XML enabled SVN or CVS?

I am curious if anyone has done any work on an XML enabled repository. 
The main features I am looking for are an XmlDiff and/or possibly 
canonicalization. The idea is that I am working with a group of 
distributed developers all plugging away on different editors-- some of 
which add in their own comments when you open a file or add editor 
specific info (especially when working with XML Schemas). So my thought 
was that it might be useful if XML was stored in the repository in a 
canonical form so that diff'ing it would be more reliable.

Bonus features would be XQuery/XPath support built in... so that queries 
could be run against either all or portions of the repository.

I am sure others on this list have experience in this area of holding 
XML in a repository... any suggestions?

Thanks,
Jeff Rafter