Implement DestructibleInterface on GitLFS refs

Summary: Ref T7789. Make sure these get cleaned up when a repository is destroyed.

Test Plan:
  - Created a new repository.
  - Pushed some LFS data to it.
  - Used `bin/remove destroy` to nuke it.
  - Verified the LFS stuff was cleaned up and the underlying files were destroyed (`SELECT * FROM repository_gitlfsref`, etc).

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T7789

Differential Revision: https://secure.phabricator.com/D15493

src/__phutil_library_map__.php

@@ -7672,6 +7672,7 @@ phutil_register_library_map(array(
     'PhabricatorRepositoryGitLFSRef' => array(
       'PhabricatorRepositoryDAO',
       'PhabricatorPolicyInterface',
+      'PhabricatorDestructibleInterface',
     ),
     'PhabricatorRepositoryGitLFSRefQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
     'PhabricatorRepositoryGraphCache' => 'Phobject',

src/applications/repository/storage/PhabricatorRepository.php

@@ -2435,6 +2435,14 @@ final class PhabricatorRepository extends PhabricatorRepositoryDAO
         $engine->destroyObject($atom);
       }
 
+      $lfs_refs = id(new PhabricatorRepositoryGitLFSRefQuery())
+        ->setViewer($engine->getViewer())
+        ->withRepositoryPHIDs(array($phid))
+        ->execute();
+      foreach ($lfs_refs as $ref) {
+        $engine->destroyObject($ref);
+      }
+
     $this->saveTransaction();
   }
 

src/applications/repository/storage/PhabricatorRepositoryGitLFSRef.php

@@ -2,7 +2,9 @@
 
 final class PhabricatorRepositoryGitLFSRef
   extends PhabricatorRepositoryDAO
-  implements PhabricatorPolicyInterface {
+  implements
+    PhabricatorPolicyInterface,
+    PhabricatorDestructibleInterface {
 
   protected $repositoryPHID;
   protected $objectHash;
@@ -48,4 +50,23 @@ final class PhabricatorRepositoryGitLFSRef
   }
 
 
+/* -(  PhabricatorDestructibleInterface  )----------------------------------- */
+
+
+  public function destroyObjectPermanently(
+    PhabricatorDestructionEngine $engine) {
+
+    $file_phid = $this->getFilePHID();
+
+    $file = id(new PhabricatorFileQuery())
+      ->setViewer($engine->getViewer())
+      ->withPHIDs(array($file_phid))
+      ->executeOne();
+    if ($file) {
+      $engine->destroyObject($file);
+    }
+
+    $this->delete();
+  }
+
 }