I had used Git for years by memorizing commands: commit, branch, checkout, and a quiet prayer whenever something went wrong. So I built a small version myself. minigit.py is a single file of about 400 lines of plain Python with no dependencies. It can init , add , commit , log , status , branch and checkout , and it stores everything in Git’s real on-disk format, so real Git can read the repositories it creates. This post walks through how it works, shows real output from it, and includes the complete code at the end. In the examples, mg is shorthand for python3 minigit.py ; the setup is in the “Try it” section.

The big idea: Git is a key-value store

Underneath the commands, Git is a content-addressable filesystem: a key-value store where the key is the hash of the value.…