diff --git a/src/applications/differential/controller/subscribe/DifferentialSubscribeController.php b/src/applications/differential/controller/subscribe/DifferentialSubscribeController.php
index 9c5f06f97..cd39209b7 100644
--- a/src/applications/differential/controller/subscribe/DifferentialSubscribeController.php
+++ b/src/applications/differential/controller/subscribe/DifferentialSubscribeController.php
@@ -1,106 +1,92 @@
 <?php
 
 /*
  * Copyright 2011 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *   http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 
 class DifferentialSubscribeController extends DifferentialController {
 
   private $id;
   private $action;
 
   public function willProcessRequest(array $data) {
     $this->id = $data['id'];
     $this->action = $data['action'];
   }
 
   public function processRequest() {
 
     $request = $this->getRequest();
     $user = $request->getUser();
 
     $revision = id(new DifferentialRevision())->load($this->id);
     if (!$revision) {
       return new Aphront404Response();
     }
 
     if (!$request->isFormPost()) {
-      // TODO: This dialog is silly but we're CSRF-able otherwise.
-
       $dialog = new AphrontDialogView();
 
       switch ($this->action) {
         case 'add':
           $button = 'Subscribe';
           $title = 'Subscribe to Revision';
           $prompt = 'Really subscribe to this revision?';
           break;
         case 'rem':
           $button = 'Unsubscribe';
           $title = 'Unsubscribe from Revision';
           // TODO: Once herald is in, add a notice about not getting any more
           // herald notifications.
           $prompt = 'Really unsubscribe from this revision?';
           break;
         default:
           return new Aphront400Response();
       }
 
       $dialog
         ->setUser($user)
         ->setTitle($title)
         ->appendChild('<p>'.$prompt.'</p>')
         ->setSubmitURI($request->getRequestURI())
         ->addSubmitButton($button)
         ->addCancelButton('/D'.$revision->getID());
 
       return id(new AphrontDialogResponse())->setDialog($dialog);
     }
 
     $revision->loadRelationships();
     $phid = $user->getPHID();
 
     switch ($this->action) {
       case 'add':
-        DifferentialRevisionEditor::addCC(
+        DifferentialRevisionEditor::addCCAndUpdateRevision(
           $revision,
           $phid,
           $phid);
-        $unsubscribed = $revision->getUnsubscribed();
-        if (isset($unsubscribed[$phid])) {
-          unset($unsubscribed[$phid]);
-          $revision->setUnsubscribed($unsubscribed);
-          $revision->save();
-        }
         break;
       case 'rem':
-        DifferentialRevisionEditor::removeCC(
+        DifferentialRevisionEditor::removeCCAndUpdateRevision(
           $revision,
-          $user->getPHID(),
-          $user->getPHID());
-        $unsubscribed = $revision->getUnsubscribed();
-        if (empty($unsubscribed[$phid])) {
-          $unsubscribed[$phid] = true;
-          $revision->setUnsubscribed($unsubscribed);
-          $revision->save();
-        }
+          $phid,
+          $phid);
         break;
       default:
         return new Aphront400Response();
     }
 
     return id(new AphrontRedirectResponse())->setURI('/D'.$revision->getID());
   }
 }
diff --git a/src/applications/differential/editor/revision/DifferentialRevisionEditor.php b/src/applications/differential/editor/revision/DifferentialRevisionEditor.php
index 3e19e25d4..c97bed440 100644
--- a/src/applications/differential/editor/revision/DifferentialRevisionEditor.php
+++ b/src/applications/differential/editor/revision/DifferentialRevisionEditor.php
@@ -1,589 +1,619 @@
 <?php
 
