function formatRawGistUrl(url) {
    inputDev.value  = url.replace(REGEX_RAW_GIST_URL, 'https://' + devDomain + '/$1');
    inputProd.value = url.replace(REGEX_RAW_GIST_URL, 'https://' + cdnDomain + '/$1');

    setValid();
  }
Matches a GitHub repo URL.

  Captures:

  1.  Username
  2.  Repo
  3.  Ref
  4.  File path