($xactions)), array());
     $xaction->setTransactionType(PhabricatorTransactions::TYPE_SUBSCRIBERS);
     $xaction->setNewValue(array('+' => $phids));
 
     return $xaction;
   }
 
   protected function getRemarkupBlocksFromTransaction(
     PhabricatorApplicationTransaction $transaction) {
     return $transaction->getRemarkupBlocks();
   }
 
   protected function mergeTransactions(
     PhabricatorApplicationTransaction $u,
     PhabricatorApplicationTransaction $v) {
 
     $type = $u->getTransactionType();
 
     switch ($type) {
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         return $this->mergePHIDOrEdgeTransactions($u, $v);
       case PhabricatorTransactions::TYPE_EDGE:
         $u_type = $u->getMetadataValue('edge:type');
         $v_type = $v->getMetadataValue('edge:type');
         if ($u_type == $v_type) {
           return $this->mergePHIDOrEdgeTransactions($u, $v);
         }
         return null;
     }
 
     // By default, do not merge the transactions.
     return null;
   }
 
   /**
    * Optionally expand transactions which imply other effects. For example,
    * resigning from a revision in Differential implies removing yourself as
    * a reviewer.
    */
   protected function expandTransactions(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $results = array();
     foreach ($xactions as $xaction) {
       foreach ($this->expandTransaction($object, $xaction) as $expanded) {
         $results[] = $expanded;
       }
     }
 
     return $results;
   }
 
   protected function expandTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     return array($xaction);
   }
 
 
   public function getExpandedSupportTransactions(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     $xactions = array($xaction);
     $xactions = $this->expandSupportTransactions(
       $object,
       $xactions);
 
     if (count($xactions) == 1) {
       return array();
     }
 
     foreach ($xactions as $index => $cxaction) {
       if ($cxaction === $xaction) {
         unset($xactions[$index]);
         break;
       }
     }
 
     return $xactions;
   }
 
   private function expandSupportTransactions(
     PhabricatorLiskDAO $object,
     array $xactions) {
     $this->loadSubscribers($object);
 
     $xactions = $this->applyImplicitCC($object, $xactions);
 
     $blocks = array();
     foreach ($xactions as $key => $xaction) {
       $blocks[$key] = $this->getRemarkupBlocksFromTransaction($xaction);
     }
 
     $subscribe_xaction = $this->buildSubscribeTransaction(
       $object,
       $xactions,
       $blocks);
     if ($subscribe_xaction) {
       $xactions[] = $subscribe_xaction;
     }
 
     // TODO: For now, this is just a placeholder.
     $engine = PhabricatorMarkupEngine::getEngine('extract');
     $engine->setConfig('viewer', $this->requireActor());
 
     $block_xactions = $this->expandRemarkupBlockTransactions(
       $object,
       $xactions,
       $blocks,
       $engine);
 
     foreach ($block_xactions as $xaction) {
       $xactions[] = $xaction;
     }
 
     return $xactions;
   }
 
   private function expandRemarkupBlockTransactions(
     PhabricatorLiskDAO $object,
     array $xactions,
     $blocks,
     PhutilMarkupEngine $engine) {
 
     $block_xactions = $this->expandCustomRemarkupBlockTransactions(
       $object,
       $xactions,
       $blocks,
       $engine);
 
     $mentioned_phids = array();
     if ($this->shouldEnableMentions($object, $xactions)) {
       foreach ($blocks as $key => $xaction_blocks) {
         foreach ($xaction_blocks as $block) {
           $engine->markupText($block);
           $mentioned_phids += $engine->getTextMetadata(
             PhabricatorObjectRemarkupRule::KEY_MENTIONED_OBJECTS,
             array());
         }
       }
     }
 
     if (!$mentioned_phids) {
       return $block_xactions;
     }
 
     $mentioned_objects = id(new PhabricatorObjectQuery())
       ->setViewer($this->getActor())
       ->withPHIDs($mentioned_phids)
       ->execute();
 
     $mentionable_phids = array();
     if ($this->shouldEnableMentions($object, $xactions)) {
       foreach ($mentioned_objects as $mentioned_object) {
         if ($mentioned_object instanceof PhabricatorMentionableInterface) {
           $mentioned_phid = $mentioned_object->getPHID();
           if (idx($this->getUnmentionablePHIDMap(), $mentioned_phid)) {
             continue;
           }
           // don't let objects mention themselves
           if ($object->getPHID() && $mentioned_phid == $object->getPHID()) {
             continue;
           }
           $mentionable_phids[$mentioned_phid] = $mentioned_phid;
         }
       }
     }
 
     if ($mentionable_phids) {
       $edge_type = PhabricatorObjectMentionsObjectEdgeType::EDGECONST;
       $block_xactions[] = newv(get_class(head($xactions)), array())
         ->setIgnoreOnNoEffect(true)
         ->setTransactionType(PhabricatorTransactions::TYPE_EDGE)
         ->setMetadataValue('edge:type', $edge_type)
         ->setNewValue(array('+' => $mentionable_phids));
     }
 
     return $block_xactions;
   }
 
   protected function expandCustomRemarkupBlockTransactions(
     PhabricatorLiskDAO $object,
     array $xactions,
     $blocks,
     PhutilMarkupEngine $engine) {
     return array();
   }
 
 
   /**
    * Attempt to combine similar transactions into a smaller number of total
    * transactions. For example, two transactions which edit the title of an
    * object can be merged into a single edit.
    */
   private function combineTransactions(array $xactions) {
     $stray_comments = array();
 
     $result = array();
     $types = array();
     foreach ($xactions as $key => $xaction) {
       $type = $xaction->getTransactionType();
       if (isset($types[$type])) {
         foreach ($types[$type] as $other_key) {
           $other_xaction = $result[$other_key];
 
           // Don't merge transactions with different authors. For example,
           // don't merge Herald transactions and owners transactions.
           if ($other_xaction->getAuthorPHID() != $xaction->getAuthorPHID()) {
             continue;
           }
 
           $merged = $this->mergeTransactions($result[$other_key], $xaction);
           if ($merged) {
             $result[$other_key] = $merged;
 
             if ($xaction->getComment() &&
                 ($xaction->getComment() !== $merged->getComment())) {
               $stray_comments[] = $xaction->getComment();
             }
 
             if ($result[$other_key]->getComment() &&
                 ($result[$other_key]->getComment() !== $merged->getComment())) {
               $stray_comments[] = $result[$other_key]->getComment();
             }
 
             // Move on to the next transaction.
             continue 2;
           }
         }
       }
       $result[$key] = $xaction;
       $types[$type][] = $key;
     }
 
     // If we merged any comments away, restore them.
     foreach ($stray_comments as $comment) {
       $xaction = newv(get_class(head($result)), array());
       $xaction->setTransactionType(PhabricatorTransactions::TYPE_COMMENT);
       $xaction->setComment($comment);
       $result[] = $xaction;
     }
 
     return array_values($result);
   }
 
   protected function mergePHIDOrEdgeTransactions(
     PhabricatorApplicationTransaction $u,
     PhabricatorApplicationTransaction $v) {
 
     $result = $u->getNewValue();
     foreach ($v->getNewValue() as $key => $value) {
       if ($u->getTransactionType() == PhabricatorTransactions::TYPE_EDGE) {
         if (empty($result[$key])) {
           $result[$key] = $value;
         } else {
           // We're merging two lists of edge adds, sets, or removes. Merge
           // them by merging individual PHIDs within them.
           $merged = $result[$key];
 
           foreach ($value as $dst => $v_spec) {
             if (empty($merged[$dst])) {
               $merged[$dst] = $v_spec;
             } else {
               // Two transactions are trying to perform the same operation on
               // the same edge. Normalize the edge data and then merge it. This
               // allows transactions to specify how data merges execute in a
               // precise way.
 
               $u_spec = $merged[$dst];
 
               if (!is_array($u_spec)) {
                 $u_spec = array('dst' => $u_spec);
               }
               if (!is_array($v_spec)) {
                 $v_spec = array('dst' => $v_spec);
               }
 
               $ux_data = idx($u_spec, 'data', array());
               $vx_data = idx($v_spec, 'data', array());
 
               $merged_data = $this->mergeEdgeData(
                 $u->getMetadataValue('edge:type'),
                 $ux_data,
                 $vx_data);
 
               $u_spec['data'] = $merged_data;
               $merged[$dst] = $u_spec;
             }
           }
 
           $result[$key] = $merged;
         }
       } else {
         $result[$key] = array_merge($value, idx($result, $key, array()));
       }
     }
     $u->setNewValue($result);
 
     // When combining an "ignore" transaction with a normal transaction, make
     // sure we don't propagate the "ignore" flag.
     if (!$v->getIgnoreOnNoEffect()) {
       $u->setIgnoreOnNoEffect(false);
     }
 
     return $u;
   }
 
   protected function mergeEdgeData($type, array $u, array $v) {
     return $v + $u;
   }
 
   protected function getPHIDTransactionNewValue(
     PhabricatorApplicationTransaction $xaction,
     $old = null) {
 
     if ($old !== null) {
       $old = array_fuse($old);
     } else {
       $old = array_fuse($xaction->getOldValue());
     }
 
     $new = $xaction->getNewValue();
     $new_add = idx($new, '+', array());
     unset($new['+']);
     $new_rem = idx($new, '-', array());
     unset($new['-']);
     $new_set = idx($new, '=', null);
     if ($new_set !== null) {
       $new_set = array_fuse($new_set);
     }
     unset($new['=']);
 
     if ($new) {
       throw new Exception(
         pht(
           "Invalid '%s' value for PHID transaction. Value should contain only ".
           "keys '%s' (add PHIDs), '%s' (remove PHIDs) and '%s' (set PHIDS).",
           'new',
           '+',
           '-',
           '='));
     }
 
     $result = array();
 
     foreach ($old as $phid) {
       if ($new_set !== null && empty($new_set[$phid])) {
         continue;
       }
       $result[$phid] = $phid;
     }
 
     if ($new_set !== null) {
       foreach ($new_set as $phid) {
         $result[$phid] = $phid;
       }
     }
 
     foreach ($new_add as $phid) {
       $result[$phid] = $phid;
     }
 
     foreach ($new_rem as $phid) {
       unset($result[$phid]);
     }
 
     return array_values($result);
   }
 
   protected function getEdgeTransactionNewValue(
     PhabricatorApplicationTransaction $xaction) {
 
     $new = $xaction->getNewValue();
     $new_add = idx($new, '+', array());
     unset($new['+']);
     $new_rem = idx($new, '-', array());
     unset($new['-']);
     $new_set = idx($new, '=', null);
     unset($new['=']);
 
     if ($new) {
       throw new Exception(
         pht(
           "Invalid '%s' value for Edge transaction. Value should contain only ".
           "keys '%s' (add edges), '%s' (remove edges) and '%s' (set edges).",
           'new',
           '+',
           '-',
           '='));
     }
 
     $old = $xaction->getOldValue();
 
     $lists = array($new_set, $new_add, $new_rem);
     foreach ($lists as $list) {
       $this->checkEdgeList($list, $xaction->getMetadataValue('edge:type'));
     }
 
     $result = array();
     foreach ($old as $dst_phid => $edge) {
       if ($new_set !== null && empty($new_set[$dst_phid])) {
         continue;
       }
       $result[$dst_phid] = $this->normalizeEdgeTransactionValue(
         $xaction,
         $edge,
         $dst_phid);
     }
 
     if ($new_set !== null) {
       foreach ($new_set as $dst_phid => $edge) {
         $result[$dst_phid] = $this->normalizeEdgeTransactionValue(
           $xaction,
           $edge,
           $dst_phid);
       }
     }
 
     foreach ($new_add as $dst_phid => $edge) {
       $result[$dst_phid] = $this->normalizeEdgeTransactionValue(
         $xaction,
         $edge,
         $dst_phid);
     }
 
     foreach ($new_rem as $dst_phid => $edge) {
       unset($result[$dst_phid]);
     }
 
     return $result;
   }
 
   private function checkEdgeList($list, $edge_type) {
     if (!$list) {
       return;
     }
     foreach ($list as $key => $item) {
       if (phid_get_type($key) === PhabricatorPHIDConstants::PHID_TYPE_UNKNOWN) {
         throw new Exception(
           pht(
             'Edge transactions must have destination PHIDs as in edge '.
             'lists (found key "%s" on transaction of type "%s").',
             $key,
             $edge_type));
       }
       if (!is_array($item) && $item !== $key) {
         throw new Exception(
           pht(
             'Edge transactions must have PHIDs or edge specs as values '.
             '(found value "%s" on transaction of type "%s").',
             $item,
             $edge_type));
       }
     }
   }
 
   private function normalizeEdgeTransactionValue(
     PhabricatorApplicationTransaction $xaction,
     $edge,
     $dst_phid) {
 
     if (!is_array($edge)) {
       if ($edge != $dst_phid) {
         throw new Exception(
           pht(
             'Transaction edge data must either be the edge PHID or an edge '.
             'specification dictionary.'));
       }
       $edge = array();
     } else {
       foreach ($edge as $key => $value) {
         switch ($key) {
           case 'src':
           case 'dst':
           case 'type':
           case 'data':
           case 'dateCreated':
           case 'dateModified':
           case 'seq':
           case 'dataID':
             break;
           default:
             throw new Exception(
               pht(
                 'Transaction edge specification contains unexpected key "%s".',
                 $key));
         }
       }
     }
 
     $edge['dst'] = $dst_phid;
 
     $edge_type = $xaction->getMetadataValue('edge:type');
     if (empty($edge['type'])) {
       $edge['type'] = $edge_type;
     } else {
       if ($edge['type'] != $edge_type) {
         $this_type = $edge['type'];
         throw new Exception(
           pht(
             "Edge transaction includes edge of type '%s', but ".
             "transaction is of type '%s'. Each edge transaction ".
             "must alter edges of only one type.",
             $this_type,
             $edge_type));
       }
     }
 
     if (!isset($edge['data'])) {
       $edge['data'] = array();
     }
 
     return $edge;
   }
 
   protected function sortTransactions(array $xactions) {
     $head = array();
     $tail = array();
 
     // Move bare comments to the end, so the actions precede them.
     foreach ($xactions as $xaction) {
       $type = $xaction->getTransactionType();
       if ($type == PhabricatorTransactions::TYPE_COMMENT) {
         $tail[] = $xaction;
       } else {
         $head[] = $xaction;
       }
     }
 
     return array_values(array_merge($head, $tail));
   }
 
 
   protected function filterTransactions(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $type_comment = PhabricatorTransactions::TYPE_COMMENT;
 
