Summary: Otherwise svn diff fails when the file is binary but the "svn:mime-type = application/x-shellscript" is missing in it.
Test Plan: arc diff succeeded against deleting a binary file which doesn't have svn:mime-type = application/x-shellscript.
Reviewers: epriestley
Reviewed By: epriestley
CC: aran, Korvin
Differential Revision: https://secure.phabricator.com/D2915
