Force pruning the git repository takes ages to be effective

Related to BCLOUD-16990, we have a repo that went over 2G.

And now force pushing on a branch and removing a commit to trigger a repo pruning takes ages to be effective. I've done it earlier today and we're almost 10hours after if I recall the correct time, and the repo still shows as 2.1G on your settings page, while it should be at 1.1. So we are stuck.