 /*
  * Copyright 2011 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *   http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 
 /**
  * Handle major edit operations to DifferentialRevision -- adding and removing
  * reviewers, diffs, and CCs. Unlike simple edits, these changes trigger
  * complicated email workflows.
  */
 class DifferentialRevisionEditor {
 
   protected $revision;
   protected $actorPHID;
 
   protected $cc         = null;
   protected $reviewers  = null;
   protected $diff;
   protected $comments;
   protected $silentUpdate;
   protected $tasks = null;
 
   public function __construct(DifferentialRevision $revision, $actor_phid) {
     $this->revision = $revision;
     $this->actorPHID = $actor_phid;
   }
 
   public static function newRevisionFromConduitWithDiff(
     array $fields,
     DifferentialDiff $diff,
     $user_phid) {
 
     $revision = new DifferentialRevision();
     $revision->setPHID($revision->generatePHID());
 
     $revision->setAuthorPHID($user_phid);
     $revision->setStatus(DifferentialRevisionStatus::NEEDS_REVIEW);
 
     $editor = new DifferentialRevisionEditor($revision, $user_phid);
 
     $editor->copyFieldsFromConduit($fields);
 
     $editor->addDiff($diff, null);
     $editor->save();
 
     // Tasks can only be updated after revision has been saved to the
     // database. Currently tasks are updated only when a revision is created.
     // UI must be used to modify tasks after creating one.
     $editor->updateTasks();
 
     return $revision;
   }
 
   public function copyFieldsFromConduit(array $fields) {
 
     $revision = $this->revision;
 
     $revision->setTitle((string)$fields['title']);
     $revision->setSummary((string)$fields['summary']);
     $revision->setTestPlan((string)$fields['testPlan']);
     $revision->setBlameRevision((string)$fields['blameRevision']);
     $revision->setRevertPlan((string)$fields['revertPlan']);
 
     $this->setReviewers($fields['reviewerPHIDs']);
     $this->setCCPHIDs($fields['ccPHIDs']);
     $this->setTasks($fields['tasks']);
   }
 
   public function getRevision() {
     return $this->revision;
   }
 
   public function setReviewers(array $reviewers) {
     $this->reviewers = $reviewers;
     return $this;
   }
 
   public function setCCPHIDs(array $cc) {
     $this->cc = $cc;
     return $this;
   }
 
   public function setTasks(array $tasks) {
     $this->tasks = $tasks;
   }
 
   public function addDiff(DifferentialDiff $diff, $comments) {
     if ($diff->getRevisionID() &&
         $diff->getRevisionID() != $this->getRevision()->getID()) {
       $diff_id = (int)$diff->getID();
       $targ_id = (int)$this->getRevision()->getID();
       $real_id = (int)$diff->getRevisionID();
       throw new Exception(
         "Can not attach diff #{$diff_id} to Revision D{$targ_id}, it is ".
         "already attached to D{$real_id}.");
     }
     $this->diff = $diff;
     $this->comments = $comments;
     return $this;
   }
 
   protected function getDiff() {
     return $this->diff;
   }
 
   protected function getComments() {
     return $this->comments;
   }
 
   protected function getActorPHID() {
     return $this->actorPHID;
   }
 
   public function isNewRevision() {
     return !$this->getRevision()->getID();
   }
 
   /**
    * A silent update does not trigger Herald rules or send emails. This is used
    * for auto-amends at commit time.
    */
   public function setSilentUpdate($silent) {
     $this->silentUpdate = $silent;
     return $this;
   }
 
   public function save() {
     $revision = $this->getRevision();
 
 // TODO
 //    $revision->openTransaction();
 
     $is_new = $this->isNewRevision();
     if ($is_new) {
       // These fields aren't nullable; set them to sensible defaults if they
       // haven't been configured. We're just doing this so we can generate an
       // ID for the revision if we don't have one already.
       $revision->setLineCount(0);
       if ($revision->getStatus() === null) {
         $revision->setStatus(DifferentialRevisionStatus::NEEDS_REVIEW);
       }
       if ($revision->getTitle() === null) {
         $revision->setTitle('Untitled Revision');
       }
       if ($revision->getAuthorPHID() === null) {
         $revision->setAuthorPHID($this->getActorPHID());
       }
 
