[Outreachy] GIT_DIR inherited by shell aliases in linked worktrees

I'm considering a small Outreachy contribution around repository environment handling in external shell aliases.

I reproduced the following behaviour:

Create a repository with a linked worktree.

Run an external shell alias from inside that worktree.

Have the alias execute git -C ../TestBaseRepo rev-parse.

The nested command reports the calling worktree's Git directory and common directory, even though --show-toplevel correctly identifies TestBaseRepo.

I traced this to the inherited GIT_DIR variable. Unsetting GIT_DIR before running the nested command makes all three results point to the target repository.

I found the earlier 2020 discussion about GIT_DIR inheritance in aliases, but I'm interested in whether there is still room for a focused contribution, particularly around regression tests for linked worktrees.

Would this be a suitable microproject for Outreachy?

Thank you,

Immaculate Mecha