plugin=diff is not implemented.
http://yellow.ribbon.to/~tuotehhou/index.php?%2BWCF%2B%E3%82%B9%E3%83%AB%E3%83%BC%E3%83%97%E3%83%83%E3%83%88%E3%82%92%E5%90%91%E4%B8%8A%E3%81%99%E3%82%8B%E3%81%9F%E3%82%81%E3%81%AE%E8%A8%AD%E5%AE%9A
plugin=diff is not implemented.