Move the logic of "git submodule--helper ensure-core-worktree" into
run-update-procedure, and since this makes the ensure-core-worktree
command obsolete, remove it.
As a result, the order of two operations in git-submodule.sh is
reversed: 'set the value of core.worktree' now happens after the call to
"git submodule--helper relative-path". This is safe - "relative-path"
does not depend on the value of core.worktree.
Signed-off-by: Glen Choo <chooglen@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>