code: function byName(a, b) {
    if (a === INDEX_FILE) {
      return a === b ? 0 : -1;
    }
    if (b === INDEX_FILE) {
      return 1;
    }
    return a.toLowerCase().localeCompare(b.toLowerCase());
  }
docs: sorts the given filename by name ensuring INDEX is the first one
  @param a
  @param b
  @returns {number}