code: function request(refs, opts, callback) {
    var url = fmt(format, endpoint, cache.user, cache.repo, refs);
  
    got.get(url, opts, function(err, res) {
      res = res ? JSON.parse(res) : {};
      if (res.ref === refs) {
        callback(null, true);
        return;
      }
  
      callback(null, false);
    });
  }
docs: Request the Github API to check for branch/tag
  in `refs/heads` and `refs/tags` endpoints.
  
  @param  {String}   `refs`
  @param  {String}   `opts`
  @param  {Function} `callback`
  @api private