branch: description for orphan branch errors

branch: description for orphan branch errors

In bcfc82bd48 (branch: description for non-existent branch errors,
2022-10-08) we checked the HEAD in the current worktree to detect if the
branch to operate with is an orphan branch, so as to avoid the confusing
error: "No branch named...".

If we are asked to operate with an orphan branch in a different working
tree than the current one, we need to check the HEAD in that different
working tree.

Let's extend the check we did in bcfc82bd48, to check the HEADs in all
worktrees linked to the current repository, using the helper introduced
in 31ad6b61bd (branch: add branch_checked_out() helper, 2022-06-15).

The helper, branch_checked_out(), does its work obtaining internally a
list of worktrees linked to the current repository.  Obtaining that list
is not a lightweight work because it implies disk access.

In copy_or_rename_branch() we already have a list of worktrees.  Let's
use that already obtained list, and avoid using here the helper.

Signed-off-by: Rubén Justo <rjusto@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>