Ignore errors in svn diff

Summary: Otherwise attaching the commit diff doesn't work.

Test Plan: Reparsed previously failing commit message.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Koolvin

Differential Revision: https://secure.phabricator.com/D2605

scripts/repository/binary_safe_diff.sh

@@ -0,0 +1,6 @@
+#!/bin/sh
+
+diff "$@"
+if [ "$?" = "2" ]; then
+  exit 1
+fi