Use HGPLAIN for local hg commands in Phabricator

Summary: See D1707 -- just in case the Phabricator server is configured
suspiciously.

Test Plan: Cursory inspection.

Reviewers: Makinde, btrahan

Reviewed By: Makinde

CC: aran, epriestley

Maniphest Tasks: T922

Differential Revision: https://secure.phabricator.com/D1708

src/applications/repository/storage/repository/PhabricatorRepository.php

@@ -263,7 +263,7 @@ class PhabricatorRepository extends PhabricatorRepositoryDAO {
         array_unshift($args, $this->getLocalPath());
         break;
       case PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL:
-        $pattern = "(cd %s && hg {$pattern})";
+        $pattern = "(cd %s && HGPLAIN=1 hg {$pattern})";
         array_unshift($args, $this->getLocalPath());
         break;
       default: