Fix commit policy stuff and anchor handling

Summary:
See discussion in D5121. Fixes T2615.

This might cause us more issues if anything is loading commit handles without passing a viewer, but I think I tested all of those cases.

Test Plan: Looked at feed, audit, maniphest, diffusion, differential, owners, repositories.

Reviewers: vrana

Reviewed By: vrana

CC: aran

Maniphest Tasks: T2615

Differential Revision: https://secure.phabricator.com/D5139

src/applications/diffusion/query/DiffusionCommitQuery.php

@@ -4,6 +4,7 @@ final class DiffusionCommitQuery
   extends PhabricatorCursorPagedPolicyAwareQuery {
 
   private $identifiers;
+  private $phids;
 
   /**
    * Load commits by partial or full identifiers, e.g. "rXab82393", "rX1234",
@@ -16,6 +17,11 @@ final class DiffusionCommitQuery
     return $this;
   }
 
+  public function withPHIDs(array $phids) {
+    $this->phids = $phids;
+    return $this;
+  }
+
   public function loadPage() {
     $table = new PhabricatorRepositoryCommit();
     $conn_r = $table->establishConnection('r');
@@ -134,6 +140,13 @@ final class DiffusionCommitQuery
       }
     }
 
+    if ($this->phids) {
+      $where[] = qsprintf(
+        $conn_r,
+        'phid IN (%Ls)',
+        $this->phids);
+    }
+
     return $this->formatWhereClause($where);
   }