code: function tryFisIdLookUp(info, file, opts) {
    // 如果是 fis id 路径且属于当前 namespace，也同样做一次查找，从根目录查起
    var nsConnector = fis.media().get('namespaceConnector', ':');
    var idx = info.rest.indexOf(nsConnector);
  
    if (~idx) {
      info.isFisId = true;
  
      var ns = info.rest.substring(0, idx);
      var subpath = info.rest.substring(idx + 1);
  
      if (ns === fis.media().get('namespace')) {
        return findResource(subpath, root, opts.extList);
      }
    }
  }
docs: fis id 查找