Don't trigger "Auto Review" if the author is already an owner; document "Auto Review"

Summary:
Ref T10939. If you already own a package, don't trigger the subscribe/review rules.

Document how these rules work.

Test Plan:
  - Read documentation.
  - Removed reviewers, updated a revision, got autoreviewed.
  - Joined package.
  - Removed reveiwers, updated a revision, no more autoreview.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10939

Differential Revision: https://secure.phabricator.com/D15918

src/applications/differential/editor/DifferentialTransactionEditor.php

@@ -1510,6 +1510,27 @@ final class DifferentialTransactionEditor
       return array();
     }
 
+    // Remove packages that the revision author is an owner of. If you own
+    // code, you don't need another owner to review it.
+    $authority = id(new PhabricatorOwnersPackageQuery())
+      ->setViewer(PhabricatorUser::getOmnipotentUser())
+      ->withPHIDs(mpull($packages, 'getPHID'))
+      ->withAuthorityPHIDs(array($object->getAuthorPHID()))
+      ->execute();
+    $authority = mpull($authority, null, 'getPHID');
+
+    foreach ($packages as $key => $package) {
+      $package_phid = $package->getPHID();
+      if ($authority[$package_phid]) {
+        unset($packages[$key]);
+        continue;
+      }
+    }
+
+    if (!$packages) {
+      return array();
+    }
+
     $auto_subscribe = array();
     $auto_review = array();
     $auto_block = array();

src/docs/user/userguide/owners.diviner

@@ -45,6 +45,32 @@ belonging to the package when you look at them in Diffusion, or look at changes
 which affect them in Diffusion or Differential.
 
 
+Auto Review
+===========
+
+You can configure **Auto Review** for packages. When a new code review is
+created in Differential which affects code in a package, the package can
+automatically be added as a subscriber or reviewer.
+
+The available settings are:
+
+  - **No Autoreview**: This package will not be added to new reviews.
+  - **Subscribe to Changes**: This package will be added to reviews as a
+    subscriber. Owners will be notified of changes, but not required to act.
+  - **Review Changes**: This package will be added to reviews as a reviewer.
+    Reviews will appear on the dashboards of package owners.
+  - **Review Changes (Blocking)** This package will be added to reviews
+    as a blocking reviewer. A package owner will be required to accept changes
+    before they may land.
+
+NOTE: These rules **do not trigger** if the change author is a package owner.
+They only apply to changes made by users who aren't already owners.
+
+The intent of this feature is to make it easy to configure simple, reasonable
+behaviors. If you want more tailored or specific triggers, you can write more
+powerful rules by using Herald.
+
+
 Files in Multiple Packages
 ==========================