Bug: Segfault when doing "git diff"

Hello dear git devs,

I just stumbled upon a segfault when doing just "git diff" in my repo.

I managed to create a minimal repo setup where the bug is reproducable.

The problem seems to be a mix of having an untracked submodule and having set an alternates file for one submodule.

Attached you'll find my setup that will reproduce the problem. Simply run 'git diff' in bugtest1.

In case the attachment is refused, I also uploaded it here:

http://supraverse.net/bugdemo.tar.gz

cheers,

     --Marenz