On Tue, 23 May 2006, Trent Piepho wrote:

> There is no easy version number like in CVS or Mercurial.  The is a large
> hash value for each patch, but I haven't found out how you get it.

You can get it by using 'darcs changes --xml-output'. Most useful output
I've seen up to now.

So you can actually:

darcs diff --match="hash 20060426130158-e4f26-95127653ab70ab4e79a2be331ac863cbc5b1d9b5.gz"

Taken from: http://darcs.net/DarcsWiki/FrequentlyAskedQuestions