Call didRejectResult() in DiffusionCommitQuery properly

Summary:
Ref T4345. This error is per object-type in the query implementations, not a mail/permissions issue.

Without `didRejectResult()`, we can't distinguish between "restricted" and "unknown" for objects filtered by `willFilterPage()`.

  - Call `didRejectResult()` on commits.
  - Make `didRejectResult()` handle both existing policy exceptions and filtering.
  - Recover from partial objects (like commits) which are missing attached data required to figure out policies.

Test Plan: Saw "Restricted Diffusion Commit" instead of "Unknown Object (Diffusion Commit)" when viewing nonvisible commit handle in Maniphest.

Reviewers: btrahan, joshuaspence

Reviewed By: joshuaspence

Subscribers: epriestley

Maniphest Tasks: T4345

Differential Revision: https://secure.phabricator.com/D13289

src/applications/diffusion/query/DiffusionCommitQuery.php

@@ -193,6 +193,7 @@ final class DiffusionCommitQuery
       if ($repo) {
         $commit->attachRepository($repo);
       } else {
+        $this->didRejectResult($commit);
         unset($commits[$key]);
         continue;
       }

src/infrastructure/query/policy/PhabricatorPolicyAwareQuery.php

@@ -338,9 +338,25 @@ abstract class PhabricatorPolicyAwareQuery extends PhabricatorOffsetPagedQuery {
   }
 
   protected function didRejectResult(PhabricatorPolicyInterface $object) {
+    // Some objects (like commits) may be rejected because related objects
+    // (like repositories) can not be loaded. In some cases, we may need these
+    // related objects to determine the object policy, so it's expected that
+    // we may occasionally be unable to determine the policy.
+
+    try {
+      $policy = $object->getPolicy(PhabricatorPolicyCapability::CAN_VIEW);
+    } catch (Exception $ex) {
+      $policy = null;
+    }
+
+    // Mark this object as filtered so handles can render "Restricted" instead
+    // of "Unknown".
+    $phid = $object->getPHID();
+    $this->addPolicyFilteredPHIDs(array($phid => $phid));
+
     $this->getPolicyFilter()->rejectObject(
       $object,
-      $object->getPolicy(PhabricatorPolicyCapability::CAN_VIEW),
+      $policy,
       PhabricatorPolicyCapability::CAN_VIEW);
   }