Git repository corrupt (incorrect header check; loose object is corrupt)

Question

I experienced a power failure yesterday evening while writing a commit message. When I booted the machine back up I couldn\'t complete the commit. I ran git reset

Answer 1

Simple answer to this question for anyone facing this problem: the git clone command is the fix, if have a remote repo then clone it to the local folder (after deleting the corrupted local repo), in case you dont have remote repo then try to push the corrupt repo to github and then clone it from there, I think that corrupted objects wont be pushed and it will fix the problem

Answer 2

As described in this answer I ran:

git reflog expire --expire-unreachable=now --all
git gc --prune=now

Which removed all of my dangling blobs and dangling commits, as well as the corrupt db objects.

It was a lot faster than tracking them down one-by-one!

Answer 3

It appears that git created files in .git/objects for the new commit, but didn't successfully write to them. I solved it by deleting them one at a time and re-running git fsck --full to find the next one. I started with the one originally reported by git fsck:

% rm -f .git/objects/43/46883490a0990e68db0187241abc1642765a73
% git fsck --full
Checking object directories: 100% (256/256), done.
error: inflate: data stream error (incorrect header check)
error: unable to unpack 86e7247af5865e857a3b61eed99986e2d9538df1 header
error: inflate: data stream error (incorrect header check)
fatal: loose object 86e7247af5865e857a3b61eed99986e2d9538df1 (stored in .git/objects/86/e7247af5865e857a3b61eed99986e2d9538df1) is corrupt
% rm -f .git/objects/86/e7247af5865e857a3b61eed99986e2d9538df1
% git fsck --full
Checking object directories: 100% (256/256), done.
error: inflate: data stream error (incorrect header check)
error: unable to unpack a94406345ac44982b00cf57b4b9660a35436637f header
error: inflate: data stream error (incorrect header check)
fatal: loose object a94406345ac44982b00cf57b4b9660a35436637f (stored in .git/objects/a9/4406345ac44982b00cf57b4b9660a35436637f) is corrupt

And so on. I deleted five objects before git fsck came up clean, corresponding (as I suppose) to the five files in the commit I was trying to make. I guess that the file history was not corrupted at all.

Incidentally, I thought of another method that seems to work as well. git clone copies the bad objects, but git push does not. After backing up, I created a new empty repository (--bare, because otherwise you can't push to master), then unstaged my changes and pushed both branches into the new repository. Then it was just a matter of checking it out again and restoring the latest changes from my backups.

Still interested if anyone cares to shed light on the failure mechanism here.