plugin=diff is not implemented.
http://yellow.ribbon.to/~tuotehhou/index.php?%E3%82%A4%E3%83%B3%E3%82%B8%E3%82%A7%E3%82%AF%E3%82%B7%E3%83%A7%E3%83%B3%E9%98%B2%E6%AD%A2
plugin=diff is not implemented.