What's wrong with just deleting the whole folder and clone repo and whatever branch you're interested in? In any case it's not an urgent thing. You don't have to do this mid-work, you can wait until you push most stuff and then rm && git clone.
The only case in which this wouldn't work is when you have a ton of necessary local branches you can't even push to remote, which is a risk and anti-pattern per se.
because of my precious stash? but also the repo is huge, the clone takes 10 minutes? And all the other branches...