Making GIT XML aware?

[david.hagood@gmail.com]

I have a project that is committing several XML files into GIT, and we
have a problem when doing merges.

The files are UML XMI 1.1 files generated by a UML tool (specifically
Enterprise Architect by Sparx), and EA "helpfully" puts things like
timestamps of modification and access into the files. As you can guess,
these are conflict-magnets. Yes, the ideal solution would be to turn that
off, and I am pursuing that avenue within EA.

However, it seems to me that if there were some way to plug into GIT's
merging logic, it would be possible to design an XML aware merging tool
that might help on this (generalizing: if you could have content-aware
merging libraries you could make all sorts of merges go more smoothly).
For the specific case of an XML file, if you could have some way to denote
tags and/or attributes that are "don't cares" you could address problems
like I am having. You could also theoretically exploit a knowledge of the
format to better identify what chunks are changes and possibly track
motion within the files better.

Absent that, is there a way to tell git "in case of an unresolvable merge
conflict, don't modify the file but put the other version of the file
somewhere (e.g. filename.other) so that I can use an external tool to
resolve the differences"? In this case, EA doesn't know how to use the
standard conflict tags within a file to extract deltas.