### Please describe the problem.
I have a git-annex repo as a submodule. When adding a file using git-annex, I get the error message:

warning: unable to convert submodule to form that will work with git-annex

This I seem to get for every file, i.e. thousands of error messages sometimes. But the repo in the submodule seems to work fine,
the .git symlink is there.

I am not able to spot the problem in Annex/Fixup.hs, maybe you have an idea what could go wrong?

### What steps will reproduce the problem?

mike@leguin experiments % date > test2     
mike@leguin experiments % git annex add test2             
add test2 (non-large file; adding content to git repository) ok
(recording state in git...)
warning: unable to convert submodule to form that will work with git-annex
mike@leguin experiments % ls -l ../.git                                   
lrwxrwxrwx. 1 mike mike 53 Nov 16 17:31 ../.git -> ../../../.git/modules/experiments/ocr-evaluation/data

### What version of git-annex are you using? On what operating system?
git-annex version: 8.20201127
Fedora 32

Also the same on CentOS 7, I was just able to reproduce it on my F32 workstation. ext4 filesystem.

### Please provide any additional information below.

[[!format sh """
# If you can, paste a complete transcript of the problem occurring here.
# If the problem is with the git-annex assistant, paste in .git/annex/daemon.log


# End of transcript or log.
"""]]

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)
Besides this problem, I am super happy with git-annex and use it at work and at home daily :-)

> [[fixed|done]] although w/o a way to reproduce it I can't be 100% sure
> --[[Joey]]
