Matt made it so that the revision number shown in SVN-Notify links to the Trac diff page for that revision. This was for the wp-svn list, but no reason it couldn’t be used elsewhere.
Figured I might need something like this one day, so here it is:
/usr/local/bin/svnnotify -r $REV -C -d -H HTML::ColorDiff -p $REPOS \ -t wp-svn@lists.automattic.com \ --from m@wordpress.org \ --reply-to wp-hackers@lists.automattic.com \ --revision-url http://trac.wordpress.org/changeset/%s \ --ticket-map '(#(\d+))=http://trac.wordpress.org/ticket/%s' \ --ticket-regex '(\[(\d+)\])' \ --ticket-url http://trac.wordpress.org/changeset/%s
And here’s Matt’s email to wp-hackers that explains it a bit more.