Have you considered Fossil (link below)? it is a SCM tool built on top of sqlite.
I have not used it myself, but I would assume it stores file revisions as diffs, and since its all just sqlite you should be able to run arbitrary queries on it.
My usecase is silly. Basically small to medium database backed cms websites. I just want to evolve them as the client already is using them to serve and store content. Also have up to date complete backup of them in git.
I could do it easily if I just kept data in text files instead of sqlite, but I really like the speed of the database queries.
Maybe the other way around? Use database triggers on inserts an updates to store the data in files as well? And create a procedure to update the database from files after git pull?