     $no_effect = array();
     $has_comment = false;
     $any_effect = false;
     foreach ($xactions as $key => $xaction) {
       if ($this->transactionHasEffect($object, $xaction)) {
         if ($xaction->getTransactionType() != $type_comment) {
           $any_effect = true;
         }
       } else if ($xaction->getIgnoreOnNoEffect()) {
         unset($xactions[$key]);
       } else {
         $no_effect[$key] = $xaction;
       }
       if ($xaction->hasComment()) {
         $has_comment = true;
       }
     }
 
     if (!$no_effect) {
       return $xactions;
     }
 
     if (!$this->getContinueOnNoEffect() && !$this->getIsPreview()) {
       throw new PhabricatorApplicationTransactionNoEffectException(
         $no_effect,
         $any_effect,
         $has_comment);
     }
 
     if (!$any_effect && !$has_comment) {
       // If we only have empty comment transactions, just drop them all.
       return array();
     }
 
     foreach ($no_effect as $key => $xaction) {
       if ($xaction->hasComment()) {
         $xaction->setTransactionType($type_comment);
         $xaction->setOldValue(null);
         $xaction->setNewValue(null);
       } else {
         unset($xactions[$key]);
       }
     }
 
     return $xactions;
   }
 
 
   /**
    * Hook for validating transactions. This callback will be invoked for each
    * available transaction type, even if an edit does not apply any transactions
    * of that type. This allows you to raise exceptions when required fields are
    * missing, by detecting that the object has no field value and there is no
    * transaction which sets one.
    *
    * @param PhabricatorLiskDAO Object being edited.
    * @param string Transaction type to validate.
    * @param list<PhabricatorApplicationTransaction> Transactions of given type,
    *   which may be empty if the edit does not apply any transactions of the
    *   given type.
    * @return list<PhabricatorApplicationTransactionValidationError> List of
    *   validation errors.
    */
   protected function validateTransaction(
     PhabricatorLiskDAO $object,
     $type,
     array $xactions) {
 
     $errors = array();
     switch ($type) {
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
         $errors[] = $this->validatePolicyTransaction(
           $object,
           $xactions,
           $type,
           PhabricatorPolicyCapability::CAN_VIEW);
         break;
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
         $errors[] = $this->validatePolicyTransaction(
           $object,
           $xactions,
           $type,
           PhabricatorPolicyCapability::CAN_EDIT);
         break;
       case PhabricatorTransactions::TYPE_SPACE:
         $errors[] = $this->validateSpaceTransactions(
           $object,
           $xactions,
           $type);
         break;
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $groups = array();
         foreach ($xactions as $xaction) {
           $groups[$xaction->getMetadataValue('customfield:key')][] = $xaction;
         }
 
         $field_list = PhabricatorCustomField::getObjectFields(
           $object,
           PhabricatorCustomField::ROLE_EDIT);
         $field_list->setViewer($this->getActor());
 
         $role_xactions = PhabricatorCustomField::ROLE_APPLICATIONTRANSACTIONS;
         foreach ($field_list->getFields() as $field) {
           if (!$field->shouldEnableForRole($role_xactions)) {
             continue;
           }
           $errors[] = $field->validateApplicationTransactions(
             $this,
             $type,
             idx($groups, $field->getFieldKey(), array()));
         }
         break;
     }
 
     return array_mergev($errors);
   }
 
   private function validatePolicyTransaction(
     PhabricatorLiskDAO $object,
     array $xactions,
     $transaction_type,
     $capability) {
 
     $actor = $this->requireActor();
     $errors = array();
     // Note $this->xactions is necessary; $xactions is $this->xactions of
     // $transaction_type
     $policy_object = $this->adjustObjectForPolicyChecks(
       $object,
       $this->xactions);
 
     // Make sure the user isn't editing away their ability to $capability this
     // object.
     foreach ($xactions as $xaction) {
       try {
         PhabricatorPolicyFilter::requireCapabilityWithForcedPolicy(
           $actor,
           $policy_object,
           $capability,
           $xaction->getNewValue());
       } catch (PhabricatorPolicyException $ex) {
         $errors[] = new PhabricatorApplicationTransactionValidationError(
           $transaction_type,
           pht('Invalid'),
           pht(
             'You can not select this %s policy, because you would no longer '.
             'be able to %s the object.',
             $capability,
             $capability),
           $xaction);
       }
     }
 
     if ($this->getIsNewObject()) {
       if (!$xactions) {
         $has_capability = PhabricatorPolicyFilter::hasCapability(
           $actor,
           $policy_object,
           $capability);
         if (!$has_capability) {
           $errors[] = new PhabricatorApplicationTransactionValidationError(
             $transaction_type,
             pht('Invalid'),
             pht(
               'The selected %s policy excludes you. Choose a %s policy '.
               'which allows you to %s the object.',
               $capability,
               $capability,
               $capability));
         }
       }
     }
 
     return $errors;
   }
 
 
   private function validateSpaceTransactions(
     PhabricatorLiskDAO $object,
     array $xactions,
     $transaction_type) {
     $errors = array();
 
     $actor = $this->getActor();
 
     $has_spaces = PhabricatorSpacesNamespaceQuery::getViewerSpacesExist($actor);
     $actor_spaces = PhabricatorSpacesNamespaceQuery::getViewerSpaces($actor);
     $active_spaces = PhabricatorSpacesNamespaceQuery::getViewerActiveSpaces(
       $actor);
     foreach ($xactions as $xaction) {
       $space_phid = $xaction->getNewValue();
 
       if ($space_phid === null) {
         if (!$has_spaces) {
           // The install doesn't have any spaces, so this is fine.
           continue;
         }
 
         // The install has some spaces, so every object needs to be put
         // in a valid space.
         $errors[] = new PhabricatorApplicationTransactionValidationError(
           $transaction_type,
           pht('Invalid'),
           pht('You must choose a space for this object.'),
           $xaction);
         continue;
       }
 
       // If the PHID isn't `null`, it needs to be a valid space that the
       // viewer can see.
       if (empty($actor_spaces[$space_phid])) {
         $errors[] = new PhabricatorApplicationTransactionValidationError(
           $transaction_type,
           pht('Invalid'),
           pht(
             'You can not shift this object in the selected space, because '.
             'the space does not exist or you do not have access to it.'),
           $xaction);
       } else if (empty($active_spaces[$space_phid])) {
 
         // It's OK to edit objects in an archived space, so just move on if
         // we aren't adjusting the value.
         $old_space_phid = $this->getTransactionOldValue($object, $xaction);
         if ($space_phid == $old_space_phid) {
           continue;
         }
 
         $errors[] = new PhabricatorApplicationTransactionValidationError(
           $transaction_type,
           pht('Archived'),
           pht(
             'You can not shift this object into the selected space, because '.
             'the space is archived. Objects can not be created inside (or '.
             'moved into) archived spaces.'),
           $xaction);
       }
     }
 
     return $errors;
   }
 
 
   protected function adjustObjectForPolicyChecks(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $copy = clone $object;
 
     foreach ($xactions as $xaction) {
       switch ($xaction->getTransactionType()) {
         case PhabricatorTransactions::TYPE_SUBSCRIBERS:
           $clone_xaction = clone $xaction;
           $clone_xaction->setOldValue(array_values($this->subscribers));
           $clone_xaction->setNewValue(
             $this->getPHIDTransactionNewValue(
               $clone_xaction));
 
           PhabricatorPolicyRule::passTransactionHintToRule(
             $copy,
             new PhabricatorSubscriptionsSubscribersPolicyRule(),
             array_fuse($clone_xaction->getNewValue()));
 
           break;
         case PhabricatorTransactions::TYPE_SPACE:
           $space_phid = $this->getTransactionNewValue($object, $xaction);
           $copy->setSpacePHID($space_phid);
           break;
       }
     }
 
     return $copy;
   }
 
   protected function validateAllTransactions(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return array();
   }
 
   /**
    * Check for a missing text field.
    *
    * A text field is missing if the object has no value and there are no
    * transactions which set a value, or if the transactions remove the value.
    * This method is intended to make implementing @{method:validateTransaction}
    * more convenient:
    *
    *   $missing = $this->validateIsEmptyTextField(
    *     $object->getName(),
    *     $xactions);
    *
    * This will return `true` if the net effect of the object and transactions
    * is an empty field.
    *
    * @param wild Current field value.
    * @param list<PhabricatorApplicationTransaction> Transactions editing the
    *          field.
    * @return bool True if the field will be an empty text field after edits.
    */
   protected function validateIsEmptyTextField($field_value, array $xactions) {
     if (strlen($field_value) && empty($xactions)) {
       return false;
     }
 
     if ($xactions && strlen(last($xactions)->getNewValue())) {
       return false;
     }
 
     return true;
   }
 
   /**
    * Check that text field input isn't longer than a specified length.
    *
    * A text field input is invalid if the length of the input is longer than a
    * specified length. This length can be determined by the space allotted in
    * the database, or given arbitrarily.
    * This method is intended to make implementing @{method:validateTransaction}
    * more convenient:
    *
    *   $overdrawn = $this->validateIsTextFieldTooLong(
    *     $object->getName(),
    *     $xactions,
    *     $field_length);
    *
    * This will return `true` if the net effect of the object and transactions
    * is a field that is too long.
    *
    * @param wild Current field value.
    * @param list<PhabricatorApplicationTransaction> Transactions editing the
    *          field.
    * @param integer for maximum field length.
    * @return bool True if the field will be too long after edits.
    */
   protected function validateIsTextFieldTooLong(
     $field_value,
     array $xactions,
     $length) {
 
     if ($xactions) {
       $new_value_length = phutil_utf8_strlen(last($xactions)->getNewValue());
       if ($new_value_length <= $length) {
         return false;
       } else {
         return true;
       }
     }
 
     $old_value_length = phutil_utf8_strlen($field_value);
     if ($old_value_length <= $length) {
       return false;
     }
 
     return true;
   }
 
 
 /* -(  Implicit CCs  )------------------------------------------------------- */
 
 
   /**
    * When a user interacts with an object, we might want to add them to CC.
    */
   final public function applyImplicitCC(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     if (!($object instanceof PhabricatorSubscribableInterface)) {
       // If the object isn't subscribable, we can't CC them.
       return $xactions;
     }
 
     $actor_phid = $this->getActingAsPHID();
 
     $type_user = PhabricatorPeopleUserPHIDType::TYPECONST;
     if (phid_get_type($actor_phid) != $type_user) {
       // Transactions by application actors like Herald, Harbormaster and
       // Diffusion should not CC the applications.
       return $xactions;
     }
 
     if ($object->isAutomaticallySubscribed($actor_phid)) {
       // If they're auto-subscribed, don't CC them.
       return $xactions;
     }
 
     $should_cc = false;
     foreach ($xactions as $xaction) {
       if ($this->shouldImplyCC($object, $xaction)) {
         $should_cc = true;
         break;
       }
     }
 
     if (!$should_cc) {
       // Only some types of actions imply a CC (like adding a comment).
       return $xactions;
     }
 
     if ($object->getPHID()) {
       if (isset($this->subscribers[$actor_phid])) {
         // If the user is already subscribed, don't implicitly CC them.
         return $xactions;
       }
 
       $unsub = PhabricatorEdgeQuery::loadDestinationPHIDs(
         $object->getPHID(),
         PhabricatorObjectHasUnsubscriberEdgeType::EDGECONST);
       $unsub = array_fuse($unsub);
       if (isset($unsub[$actor_phid])) {
         // If the user has previously unsubscribed from this object explicitly,
         // don't implicitly CC them.
         return $xactions;
       }
     }
 
     $xaction = newv(get_class(head($xactions)), array());
     $xaction->setTransactionType(PhabricatorTransactions::TYPE_SUBSCRIBERS);
     $xaction->setNewValue(array('+' => array($actor_phid)));
 
     array_unshift($xactions, $xaction);
 
     return $xactions;
   }
 
   protected function shouldImplyCC(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     return $xaction->isCommentTransaction();
   }
 
 
 /* -(  Sending Mail  )------------------------------------------------------- */
 
 
   /**
    * @task mail
    */
   protected function shouldSendMail(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return false;
   }
 
 
   /**
    * @task mail
    */
   private function buildMail(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $email_to = $this->mailToPHIDs;
     $email_cc = $this->mailCCPHIDs;
     $email_cc = array_merge($email_cc, $this->heraldEmailPHIDs);
 
     $targets = $this->buildReplyHandler($object)
       ->getMailTargets($email_to, $email_cc);
 
     // Set this explicitly before we start swapping out the effective actor.
     $this->setActingAsPHID($this->getActingAsPHID());
 
     $messages = array();
     foreach ($targets as $target) {
       $original_actor = $this->getActor();
 
       $viewer = $target->getViewer();
       $this->setActor($viewer);
       $locale = PhabricatorEnv::beginScopedLocale($viewer->getTranslation());
 
       $caught = null;
       $mail = null;
       try {
         // Reload handles for the new viewer.
         $this->loadHandles($xactions);
 
         $mail = $this->buildMailForTarget($object, $xactions, $target);
       } catch (Exception $ex) {
         $caught = $ex;
       }
 
       $this->setActor($original_actor);
       unset($locale);
 
       if ($caught) {
         throw $ex;
       }
 
       if ($mail) {
         $messages[] = $mail;
       }
     }
 
     $this->runHeraldMailRules($messages);
 
     return $messages;
   }
 
   private function buildMailForTarget(
     PhabricatorLiskDAO $object,
     array $xactions,
     PhabricatorMailTarget $target) {
 
     // Check if any of the transactions are visible for this viewer. If we
     // don't have any visible transactions, don't send the mail.
 
     $any_visible = false;
     foreach ($xactions as $xaction) {
       if (!$xaction->shouldHideForMail($xactions)) {
         $any_visible = true;
         break;
       }
     }
 
     if (!$any_visible) {
       return null;
     }
 
     $mail = $this->buildMailTemplate($object);
     $body = $this->buildMailBody($object, $xactions);
 
     $mail_tags = $this->getMailTags($object, $xactions);
     $action = $this->getMailAction($object, $xactions);
 
     if (PhabricatorEnv::getEnvConfig('metamta.email-preferences')) {
       $this->addEmailPreferenceSectionToMailBody(
         $body,
         $object,
         $xactions);
     }
 
     $mail
       ->setSensitiveContent(false)
       ->setFrom($this->getActingAsPHID())
       ->setSubjectPrefix($this->getMailSubjectPrefix())
       ->setVarySubjectPrefix('['.$action.']')
       ->setThreadID($this->getMailThreadID($object), $this->getIsNewObject())
       ->setRelatedPHID($object->getPHID())
       ->setExcludeMailRecipientPHIDs($this->getExcludeMailRecipientPHIDs())
       ->setForceHeraldMailRecipientPHIDs($this->heraldForcedEmailPHIDs)
       ->setMailTags($mail_tags)
       ->setIsBulk(true)
       ->setBody($body->render())
       ->setHTMLBody($body->renderHTML());
 
     foreach ($body->getAttachments() as $attachment) {
       $mail->addAttachment($attachment);
     }
 
     if ($this->heraldHeader) {
       $mail->addHeader('X-Herald-Rules', $this->heraldHeader);
     }
 
     if ($object instanceof PhabricatorProjectInterface) {
       $this->addMailProjectMetadata($object, $mail);
     }
 
     if ($this->getParentMessageID()) {
       $mail->setParentMessageID($this->getParentMessageID());
     }
 
     return $target->willSendMail($mail);
   }
 
   private function addMailProjectMetadata(
     PhabricatorLiskDAO $object,
     PhabricatorMetaMTAMail $template) {
 
     $project_phids = PhabricatorEdgeQuery::loadDestinationPHIDs(
       $object->getPHID(),
       PhabricatorProjectObjectHasProjectEdgeType::EDGECONST);
 
     if (!$project_phids) {
       return;
     }
 
     // TODO: This viewer isn't quite right. It would be slightly better to use
     // the mail recipient, but that's not very easy given the way rendering
     // works today.
 
