Great writeup! It's always fun to learn the details of the tools we use daily.

For others, I highly recommend Git from the Bottom Up[1]. It is a very well-written piece on internal data structures and does a great job of demystifying the opaque git commands that most beginners blindly follow. Best thing you'll learn in 20ish minutes.

1. https://jwiegley.github.io/git-from-the-bottom-up/