       $revision->save();
     }
 
     $revision->loadRelationships();
 
     if ($this->reviewers === null) {
       $this->reviewers = $revision->getReviewers();
     }
 
     if ($this->cc === null) {
       $this->cc = $revision->getCCPHIDs();
     }
 
     // We're going to build up three dictionaries: $add, $rem, and $stable. The
     // $add dictionary has added reviewers/CCs. The $rem dictionary has
     // reviewers/CCs who have been removed, and the $stable array is
     // reviewers/CCs who haven't changed. We're going to send new reviewers/CCs
     // a different ("welcome") email than we send stable reviewers/CCs.
 
     $old = array(
       'rev' => array_fill_keys($revision->getReviewers(), true),
       'ccs' => array_fill_keys($revision->getCCPHIDs(), true),
     );
 
     $diff = $this->getDiff();
 
     $xscript_header = null;
     $xscript_uri = null;
 
     $new = array(
       'rev' => array_fill_keys($this->reviewers, true),
       'ccs' => array_fill_keys($this->cc, true),
     );
 
 
     $rem_ccs = array();
     if ($diff) {
       $diff->setRevisionID($revision->getID());
       $revision->setLineCount($diff->getLineCount());
 
       $adapter = new HeraldDifferentialRevisionAdapter(
         $revision,
         $diff);
       $adapter->setExplicitCCs($new['ccs']);
       $adapter->setExplicitReviewers($new['rev']);
       $adapter->setForbiddenCCs($revision->getUnsubscribedPHIDs());
 
       $xscript = HeraldEngine::loadAndApplyRules($adapter);
       $xscript_uri = PhabricatorEnv::getProductionURI(
         '/herald/transcript/'.$xscript->getID().'/');
       $xscript_phid = $xscript->getPHID();
       $xscript_header = $xscript->getXHeraldRulesHeader();
 
       HeraldTranscript::saveXHeraldRulesHeader(
         $revision->getPHID(),
         $xscript_header);
 
       $sub = array(
         'rev' => array(),
         'ccs' => $adapter->getCCsAddedByHerald(),
       );
       $rem_ccs = $adapter->getCCsRemovedByHerald();
     } else {
       $sub = array(
         'rev' => array(),
         'ccs' => array(),
       );
     }
 
     // Remove any CCs which are prevented by Herald rules.
     $sub['ccs'] = array_diff_key($sub['ccs'], $rem_ccs);
     $new['ccs'] = array_diff_key($new['ccs'], $rem_ccs);
 
     $add = array();
     $rem = array();
     $stable = array();
     foreach (array('rev', 'ccs') as $key) {
       $add[$key] = array();
       if ($new[$key] !== null) {
         $add[$key] += array_diff_key($new[$key], $old[$key]);
       }
       $add[$key] += array_diff_key($sub[$key], $old[$key]);
 
       $combined = $sub[$key];
       if ($new[$key] !== null) {
         $combined += $new[$key];
       }
       $rem[$key] = array_diff_key($old[$key], $combined);
 
       $stable[$key] = array_diff_key($old[$key], $add[$key] + $rem[$key]);
     }
 
     self::alterReviewers(
       $revision,
       $this->reviewers,
       array_keys($rem['rev']),
       array_keys($add['rev']),
       $this->actorPHID);
 
 /*
 
     // TODO: When Herald is brought over, run through this stuff to figure
     // out which adds are Herald's fault.
 
