Comment by jsmthrowaway

Yep. That is the important tip, right here.

    $ pushd ..
    $ cp -a my-project my-project-before-I-did-git-surgery
    $ popd

Then relax. This is extremely important before playing with nasty Git surgical tools such as huge rebases. Borked it up?

    $ pushd ..
    $ rm -rf my-project
    $ cp -a my-project-before-I-did-git-surgery my-project
    $ popd

Undo is a great thing, and it's also important to triple check the entire state of the repository before you push, because pushing is basically committing to whatever surgery you've done. If you're having to fix stuff with -f, you're going to run into trouble; try to avoid -f ever.