docs: @CheckForNull
      public static File resolveSymlinkToFile(@Nonnull File link) throws InterruptedException, IOException {
          String target = resolveSymlink(link);
          if (target==null)   return null;
  
          File f = new File(target);
          if (f.isAbsolute()) return f;   // absolute symlink
          return new File(link.getParentFile(),target);   // relative symlink
      }