> Try diffmk:
> 
> http://sourceforge.net/projects/diffmk/

Tangential note: it's interesting that a project that hasn't released
anything in nearly three years and has fewer than 2000 downloads can be in
the top 10% of projects at SourceForge. That's not intended as a comment
(positive or negative) on this project, just as an observation on the state
of the world in general and SourceForge in particular.

Michael Kay
http://www.saxonica.com/