function reducer(acc, cur) {
  const pieces = cur.trim().split(';');
  const link = url.parse(pieces[0].trim().slice(1, -1), true);
  const rel = pieces[1].trim().slice(4);

  if (rel === '"next"') acc.next = link;
  else acc.previous = link;

  return acc;
}
The callback function for `Array.prototype.reduce()` used by
`parseLinkHeader()`.

@param {Array} acc The accumulator
@param {Object} cur The current element being processed in the array
@return {Object} The accumulator
@private