I've created a very brief document explaining how to tell git to use
odt2txt in order to get "git diff" and friends to generate textual
diffs of OpenDocument files, in the spirit of the current explanation
of how to integrate with mutt.

See git://github.com/barak/odt2txt commit 4ec2e340582ce29f

It would be possible to do the git hook-in by modifying system-wide
git config files in /etc/, presumably guarded by a package config
option.  Not sure if that would be a good idea - just a thought.

I also did some other thumb-twiddling packaging tweaks, see branch
debian-barak in that same repo.