     // TODO: Still need to do this.
 
     if ($add['ccs'] || $rem['ccs']) {
       foreach (array_keys($add['ccs']) as $id) {
         if (empty($new['ccs'][$id])) {
           $reason_phid = 'TODO';//$xscript_phid;
         } else {
           $reason_phid = $this->getActorPHID();
         }
       }
       foreach (array_keys($rem['ccs']) as $id) {
         if (empty($new['ccs'][$id])) {
           $reason_phid = $this->getActorPHID();
         } else {
           $reason_phid = 'TODO';//$xscript_phid;
         }
       }
     }
 */
     self::alterCCs(
       $revision,
       $this->cc,
       array_keys($rem['ccs']),
       array_keys($add['ccs']),
       $this->actorPHID);
 
     // Add the author to the relevant set of users so they get a copy of the
     // email.
     if (!$this->silentUpdate) {
       if ($is_new) {
         $add['rev'][$this->getActorPHID()] = true;
       } else {
         $stable['rev'][$this->getActorPHID()] = true;
       }
     }
 
     $mail = array();
 
     $phids = array($this->getActorPHID());
 
     $handles = id(new PhabricatorObjectHandleData($phids))
       ->loadHandles();
     $actor_handle = $handles[$this->getActorPHID()];
 
     $changesets = null;
     $comment = null;
     if ($diff) {
       $changesets = $diff->loadChangesets();
       // TODO: This should probably be in DifferentialFeedbackEditor?
       if (!$is_new) {
         $comment = $this->createComment();
       }
       if ($comment) {
         $mail[] = id(new DifferentialNewDiffMail(
             $revision,
             $actor_handle,
             $changesets))
           ->setIsFirstMailAboutRevision($is_new)
           ->setIsFirstMailToRecipients($is_new)
           ->setComments($this->getComments())
           ->setToPHIDs(array_keys($stable['rev']))
           ->setCCPHIDs(array_keys($stable['ccs']));
       }
 
       // Save the changes we made above.
 
       $diff->setDescription(substr($this->getComments(), 0, 80));
       $diff->save();
 
       // An updated diff should require review, as long as it's not committed
       // or accepted. The "accepted" status is "sticky" to encourage courtesy
       // re-diffs after someone accepts with minor changes/suggestions.
 
       $status = $revision->getStatus();
       if ($status != DifferentialRevisionStatus::COMMITTED &&
           $status != DifferentialRevisionStatus::ACCEPTED) {
         $revision->setStatus(DifferentialRevisionStatus::NEEDS_REVIEW);
       }
 
     } else {
       $diff = $revision->loadActiveDiff();
       if ($diff) {
         $changesets = $diff->loadChangesets();
       } else {
         $changesets = array();
       }
     }
 
     $revision->save();
 
 // TODO
 //    $revision->saveTransaction();
 
     $event = array(
       'revision_id' => $revision->getID(),
       'PHID'        => $revision->getPHID(),
       'action'      => $is_new ? 'create' : 'update',
       'actor'       => $this->getActorPHID(),
     );
 
 //  TODO: Move this into a worker task thing.
     PhabricatorSearchDifferentialIndexer::indexRevision($revision);
 
     if ($this->silentUpdate) {
       return;
     }
 
     $revision->loadRelationships();
 
     if ($add['rev']) {
       $message = id(new DifferentialNewDiffMail(
           $revision,
           $actor_handle,
           $changesets))
         ->setIsFirstMailAboutRevision($is_new)
         ->setIsFirstMailToRecipients(true)
         ->setToPHIDs(array_keys($add['rev']));
 
       if ($is_new) {
         // The first time we send an email about a revision, put the CCs in
         // the "CC:" field of the same "Review Requested" email that reviewers
         // get, so you don't get two initial emails if you're on a list that
         // is CC'd.
         $message->setCCPHIDs(array_keys($add['ccs']));
       }
 
