Function superproject_work_tree_from_nested_git_modules 

pub fn superproject_work_tree_from_nested_git_modules(
    git_dir: &Path,
) -> Option<PathBuf>

Superproject work tree when git_dir lives under .../<wt>/.git/modules/... (nested submodule).

Used when the submodule’s recorded path in the superproject index does not match the on-disk layout (e.g. dir/sub recorded but git dir is .../modules/dir/modules/sub), so ls-files-based superproject detection cannot find a gitlink.