While this is a great development, hosting AUTHORITATIVE text of the law at a private service (GitHub, owned by Microsoft) doesn't sound like a good idea.
Consider what would happen if Microsoft decided to delete the repo. There will still be copies of the law at different places, but there would no authoritative version. Imagine a lawsuit where each party is arguing that their copy of the law is the "correct" one.
That's because Git already provides the same solutions for problems which exist in reality (immutability, trustless, distributed). All that's left out is the opportunity for some grifter to [if we're lucky] match it at substantially greater cost.
Surely there was an open procurement process, where they considered the available options for web-based version control, and came to the conclusion that GitHub was justifiably better than its competitors.
They wouldn't just have picked someone's favourite service without thinking, because fair competition is a fundamental ingredient of a well-functioning capitalist market economy.
Consider what would happen if Microsoft decided to delete the repo. There will still be copies of the law at different places, but there would no authoritative version. Imagine a lawsuit where each party is arguing that their copy of the law is the "correct" one.