       $mail[] = $message;
     }
 
     // If you were added as a reviewer and a CC, just give you the reviewer
     // email. We could go to greater lengths to prevent this, but there's
     // bunch of stuff with list subscriptions anyway. You can still get two
     // emails, but only if a revision is updated and you are added as a reviewer
     // at the same time a list you are on is added as a CC, which is rare and
     // reasonable.
     $add['ccs'] = array_diff_key($add['ccs'], $add['rev']);
 
     if (!$is_new && $add['ccs']) {
       $mail[] = id(new DifferentialCCWelcomeMail(
           $revision,
           $actor_handle,
           $changesets))
         ->setIsFirstMailToRecipients(true)
         ->setToPHIDs(array_keys($add['ccs']));
     }
 
     foreach ($mail as $message) {
       $message->setHeraldTranscriptURI($xscript_uri);
       $message->setXHeraldRulesHeader($xscript_header);
       $message->send();
     }
   }
 
+  public static function addCCAndUpdateRevision(
+    $revision,
+    $phid,
+    $reason) {
+
+    self::addCC($revision, $phid, $reason);
+
+    $unsubscribed = $revision->getUnsubscribed();
+    if (isset($unsubscribed[$phid])) {
+      unset($unsubscribed[$phid]);
+      $revision->setUnsubscribed($unsubscribed);
+      $revision->save();
+    }
+  }
+
+  public static function removeCCAndUpdateRevision(
+    $revision,
+    $phid,
+    $reason) {
+
+    self::removeCC($revision, $phid, $reason);
+
+    $unsubscribed = $revision->getUnsubscribed();
+    if (empty($unsubscribed[$phid])) {
+      $unsubscribed[$phid] = true;
+      $revision->setUnsubscribed($unsubscribed);
+      $revision->save();
+    }
+  }
+
   public static function addCC(
     DifferentialRevision $revision,
     $phid,
     $reason) {
     return self::alterCCs(
       $revision,
       $revision->getCCPHIDs(),
       $rem = array(),
       $add = array($phid),
       $reason);
   }
 
   public static function removeCC(
     DifferentialRevision $revision,
     $phid,
     $reason) {
     return self::alterCCs(
       $revision,
       $revision->getCCPHIDs(),
       $rem = array($phid),
       $add = array(),
       $reason);
   }
 
   protected static function alterCCs(
     DifferentialRevision $revision,
     array $stable_phids,
     array $rem_phids,
     array $add_phids,
     $reason_phid) {
 
     return self::alterRelationships(
       $revision,
       $stable_phids,
       $rem_phids,
       $add_phids,
       $reason_phid,
       DifferentialRevision::RELATION_SUBSCRIBED);
   }
 
 
   public static function alterReviewers(
     DifferentialRevision $revision,
     array $stable_phids,
     array $rem_phids,
     array $add_phids,
     $reason_phid) {
 
     return self::alterRelationships(
       $revision,
       $stable_phids,
       $rem_phids,
       $add_phids,
       $reason_phid,
       DifferentialRevision::RELATION_REVIEWER);
   }
 
   private static function alterRelationships(
     DifferentialRevision $revision,
     array $stable_phids,
     array $rem_phids,
     array $add_phids,
     $reason_phid,
     $relation_type) {
 
     $rem_map = array_fill_keys($rem_phids, true);
     $add_map = array_fill_keys($add_phids, true);
 
     $seq_map = array_values($stable_phids);
     $seq_map = array_flip($seq_map);
     foreach ($rem_map as $phid => $ignored) {
       if (!isset($seq_map[$phid])) {
         $seq_map[$phid] = count($seq_map);
       }
     }
     foreach ($add_map as $phid => $ignored) {
       if (!isset($seq_map[$phid])) {
         $seq_map[$phid] = count($seq_map);
       }
     }
 
     $raw = $revision->getRawRelations($relation_type);
     $raw = ipull($raw, null, 'objectPHID');
 
     $sequence = count($seq_map);
     foreach ($raw as $phid => $ignored) {
       if (isset($seq_map[$phid])) {
         $raw[$phid]['sequence'] = $seq_map[$phid];
       } else {
         $raw[$phid]['sequence'] = $sequence++;
       }
     }
     $raw = isort($raw, 'sequence');
 
     foreach ($raw as $phid => $ignored) {
       if (isset($rem_map[$phid])) {
         unset($raw[$phid]);
       }
     }
 
     foreach ($add_phids as $add) {
       $raw[$add] = array(
         'objectPHID'  => $add,
         'sequence'    => idx($seq_map, $add, $sequence++),
         'reasonPHID'  => $reason_phid,
       );
     }
 
