Support "!unsubscribe" in Differential reply handler

Summary:
See task. Allows users to unsubscribe via email.

Test Plan:
Used mail receiver to unsubscribe from a revision. Tested subscribe/unsubscribe
buttons. Verified "!unsubscribe" appears as an avilable action in email.

Reviewed By: ola
Reviewers: ola, mroch, jungejason, tuomaspelkonen, aran
CC: aran, epriestley, ola
Differential Revision: 385

src/applications/differential/controller/subscribe/DifferentialSubscribeController.php

@@ -37,8 +37,6 @@ class DifferentialSubscribeController extends DifferentialController {
     }
 
     if (!$request->isFormPost()) {
-      // TODO: This dialog is silly but we're CSRF-able otherwise.
-
       $dialog = new AphrontDialogView();
 
       switch ($this->action) {
@@ -74,28 +72,16 @@ class DifferentialSubscribeController extends DifferentialController {
 
     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(),
+          $phid,
-          $user->getPHID());
+          $phid);
-        $unsubscribed = $revision->getUnsubscribed();
-        if (empty($unsubscribed[$phid])) {
-          $unsubscribed[$phid] = true;
-          $revision->setUnsubscribed($unsubscribed);
-          $revision->save();
-        }
         break;
       default:
         return new Aphront400Response();

src/applications/differential/editor/revision/DifferentialRevisionEditor.php

@@ -416,6 +416,36 @@ class DifferentialRevisionEditor {
     }
   }
 
+  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,

src/applications/differential/replyhandler/DifferentialReplyHandler.php

@@ -89,6 +89,7 @@ class DifferentialReplyHandler extends PhabricatorMailReplyHandler {
       DifferentialAction::ACTION_RECLAIM,
       DifferentialAction::ACTION_RESIGN,
       DifferentialAction::ACTION_RETHINK,
+      'unsubscribe',
     );
   }
 
@@ -114,6 +115,13 @@ class DifferentialReplyHandler extends PhabricatorMailReplyHandler {
       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(),
@@ -139,4 +147,16 @@ class DifferentialReplyHandler extends PhabricatorMailReplyHandler {
     }
   }
 
+  private function unsubscribeUser(
+    DifferentialRevision $revision,
+    PhabricatorUser $user) {
+
+    $revision->loadRelationships();
+    DifferentialRevisionEditor::removeCCAndUpdateRevision(
+      $revision,
+      $user->getPHID(),
+      $user->getPHID());
+  }
+
+
 }

src/applications/differential/replyhandler/__init__.php

@@ -8,6 +8,7 @@
 
 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');