We show this with a worktree icon (which is only shown when nerd fonts
are used, so turn these on), but also we strip the trailing `/` that
"git status" reports, so that it shows as a file rather than a directory
with a bogus file in it.
The reason for adding the test is that we are going to touch the logic
that determines whether an item in the Files panel is a linked worktree,
and this guards against regressing.
Stefan Haller
a1f5db6bce