0.1.0 has a nasty bug that corrupts a checked out external’s .git repository. This happens because giternal sorts the files in .git before piping them to tar, in order to minimize repo bloat. Unfortunately, tar doesn’t seem to like that, and so when unfreezing the repository it loses many of the files in .git/objects. Instant repository corruption.
What you can do
The best thing to do is probably to wipe your external dir and do a giternal update after upgrading to 1.1. This will check out a fresh copy of the dependency, along with its uncorrupted git repo.
I don’t actually think there’s anything else you can do. Sorry