     $handles = id(new PhabricatorHandleQuery())
       ->setViewer($this->requireActor())
       ->withPHIDs($project_phids)
       ->execute();
 
     $project_tags = array();
     foreach ($handles as $handle) {
       if (!$handle->isComplete()) {
         continue;
       }
       $project_tags[] = '<'.$handle->getObjectName().'>';
     }
 
     if (!$project_tags) {
       return;
     }
 
     $project_tags = implode(', ', $project_tags);
     $template->addHeader('X-Phabricator-Projects', $project_tags);
   }
 
 
   protected function getMailThreadID(PhabricatorLiskDAO $object) {
     return $object->getPHID();
   }
 
 
   /**
    * @task mail
    */
   protected function getStrongestAction(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return last(msort($xactions, 'getActionStrength'));
   }
 
 
   /**
    * @task mail
    */
   protected function buildReplyHandler(PhabricatorLiskDAO $object) {
     throw new Exception(pht('Capability not supported.'));
   }
 
   /**
    * @task mail
    */
   protected function getMailSubjectPrefix() {
     throw new Exception(pht('Capability not supported.'));
   }
 
 
   /**
    * @task mail
    */
   protected function getMailTags(
     PhabricatorLiskDAO $object,
     array $xactions) {
     $tags = array();
 
     foreach ($xactions as $xaction) {
       $tags[] = $xaction->getMailTags();
     }
 
     return array_mergev($tags);
   }
 
   /**
    * @task mail
    */
   public function getMailTagsMap() {
     // TODO: We should move shared mail tags, like "comment", here.
     return array();
   }
 
 
   /**
    * @task mail
    */
   protected function getMailAction(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return $this->getStrongestAction($object, $xactions)->getActionName();
   }
 
 
   /**
    * @task mail
    */
   protected function buildMailTemplate(PhabricatorLiskDAO $object) {
     throw new Exception(pht('Capability not supported.'));
   }
 
 
   /**
    * @task mail
    */
   protected function getMailTo(PhabricatorLiskDAO $object) {
     throw new Exception(pht('Capability not supported.'));
   }
 
 
   /**
    * @task mail
    */
   protected function getMailCC(PhabricatorLiskDAO $object) {
     $phids = array();
     $has_support = false;
 
     if ($object instanceof PhabricatorSubscribableInterface) {
       $phid = $object->getPHID();
       $phids[] = PhabricatorSubscribersQuery::loadSubscribersForPHID($phid);
       $has_support = true;
     }
 
     if ($object instanceof PhabricatorProjectInterface) {
       $project_phids = PhabricatorEdgeQuery::loadDestinationPHIDs(
         $object->getPHID(),
         PhabricatorProjectObjectHasProjectEdgeType::EDGECONST);
 
       if ($project_phids) {
         $projects = id(new PhabricatorProjectQuery())
           ->setViewer(PhabricatorUser::getOmnipotentUser())
           ->withPHIDs($project_phids)
           ->needWatchers(true)
           ->execute();
 
         $watcher_phids = array();
         foreach ($projects as $project) {
           foreach ($project->getAllAncestorWatcherPHIDs() as $phid) {
             $watcher_phids[$phid] = $phid;
           }
         }
 
         if ($watcher_phids) {
           // We need to do a visibility check for all the watchers, as
           // watching a project is not a guarantee that you can see objects
           // associated with it.
           $users = id(new PhabricatorPeopleQuery())
             ->setViewer($this->requireActor())
             ->withPHIDs($watcher_phids)
             ->execute();
 
           $watchers = array();
           foreach ($users as $user) {
             $can_see = PhabricatorPolicyFilter::hasCapability(
               $user,
               $object,
               PhabricatorPolicyCapability::CAN_VIEW);
             if ($can_see) {
               $watchers[] = $user->getPHID();
             }
           }
           $phids[] = $watchers;
         }
       }
 
       $has_support = true;
     }
 
     if (!$has_support) {
       throw new Exception(pht('Capability not supported.'));
     }
 
     return array_mergev($phids);
   }
 
 
   /**
    * @task mail
    */
   protected function buildMailBody(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $body = new PhabricatorMetaMTAMailBody();
     $body->setViewer($this->requireActor());
 
     $this->addHeadersAndCommentsToMailBody($body, $xactions);
     $this->addCustomFieldsToMailBody($body, $object, $xactions);
     return $body;
   }
 
 
   /**
    * @task mail
    */
   protected function addEmailPreferenceSectionToMailBody(
     PhabricatorMetaMTAMailBody $body,
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $href = PhabricatorEnv::getProductionURI(
       '/settings/panel/emailpreferences/');
     $body->addLinkSection(pht('EMAIL PREFERENCES'), $href);
   }
 
 
   /**
    * @task mail
    */
   protected function addHeadersAndCommentsToMailBody(
     PhabricatorMetaMTAMailBody $body,
     array $xactions,
     $object_label = null,
     $object_href = null) {
 
     $headers = array();
+    $headers_html = array();
     $comments = array();
+    $details = array();
 
     foreach ($xactions as $xaction) {
       if ($xaction->shouldHideForMail($xactions)) {
         continue;
       }
 
       $header = $xaction->getTitleForMail();
       if ($header !== null) {
         $headers[] = $header;
       }
 
+      $header_html = $xaction->getTitleForHTMLMail();
+      if ($header_html !== null) {
+        $headers_html[] = $header_html;
+      }
+
       $comment = $xaction->getBodyForMail();
       if ($comment !== null) {
         $comments[] = $comment;
       }
+
+      if ($xaction->hasChangeDetailsForMail()) {
+        $details[] = $xaction;
+      }
     }
 
     $headers_text = implode("\n", $headers);
     $body->addRawPlaintextSection($headers_text);
 
-    $headers_html = phutil_implode_html(phutil_tag('br'), $headers);
+    $headers_html = phutil_implode_html(phutil_tag('br'), $headers_html);
 
     $header_button = null;
     if ($object_label !== null) {
       $button_style = array(
         'text-decoration: none;',
         'padding: 4px 8px;',
         'margin: 0 8px 8px;',
         'float: right;',
         'color: #464C5C;',
         'font-weight: bold;',
         'border-radius: 3px;',
         'background-color: #F7F7F9;',
         'background-image: linear-gradient(to bottom,#fff,#f1f0f1);',
         'display: inline-block;',
         'border: 1px solid rgba(71,87,120,.2);',
       );
 
       $header_button = phutil_tag(
         'a',
         array(
           'style' => implode(' ', $button_style),
           'href' => $object_href,
         ),
         $object_label);
     }
 
     $xactions_style = array(
     );
 
     $header_action = phutil_tag(
       'td',
       array(),
       $header_button);
 
     $header_action = phutil_tag(
       'td',
       array(
         'style' => implode(' ', $xactions_style),
       ),
-      $headers_html);
+      array(
+        $headers_html,
+        // Add an extra newline to prevent the "View Object" button from
+        // running into the transaction text in Mail.app text snippet
+        // previews.
+        "\n",
+      ));
 
     $headers_html = phutil_tag(
       'table',
       array(),
       phutil_tag('tr', array(), array($header_action, $header_button)));
 
     $body->addRawHTMLSection($headers_html);
 
     foreach ($comments as $comment) {
       $body->addRemarkupSection(null, $comment);
     }
+
+    foreach ($details as $xaction) {
+      $details = $xaction->renderChangeDetailsForMail($body->getViewer());
+      if ($details !== null) {
+        $body->addHTMLSection(pht('EDIT DETAILS'), $details);
+      }
+    }
+
   }
 
   /**
    * @task mail
    */
   protected function addCustomFieldsToMailBody(
     PhabricatorMetaMTAMailBody $body,
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     if ($object instanceof PhabricatorCustomFieldInterface) {
       $field_list = PhabricatorCustomField::getObjectFields(
         $object,
         PhabricatorCustomField::ROLE_TRANSACTIONMAIL);
       $field_list->setViewer($this->getActor());
       $field_list->readFieldsFromStorage($object);
 
       foreach ($field_list->getFields() as $field) {
         $field->updateTransactionMailBody(
           $body,
           $this,
           $xactions);
       }
     }
   }
 
 
   /**
    * @task mail
    */
   private function runHeraldMailRules(array $messages) {
     foreach ($messages as $message) {
       $engine = new HeraldEngine();
       $adapter = id(new PhabricatorMailOutboundMailHeraldAdapter())
         ->setObject($message);
 
       $rules = $engine->loadRulesForAdapter($adapter);
       $effects = $engine->applyRules($rules, $adapter);
       $engine->applyEffects($effects, $adapter, $rules);
     }
   }
 
 
 /* -(  Publishing Feed Stories  )-------------------------------------------- */
 
 
   /**
    * @task feed
    */
   protected function shouldPublishFeedStory(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return false;
   }
 
 
   /**
    * @task feed
    */
   protected function getFeedStoryType() {
     return 'PhabricatorApplicationTransactionFeedStory';
   }
 
 
   /**
    * @task feed
    */
   protected function getFeedRelatedPHIDs(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $phids = array(
       $object->getPHID(),
       $this->getActingAsPHID(),
     );
 
     if ($object instanceof PhabricatorProjectInterface) {
       $project_phids = PhabricatorEdgeQuery::loadDestinationPHIDs(
         $object->getPHID(),
         PhabricatorProjectObjectHasProjectEdgeType::EDGECONST);
       foreach ($project_phids as $project_phid) {
         $phids[] = $project_phid;
       }
     }
 
     return $phids;
   }
 
 
   /**
    * @task feed
    */
   protected function getFeedNotifyPHIDs(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     return array_unique(array_merge(
       $this->getMailTo($object),
       $this->getMailCC($object)));
   }
 
 
   /**
    * @task feed
    */
   protected function getFeedStoryData(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $xactions = msort($xactions, 'getActionStrength');
     $xactions = array_reverse($xactions);
 
     return array(
       'objectPHID'        => $object->getPHID(),
       'transactionPHIDs'  => mpull($xactions, 'getPHID'),
     );
   }
 
 
   /**
    * @task feed
    */
   protected function publishFeedStory(
     PhabricatorLiskDAO $object,
     array $xactions,
     array $mailed_phids) {
 
     $xactions = mfilter($xactions, 'shouldHideForFeed', true);
 
     if (!$xactions) {
       return;
     }
 
     $related_phids = $this->feedRelatedPHIDs;
     $subscribed_phids = $this->feedNotifyPHIDs;
 
     $story_type = $this->getFeedStoryType();
     $story_data = $this->getFeedStoryData($object, $xactions);
 
     id(new PhabricatorFeedStoryPublisher())
       ->setStoryType($story_type)
       ->setStoryData($story_data)
       ->setStoryTime(time())
       ->setStoryAuthorPHID($this->getActingAsPHID())
       ->setRelatedPHIDs($related_phids)
       ->setPrimaryObjectPHID($object->getPHID())
       ->setSubscribedPHIDs($subscribed_phids)
       ->setMailRecipientPHIDs($mailed_phids)
       ->setMailTags($this->getMailTags($object, $xactions))
       ->publish();
   }
 
 
 /* -(  Search Index  )------------------------------------------------------- */
 
 
   /**
    * @task search
    */
   protected function supportsSearch() {
     return false;
   }
 
 
 /* -(  Herald Integration )-------------------------------------------------- */
 
 
   protected function shouldApplyHeraldRules(
     PhabricatorLiskDAO $object,
     array $xactions) {
     return false;
   }
 
   protected function buildHeraldAdapter(
     PhabricatorLiskDAO $object,
     array $xactions) {
     throw new Exception(pht('No herald adapter specified.'));
   }
 
   private function setHeraldAdapter(HeraldAdapter $adapter) {
     $this->heraldAdapter = $adapter;
     return $this;
   }
 
   protected function getHeraldAdapter() {
     return $this->heraldAdapter;
   }
 
   private function setHeraldTranscript(HeraldTranscript $transcript) {
     $this->heraldTranscript = $transcript;
     return $this;
   }
 
   protected function getHeraldTranscript() {
     return $this->heraldTranscript;
   }
 
   private function applyHeraldRules(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $adapter = $this->buildHeraldAdapter($object, $xactions)
       ->setContentSource($this->getContentSource())
       ->setIsNewObject($this->getIsNewObject())
       ->setAppliedTransactions($xactions);
 
     if ($this->getApplicationEmail()) {
       $adapter->setApplicationEmail($this->getApplicationEmail());
     }
 
     $xscript = HeraldEngine::loadAndApplyRules($adapter);
 
     $this->setHeraldAdapter($adapter);
     $this->setHeraldTranscript($xscript);
 
     if ($adapter instanceof HarbormasterBuildableAdapterInterface) {
       HarbormasterBuildable::applyBuildPlans(
         $adapter->getHarbormasterBuildablePHID(),
         $adapter->getHarbormasterContainerPHID(),
         $adapter->getQueuedHarbormasterBuildRequests());
     }
 
     return array_merge(
       $this->didApplyHeraldRules($object, $adapter, $xscript),
       $adapter->getQueuedTransactions());
   }
 
   protected function didApplyHeraldRules(
     PhabricatorLiskDAO $object,
     HeraldAdapter $adapter,
     HeraldTranscript $transcript) {
     return array();
   }
 
 
 /* -(  Custom Fields  )------------------------------------------------------ */
 
 
   /**
    * @task customfield
    */
   private function getCustomFieldForTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
 
     $field_key = $xaction->getMetadataValue('customfield:key');
     if (!$field_key) {
       throw new Exception(
         pht(
         "Custom field transaction has no '%s'!",
         'customfield:key'));
     }
 
     $field = PhabricatorCustomField::getObjectField(
       $object,
       PhabricatorCustomField::ROLE_APPLICATIONTRANSACTIONS,
       $field_key);
 
     if (!$field) {
       throw new Exception(
         pht(
           "Custom field transaction has invalid '%s'; field '%s' ".
           "is disabled or does not exist.",
           'customfield:key',
           $field_key));
     }
 
     if (!$field->shouldAppearInApplicationTransactions()) {
       throw new Exception(
         pht(
           "Custom field transaction '%s' does not implement ".
           "integration for %s.",
           $field_key,
           'ApplicationTransactions'));
     }
 
     $field->setViewer($this->getActor());
 
     return $field;
   }
 
 
 /* -(  Files  )-------------------------------------------------------------- */
 
 
   /**
    * Extract the PHIDs of any files which these transactions attach.
    *
    * @task files
    */
   private function extractFilePHIDs(
     PhabricatorLiskDAO $object,
     array $xactions) {
 
     $blocks = array();
     foreach ($xactions as $xaction) {
       $blocks[] = $this->getRemarkupBlocksFromTransaction($xaction);
     }
     $blocks = array_mergev($blocks);
 
     $phids = array();
     if ($blocks) {
       $phids[] = PhabricatorMarkupEngine::extractFilePHIDsFromEmbeddedFiles(
         $this->getActor(),
         $blocks);
     }
 
     foreach ($xactions as $xaction) {
       $phids[] = $this->extractFilePHIDsFromCustomTransaction(
         $object,
         $xaction);
     }
 
     $phids = array_unique(array_filter(array_mergev($phids)));
     if (!$phids) {
       return array();
     }
 
     // Only let a user attach files they can actually see, since this would
     // otherwise let you access any file by attaching it to an object you have
     // view permission on.
 
