docs: private static void usage(PrintStream s, String msg) {
      if (msg != null) {
        s.println(msg);
        s.println();
      }
  
      s.println("usage: Torrent [options] [file|directory]");
      s.println();
      s.println("Available options:");
      s.println("  -h,--help             Show this help and exit.");
      s.println("  -t,--torrent FILE     Use FILE to read/write torrent file.");
      s.println();
      s.println("  -c,--create           Create a new torrent file using " +
              "the given announce URL and data.");
      s.println("  -l,--length           Define the piece length for hashing data");
      s.println("  -a,--announce         Tracker URL (can be repeated).");
      s.println();
    }