Return an error when drush vc-sync fails.

  $repository = versioncontrol_repository_load($repo_id);

  try {

    drush_log(dt('Beginning synchronization of repository !name', array('!name' => $repository->name)), 'ok');

    $flush ? $repository->reSyncFromScratch() : $repository->sync();

    // FIXME this often echoes success even if it didn't work

    $sync_status = $flush ? $repository->reSyncFromScratch() : $repository->sync();

    if ($sync_status) {

      drush_log(dt('Successfully synchronized repository !name', array('!name' => $repository->name)), 'success');

    }

    else {

      drush_log(dt('There was an error during the synchronization, review the sync log table for details.'), 'error');

    }

  }

  catch (Exception $e) {

    // @todo is there a way to end up here? reSyncFromScratch() and sync() should handle the exceptions IIRC.

    drush_set_error('Exception while synchronizing', dt('An error occurred while performing history synchronziation on repository !name. Error info: ' . $e->__toString()), array('!name' => $repository->name));

    // There'll be a stale lock on the repository now, so clear it.

    $repository->updateLock(0);