     $files = id(new PhabricatorFileQuery())
       ->setViewer($this->getActor())
       ->withPHIDs($phids)
       ->execute();
 
     return mpull($files, 'getPHID');
   }
 
   /**
    * @task files
    */
   protected function extractFilePHIDsFromCustomTransaction(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
     return array();
   }
 
 
   /**
    * @task files
    */
   private function attachFiles(
     PhabricatorLiskDAO $object,
     array $file_phids) {
 
     if (!$file_phids) {
       return;
     }
 
     $editor = new PhabricatorEdgeEditor();
 
     $src = $object->getPHID();
     $type = PhabricatorObjectHasFileEdgeType::EDGECONST;
     foreach ($file_phids as $dst) {
       $editor->addEdge($src, $type, $dst);
     }
 
     $editor->save();
   }
 
   private function applyInverseEdgeTransactions(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction,
     $inverse_type) {
 
     $old = $xaction->getOldValue();
     $new = $xaction->getNewValue();
 
     $add = array_keys(array_diff_key($new, $old));
     $rem = array_keys(array_diff_key($old, $new));
 
     $add = array_fuse($add);
     $rem = array_fuse($rem);
     $all = $add + $rem;
 
     $nodes = id(new PhabricatorObjectQuery())
       ->setViewer($this->requireActor())
       ->withPHIDs($all)
       ->execute();
 
     foreach ($nodes as $node) {
       if (!($node instanceof PhabricatorApplicationTransactionInterface)) {
         continue;
       }
 
       if ($node instanceof PhabricatorUser) {
         // TODO: At least for now, don't record inverse edge transactions
         // for users (for example, "alincoln joined project X"): Feed fills
         // this role instead.
         continue;
       }
 
       $editor = $node->getApplicationTransactionEditor();
       $template = $node->getApplicationTransactionTemplate();
       $target = $node->getApplicationTransactionObject();
 
       if (isset($add[$node->getPHID()])) {
         $edge_edit_type = '+';
       } else {
         $edge_edit_type = '-';
       }
 
       $template
         ->setTransactionType($xaction->getTransactionType())
         ->setMetadataValue('edge:type', $inverse_type)
         ->setNewValue(
           array(
             $edge_edit_type => array($object->getPHID() => $object->getPHID()),
           ));
 
       $editor
         ->setContinueOnNoEffect(true)
         ->setContinueOnMissingFields(true)
         ->setParentMessageID($this->getParentMessageID())
         ->setIsInverseEdgeEditor(true)
         ->setActor($this->requireActor())
         ->setActingAsPHID($this->getActingAsPHID())
         ->setContentSource($this->getContentSource());
 
       $editor->applyTransactions($target, array($template));
     }
   }
 
 
 /* -(  Workers  )------------------------------------------------------------ */
 
 
   /**
    * Load any object state which is required to publish transactions.
    *
    * This hook is invoked in the main process before we compute data related
    * to publishing transactions (like email "To" and "CC" lists), and again in
    * the worker before publishing occurs.
    *
    * @return object Publishable object.
    * @task workers
    */
   protected function willPublish(PhabricatorLiskDAO $object, array $xactions) {
     return $object;
   }
 
 
   /**
    * Convert the editor state to a serializable dictionary which can be passed
    * to a worker.
    *
    * This data will be loaded with @{method:loadWorkerState} in the worker.
    *
    * @return dict<string, wild> Serializable editor state.
    * @task workers
    */
   final private function getWorkerState() {
     $state = array();
     foreach ($this->getAutomaticStateProperties() as $property) {
       $state[$property] = $this->$property;
     }
 
     $custom_state = $this->getCustomWorkerState();
     $custom_encoding = $this->getCustomWorkerStateEncoding();
 
     $state += array(
       'excludeMailRecipientPHIDs' => $this->getExcludeMailRecipientPHIDs(),
       'custom' => $this->encodeStateForStorage($custom_state, $custom_encoding),
       'custom.encoding' => $custom_encoding,
     );
 
     return $state;
   }
 
 
   /**
    * Hook; return custom properties which need to be passed to workers.
    *
    * @return dict<string, wild> Custom properties.
    * @task workers
    */
   protected function getCustomWorkerState() {
     return array();
   }
 
 
   /**
    * Hook; return storage encoding for custom properties which need to be
    * passed to workers.
    *
    * This primarily allows binary data to be passed to workers and survive
    * JSON encoding.
    *
    * @return dict<string, string> Property encodings.
    * @task workers
    */
   protected function getCustomWorkerStateEncoding() {
     return array();
   }
 
 
   /**
    * Load editor state using a dictionary emitted by @{method:getWorkerState}.
    *
    * This method is used to load state when running worker operations.
    *
    * @param dict<string, wild> Editor state, from @{method:getWorkerState}.
    * @return this
    * @task workers
    */
   final public function loadWorkerState(array $state) {
     foreach ($this->getAutomaticStateProperties() as $property) {
       $this->$property = idx($state, $property);
     }
 
     $exclude = idx($state, 'excludeMailRecipientPHIDs', array());
     $this->setExcludeMailRecipientPHIDs($exclude);
 
     $custom_state = idx($state, 'custom', array());
     $custom_encodings = idx($state, 'custom.encoding', array());
     $custom = $this->decodeStateFromStorage($custom_state, $custom_encodings);
 
     $this->loadCustomWorkerState($custom);
 
     return $this;
   }
 
 
   /**
    * Hook; set custom properties on the editor from data emitted by
    * @{method:getCustomWorkerState}.
    *
    * @param dict<string, wild> Custom state,
    *   from @{method:getCustomWorkerState}.
    * @return this
    * @task workers
    */
   protected function loadCustomWorkerState(array $state) {
     return $this;
   }
 
 
   /**
    * Get a list of object properties which should be automatically sent to
    * workers in the state data.
    *
    * These properties will be automatically stored and loaded by the editor in
    * the worker.
    *
    * @return list<string> List of properties.
    * @task workers
    */
   private function getAutomaticStateProperties() {
     return array(
       'parentMessageID',
       'disableEmail',
       'isNewObject',
       'heraldEmailPHIDs',
       'heraldForcedEmailPHIDs',
       'heraldHeader',
       'mailToPHIDs',
       'mailCCPHIDs',
       'feedNotifyPHIDs',
       'feedRelatedPHIDs',
     );
   }
 
   /**
    * Apply encodings prior to storage.
    *
    * See @{method:getCustomWorkerStateEncoding}.
    *
    * @param map<string, wild> Map of values to encode.
    * @param map<string, string> Map of encodings to apply.
    * @return map<string, wild> Map of encoded values.
    * @task workers
    */
   final private function encodeStateForStorage(
     array $state,
     array $encodings) {
 
     foreach ($state as $key => $value) {
       $encoding = idx($encodings, $key);
       switch ($encoding) {
         case self::STORAGE_ENCODING_BINARY:
           // The mechanics of this encoding (serialize + base64) are a little
           // awkward, but it allows us encode arrays and still be JSON-safe
           // with binary data.
 
           $value = @serialize($value);
           if ($value === false) {
             throw new Exception(
               pht(
                 'Failed to serialize() value for key "%s".',
                 $key));
           }
 
           $value = base64_encode($value);
           if ($value === false) {
             throw new Exception(
               pht(
                 'Failed to base64 encode value for key "%s".',
                 $key));
           }
           break;
       }
       $state[$key] = $value;
     }
 
     return $state;
   }
 
 
   /**
    * Undo storage encoding applied when storing state.
    *
    * See @{method:getCustomWorkerStateEncoding}.
    *
    * @param map<string, wild> Map of encoded values.
    * @param map<string, string> Map of encodings.
    * @return map<string, wild> Map of decoded values.
    * @task workers
    */
   final private function decodeStateFromStorage(
     array $state,
     array $encodings) {
 
     foreach ($state as $key => $value) {
       $encoding = idx($encodings, $key);
       switch ($encoding) {
         case self::STORAGE_ENCODING_BINARY:
           $value = base64_decode($value);
           if ($value === false) {
             throw new Exception(
               pht(
                 'Failed to base64_decode() value for key "%s".',
                 $key));
           }
 
           $value = unserialize($value);
           break;
       }
       $state[$key] = $value;
     }
 
     return $state;
   }
 
 
   /**
    * Remove conflicts from a list of projects.
    *
    * Objects aren't allowed to be tagged with multiple milestones in the same
    * group, nor projects such that one tag is the ancestor of any other tag.
    * If the list of PHIDs include mutually exclusive projects, remove the
    * conflicting projects.
    *
    * @param list<phid> List of project PHIDs.
    * @return list<phid> List with conflicts removed.
    */
   private function applyProjectConflictRules(array $phids) {
     if (!$phids) {
       return array();
     }
 
     // Overall, the last project in the list wins in cases of conflict (so when
     // you add something, the thing you just added sticks and removes older
     // values).
 
     // Beyond that, there are two basic cases:
 
     // Milestones: An object can't be in "A > Sprint 3" and "A > Sprint 4".
     // If multiple projects are milestones of the same parent, we only keep the
     // last one.
 
     // Ancestor: You can't be in "A" and "A > B". If "A > B" comes later
     // in the list, we remove "A" and keep "A > B". If "A" comes later, we
     // remove "A > B" and keep "A".
 
     // Note that it's OK to be in "A > B" and "A > C". There's only a conflict
     // if one project is an ancestor of another. It's OK to have something
     // tagged with multiple projects which share a common ancestor, so long as
     // they are not mutual ancestors.
 
     $viewer = PhabricatorUser::getOmnipotentUser();
 
     $projects = id(new PhabricatorProjectQuery())
       ->setViewer($viewer)
       ->withPHIDs(array_keys($phids))
       ->execute();
     $projects = mpull($projects, null, 'getPHID');
 
     // We're going to build a map from each project with milestones to the last
     // milestone in the list. This last milestone is the milestone we'll keep.
     $milestone_map = array();
 
     // We're going to build a set of the projects which have no descendants
     // later in the list. This allows us to apply both ancestor rules.
     $ancestor_map = array();
 
     foreach ($phids as $phid => $ignored) {
       $project = idx($projects, $phid);
       if (!$project) {
         continue;
       }
 
       // This is the last milestone we've seen, so set it as the selection for
       // the project's parent. This might be setting a new value or overwriting
       // an earlier value.
       if ($project->isMilestone()) {
         $parent_phid = $project->getParentProjectPHID();
         $milestone_map[$parent_phid] = $phid;
       }
 
       // Since this is the last item in the list we've examined so far, add it
       // to the set of projects with no later descendants.
       $ancestor_map[$phid] = $phid;
 
       // Remove any ancestors from the set, since this is a later descendant.
       foreach ($project->getAncestorProjects() as $ancestor) {
         $ancestor_phid = $ancestor->getPHID();
         unset($ancestor_map[$ancestor_phid]);
       }
     }
 
     // Now that we've built the maps, we can throw away all the projects which
     // have conflicts.
     foreach ($phids as $phid => $ignored) {
       $project = idx($projects, $phid);
 
       if (!$project) {
         // If a PHID is invalid, we just leave it as-is. We could clean it up,
         // but leaving it untouched is less likely to cause collateral damage.
         continue;
       }
 
       // If this was a milestone, check if it was the last milestone from its
       // group in the list. If not, remove it from the list.
       if ($project->isMilestone()) {
         $parent_phid = $project->getParentProjectPHID();
         if ($milestone_map[$parent_phid] !== $phid) {
           unset($phids[$phid]);
           continue;
         }
       }
 
       // If a later project in the list is a subproject of this one, it will
       // have removed ancestors from the map. If this project does not point
       // at itself in the ancestor map, it should be discarded in favor of a
       // subproject that comes later.
       if (idx($ancestor_map, $phid) !== $phid) {
         unset($phids[$phid]);
         continue;
       }
 
       // If a later project in the list is an ancestor of this one, it will
       // have added itself to the map. If any ancestor of this project points
       // at itself in the map, this project should be dicarded in favor of
       // that later ancestor.
       foreach ($project->getAncestorProjects() as $ancestor) {
         $ancestor_phid = $ancestor->getPHID();
         if (isset($ancestor_map[$ancestor_phid])) {
           unset($phids[$phid]);
           continue 2;
         }
       }
     }
 
     return $phids;
   }
 
   /**
    * When the view policy for an object is changed, scramble the secret keys
    * for attached files to invalidate existing URIs.
    */
   private function scrambleFileSecrets($object) {
     // If this is a newly created object, we don't need to scramble anything
     // since it couldn't have been previously published.
     if ($this->getIsNewObject()) {
       return;
     }
 
     // If the object is a file itself, scramble it.
     if ($object instanceof PhabricatorFile) {
       if ($this->shouldScramblePolicy($object->getViewPolicy())) {
         $object->scrambleSecret();
         $object->save();
       }
     }
 
     $phid = $object->getPHID();
 
     $attached_phids = PhabricatorEdgeQuery::loadDestinationPHIDs(
       $phid,
       PhabricatorObjectHasFileEdgeType::EDGECONST);
     if (!$attached_phids) {
       return;
     }
 
     $omnipotent_viewer = PhabricatorUser::getOmnipotentUser();
 
     $files = id(new PhabricatorFileQuery())
       ->setViewer($omnipotent_viewer)
       ->withPHIDs($attached_phids)
       ->execute();
     foreach ($files as $file) {
       $view_policy = $file->getViewPolicy();
       if ($this->shouldScramblePolicy($view_policy)) {
         $file->scrambleSecret();
         $file->save();
       }
     }
   }
 
 
   /**
    * Check if a policy is strong enough to justify scrambling. Objects which
    * are set to very open policies don't need to scramble their files, and
    * files with very open policies don't need to be scrambled when associated
    * objects change.
    */
   private function shouldScramblePolicy($policy) {
     switch ($policy) {
       case PhabricatorPolicies::POLICY_PUBLIC:
       case PhabricatorPolicies::POLICY_USER:
         return false;
     }
 
     return true;
   }
 
   private function updateWorkboardColumns($object, $const, $old, $new) {
     // If an object is removed from a project, remove it from any proxy
     // columns for that project. This allows a task which is moved up from a
     // milestone to the parent to move back into the "Backlog" column on the
     // parent workboard.
 
     if ($const != PhabricatorProjectObjectHasProjectEdgeType::EDGECONST) {
       return;
     }
 
     // TODO: This should likely be some future WorkboardInterface.
     $appears_on_workboards = ($object instanceof ManiphestTask);
     if (!$appears_on_workboards) {
       return;
     }
 
     $removed_phids = array_keys(array_diff_key($old, $new));
     if (!$removed_phids) {
       return;
     }
 
     // Find any proxy columns for the removed projects.
     $proxy_columns = id(new PhabricatorProjectColumnQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withProxyPHIDs($removed_phids)
       ->execute();
     if (!$proxy_columns) {
       return array();
     }
 
     $proxy_phids = mpull($proxy_columns, 'getPHID');
 
     $position_table = new PhabricatorProjectColumnPosition();
     $conn_w = $position_table->establishConnection('w');
 
     queryfx(
       $conn_w,
       'DELETE FROM %T WHERE objectPHID = %s AND columnPHID IN (%Ls)',
       $position_table->getTableName(),
       $object->getPHID(),
       $proxy_phids);
   }
 
