Allow users to resign if they have authority over any reviewer

Summary:
Ref T11050. The old rule was "you can only resign if you're a reviewer".

With the new behavior of "resign", the rule should be "you can resign if you're a reviewer, or you have authority over any reviewer". Make it so.

Also fixes T12446. I don't know how to reproduce that but I'm pretty sure this'll fix it?

Test Plan:
  - Could not resign from a revision with no authority/reviewer.
  - Resigned from a revision with myself as a reviewer.
  - Resigned from a revision with a package I owned as a reviewer.
  - Could not resign from a revision I had already resigned from.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12446, T11050

Differential Revision: https://secure.phabricator.com/D17558

src/applications/differential/xaction/DifferentialRevisionResignTransaction.php

@@ -44,7 +44,9 @@ final class DifferentialRevisionResignTransaction
 
   public function generateOldValue($object) {
     $actor = $this->getActor();
-    return !$this->isViewerAnyReviewer($object, $actor);
+    $resigned = DifferentialReviewerStatus::STATUS_RESIGNED;
+
+    return ($this->getViewerReviewerStatus($object, $actor) == $resigned);
   }
 
   public function applyExternalEffects($object, $value) {
@@ -61,12 +63,19 @@ final class DifferentialRevisionResignTransaction
           'been closed. You can only resign from open revisions.'));
     }
 
-    if (!$this->isViewerAnyReviewer($object, $viewer)) {
+    $resigned = DifferentialReviewerStatus::STATUS_RESIGNED;
+    if ($this->getViewerReviewerStatus($object, $viewer) == $resigned) {
+      throw new Exception(
+        pht(
+          'You can not resign from this revision because you have already '.
+          'resigned.'));
+    }
+
+    if (!$this->isViewerAnyAuthority($object, $viewer)) {
       throw new Exception(
         pht(
           'You can not resign from this revision because you are not a '.
-          'reviewer. You can only resign from revisions where you are a '.
-          'reviewer.'));
+          'reviewer, and do not have authority over any reviewer.'));
     }
   }
 

src/applications/differential/xaction/DifferentialRevisionReviewTransaction.php

@@ -33,6 +33,20 @@ abstract class DifferentialRevisionReviewTransaction
     return ($this->getViewerReviewerStatus($revision, $viewer) !== null);
   }
 
+  protected function isViewerAnyAuthority(
+    DifferentialRevision $revision,
+    PhabricatorUser $viewer) {
+
+    $reviewers = $revision->getReviewers();
+    foreach ($revision->getReviewers() as $reviewer) {
+      if ($reviewer->hasAuthority($viewer)) {
+        return true;
+      }
+    }
+
+    return false;
+  }
+
   protected function isViewerFullyAccepted(
     DifferentialRevision $revision,
     PhabricatorUser $viewer) {

src/applications/differential/xaction/DifferentialRevisionTransactionType.php

@@ -60,6 +60,9 @@ abstract class DifferentialRevisionTransactionType
   protected function getActiveDiffPHID(DifferentialRevision $revision) {
     try {
       $diff = $revision->getActiveDiff();
+      if (!$diff) {
+        return null;
+      }
       return $diff->getPHID();
     } catch (Exception $ex) {
       return null;