I have a problem with git on Windows Azure. Git status shows - \"fatal: bad object HEAD\" and I tried running:
git fsck --full
git gc
But
I managed to fix a similar problem to this when some of git's files were corrupted:
https://stackoverflow.com/a/30871926/1737957
In my answer on that question, look for the part where I had the same error message as here:
fatal: bad object HEAD.
You could try following what I did from that point on. Make sure to back up the whole folder first.
Of course, your repository might be corrupted in a completely different way, and what I did won't solve your problem. But it might give you some ideas! Git internals seem like magic, but it's really just a bunch of files which can be edited, moved, deleted the same as any others. Once you have a good idea of what they do and how they fit together you have a good chance of success.