plugin=diff is not implemented.
http://yellow.ribbon.to/~tuotehhou/index.php?%2BWCF%2B%E6%97%A2%E7%9F%A5%E3%81%AE%E3%83%87%E3%83%BC%E3%82%BF%E3%82%B3%E3%83%B3%E3%83%88%E3%83%A9%E3%82%AF%E3%83%88%E5%9E%8B
plugin=diff is not implemented.