Depending on the level of corruption, this may or may not be feasible. The data structure and associated Git snap-in are more capable of detecting corruption than fixing it.
In particular, the index itself is not part of the repository, it is obtained from the current content, so in most cases, you probably would be better off deleting it and doing a git reset to recreate it. Anyone reading your question is probably wondering how your repository got into this state.
With that in mind, here are a couple of thoughts:
The last 20 bytes of the index are sha1 of the file contents to this point. If they are damaged, you can overwrite them with a hex editor.
~$ python3 >>> data = open('.git/index', 'rb').read() >>> data[-20:].hex() 'e211d8f60209ca8571c2acc73f9a24ef523b5fa3' >>> hashlib.sha1(data[:-20]).hexdigest() 'e211d8f60209ca8571c2acc73f9a24ef523b5fa3'
This can eliminate simple damage caused by a brain damaged instrument.
If you really want to recover something from a completely damaged index file, you probably want to:
- In the reference implementation, read index-format.txt .
- Take a look at the
parse_index procedure in libgit2 . - Look at the specific error caused by your index file.
- Correct this procedure carefully to continue bad data without failures.
Another approach might be to use the strings utility if you just want to see a list of file names. You will lose the corresponding binary information (and part of the binary information will contain an unwanted ASCII file).