 
 }
diff --git a/src/applications/transactions/storage/PhabricatorApplicationTransaction.php b/src/applications/transactions/storage/PhabricatorApplicationTransaction.php
index 1e6bb14481..3a7e3841a3 100644
--- a/src/applications/transactions/storage/PhabricatorApplicationTransaction.php
+++ b/src/applications/transactions/storage/PhabricatorApplicationTransaction.php
@@ -1,1562 +1,1596 @@
 <?php
 
 abstract class PhabricatorApplicationTransaction
   extends PhabricatorLiskDAO
   implements
     PhabricatorPolicyInterface,
     PhabricatorDestructibleInterface {
 
   const TARGET_TEXT = 'text';
   const TARGET_HTML = 'html';
 
   protected $phid;
   protected $objectPHID;
   protected $authorPHID;
   protected $viewPolicy;
   protected $editPolicy;
 
   protected $commentPHID;
   protected $commentVersion = 0;
   protected $transactionType;
   protected $oldValue;
   protected $newValue;
   protected $metadata = array();
 
   protected $contentSource;
 
   private $comment;
   private $commentNotLoaded;
 
   private $handles;
   private $renderingTarget = self::TARGET_HTML;
   private $transactionGroup = array();
   private $viewer = self::ATTACHABLE;
   private $object = self::ATTACHABLE;
   private $oldValueHasBeenSet = false;
 
   private $ignoreOnNoEffect;
 
 
   /**
    * Flag this transaction as a pure side-effect which should be ignored when
    * applying transactions if it has no effect, even if transaction application
    * would normally fail. This both provides users with better error messages
    * and allows transactions to perform optional side effects.
    */
   public function setIgnoreOnNoEffect($ignore) {
     $this->ignoreOnNoEffect = $ignore;
     return $this;
   }
 
   public function getIgnoreOnNoEffect() {
     return $this->ignoreOnNoEffect;
   }
 
   public function shouldGenerateOldValue() {
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_BUILDABLE:
       case PhabricatorTransactions::TYPE_TOKEN:
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
       case PhabricatorTransactions::TYPE_INLINESTATE:
         return false;
     }
     return true;
   }
 
   abstract public function getApplicationTransactionType();
 
   private function getApplicationObjectTypeName() {
     $types = PhabricatorPHIDType::getAllTypes();
 
     $type = idx($types, $this->getApplicationTransactionType());
     if ($type) {
       return $type->getTypeName();
     }
 
     return pht('Object');
   }
 
   public function getApplicationTransactionCommentObject() {
     throw new PhutilMethodNotImplementedException();
   }
 
   public function getApplicationTransactionViewObject() {
     return new PhabricatorApplicationTransactionView();
   }
 
   public function getMetadataValue($key, $default = null) {
     return idx($this->metadata, $key, $default);
   }
 
   public function setMetadataValue($key, $value) {
     $this->metadata[$key] = $value;
     return $this;
   }
 
   public function generatePHID() {
     $type = PhabricatorApplicationTransactionTransactionPHIDType::TYPECONST;
     $subtype = $this->getApplicationTransactionType();
 
     return PhabricatorPHID::generateNewPHID($type, $subtype);
   }
 
   protected function getConfiguration() {
     return array(
       self::CONFIG_AUX_PHID => true,
       self::CONFIG_SERIALIZATION => array(
         'oldValue' => self::SERIALIZATION_JSON,
         'newValue' => self::SERIALIZATION_JSON,
         'metadata' => self::SERIALIZATION_JSON,
       ),
       self::CONFIG_COLUMN_SCHEMA => array(
         'commentPHID' => 'phid?',
         'commentVersion' => 'uint32',
         'contentSource' => 'text',
         'transactionType' => 'text32',
       ),
       self::CONFIG_KEY_SCHEMA => array(
         'key_object' => array(
           'columns' => array('objectPHID'),
         ),
       ),
     ) + parent::getConfiguration();
   }
 
   public function setContentSource(PhabricatorContentSource $content_source) {
     $this->contentSource = $content_source->serialize();
     return $this;
   }
 
   public function getContentSource() {
     return PhabricatorContentSource::newFromSerialized($this->contentSource);
   }
 
   public function hasComment() {
     return $this->getComment() && strlen($this->getComment()->getContent());
   }
 
   public function getComment() {
     if ($this->commentNotLoaded) {
       throw new Exception(pht('Comment for this transaction was not loaded.'));
     }
     return $this->comment;
   }
 
   public function setIsCreateTransaction($create) {
     return $this->setMetadataValue('core.create', $create);
   }
 
   public function getIsCreateTransaction() {
     return (bool)$this->getMetadataValue('core.create', false);
   }
 
   public function setIsDefaultTransaction($default) {
     return $this->setMetadataValue('core.default', $default);
   }
 
   public function getIsDefaultTransaction() {
     return (bool)$this->getMetadataValue('core.default', false);
   }
 
   public function attachComment(
     PhabricatorApplicationTransactionComment $comment) {
     $this->comment = $comment;
     $this->commentNotLoaded = false;
     return $this;
   }
 
   public function setCommentNotLoaded($not_loaded) {
     $this->commentNotLoaded = $not_loaded;
     return $this;
   }
 
   public function attachObject($object) {
     $this->object = $object;
     return $this;
   }
 
   public function getObject() {
     return $this->assertAttached($this->object);
   }
 
   public function getRemarkupBlocks() {
     $blocks = array();
 
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $field = $this->getTransactionCustomField();
         if ($field) {
           $custom_blocks = $field->getApplicationTransactionRemarkupBlocks(
             $this);
           foreach ($custom_blocks as $custom_block) {
             $blocks[] = $custom_block;
           }
         }
         break;
     }
 
     if ($this->getComment()) {
       $blocks[] = $this->getComment()->getContent();
     }
 
     return $blocks;
   }
 
   public function setOldValue($value) {
     $this->oldValueHasBeenSet = true;
     $this->writeField('oldValue', $value);
     return $this;
   }
 
   public function hasOldValue() {
     return $this->oldValueHasBeenSet;
   }
 
 
 /* -(  Rendering  )---------------------------------------------------------- */
 
   public function setRenderingTarget($rendering_target) {
     $this->renderingTarget = $rendering_target;
     return $this;
   }
 
   public function getRenderingTarget() {
     return $this->renderingTarget;
   }
 
   public function attachViewer(PhabricatorUser $viewer) {
     $this->viewer = $viewer;
     return $this;
   }
 
   public function getViewer() {
     return $this->assertAttached($this->viewer);
   }
 
   public function getRequiredHandlePHIDs() {
     $phids = array();
 
     $old = $this->getOldValue();
     $new = $this->getNewValue();
 
     $phids[] = array($this->getAuthorPHID());
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $field = $this->getTransactionCustomField();
         if ($field) {
           $phids[] = $field->getApplicationTransactionRequiredHandlePHIDs(
             $this);
         }
         break;
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         $phids[] = $old;
         $phids[] = $new;
         break;
       case PhabricatorTransactions::TYPE_EDGE:
         $phids[] = ipull($old, 'dst');
         $phids[] = ipull($new, 'dst');
         break;
       case PhabricatorTransactions::TYPE_COLUMNS:
         foreach ($new as $move) {
           $phids[] = array(
             $move['columnPHID'],
             $move['boardPHID'],
           );
           $phids[] = $move['fromColumnPHIDs'];
         }
         break;
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
         if (!PhabricatorPolicyQuery::isSpecialPolicy($old)) {
           $phids[] = array($old);
         }
         if (!PhabricatorPolicyQuery::isSpecialPolicy($new)) {
           $phids[] = array($new);
         }
         break;
       case PhabricatorTransactions::TYPE_SPACE:
         if ($old) {
           $phids[] = array($old);
         }
         if ($new) {
           $phids[] = array($new);
         }
         break;
       case PhabricatorTransactions::TYPE_TOKEN:
         break;
       case PhabricatorTransactions::TYPE_BUILDABLE:
         $phid = $this->getMetadataValue('harbormaster:buildablePHID');
         if ($phid) {
           $phids[] = array($phid);
         }
         break;
     }
 
     if ($this->getComment()) {
       $phids[] = array($this->getComment()->getAuthorPHID());
     }
 
     return array_mergev($phids);
   }
 
   public function setHandles(array $handles) {
     $this->handles = $handles;
     return $this;
   }
 
   public function getHandle($phid) {
     if (empty($this->handles[$phid])) {
       throw new Exception(
         pht(
           'Transaction ("%s", of type "%s") requires a handle ("%s") that it '.
           'did not load.',
           $this->getPHID(),
           $this->getTransactionType(),
           $phid));
     }
     return $this->handles[$phid];
   }
 
   public function getHandleIfExists($phid) {
     return idx($this->handles, $phid);
   }
 
   public function getHandles() {
     if ($this->handles === null) {
       throw new Exception(
         pht('Transaction requires handles and it did not load them.'));
     }
     return $this->handles;
   }
 
   public function renderHandleLink($phid) {
     if ($this->renderingTarget == self::TARGET_HTML) {
       return $this->getHandle($phid)->renderLink();
     } else {
       return $this->getHandle($phid)->getLinkName();
     }
   }
 
   public function renderHandleList(array $phids) {
     $links = array();
     foreach ($phids as $phid) {
       $links[] = $this->renderHandleLink($phid);
     }
     if ($this->renderingTarget == self::TARGET_HTML) {
       return phutil_implode_html(', ', $links);
     } else {
       return implode(', ', $links);
     }
   }
 
   private function renderSubscriberList(array $phids, $change_type) {
     if ($this->getRenderingTarget() == self::TARGET_TEXT) {
       return $this->renderHandleList($phids);
     } else {
       $handles = array_select_keys($this->getHandles(), $phids);
       return id(new SubscriptionListStringBuilder())
         ->setHandles($handles)
         ->setObjectPHID($this->getPHID())
         ->buildTransactionString($change_type);
     }
   }
 
   protected function renderPolicyName($phid, $state = 'old') {
     $policy = PhabricatorPolicy::newFromPolicyAndHandle(
       $phid,
       $this->getHandleIfExists($phid));
     if ($this->renderingTarget == self::TARGET_HTML) {
       switch ($policy->getType()) {
         case PhabricatorPolicyType::TYPE_CUSTOM:
           $policy->setHref('/transactions/'.$state.'/'.$this->getPHID().'/');
           $policy->setWorkflow(true);
           break;
         default:
           break;
       }
       $output = $policy->renderDescription();
     } else {
       $output = hsprintf('%s', $policy->getFullName());
     }
     return $output;
   }
 
   public function getIcon() {
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_COMMENT:
         $comment = $this->getComment();
         if ($comment && $comment->getIsRemoved()) {
           return 'fa-trash';
         }
         return 'fa-comment';
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         $old = $this->getOldValue();
         $new = $this->getNewValue();
         $add = array_diff($new, $old);
         $rem = array_diff($old, $new);
         if ($add && $rem) {
           return 'fa-user';
         } else if ($add) {
           return 'fa-user-plus';
         } else if ($rem) {
           return 'fa-user-times';
         } else {
           return 'fa-user';
         }
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
         return 'fa-lock';
       case PhabricatorTransactions::TYPE_EDGE:
         return 'fa-link';
       case PhabricatorTransactions::TYPE_BUILDABLE:
         return 'fa-wrench';
       case PhabricatorTransactions::TYPE_TOKEN:
         return 'fa-trophy';
       case PhabricatorTransactions::TYPE_SPACE:
         return 'fa-th-large';
       case PhabricatorTransactions::TYPE_COLUMNS:
         return 'fa-columns';
     }
 
     return 'fa-pencil';
   }
 
   public function getToken() {
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_TOKEN:
         $old = $this->getOldValue();
         $new = $this->getNewValue();
         if ($new) {
           $icon = substr($new, 10);
         } else {
           $icon = substr($old, 10);
         }
         return array($icon, !$this->getNewValue());
     }
 
     return array(null, null);
   }
 
   public function getColor() {
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_COMMENT;
         $comment = $this->getComment();
         if ($comment && $comment->getIsRemoved()) {
           return 'black';
         }
         break;
       case PhabricatorTransactions::TYPE_BUILDABLE:
         switch ($this->getNewValue()) {
           case HarbormasterBuildable::STATUS_PASSED:
             return 'green';
           case HarbormasterBuildable::STATUS_FAILED:
             return 'red';
         }
         break;
     }
     return null;
   }
 
   protected function getTransactionCustomField() {
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $key = $this->getMetadataValue('customfield:key');
         if (!$key) {
           return null;
         }
 
         $object = $this->getObject();
 
         if (!($object instanceof PhabricatorCustomFieldInterface)) {
           return null;
         }
 
         $field = PhabricatorCustomField::getObjectField(
           $object,
           PhabricatorCustomField::ROLE_APPLICATIONTRANSACTIONS,
           $key);
         if (!$field) {
           return null;
         }
 
         $field->setViewer($this->getViewer());
         return $field;
     }
 
     return null;
   }
 
   public function shouldHide() {
     // Never hide comments.
     if ($this->hasComment()) {
       return false;
     }
 
     // Hide creation transactions if the old value is empty. These are
     // transactions like "alice set the task tile to: ...", which are
     // essentially never interesting.
     if ($this->getIsCreateTransaction()) {
       switch ($this->getTransactionType()) {
         case PhabricatorTransactions::TYPE_CREATE:
         case PhabricatorTransactions::TYPE_VIEW_POLICY:
         case PhabricatorTransactions::TYPE_EDIT_POLICY:
         case PhabricatorTransactions::TYPE_JOIN_POLICY:
         case PhabricatorTransactions::TYPE_SPACE:
           break;
         default:
           $old = $this->getOldValue();
 
           if (is_array($old) && !$old) {
             return true;
           }
 
           if (!is_array($old) && !strlen($old)) {
             return true;
           }
 
           break;
       }
     }
 
     // Hide creation transactions setting values to defaults, even if
     // the old value is not empty. For example, tasks may have a global
     // default view policy of "All Users", but a particular form sets the
     // policy to "Administrators". The transaction corresponding to this
     // change is not interesting, since it is the default behavior of the
     // form.
 
     if ($this->getIsCreateTransaction()) {
       if ($this->getIsDefaultTransaction()) {
         return true;
       }
     }
 
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
       case PhabricatorTransactions::TYPE_SPACE:
         if ($this->getIsCreateTransaction()) {
           break;
         }
 
         // TODO: Remove this eventually, this is handling old changes during
         // object creation prior to the introduction of "create" and "default"
         // transaction display flags.
 
