Git 'fatal: No such ref: HEAD'

For me the problem was that on Mac OS X either the 'uchg' or 'uappnd' flag was set, locking some git files regardless of the perms. I reset the chflags like this and it solved it for me:

sudo chflags -R 0000 .

HEAD is usually a reference to a particular branch; in your case, it seems the branch pointers have gone missing, so the HEAD reference cannot be resolved.

You can use git fsck --lost-found to scan the object cache for unreachable objects; specifically, you are interested in commits, which can then be found below .git/lost-found/commit/; these are pointers to your branches, all you need to do then is find out which is which, and create new references using git branch.

You've lost your HEAD so you'll need to recreate it. The simplest thing to do is this.

echo ref: refs/heads/master >.git/HEAD

Now you should be able to run other git commands and see where you're at.

(Although, in theory, you could attempt to do git symbolic-ref HEAD refs/heads/master newer git versions don't recognize a .git as a git repository unless it already contains a HEAD so this won't work to create a new one.)

I think this answer maybe helpful for someone. I resolved this problem nearly. First what I did was, like Charles Bailey wrote, use

echo ref: refs/heads/master >.git/HEAD

Then my branch changed to master. I commited changes and was able to switch to my main branch. The problem was that I wasn`t able to use any of my local branches. Especially I wanted to work on branch 812. So I found last commit to branch 812 (create message when commit is very helpful ;)) and switched to it. Next I created branch 812 based on the one I switched to. Unfortunately some files were missing. Luckily I had them on the broken repo which I copied before 'echo'