I'm looking for version control system which I can adapt to store and retrieve XML diffs (as opposed to line-based diffs).  We already have software to generate the XML diffs and apply the XML patches so we're looking for a version control system which can be easily modified to use external programs for diff & patch. This <a title="academic paper examines XML diff tools" href="http://www.unibw.de/rz/dokumente/getFILE?fid=1076019" id="aix7">academic paper</a> describes altering darcs (a version control system written in Haskell) to support xydiff (an external XML diff and patching program).  However, darcs website is down and the project appears to be unsupported while Bazaar seems like a thriving version control project. Is Bazaar is a good choice...or what might be a better choice?  Thanks,    Rocky Kahn    rocky at teampatent dot com