ViewCVS URL in mailer hook script

I'm sure this has been asked a gazillion times before, but I can't seem
to find an answer in the source code or the mailing list archives.

How does the mailer hook script used by the subversion repository on
svn.collab.net (i.e. the repository holding the subversion source code
itself) generate the ViewCVS URLs in the mails that go to svn@? I want
to do something similar (the server runs FreeBSD 4.10-STABLE, if it
matters) but I'm not sure how to make this happen. Is there some option
to commit-email.pl that I'm missing, or is it a different hook script
entirely?

My kingdom...my kingdom for a clue...

Thanks in advance,

Bruce.