fetch: protect branches checked out in all worktrees
Refuse to fetch into the currently checked out branch of any working
tree, not just the current one.
Fixes this previously reported bug:
https://lore.kernel.org/git/
cb957174-5e9a-5603-ea9e-
ac9b58a2eaad@mathema.de/
As a side effect of using find_shared_symref, we’ll also refuse the
fetch when we’re on a detached HEAD because we’re rebasing or bisecting
on the branch in question. This seems like a sensible change.
Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>