https://github.com/git/git/tree/e83c5163316f89bfbde7d9ab23ca...
Of course, he also didn't have as much to explain at that stage :)
[1] https://jwiegley.github.io/git-from-the-bottom-up/
https://github.com/git/git/tree/e83c5163316f89bfbde7d9ab23ca...