If my very first commit is wrong, yet pushed to a (currently private) remote, how do I undo that commit on the remote?
I'm guessing I can just amend and then push --force?
By deleting your HEAD you can restore your repository to a new state, where you can create a new initial commit:
git update-ref -d HEAD
After you create a new commit you will need to force it to the remote in order to overwrite the previous initial commit:
git push --force origin
If you've just one commit (initial commit), you can do as
git commit --amend
git push --force origin
来源：https://stackoverflow.com/questions/18874613/how-to-undo-the-initial-commit-on-a-remote-repository-in-git