Working with svnindex.xsl

I've been reading documentation on using XSLT to make browsing SVN
repos hosted from Apache, and found several mentions of "the default
svnindex.xsl", but it's not on my system. I'm running Mac OS X 10.5.4
with SVN 1.4.4 built-in. I'd be happy to download it from wherever it
may be available.

However, even more important, where can I find documentation of or an
example XML file that would be passed to the XSL stylesheet for
transformation? I imagine it's a simple format, but I'd like to know
what I'm dealing with, not have to reconstruct it from someone else's
XSL.

(The SVN book only has one occurrence of svnindex.xsl, and it's in the
section on configuring for Apache.)

Thanks,
  - Quinn