plugin=diff is not implemented.
http://yellow.ribbon.to/~tuotehhou/index.php?%2BWCF%2B%E3%83%AB%E3%83%BC%E3%83%86%E3%82%A3%E3%83%B3%E3%82%B0%E3%82%B5%E3%83%BC%E3%83%93%E3%82%B9
plugin=diff is not implemented.