EDIT: I’ll add that, IMO, hooks should never modify files. They should simply check that your code meets whatever requirements you want your code-base to meet

This, I think, is the way. This is also how I've seen it in every actual real project I've encountered, and I sort of wish they would make it a little more clear what is the command I can run to make the checks pass by doing an auto-format or whatever, but yes I agree that the author should have spent a little more time on explaining what the actual solution is.