* the path {@code a/../b}, which {@code simplifyPath} will change to {@code b}. If {@code a} is a
   * symlink to {@code x}, {@code a/../b} may refer to a sibling of {@code x}, rather than the
   * sibling of {@code a} referred to by {@code b}.
   *
   * @since 11.0
   */
  public static String simplifyPath(String pathname) {
    checkNotNull(pathname);
    if (pathname.length() == 0) {