I see. Very well, I was searching for something small enough to count
as a microproject. If I may ask, can you give some directions ?

I don't think this is small enough to count as a microproject. A
microproject is something simpler than that. See the microprojects
page [1] for suggestions. They are more straightforward things that
have more chances of being accepted quickly. And since having an accepted
microproject is a mandatory step, you'll probably want it to be merged
as soon as possible.

I though about doing the group key thing : 

quoted

Use the category as key (e.g., git repo info layout would return all 
layout-related values)

But its already on the SoC 2026 Ideas , and I dont know if I should do
it.

I think that this seems to be easy to do, but the reviewing process
may take some time, so it would be better if you stick to a
one of the selected microprojects [1].

quoted

Something that I would question here if isn't it possible to make
is_inside_work_tree accept a repository as parameter and then use it
here.

Like change the function in setup.c ? wouldnt that break every call of 
is_inside_work_tree ?

Yeah, but then we would need to change all the calls to it, using
the_repository at first. But I really don't know, I'll leave this
discussion for more experienced people.

Yeah ... I missed that. Suppose we were adding this path.is-in-worktree
to repo.c , then would the below test be sufficient ? 
1: cd .git and then checking if path.is-in-worktree is false 
2: cd .. and then checking if path.is-in-worktree is true

You can take a look on how `git rev-parse --is-inside-work-tree` is
being tested today and use it as a base, since
`git repo info path.is-inside-work-tree` would return true or false
in the same situations.

[1] https://git.github.io/SoC-2024-Microprojects/