How do I recover from a corrupted git state?

[anka-213]

I have this issue, where the 3 latest .git/objects/... are completely empty, so all jj commands crash with this error:

Unexpected error from commit backend
Object b619f8c818dcd21e0c9db4c363b4dac3a00492c5 of type commit not found
An object with id b619f8c818dcd21e0c9db4c363b4dac3a00492c5 could not be found
Internal error: Failed to check out a commit
Caused by:
1: Failed to edit commit
2: Current working-copy commit not found
3: Object b619f8c818dcd21e0c9db4c363b4dac3a00492c5 of type commit not found
4: An object with id b619f8c818dcd21e0c9db4c363b4dac3a00492c5 could not be found

I have managed to find a few recent good commits using git fsck and good states in the op log (the command op log also crashes, but I found the files in the .jj directory), but now any command I would run to tell jj to use these good states instead will also crash with the same error. What can I do?

For example, op abandon complains Cannot abandon current operation, but op restore crashes with the error above.

I can run op log --at-operation=good-op, but that doesn't really help me, since I can't recover using that. Using op restore --at-operation isn't helpful either.

[anka-213]

Removing the file .jj/repo/op_heads/heads/<bad_op> and replacing it with the latest other op hash in ls -lt .jj/repo/op_store/operations/ | head seems to have done it!