> One big caveat of this is that since git doesn't really store just a stack of diffs, despite the fact it presents itself as such to the user, a custom merge driver will not make your .git grow any less than it would normally.

Note that git does support using deltas for storage. But according to docs, custom diff drivers aren't used for those, instead it's a instruction based format.

https://git-scm.com/docs/pack-format#_deltified_representati...