The original author sold it as a stupid content tracker. Which in part meant that the implementation was simple.

There ain’t a whole lot to the first commit of Git. Some hundred lines which consists of manually preparing a commit by sending the current snapshot to the “cache” (nowadays “index”) which compresses it and then building a commit by specifying the parents and a commit message (like git-commit-tree but I don’t know if that was around back then).

Beyond that I don’t know much.