Exit instead of throw from reparse.php without commits

Summary: I need to run this in `xargs`.

Test Plan:
  $ echo 'E' | xargs -n 1 ./reparse.php --message --all

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4094

Author: vrana

scripts/repository/reparse.php

@@ -121,10 +121,11 @@
     'repositoryID = %d %Q',
     $repository->getID(),
     $constraint);
+  $callsign = $repository->getCallsign();
   if (!$commits) {
-    throw new Exception("No commits have been discovered in that repository!");
+    echo "No commits have been discovered in {$callsign} repository!\n";
+    exit;
   }
-  $callsign = $repository->getCallsign();
 } else {
   $commits = array();
   foreach ($reparse_what as $identifier) {