[Sander_Marechal]

I tried doing something like this a couple of years ago by embedding an actual git repository inside a docx or ODF file. Unfortunately, most popular word processing suites back then trashed the git directory instead of leaving it alone (as they should, according to the standards)

[WorldMaker]

I did something similar: I built a tool in Python called musdex to use in git (or any other VCS) hooks to extract the zip file that a docx/odf file is before commits and recombine them on pull/merge (essentially treating the docx/odf as something of the build product of the repo). Run an xml lint tool on the XML in them and you get decent diffs.