BFG Repo Cleaner is also a good tool which I don't see mentioned in the article: https://rtyley.github.io/bfg-repo-cleaner/
This looks very interesting, but I'm a little nervous about it since it would appear it operates directly on the repo internal files. Anything you can say to make me feel better about using it?
In addition to the other reply, git is a distributed version control system. You can trivially run it on a copy of your repo and put it through whatever tests you like.