When setup_work_tree() is called, it moves cwd to $GIT_WORK_TREE and
makes internal copy of $GIT_WORK_TREE absolute. The environt variable,
if set by user, remains unchanged. If the variable is relative, it is
no longer correct because its base dir has changed.
Instead of making $GIT_WORK_TREE absolute too, we just say "." and let
subsequent git processes handle it.
Reported-by: Michel Briand <firstname.lastname@example.org>
Signed-off-by: Nguyễn Thái Ngọc Duy <email@example.com>
Signed-off-by: Junio C Hamano <firstname.lastname@example.org>