Re: corrupted Git repository

[Michael J Gruber <git@drmicha.warpmail.net>]

Kasra Khosoussi venit, vidit, dixit 21.06.2011 08:58:
> Hi all,
> 
> My thesis repository is corrupted and I don't have any recent backup
> (my files are OK, but the history is lost). I've seen the recovery

Backup now!
I guess you've done that meanwhile anyways, but it's important before
any recovery attempts.

Is your reflog OK, i.e. do you get proper output from "git reflog" or
"git log -g"?

> examples in the manual, but I believe my case is somehow different.
> The repository is linear.
> 
> 1- At the beginning, git status/log/fsck -full said:
> 
>> fatal: object 0a83757505387aacc2fd36b3c996729e6bf9d6e5 is corrupted

Hopefully and probably only the most recent commit (the one above) is
lost, not all of our history.

> 
> and there was an empty file in .git/objects/01/8375... .

.git/objects/0a83... probably

> 
> 2- If I move the corrupted object, git fsck --ful would return this:
> 
>> error: HEAD: invalid sha1 pointer 0a83757505387aacc2fd36b3c996729e6bf9d6e5
>> error: refs/heads/master does not point to a valid object!
>> dangling tree 06f388dc60cfb014b5e1f70ecdaa568efe6bd0fa
>> dangling tree d86f8c75e836e13b6e0336361641223f48fde722
> 
> 3- I guess I have to edit refs/heads/master and replace the corrupted
> sha1 with another hash, but I'm not sure how I can find the proper
> commit (e.g.,maybe by using find -mtime?).
> 
> Thanks in advance,
> 
> -Kasra

The reflog will give you the previous value of HEAD. You can set
refs/heads/master to that (git update-ref) and then rebuild the lost
commit on top of that (assuming only one commit is lost). The dangling
trees are not necessarily due to the corrupt commit object. Have you
changed any files since the corrupt commit? Do you remember which files
you changed in that commit?

Michael