Thanks for your contribution! It looks like travis failed, could you have a look?
Usually I would link the exact line of failure here, but it seems I can't access travis-ci right now.
My guess is that git_dir can't always be used safely.

I do not know why AppVeyor is failing. It does not seem related to my changes.

Thanks a lot, and sorry for the late reply. Unfortunately the release train just left the station, which means this fix will land in 3.0.8.