submodule: ensure core.worktree is set after update

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-submodule.sh

@@ -615,6 +615,11 @@ cmd_update()
 			die "$(eval_gettext "Unable to find current \${remote_name}/\${branch} revision in submodule path '\$sm_path'")"
 		fi
 
+		if ! $(git config -f "$(git rev-parse --git-common-dir)/modules/$name/config" core.worktree) 2>/dev/null
+		then
+			git submodule--helper connect-gitdir-workingtree "$name" "$sm_path"
+		fi
+
 		if test "$subsha1" != "$sha1" || test -n "$force"
 		then
 			subforce=$force