Computing diffs is what takes large amounts of time as the object database is used intensively along with limited efficiency of object caches.

I couldn't resist and threw `gitoxide` at it, and it turned out to be more than 2x as fast (even though it uses way more CPU to do that, there is definitely room for improvement).

The PR which adds the `db-gen` program: https://github.com/jmforsythe/Git-Heat-Map/pull/6