         // NOTE: We can also hit this case with Space transactions that later
         // update a default space (`null`) to an explicit space, so handling
         // the Space case may require some finesse.
 
         if ($this->getOldValue() === null) {
           return true;
         } else {
           return false;
         }
         break;
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $field = $this->getTransactionCustomField();
         if ($field) {
           return $field->shouldHideInApplicationTransactions($this);
         }
         break;
       case PhabricatorTransactions::TYPE_COLUMNS:
         return !$this->getInterestingMoves($this->getNewValue());
       case PhabricatorTransactions::TYPE_EDGE:
         $edge_type = $this->getMetadataValue('edge:type');
         switch ($edge_type) {
           case PhabricatorObjectMentionsObjectEdgeType::EDGECONST:
             return true;
             break;
           case PhabricatorObjectMentionedByObjectEdgeType::EDGECONST:
             $new = ipull($this->getNewValue(), 'dst');
             $old = ipull($this->getOldValue(), 'dst');
             $add = array_diff($new, $old);
             $add_value = reset($add);
             $add_handle = $this->getHandle($add_value);
             if ($add_handle->getPolicyFiltered()) {
               return true;
             }
             return false;
             break;
           default:
             break;
         }
         break;
     }
 
     return false;
   }
 
   public function shouldHideForMail(array $xactions) {
     if ($this->isSelfSubscription()) {
       return true;
     }
 
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_TOKEN:
         return true;
       case PhabricatorTransactions::TYPE_BUILDABLE:
         switch ($this->getNewValue()) {
           case HarbormasterBuildable::STATUS_FAILED:
             // For now, only ever send mail when builds fail. We might let
             // you customize this later, but in most cases this is probably
             // completely uninteresting.
             return false;
         }
         return true;
      case PhabricatorTransactions::TYPE_EDGE:
         $edge_type = $this->getMetadataValue('edge:type');
         switch ($edge_type) {
           case PhabricatorObjectMentionsObjectEdgeType::EDGECONST:
           case PhabricatorObjectMentionedByObjectEdgeType::EDGECONST:
             return true;
           case PhabricatorProjectObjectHasProjectEdgeType::EDGECONST:
             // When an object is first created, we hide any corresponding
             // project transactions in the web UI because you can just look at
             // the UI element elsewhere on screen to see which projects it
             // is tagged with. However, in mail there's no other way to get
             // this information, and it has some amount of value to users, so
             // we keep the transaction. See T10493.
             return false;
           default:
             break;
         }
         break;
     }
 
     if ($this->isInlineCommentTransaction()) {
       $inlines = array();
 
       // If there's a normal comment, we don't need to publish the inline
       // transaction, since the normal comment covers things.
       foreach ($xactions as $xaction) {
         if ($xaction->isInlineCommentTransaction()) {
           $inlines[] = $xaction;
           continue;
         }
 
         // We found a normal comment, so hide this inline transaction.
         if ($xaction->hasComment()) {
           return true;
         }
       }
 
       // If there are several inline comments, only publish the first one.
       if ($this !== head($inlines)) {
         return true;
       }
     }
 
     return $this->shouldHide();
   }
 
   public function shouldHideForFeed() {
     if ($this->isSelfSubscription()) {
       return true;
     }
 
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_TOKEN:
         return true;
       case PhabricatorTransactions::TYPE_BUILDABLE:
         switch ($this->getNewValue()) {
           case HarbormasterBuildable::STATUS_FAILED:
             // For now, don't notify on build passes either. These are pretty
             // high volume and annoying, with very little present value. We
             // might want to turn them back on in the specific case of
             // build successes on the current document?
             return false;
         }
         return true;
      case PhabricatorTransactions::TYPE_EDGE:
         $edge_type = $this->getMetadataValue('edge:type');
         switch ($edge_type) {
           case PhabricatorObjectMentionsObjectEdgeType::EDGECONST:
           case PhabricatorObjectMentionedByObjectEdgeType::EDGECONST:
             return true;
             break;
           default:
             break;
         }
         break;
      case PhabricatorTransactions::TYPE_INLINESTATE:
        return true;
     }
 
     return $this->shouldHide();
   }
 
   public function getTitleForMail() {
     return id(clone $this)->setRenderingTarget('text')->getTitle();
   }
 
+  public function getTitleForHTMLMail() {
+    $title = $this->getTitleForMail();
+    if ($title === null) {
+      return null;
+    }
+
+    if ($this->hasChangeDetails()) {
+      $details_uri = $this->getChangeDetailsURI();
+      $details_uri = PhabricatorEnv::getProductionURI($details_uri);
+
+      $show_details = phutil_tag(
+        'a',
+        array(
+          'href' => $details_uri,
+        ),
+        pht('(Show Details)'));
+
+      $title = array($title, ' ', $show_details);
+    }
+
+    return $title;
+  }
+
+  public function getChangeDetailsURI() {
+    return '/transactions/detail/'.$this->getPHID().'/';
+  }
+
   public function getBodyForMail() {
     if ($this->isInlineCommentTransaction()) {
       // We don't return inline comment content as mail body content, because
       // applications need to contextualize it (by adding line numbers, for
       // example) in order for it to make sense.
       return null;
     }
 
     $comment = $this->getComment();
     if ($comment && strlen($comment->getContent())) {
       return $comment->getContent();
     }
 
     return null;
   }
 
   public function getNoEffectDescription() {
 
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_COMMENT:
         return pht('You can not post an empty comment.');
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
         return pht(
           'This %s already has that view policy.',
           $this->getApplicationObjectTypeName());
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
         return pht(
           'This %s already has that edit policy.',
           $this->getApplicationObjectTypeName());
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
         return pht(
           'This %s already has that join policy.',
           $this->getApplicationObjectTypeName());
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         return pht(
           'All users are already subscribed to this %s.',
           $this->getApplicationObjectTypeName());
       case PhabricatorTransactions::TYPE_SPACE:
         return pht('This object is already in that space.');
       case PhabricatorTransactions::TYPE_EDGE:
         return pht('Edges already exist; transaction has no effect.');
       case PhabricatorTransactions::TYPE_COLUMNS:
         return pht(
           'You have not moved this object to any columns it is not '.
           'already in.');
     }
 
     return pht(
       'Transaction (of type "%s") has no effect.',
       $this->getTransactionType());
   }
 
   public function getTitle() {
     $author_phid = $this->getAuthorPHID();
 
     $old = $this->getOldValue();
     $new = $this->getNewValue();
 
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_CREATE:
         return pht(
           '%s created this object.',
           $this->renderHandleLink($author_phid));
       case PhabricatorTransactions::TYPE_COMMENT:
         return pht(
           '%s added a comment.',
           $this->renderHandleLink($author_phid));
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
         if ($this->getIsCreateTransaction()) {
           return pht(
             '%s created this object with visibility "%s".',
             $this->renderHandleLink($author_phid),
             $this->renderPolicyName($new, 'new'));
         } else {
           return pht(
             '%s changed the visibility from "%s" to "%s".',
             $this->renderHandleLink($author_phid),
             $this->renderPolicyName($old, 'old'),
             $this->renderPolicyName($new, 'new'));
         }
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
         if ($this->getIsCreateTransaction()) {
           return pht(
             '%s created this object with edit policy "%s".',
             $this->renderHandleLink($author_phid),
             $this->renderPolicyName($new, 'new'));
         } else {
           return pht(
             '%s changed the edit policy from "%s" to "%s".',
             $this->renderHandleLink($author_phid),
             $this->renderPolicyName($old, 'old'),
             $this->renderPolicyName($new, 'new'));
         }
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
         if ($this->getIsCreateTransaction()) {
           return pht(
             '%s created this object with join policy "%s".',
             $this->renderHandleLink($author_phid),
             $this->renderPolicyName($new, 'new'));
         } else {
           return pht(
             '%s changed the join policy from "%s" to "%s".',
             $this->renderHandleLink($author_phid),
             $this->renderPolicyName($old, 'old'),
             $this->renderPolicyName($new, 'new'));
         }
       case PhabricatorTransactions::TYPE_SPACE:
         if ($this->getIsCreateTransaction()) {
           return pht(
             '%s created this object in space %s.',
             $this->renderHandleLink($author_phid),
             $this->renderHandleLink($new));
         } else {
           return pht(
             '%s shifted this object from the %s space to the %s space.',
             $this->renderHandleLink($author_phid),
             $this->renderHandleLink($old),
             $this->renderHandleLink($new));
         }
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         $add = array_diff($new, $old);
         $rem = array_diff($old, $new);
 
         if ($add && $rem) {
           return pht(
             '%s edited subscriber(s), added %d: %s; removed %d: %s.',
             $this->renderHandleLink($author_phid),
             count($add),
             $this->renderSubscriberList($add, 'add'),
             count($rem),
             $this->renderSubscriberList($rem, 'rem'));
         } else if ($add) {
           return pht(
             '%s added %d subscriber(s): %s.',
             $this->renderHandleLink($author_phid),
             count($add),
             $this->renderSubscriberList($add, 'add'));
         } else if ($rem) {
           return pht(
             '%s removed %d subscriber(s): %s.',
             $this->renderHandleLink($author_phid),
             count($rem),
             $this->renderSubscriberList($rem, 'rem'));
         } else {
           // This is used when rendering previews, before the user actually
           // selects any CCs.
           return pht(
             '%s updated subscribers...',
             $this->renderHandleLink($author_phid));
         }
         break;
       case PhabricatorTransactions::TYPE_EDGE:
         $new = ipull($new, 'dst');
         $old = ipull($old, 'dst');
         $add = array_diff($new, $old);
         $rem = array_diff($old, $new);
         $type = $this->getMetadata('edge:type');
         $type = head($type);
 
         $type_obj = PhabricatorEdgeType::getByConstant($type);
 
         if ($add && $rem) {
           return $type_obj->getTransactionEditString(
             $this->renderHandleLink($author_phid),
             new PhutilNumber(count($add) + count($rem)),
             phutil_count($add),
             $this->renderHandleList($add),
             phutil_count($rem),
             $this->renderHandleList($rem));
         } else if ($add) {
           return $type_obj->getTransactionAddString(
             $this->renderHandleLink($author_phid),
             phutil_count($add),
             $this->renderHandleList($add));
         } else if ($rem) {
           return $type_obj->getTransactionRemoveString(
             $this->renderHandleLink($author_phid),
             phutil_count($rem),
             $this->renderHandleList($rem));
         } else {
           return $type_obj->getTransactionPreviewString(
             $this->renderHandleLink($author_phid));
         }
 
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $field = $this->getTransactionCustomField();
         if ($field) {
           return $field->getApplicationTransactionTitle($this);
         } else {
           return pht(
             '%s edited a custom field.',
             $this->renderHandleLink($author_phid));
         }
 
       case PhabricatorTransactions::TYPE_TOKEN:
         if ($old && $new) {
           return pht(
             '%s updated a token.',
             $this->renderHandleLink($author_phid));
         } else if ($old) {
           return pht(
             '%s rescinded a token.',
             $this->renderHandleLink($author_phid));
         } else {
           return pht(
             '%s awarded a token.',
             $this->renderHandleLink($author_phid));
         }
 
       case PhabricatorTransactions::TYPE_BUILDABLE:
         switch ($this->getNewValue()) {
           case HarbormasterBuildable::STATUS_BUILDING:
             return pht(
               '%s started building %s.',
               $this->renderHandleLink($author_phid),
               $this->renderHandleLink(
                 $this->getMetadataValue('harbormaster:buildablePHID')));
           case HarbormasterBuildable::STATUS_PASSED:
             return pht(
               '%s completed building %s.',
               $this->renderHandleLink($author_phid),
               $this->renderHandleLink(
                 $this->getMetadataValue('harbormaster:buildablePHID')));
           case HarbormasterBuildable::STATUS_FAILED:
             return pht(
               '%s failed to build %s!',
               $this->renderHandleLink($author_phid),
               $this->renderHandleLink(
                 $this->getMetadataValue('harbormaster:buildablePHID')));
           default:
             return null;
         }
 
       case PhabricatorTransactions::TYPE_INLINESTATE:
         $done = 0;
         $undone = 0;
         foreach ($new as $phid => $state) {
           if ($state == PhabricatorInlineCommentInterface::STATE_DONE) {
             $done++;
           } else {
             $undone++;
           }
         }
         if ($done && $undone) {
           return pht(
             '%s marked %s inline comment(s) as done and %s inline comment(s) '.
             'as not done.',
             $this->renderHandleLink($author_phid),
             new PhutilNumber($done),
             new PhutilNumber($undone));
         } else if ($done) {
           return pht(
             '%s marked %s inline comment(s) as done.',
             $this->renderHandleLink($author_phid),
             new PhutilNumber($done));
         } else {
           return pht(
             '%s marked %s inline comment(s) as not done.',
             $this->renderHandleLink($author_phid),
             new PhutilNumber($undone));
         }
         break;
 
       case PhabricatorTransactions::TYPE_COLUMNS:
         $moves = $this->getInterestingMoves($new);
         if (count($moves) == 1) {
           $move = head($moves);
           $from_columns = $move['fromColumnPHIDs'];
           $to_column = $move['columnPHID'];
           $board_phid = $move['boardPHID'];
           if (count($from_columns) == 1) {
             return pht(
               '%s moved this task from %s to %s on the %s board.',
               $this->renderHandleLink($author_phid),
               $this->renderHandleLink(head($from_columns)),
               $this->renderHandleLink($to_column),
               $this->renderHandleLink($board_phid));
           } else {
             return pht(
               '%s moved this task to %s on the %s board.',
               $this->renderHandleLink($author_phid),
               $this->renderHandleLink($to_column),
               $this->renderHandleLink($board_phid));
           }
         } else {
           $fragments = array();
           foreach ($moves as $move) {
             $fragments[] = pht(
               '%s (%s)',
               $this->renderHandleLink($board_phid),
               $this->renderHandleLink($to_column));
           }
 
           return pht(
             '%s moved this task on %s board(s): %s.',
             $this->renderHandleLink($author_phid),
             phutil_count($moves),
             phutil_implode_html(', ', $fragments));
         }
         break;
 
       default:
         return pht(
           '%s edited this %s.',
           $this->renderHandleLink($author_phid),
           $this->getApplicationObjectTypeName());
     }
   }
 
   public function getTitleForFeed() {
     $author_phid = $this->getAuthorPHID();
     $object_phid = $this->getObjectPHID();
 
     $old = $this->getOldValue();
     $new = $this->getNewValue();
 
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_CREATE:
         return pht(
           '%s created %s.',
           $this->renderHandleLink($author_phid),
           $this->renderHandleLink($object_phid));
       case PhabricatorTransactions::TYPE_COMMENT:
         return pht(
           '%s added a comment to %s.',
           $this->renderHandleLink($author_phid),
           $this->renderHandleLink($object_phid));
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
         return pht(
           '%s changed the visibility for %s.',
           $this->renderHandleLink($author_phid),
           $this->renderHandleLink($object_phid));
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
         return pht(
           '%s changed the edit policy for %s.',
           $this->renderHandleLink($author_phid),
           $this->renderHandleLink($object_phid));
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
         return pht(
           '%s changed the join policy for %s.',
           $this->renderHandleLink($author_phid),
           $this->renderHandleLink($object_phid));
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         return pht(
           '%s updated subscribers of %s.',
           $this->renderHandleLink($author_phid),
           $this->renderHandleLink($object_phid));
       case PhabricatorTransactions::TYPE_SPACE:
         return pht(
           '%s shifted %s from the %s space to the %s space.',
           $this->renderHandleLink($author_phid),
           $this->renderHandleLink($object_phid),
           $this->renderHandleLink($old),
           $this->renderHandleLink($new));
       case PhabricatorTransactions::TYPE_EDGE:
         $new = ipull($new, 'dst');
         $old = ipull($old, 'dst');
         $add = array_diff($new, $old);
         $rem = array_diff($old, $new);
         $type = $this->getMetadata('edge:type');
         $type = head($type);
 
         $type_obj = PhabricatorEdgeType::getByConstant($type);
 
         if ($add && $rem) {
           return $type_obj->getFeedEditString(
             $this->renderHandleLink($author_phid),
             $this->renderHandleLink($object_phid),
             new PhutilNumber(count($add) + count($rem)),
             phutil_count($add),
             $this->renderHandleList($add),
             phutil_count($rem),
             $this->renderHandleList($rem));
         } else if ($add) {
           return $type_obj->getFeedAddString(
             $this->renderHandleLink($author_phid),
             $this->renderHandleLink($object_phid),
             phutil_count($add),
             $this->renderHandleList($add));
         } else if ($rem) {
           return $type_obj->getFeedRemoveString(
             $this->renderHandleLink($author_phid),
             $this->renderHandleLink($object_phid),
             phutil_count($rem),
             $this->renderHandleList($rem));
         } else {
           return pht(
             '%s edited edge metadata for %s.',
             $this->renderHandleLink($author_phid),
             $this->renderHandleLink($object_phid));
         }
 
