I'm really missing support for remotes. There are lots of tools for local-only development (like https://gitexercises.fracz.com/), but very few allow to demonstrate stuff like "Syncing a GitHub fork with the original repository" which involves two remotes and three copies of the same branch at the very least.
My initial goals for this tool are to purely simulate actions on Git repos without actually modifying them, but I might be flexible on that going forward, as I mention in the article with the --execute flag.
One way around this could be to create a new temporary directory in /tmp, copy .git over there and symlink the rest, then run whatever operation in the newly copied workspace and compare it with the original.
Then you can mutate things however you want and the original stays the same.
Will need to think about it more...
Personally I use it a lot for backing up git repositories to a USB stick where I have a backup of every single repository + its branches and commits in case I ever need to recover from them. And I can keep my GitHub remotes clean without 100s of branches.