public function append_zip(ZipArchive $zip, $root, $local_prefix, FW_Backup_Interface_Feedback $feedback, $exclude = array())
 {
     /**
      * @var FW_Extension_Backup $backup
      */
     $feedback->set_task(__('Scanning file system...', 'fw'));
     $fs = new FW_Backup_Helper_File_System();
     $backup = fw()->extensions->get('backup');
     $exclude[] = $backup->get_backup_dir();
     $upload_dir = wp_upload_dir();
     $exclude[] = $upload_dir['basedir'] . '/fw-style.css';
     list($file_list, $file_size) = $fs->file_list_exclude($root, $exclude);
     $feedback->set_task(sprintf(__('%d file(s) found [%s]', 'fw'), count($file_list), $fs->format_bytes(array_sum($file_size))));
     $fs->append_zip($zip, $file_list, $root, $local_prefix, $feedback);
 }