config-rsync - not yet tested

gistfile1.php

/*
 * Command callback.
 */
function drush_config_rsync() {
  // Some boring option init stuff.
  $backend_options = array('integrate' => TRUE);
  $global_options = drush_redispatch_get_options() + array(
      'strict' => 0,
    );
  if (drush_get_context('DRUSH_SIMULATE')) {
    $backend_options['backend-simulate'] = TRUE;
  }

  $alias = drush_get_context('DRUSH_TARGET_SITE_ALIAS');
  $site_record = drush_sitealias_get_record($alias);
  $target_destination_dir = drush_config_destination_dir();
  if (drush_sitealias_is_remote_site($alias)) {
    // Get a temp dir on Source. The Staging dir might be read-only, esp in Production.
    $status_options = array('fields' => 'temp', 'field-labels' => 0);
    $return = drush_invoke_process($site_record, 'core-status', array(), $global_options + $status_options, $backend_options);
    if ($return['error_status']) {
      return drush_set_error('Unable to execute core-status command on the Source.');
    }
    else {
      $dir_export = $return['object']['temp'] . '/staging';
    }

    //Perform export on the Source
    $export_options = array('destination' => $dir_export);
    $return = drush_invoke_process($site_record, 'config-export', array(), $global_options + $export_options, $backend_options);
    if ($return['error_status']) {
      return drush_set_error('Unable to execute config-export command on remote alias.');
    }

    // Rsync config files to staging dir on Local.
    $rsync_options = array('remove-source-files' => TRUE);
    $return = drush_invoke_process('@self', 'core-rsync', array("$alias:$dir_export", "@self:$target_destination_dir"), $global_options + $rsync_options, $backend_options);
    if ($return['error_status']) {
      return drush_set_error('Unable to execute core-rsync command on remote alias.');
    }
  }
  else {
    // Two local sites so we skip the rsync.
    $export_options = array('destination' => $target_destination_dir);
    $return = drush_invoke_process($site_record, 'config-export', array(), $global_options + $export_options, $backend_options);
    if ($return['error_status']) {
      return drush_set_error('Unable to execute config-export command on remote alias.');
    }
  }

  if (drush_get_option('add')) {
    drush_shell_exec_interactive('git add -p %s', $target_destination_dir);
  }
}