     $conn_w = $revision->establishConnection('w');
 
     $sql = array();
     foreach ($raw as $relation) {
       $sql[] = qsprintf(
         $conn_w,
         '(%d, %s, %s, %d, %s)',
         $revision->getID(),
         $relation_type,
         $relation['objectPHID'],
         $relation['sequence'],
         $relation['reasonPHID']);
     }
 
     $conn_w->openTransaction();
       queryfx(
         $conn_w,
         'DELETE FROM %T WHERE revisionID = %d AND relation = %s',
         DifferentialRevision::RELATIONSHIP_TABLE,
         $revision->getID(),
         $relation_type);
       if ($sql) {
         queryfx(
           $conn_w,
           'INSERT INTO %T
             (revisionID, relation, objectPHID, sequence, reasonPHID)
           VALUES %Q',
           DifferentialRevision::RELATIONSHIP_TABLE,
           implode(', ', $sql));
       }
     $conn_w->saveTransaction();
   }
 
 
   private function createComment() {
     $revision_id = $this->revision->getID();
     $comment = id(new DifferentialComment())
       ->setAuthorPHID($this->getActorPHID())
       ->setRevisionID($revision_id)
       ->setContent($this->getComments())
       ->setAction('update');
     $comment->save();
 
     return $comment;
   }
 
   private function updateTasks() {
     if ($this->tasks) {
       $task_class = PhabricatorEnv::getEnvConfig(
         'differential.attach-task-class');
       if ($task_class) {
         PhutilSymbolLoader::loadClass($task_class);
         $task_attacher = newv($task_class, array());
         $ret = $task_attacher->attachTasksToRevision(
           $this->actorPHID,
           $this->revision,
           $this->tasks);
       }
     }
   }
 
 }
 
diff --git a/src/applications/differential/replyhandler/DifferentialReplyHandler.php b/src/applications/differential/replyhandler/DifferentialReplyHandler.php
index 37e1bc60d..df0e11077 100644
--- a/src/applications/differential/replyhandler/DifferentialReplyHandler.php
+++ b/src/applications/differential/replyhandler/DifferentialReplyHandler.php
@@ -1,142 +1,162 @@
 <?php
 
 /*
  * Copyright 2011 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *   http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 
 class DifferentialReplyHandler extends PhabricatorMailReplyHandler {
 
   public function validateMailReceiver($mail_receiver) {
     if (!($mail_receiver instanceof DifferentialRevision)) {
       throw new Exception("Receiver is not a DifferentialRevision!");
     }
   }
 
   public function getPrivateReplyHandlerEmailAddress(
     PhabricatorObjectHandle $handle) {
     return $this->getDefaultPrivateReplyHandlerEmailAddress($handle, 'D');
   }
 
   public function getReplyHandlerDomain() {
     return PhabricatorEnv::getEnvConfig(
       'metamta.differential.reply-handler-domain');
   }
 
   /*
    * Generate text like the following from the supported commands.
    * "
    *
    * ACTIONS
    * Reply to comment, or !accept, !reject, !abandon, !resign, !reclaim.
    *
    * "
    */
   public function getReplyHandlerInstructions() {
     if (!$this->supportsReplies()) {
       return null;
     }
 
     $supported_commands = $this->getSupportedCommands();
     $text = '';
     if (empty($supported_commands)) {
       return $text;
     }
 
     $comment_command_printed = false;
     if (in_array(DifferentialAction::ACTION_COMMENT, $supported_commands)) {
       $text .= 'Reply to comment';
       $comment_command_printed = true;
 