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $field = $this->getTransactionCustomField();
         if ($field) {
           return $field->getApplicationTransactionTitleForFeed($this);
         } else {
           return pht(
             '%s edited a custom field on %s.',
             $this->renderHandleLink($author_phid),
             $this->renderHandleLink($object_phid));
         }
       case PhabricatorTransactions::TYPE_BUILDABLE:
         switch ($this->getNewValue()) {
           case HarbormasterBuildable::STATUS_BUILDING:
             return pht(
               '%s started building %s for %s.',
               $this->renderHandleLink($author_phid),
               $this->renderHandleLink(
                 $this->getMetadataValue('harbormaster:buildablePHID')),
               $this->renderHandleLink($object_phid));
           case HarbormasterBuildable::STATUS_PASSED:
             return pht(
               '%s completed building %s for %s.',
               $this->renderHandleLink($author_phid),
               $this->renderHandleLink(
                 $this->getMetadataValue('harbormaster:buildablePHID')),
               $this->renderHandleLink($object_phid));
           case HarbormasterBuildable::STATUS_FAILED:
             return pht(
               '%s failed to build %s for %s.',
               $this->renderHandleLink($author_phid),
               $this->renderHandleLink(
                 $this->getMetadataValue('harbormaster:buildablePHID')),
               $this->renderHandleLink($object_phid));
           default:
             return null;
         }
 
       case PhabricatorTransactions::TYPE_COLUMNS:
         $moves = $this->getInterestingMoves($new);
         if (count($moves) == 1) {
           $move = head($moves);
           $from_columns = $move['fromColumnPHIDs'];
           $to_column = $move['columnPHID'];
           $board_phid = $move['boardPHID'];
           if (count($from_columns) == 1) {
             return pht(
               '%s moved %s from %s to %s on the %s board.',
               $this->renderHandleLink($author_phid),
               $this->renderHandleLink($object_phid),
               $this->renderHandleLink(head($from_columns)),
               $this->renderHandleLink($to_column),
               $this->renderHandleLink($board_phid));
           } else {
             return pht(
               '%s moved %s to %s on the %s board.',
               $this->renderHandleLink($author_phid),
               $this->renderHandleLink($object_phid),
               $this->renderHandleLink($to_column),
               $this->renderHandleLink($board_phid));
           }
         } else {
           $fragments = array();
           foreach ($moves as $move) {
             $fragments[] = pht(
               '%s (%s)',
               $this->renderHandleLink($board_phid),
               $this->renderHandleLink($to_column));
           }
 
           return pht(
             '%s moved %s on %s board(s): %s.',
             $this->renderHandleLink($author_phid),
             $this->renderHandleLink($object_phid),
             phutil_count($moves),
             phutil_implode_html(', ', $fragments));
         }
         break;
 
     }
 
     return $this->getTitle();
   }
 
   public function getMarkupFieldsForFeed(PhabricatorFeedStory $story) {
     $fields = array();
 
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_COMMENT:
         $text = $this->getComment()->getContent();
         if (strlen($text)) {
           $fields[] = 'comment/'.$this->getID();
         }
         break;
     }
 
     return $fields;
   }
 
   public function getMarkupTextForFeed(PhabricatorFeedStory $story, $field) {
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_COMMENT:
         $text = $this->getComment()->getContent();
         return PhabricatorMarkupEngine::summarize($text);
     }
 
     return null;
   }
 
   public function getBodyForFeed(PhabricatorFeedStory $story) {
     $remarkup = $this->getRemarkupBodyForFeed($story);
     if ($remarkup !== null) {
       $remarkup = PhabricatorMarkupEngine::summarize($remarkup);
       return new PHUIRemarkupView($this->viewer, $remarkup);
     }
 
     $old = $this->getOldValue();
     $new = $this->getNewValue();
 
     $body = null;
 
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_COMMENT:
         $text = $this->getComment()->getContent();
         if (strlen($text)) {
           $body = $story->getMarkupFieldOutput('comment/'.$this->getID());
         }
         break;
     }
 
     return $body;
   }
 
   public function getRemarkupBodyForFeed(PhabricatorFeedStory $story) {
     return null;
   }
 
   public function getActionStrength() {
     if ($this->isInlineCommentTransaction()) {
       return 0.25;
     }
 
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_COMMENT:
         return 0.5;
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         if ($this->isSelfSubscription()) {
           // Make this weaker than TYPE_COMMENT.
           return 0.25;
         }
 
         if ($this->isApplicationAuthor()) {
           // When applications (most often: Herald) change subscriptions it
           // is very uninteresting.
           return 0.000000001;
         }
 
         // In other cases, subscriptions are more interesting than comments
         // (which are shown anyway) but less interesting than any other type of
         // transaction.
         return 0.75;
     }
 
     return 1.0;
   }
 
   public function isCommentTransaction() {
     if ($this->hasComment()) {
       return true;
     }
 
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_COMMENT:
         return true;
     }
 
     return false;
   }
 
   public function isInlineCommentTransaction() {
     return false;
   }
 
   public function getActionName() {
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_COMMENT:
         return pht('Commented On');
       case PhabricatorTransactions::TYPE_VIEW_POLICY:
       case PhabricatorTransactions::TYPE_EDIT_POLICY:
       case PhabricatorTransactions::TYPE_JOIN_POLICY:
         return pht('Changed Policy');
       case PhabricatorTransactions::TYPE_SUBSCRIBERS:
         return pht('Changed Subscribers');
       case PhabricatorTransactions::TYPE_BUILDABLE:
         switch ($this->getNewValue()) {
           case HarbormasterBuildable::STATUS_PASSED:
             return pht('Build Passed');
           case HarbormasterBuildable::STATUS_FAILED:
             return pht('Build Failed');
           default:
             return pht('Build Status');
         }
       default:
         return pht('Updated');
     }
   }
 
   public function getMailTags() {
     return array();
   }
 
   public function hasChangeDetails() {
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $field = $this->getTransactionCustomField();
         if ($field) {
           return $field->getApplicationTransactionHasChangeDetails($this);
         }
         break;
     }
     return false;
   }
 
+  public function hasChangeDetailsForMail() {
+    return $this->hasChangeDetails();
+  }
+
+  public function renderChangeDetailsForMail(PhabricatorUser $viewer) {
+    $view = $this->renderChangeDetails($viewer);
+    if ($view instanceof PhabricatorApplicationTransactionTextDiffDetailView) {
+      return $view->renderForMail();
+    }
+    return null;
+  }
+
   public function renderChangeDetails(PhabricatorUser $viewer) {
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_CUSTOMFIELD:
         $field = $this->getTransactionCustomField();
         if ($field) {
           return $field->getApplicationTransactionChangeDetails($this, $viewer);
         }
         break;
     }
 
     return $this->renderTextCorpusChangeDetails(
       $viewer,
       $this->getOldValue(),
       $this->getNewValue());
   }
 
   public function renderTextCorpusChangeDetails(
     PhabricatorUser $viewer,
     $old,
     $new) {
-
-    require_celerity_resource('differential-changeset-view-css');
-
-    $view = id(new PhabricatorApplicationTransactionTextDiffDetailView())
+    return id(new PhabricatorApplicationTransactionTextDiffDetailView())
       ->setUser($viewer)
       ->setOldText($old)
       ->setNewText($new);
-
-    return $view->render();
   }
 
   public function attachTransactionGroup(array $group) {
     assert_instances_of($group, __CLASS__);
     $this->transactionGroup = $group;
     return $this;
   }
 
   public function getTransactionGroup() {
     return $this->transactionGroup;
   }
 
   /**
    * Should this transaction be visually grouped with an existing transaction
    * group?
    *
    * @param list<PhabricatorApplicationTransaction> List of transactions.
    * @return bool True to display in a group with the other transactions.
    */
   public function shouldDisplayGroupWith(array $group) {
     $this_source = null;
     if ($this->getContentSource()) {
       $this_source = $this->getContentSource()->getSource();
     }
 
     foreach ($group as $xaction) {
       // Don't group transactions by different authors.
       if ($xaction->getAuthorPHID() != $this->getAuthorPHID()) {
         return false;
       }
 
       // Don't group transactions for different objects.
       if ($xaction->getObjectPHID() != $this->getObjectPHID()) {
         return false;
       }
 
       // Don't group anything into a group which already has a comment.
       if ($xaction->isCommentTransaction()) {
         return false;
       }
 
       // Don't group transactions from different content sources.
       $other_source = null;
       if ($xaction->getContentSource()) {
         $other_source = $xaction->getContentSource()->getSource();
       }
 
       if ($other_source != $this_source) {
         return false;
       }
 
       // Don't group transactions which happened more than 2 minutes apart.
       $apart = abs($xaction->getDateCreated() - $this->getDateCreated());
       if ($apart > (60 * 2)) {
         return false;
       }
     }
 
     return true;
   }
 
   public function renderExtraInformationLink() {
     $herald_xscript_id = $this->getMetadataValue('herald:transcriptID');
 
     if ($herald_xscript_id) {
       return phutil_tag(
         'a',
         array(
           'href' => '/herald/transcript/'.$herald_xscript_id.'/',
         ),
         pht('View Herald Transcript'));
     }
 
     return null;
   }
 
   public function renderAsTextForDoorkeeper(
     DoorkeeperFeedStoryPublisher $publisher,
     PhabricatorFeedStory $story,
     array $xactions) {
 
     $text = array();
     $body = array();
 
     foreach ($xactions as $xaction) {
       $xaction_body = $xaction->getBodyForMail();
       if ($xaction_body !== null) {
         $body[] = $xaction_body;
       }
 
       if ($xaction->shouldHideForMail($xactions)) {
         continue;
       }
 
       $old_target = $xaction->getRenderingTarget();
       $new_target = self::TARGET_TEXT;
       $xaction->setRenderingTarget($new_target);
 
       if ($publisher->getRenderWithImpliedContext()) {
         $text[] = $xaction->getTitle();
       } else {
         $text[] = $xaction->getTitleForFeed();
       }
 
       $xaction->setRenderingTarget($old_target);
     }
 
     $text = implode("\n", $text);
     $body = implode("\n\n", $body);
 
     return rtrim($text."\n\n".$body);
   }
 
   /**
    * Test if this transaction is just a user subscribing or unsubscribing
    * themselves.
    */
   private function isSelfSubscription() {
     $type = $this->getTransactionType();
     if ($type != PhabricatorTransactions::TYPE_SUBSCRIBERS) {
       return false;
     }
 
     $old = $this->getOldValue();
     $new = $this->getNewValue();
 
     $add = array_diff($old, $new);
     $rem = array_diff($new, $old);
 
     if ((count($add) + count($rem)) != 1) {
       // More than one user affected.
       return false;
     }
 
     $affected_phid = head(array_merge($add, $rem));
     if ($affected_phid != $this->getAuthorPHID()) {
       // Affected user is someone else.
       return false;
     }
 
     return true;
   }
 
   private function isApplicationAuthor() {
     $author_phid = $this->getAuthorPHID();
     $author_type = phid_get_type($author_phid);
     $application_type = PhabricatorApplicationApplicationPHIDType::TYPECONST;
     return ($author_type == $application_type);
   }
 
 
   private function getInterestingMoves(array $moves) {
     // Remove moves which only shift the position of a task within a column.
     foreach ($moves as $key => $move) {
       $from_phids = array_fuse($move['fromColumnPHIDs']);
       if (isset($from_phids[$move['columnPHID']])) {
         unset($moves[$key]);
       }
     }
 
     return $moves;
   }
 
 
 /* -(  PhabricatorPolicyInterface Implementation  )-------------------------- */
 
 
   public function getCapabilities() {
     return array(
       PhabricatorPolicyCapability::CAN_VIEW,
       PhabricatorPolicyCapability::CAN_EDIT,
     );
   }
 
   public function getPolicy($capability) {
     switch ($capability) {
       case PhabricatorPolicyCapability::CAN_VIEW:
         return $this->getViewPolicy();
       case PhabricatorPolicyCapability::CAN_EDIT:
         return $this->getEditPolicy();
     }
   }
 
   public function hasAutomaticCapability($capability, PhabricatorUser $viewer) {
     return ($viewer->getPHID() == $this->getAuthorPHID());
   }
 
   public function describeAutomaticCapability($capability) {
     return pht(
       'Transactions are visible to users that can see the object which was '.
       'acted upon. Some transactions - in particular, comments - are '.
       'editable by the transaction author.');
   }
 
 
 /* -(  PhabricatorDestructibleInterface  )----------------------------------- */
 
 
   public function destroyObjectPermanently(
     PhabricatorDestructionEngine $engine) {
 
     $this->openTransaction();
       $comment_template = null;
       try {
         $comment_template = $this->getApplicationTransactionCommentObject();
       } catch (Exception $ex) {
         // Continue; no comments for these transactions.
       }
 
       if ($comment_template) {
         $comments = $comment_template->loadAllWhere(
           'transactionPHID = %s',
           $this->getPHID());
         foreach ($comments as $comment) {
           $engine->destroyObject($comment);
         }
       }
 
       $this->delete();
     $this->saveTransaction();
   }
 
 
 }
diff --git a/src/applications/transactions/view/PhabricatorApplicationTransactionTextDiffDetailView.php b/src/applications/transactions/view/PhabricatorApplicationTransactionTextDiffDetailView.php
index 5b337c6d95..a8f92866b2 100644
--- a/src/applications/transactions/view/PhabricatorApplicationTransactionTextDiffDetailView.php
+++ b/src/applications/transactions/view/PhabricatorApplicationTransactionTextDiffDetailView.php
@@ -1,64 +1,120 @@
 <?php
 
 final class PhabricatorApplicationTransactionTextDiffDetailView
   extends AphrontView {
 
   private $oldText;
   private $newText;
 
   public function setNewText($new_text) {
     $this->newText = $new_text;
     return $this;
   }
 
   public function setOldText($old_text) {
     $this->oldText = $old_text;
     return $this;
   }
 
+  public function renderForMail() {
+    $diff = $this->buildDiff();
+
+    $old_styles = array(
+      'padding: 0 2px;',
+      'color: #802b2b;',
+      'background: rgba(251, 175, 175, .7);',
+    );
+    $old_styles = implode(' ', $old_styles);
+
+    $new_styles = array(
+      'padding: 0 2px;',
+      'color: #3e6d35;',
+      'background: rgba(151, 234, 151, .6);',
+    );
+    $new_styles = implode(' ', $new_styles);
+
+    $result = array();
+    foreach ($diff->getParts() as $part) {
+      $type = $part['type'];
+      $text = $part['text'];
+      switch ($type) {
+        case '-':
+          $result[] = phutil_tag(
+            'span',
+            array(
+              'style' => $old_styles,
+            ),
+            $text);
+          break;
+        case '+':
+          $result[] = phutil_tag(
+            'span',
+            array(
+              'style' => $new_styles,
+            ),
+            $text);
+          break;
+        case '=':
+          $result[] = $text;
+          break;
+      }
+    }
+
+    $styles = array(
+      'white-space: pre-wrap;',
+    );
+
+    return phutil_tag(
+      'div',
+      array(
+        'style' => implode(' ', $styles),
+      ),
+      $result);
+  }
+
   public function render() {
     $diff = $this->buildDiff();
 
     require_celerity_resource('differential-changeset-view-css');
 
