That's not how git works. Unless every commit changes every single file in the repo (without ever reverting to a previous state). Most repos don't work that way

That's not how git works. Unless every commit changes every single file in the repo (without ever reverting to a previous state). Most repos don't work that way. 22 million commits is a lot though; the author states that the repo was over 8GB "last they checked", and the entire thing looked to be an experiment to determine "Github's or git's breaking point" - I guess they found it.