Invalidate SVN status cache after adding files

Summary: Cache invalidation is really one of the two hardest computer science problems.

Test Plan:
  lang=sh
  # in Subversion repository
  $ arc diff .arcconfig # untracked

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin, AnhNhan

Differential Revision: https://secure.phabricator.com/D5600

src/repository/api/ArcanistSubversionAPI.php

@@ -195,6 +195,7 @@ final class ArcanistSubversionAPI extends ArcanistRepositoryAPI {
         'delete -- %Ls',
         array_diff($paths, $add));
     }
+    $this->svnStatus = null;
   }
 
   public function getSVNProperty($path, $property) {