     $result = array();
     foreach ($diff->getParts() as $part) {
       $type = $part['type'];
       $text = $part['text'];
       switch ($type) {
         case '-':
           $result[] = phutil_tag(
             'span',
             array(
               'class' => 'old',
             ),
             $text);
           break;
         case '+':
           $result[] = phutil_tag(
             'span',
             array(
               'class' => 'new',
             ),
             $text);
           break;
         case '=':
           $result[] = $text;
           break;
       }
     }
 
     return phutil_tag(
       'div',
       array(
         'class' => 'prose-diff',
       ),
       $result);
   }
 
   private function buildDiff() {
     $engine = new PhutilProseDifferenceEngine();
     return $engine->getDiff($this->oldText, $this->newText);
   }
 
 }
diff --git a/src/applications/transactions/view/PhabricatorApplicationTransactionView.php b/src/applications/transactions/view/PhabricatorApplicationTransactionView.php
index 8b9955a739..6e27f8540b 100644
--- a/src/applications/transactions/view/PhabricatorApplicationTransactionView.php
+++ b/src/applications/transactions/view/PhabricatorApplicationTransactionView.php
@@ -1,540 +1,540 @@
 <?php
 
 /**
  * @concrete-extensible
  */
 class PhabricatorApplicationTransactionView extends AphrontView {
 
   private $transactions;
   private $engine;
   private $showEditActions = true;
   private $isPreview;
   private $objectPHID;
   private $shouldTerminate = false;
   private $quoteTargetID;
   private $quoteRef;
   private $pager;
   private $renderAsFeed;
   private $renderData = array();
   private $hideCommentOptions = false;
 
   public function setRenderAsFeed($feed) {
     $this->renderAsFeed = $feed;
     return $this;
   }
 
   public function setQuoteRef($quote_ref) {
     $this->quoteRef = $quote_ref;
     return $this;
   }
 
   public function getQuoteRef() {
     return $this->quoteRef;
   }
 
   public function setQuoteTargetID($quote_target_id) {
     $this->quoteTargetID = $quote_target_id;
     return $this;
   }
 
   public function getQuoteTargetID() {
     return $this->quoteTargetID;
   }
 
   public function setObjectPHID($object_phid) {
     $this->objectPHID = $object_phid;
     return $this;
   }
 
   public function getObjectPHID() {
     return $this->objectPHID;
   }
 
   public function setIsPreview($is_preview) {
     $this->isPreview = $is_preview;
     return $this;
   }
 
   public function setShowEditActions($show_edit_actions) {
     $this->showEditActions = $show_edit_actions;
     return $this;
   }
 
   public function getShowEditActions() {
     return $this->showEditActions;
   }
 
   public function setMarkupEngine(PhabricatorMarkupEngine $engine) {
     $this->engine = $engine;
     return $this;
   }
 
   public function setTransactions(array $transactions) {
     assert_instances_of($transactions, 'PhabricatorApplicationTransaction');
     $this->transactions = $transactions;
     return $this;
   }
 
   public function getTransactions() {
     return $this->transactions;
   }
 
   public function setShouldTerminate($term) {
     $this->shouldTerminate = $term;
     return $this;
   }
 
   public function setPager(AphrontCursorPagerView $pager) {
     $this->pager = $pager;
     return $this;
   }
 
   public function getPager() {
     return $this->pager;
   }
 
   /**
    * This is additional data that may be necessary to render the next set
    * of transactions. Objects that implement
    * PhabricatorApplicationTransactionInterface use this data in
    * willRenderTimeline.
    */
   public function setRenderData(array $data) {
     $this->renderData = $data;
     return $this;
   }
 
   public function getRenderData() {
     return $this->renderData;
   }
 
   public function setHideCommentOptions($hide_comment_options) {
     $this->hideCommentOptions = $hide_comment_options;
     return $this;
   }
 
   public function getHideCommentOptions() {
     return $this->hideCommentOptions;
   }
 
   public function buildEvents($with_hiding = false) {
     $user = $this->getUser();
 
     $xactions = $this->transactions;
 
     $xactions = $this->filterHiddenTransactions($xactions);
     $xactions = $this->groupRelatedTransactions($xactions);
     $groups = $this->groupDisplayTransactions($xactions);
 
     // If the viewer has interacted with this object, we hide things from
     // before their most recent interaction by default. This tends to make
     // very long threads much more manageable, because you don't have to
     // scroll through a lot of history and can focus on just new stuff.
 
     $show_group = null;
 
     if ($with_hiding) {
       // Find the most recent comment by the viewer.
       $group_keys = array_keys($groups);
       $group_keys = array_reverse($group_keys);
 
       // If we would only hide a small number of transactions, don't hide
       // anything. Just don't examine the last few keys. Also, we always
       // want to show the most recent pieces of activity, so don't examine
       // the first few keys either.
       $group_keys = array_slice($group_keys, 2, -2);
 
       $type_comment = PhabricatorTransactions::TYPE_COMMENT;
       foreach ($group_keys as $group_key) {
         $group = $groups[$group_key];
         foreach ($group as $xaction) {
           if ($xaction->getAuthorPHID() == $user->getPHID() &&
               $xaction->getTransactionType() == $type_comment) {
             // This is the most recent group where the user commented.
             $show_group = $group_key;
             break 2;
           }
         }
       }
     }
 
     $events = array();
     $hide_by_default = ($show_group !== null);
     $set_next_page_id = false;
 
     foreach ($groups as $group_key => $group) {
       if ($hide_by_default && ($show_group === $group_key)) {
         $hide_by_default = false;
         $set_next_page_id = true;
       }
 
       $group_event = null;
       foreach ($group as $xaction) {
         $event = $this->renderEvent($xaction, $group);
         $event->setHideByDefault($hide_by_default);
         if (!$group_event) {
           $group_event = $event;
         } else {
           $group_event->addEventToGroup($event);
         }
         if ($set_next_page_id) {
           $set_next_page_id = false;
           $pager = $this->getPager();
           if ($pager) {
             $pager->setNextPageID($xaction->getID());
           }
         }
       }
       $events[] = $group_event;
 
     }
 
     return $events;
   }
 
   public function render() {
     if (!$this->getObjectPHID()) {
       throw new PhutilInvalidStateException('setObjectPHID');
     }
 
     $view = $this->buildPHUITimelineView();
 
     if ($this->getShowEditActions()) {
       Javelin::initBehavior('phabricator-transaction-list');
     }
 
     return $view->render();
   }
 
   public function buildPHUITimelineView($with_hiding = true) {
     if (!$this->getObjectPHID()) {
       throw new PhutilInvalidStateException('setObjectPHID');
     }
 
     $view = id(new PHUITimelineView())
       ->setUser($this->getUser())
       ->setShouldTerminate($this->shouldTerminate)
       ->setQuoteTargetID($this->getQuoteTargetID())
       ->setQuoteRef($this->getQuoteRef());
 
     $events = $this->buildEvents($with_hiding);
     foreach ($events as $event) {
       $view->addEvent($event);
     }
 
     if ($this->getPager()) {
       $view->setPager($this->getPager());
     }
 
     if ($this->getRenderData()) {
       $view->setRenderData($this->getRenderData());
     }
 
     return $view;
   }
 
   protected function getOrBuildEngine() {
     if (!$this->engine) {
       $field = PhabricatorApplicationTransactionComment::MARKUP_FIELD_COMMENT;
 
       $engine = id(new PhabricatorMarkupEngine())
         ->setViewer($this->getUser());
       foreach ($this->transactions as $xaction) {
         if (!$xaction->hasComment()) {
           continue;
         }
         $engine->addObject($xaction->getComment(), $field);
       }
       $engine->process();
 
       $this->engine = $engine;
     }
 
     return $this->engine;
   }
 
   private function buildChangeDetailsLink(
     PhabricatorApplicationTransaction $xaction) {
 
     return javelin_tag(
       'a',
       array(
-        'href' => '/transactions/detail/'.$xaction->getPHID().'/',
+        'href' => $xaction->getChangeDetailsURI(),
         'sigil' => 'workflow',
       ),
       pht('(Show Details)'));
   }
 
   private function buildExtraInformationLink(
     PhabricatorApplicationTransaction $xaction) {
 
     $link = $xaction->renderExtraInformationLink();
     if (!$link) {
       return null;
     }
 
     return phutil_tag(
       'span',
       array(
         'class' => 'phui-timeline-extra-information',
       ),
       array(" \xC2\xB7  ", $link));
   }
 
   protected function shouldGroupTransactions(
     PhabricatorApplicationTransaction $u,
     PhabricatorApplicationTransaction $v) {
     return false;
   }
 
   protected function renderTransactionContent(
     PhabricatorApplicationTransaction $xaction) {
 
     $field = PhabricatorApplicationTransactionComment::MARKUP_FIELD_COMMENT;
     $engine = $this->getOrBuildEngine();
     $comment = $xaction->getComment();
 
     if ($comment) {
       if ($comment->getIsRemoved()) {
         return javelin_tag(
           'span',
           array(
             'class' => 'comment-deleted',
             'sigil' => 'transaction-comment',
             'meta'  => array('phid' => $comment->getTransactionPHID()),
           ),
           pht(
             'This comment was removed by %s.',
             $xaction->getHandle($comment->getAuthorPHID())->renderLink()));
       } else if ($comment->getIsDeleted()) {
         return javelin_tag(
           'span',
           array(
             'class' => 'comment-deleted',
             'sigil' => 'transaction-comment',
             'meta'  => array('phid' => $comment->getTransactionPHID()),
           ),
           pht('This comment has been deleted.'));
       } else if ($xaction->hasComment()) {
         return javelin_tag(
           'span',
           array(
             'class' => 'transaction-comment',
             'sigil' => 'transaction-comment',
             'meta'  => array('phid' => $comment->getTransactionPHID()),
           ),
           $engine->getOutput($comment, $field));
       } else {
         // This is an empty, non-deleted comment. Usually this happens when
         // rendering previews.
         return null;
       }
     }
 
     return null;
   }
 
   private function filterHiddenTransactions(array $xactions) {
     foreach ($xactions as $key => $xaction) {
       if ($xaction->shouldHide()) {
         unset($xactions[$key]);
       }
     }
     return $xactions;
   }
 
   private function groupRelatedTransactions(array $xactions) {
     $last = null;
     $last_key = null;
     $groups = array();
     foreach ($xactions as $key => $xaction) {
       if ($last && $this->shouldGroupTransactions($last, $xaction)) {
         $groups[$last_key][] = $xaction;
         unset($xactions[$key]);
       } else {
         $last = $xaction;
         $last_key = $key;
       }
     }
 
     foreach ($xactions as $key => $xaction) {
       $xaction->attachTransactionGroup(idx($groups, $key, array()));
     }
 
     return $xactions;
   }
 
   private function groupDisplayTransactions(array $xactions) {
     $groups = array();
     $group = array();
     foreach ($xactions as $xaction) {
       if ($xaction->shouldDisplayGroupWith($group)) {
         $group[] = $xaction;
       } else {
         if ($group) {
           $groups[] = $group;
         }
         $group = array($xaction);
       }
     }
 
     if ($group) {
       $groups[] = $group;
     }
 
     foreach ($groups as $key => $group) {
       $results = array();
 
       // Sort transactions within the group by action strength, then by
       // chronological order. This makes sure that multiple actions of the
       // same type (like a close, then a reopen) render in the order they
       // were performed.
       $strength_groups = mgroup($group, 'getActionStrength');
       krsort($strength_groups);
       foreach ($strength_groups as $strength_group) {
         foreach (msort($strength_group, 'getID') as $xaction) {
           $results[] = $xaction;
         }
       }
 
       $groups[$key] = $results;
     }
 
     return $groups;
   }
 
   private function renderEvent(
     PhabricatorApplicationTransaction $xaction,
     array $group) {
     $viewer = $this->getUser();
 
     $event = id(new PHUITimelineEventView())
       ->setUser($viewer)
       ->setAuthorPHID($xaction->getAuthorPHID())
       ->setTransactionPHID($xaction->getPHID())
       ->setUserHandle($xaction->getHandle($xaction->getAuthorPHID()))
       ->setIcon($xaction->getIcon())
       ->setColor($xaction->getColor())
       ->setHideCommentOptions($this->getHideCommentOptions());
 
     list($token, $token_removed) = $xaction->getToken();
     if ($token) {
       $event->setToken($token, $token_removed);
     }
 
     if (!$this->shouldSuppressTitle($xaction, $group)) {
       if ($this->renderAsFeed) {
         $title = $xaction->getTitleForFeed();
       } else {
         $title = $xaction->getTitle();
       }
       if ($xaction->hasChangeDetails()) {
         if (!$this->isPreview) {
           $details = $this->buildChangeDetailsLink($xaction);
           $title = array(
             $title,
             ' ',
             $details,
           );
         }
       }
 
       if (!$this->isPreview) {
         $more = $this->buildExtraInformationLink($xaction);
         if ($more) {
           $title = array($title, ' ', $more);
         }
       }
 
       $event->setTitle($title);
     }
 
     if ($this->isPreview) {
       $event->setIsPreview(true);
     } else {
       $event
         ->setDateCreated($xaction->getDateCreated())
         ->setContentSource($xaction->getContentSource())
         ->setAnchor($xaction->getID());
     }
 
     $transaction_type = $xaction->getTransactionType();
     $comment_type = PhabricatorTransactions::TYPE_COMMENT;
     $is_normal_comment = ($transaction_type == $comment_type);
 
     if ($this->getShowEditActions() &&
         !$this->isPreview &&
         $is_normal_comment) {
 
       $has_deleted_comment =
         $xaction->getComment() &&
         $xaction->getComment()->getIsDeleted();
 
       $has_removed_comment =
         $xaction->getComment() &&
         $xaction->getComment()->getIsRemoved();
 
       if ($xaction->getCommentVersion() > 1 && !$has_removed_comment) {
         $event->setIsEdited(true);
       }
 
       if (!$has_removed_comment) {
         $event->setIsNormalComment(true);
       }
 
       // If we have a place for quoted text to go and this is a quotable
       // comment, pass the quote target ID to the event view.
       if ($this->getQuoteTargetID()) {
         if ($xaction->hasComment()) {
           if (!$has_removed_comment && !$has_deleted_comment) {
             $event->setQuoteTargetID($this->getQuoteTargetID());
             $event->setQuoteRef($this->getQuoteRef());
           }
         }
       }
 
       $can_edit = PhabricatorPolicyCapability::CAN_EDIT;
 
       if ($xaction->hasComment() || $has_deleted_comment) {
         $has_edit_capability = PhabricatorPolicyFilter::hasCapability(
           $viewer,
           $xaction,
           $can_edit);
         if ($has_edit_capability && !$has_removed_comment) {
           $event->setIsEditable(true);
         }
         if ($has_edit_capability || $viewer->getIsAdmin()) {
           if (!$has_removed_comment) {
             $event->setIsRemovable(true);
           }
         }
       }
     }
 
     $comment = $this->renderTransactionContent($xaction);
     if ($comment) {
       $event->appendChild($comment);
     }
 
     return $event;
   }
 
   private function shouldSuppressTitle(
     PhabricatorApplicationTransaction $xaction,
     array $group) {
 
     // This is a little hard-coded, but we don't have any other reasonable
     // cases for now. Suppress "commented on" if there are other actions in
     // the display group.
 
     if (count($group) > 1) {
       $type_comment = PhabricatorTransactions::TYPE_COMMENT;
       if ($xaction->getTransactionType() == $type_comment) {
         return true;
       }
     }
 
     return false;
   }
 
 }