Setting a broken git branch to a detached head

Question

After a power loss during a commit, one of the branches in my git repository got corrupted. I did git fsck --full and deleted all the empty object files until fsck gave me:

Checking object directories: 100% (256/256), done.
Checking objects: 100% (894584/894584), done.
error: refs/heads/git-annex does not point to a valid object!
Checking connectivity: 862549, done.

I then used git fsck --lost-found to find my last good dangling commit on the git-annex branch. I checked it out.

I want this to be my replacement git-annex HEAD. I tried git checkout -b git-annex but got that the branch already exists. So I tried git branch -d git-annex but got error: Couldn't look up commit object for 'refs/heads/git-annex'.

How can I get rid of the broken git-annex branch in order to set it to the commit I want? I have already tried just removing .git/refs/heads/git-annex but that doesn't work. Thanks.

Answer 1

This works for me (after "cheating" to insert a broken branch, and seeing the same error when trying to delete it):

git branch -f broked HEAD  # or some other valid point
git branch -d broked

The second command gripes as it deletes the broken ref from .git/packed-refs (which is where I assume it must be if removing .git/refs/heads/git-annex was unhelpful). (But the branch name "git-annex" makes me wonder if you're using git-annex, as in, the thing that stores large files outside the repo. I have not used that myself and am not sure if this changes anything.)