drupal/core/modules/config/config.module

<?php

/**
 * @file
 * Allows site administrators to modify configuration.
 */

use Drupal\Core\Routing\RouteMatchInterface;

/**
 * Implements hook_help().
 */
function config_help($route_name, RouteMatchInterface $route_match) {
  switch ($route_name) {
    case 'help.page.config':
      $output = '';
      $output .= '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('The Configuration manager module provides a user interface for importing and exporting configuration changes; i.e., for staging configuration data between multiple instances of this web site. For more information, see the online handbook entry for <a href="!url">Configuration manager module</a>', array(
        '!url' => 'http://drupal.org/documentation/administer/config',
      )) . '</p>';
      return $output;

    case 'config.sync':
      $output = '';
      $output .= '<p>' . t('Import configuration that is placed in your staging directory. All changes, deletions, renames, and additions are listed below.') . '</p>';
      return $output;
  }
}

/**
 * Implements hook_file_download().
 */
function config_file_download($uri) {
  $scheme = file_uri_scheme($uri);
  $target = file_uri_target($uri);
  if ($scheme == 'temporary' && $target == 'config.tar.gz') {
    return array(
      'Content-disposition' => 'attachment; filename="config.tar.gz"',
    );
  }
}