       $supported_commands = array_diff(
         $supported_commands, array(DifferentialAction::ACTION_COMMENT));
     }
 
     if (!empty($supported_commands)) {
       if ($comment_command_printed) {
         $text .= ', or ';
       }
 
       $modified_commands = array();
       foreach ($supported_commands as $command) {
         $modified_commands[] = '!'.$command;
       }
 
       $text .= implode(', ', $modified_commands);
     }
 
     $text .= ".";
 
     return $text;
   }
 
   public function getSupportedCommands() {
     return array(
       DifferentialAction::ACTION_COMMENT,
       DifferentialAction::ACTION_REJECT,
       DifferentialAction::ACTION_ABANDON,
       DifferentialAction::ACTION_RECLAIM,
       DifferentialAction::ACTION_RESIGN,
       DifferentialAction::ACTION_RETHINK,
+      'unsubscribe',
     );
   }
 
   public function receiveEmail(PhabricatorMetaMTAReceivedMail $mail) {
     $this->handleAction($mail->getCleanTextBody());
   }
 
   public function handleAction($body) {
     // all commands start with a bang and separated from the body by a newline
     // to make sure that actual feedback text couldn't trigger an action.
     // unrecognized commands will be parsed as part of the comment.
     $command = DifferentialAction::ACTION_COMMENT;
     $supported_commands = $this->getSupportedCommands();
     $regex = "/\A\n*!(" . implode('|', $supported_commands) . ")\n*/";
     $matches = array();
     if (preg_match($regex, $body, $matches)) {
       $command = $matches[1];
       $body = trim(str_replace('!' . $command, '', $body));
     }
 
     $actor = $this->getActor();
     if (!$actor) {
       throw new Exception('No actor is set for the reply action.');
     }
 
+    switch ($command) {
+      case 'unsubscribe':
+        $this->unsubscribeUser($this->getMailReceiver(), $actor);
+        // TODO: Send the user a confirmation email?
+        return null;
+    }
+
     try {
       $editor = new DifferentialCommentEditor(
         $this->getMailReceiver(),
         $actor->getPHID(),
         $command);
 
       $editor->setMessage($body);
       $editor->setAddCC(($command != DifferentialAction::ACTION_RESIGN));
       $comment = $editor->save();
 
       return $comment->getID();
 
     } catch (Exception $ex) {
       $exception_mail = new DifferentialExceptionMail(
         $this->getMailReceiver(),
         $ex,
         $body);
 
       $exception_mail->setToPHIDs(array($this->getActor()->getPHID()));
       $exception_mail->send();
 
       throw $ex;
     }
   }
 
+  private function unsubscribeUser(
+    DifferentialRevision $revision,
+    PhabricatorUser $user) {
+
+    $revision->loadRelationships();
+    DifferentialRevisionEditor::removeCCAndUpdateRevision(
+      $revision,
+      $user->getPHID(),
+      $user->getPHID());
+  }
+
+
 }
diff --git a/src/applications/differential/replyhandler/__init__.php b/src/applications/differential/replyhandler/__init__.php
index ada5f63ba..c857d4738 100644
--- a/src/applications/differential/replyhandler/__init__.php
+++ b/src/applications/differential/replyhandler/__init__.php
@@ -1,16 +1,17 @@
 <?php
 /**
  * This file is automatically generated. Lint this module to rebuild it.
  * @generated
  */
 
 
 
 phutil_require_module('phabricator', 'applications/differential/constants/action');
 phutil_require_module('phabricator', 'applications/differential/editor/comment');
+phutil_require_module('phabricator', 'applications/differential/editor/revision');
 phutil_require_module('phabricator', 'applications/differential/mail/exception');
 phutil_require_module('phabricator', 'applications/metamta/replyhandler/base');
 phutil_require_module('phabricator', 'infrastructure/env');
 
 
 phutil_require_source('DifferentialReplyHandler.php');