Define cd_to_toplevel shell function in git-sh-setup

Signed-off-by: Junio C Hamano <junkio@cox.net>

git-sh-setup.sh

@@ -36,6 +36,17 @@ is_bare_repository () {
 	esac
 }
 
+cd_to_toplevel () {
+	cdup=$(git-rev-parse --show-cdup)
+	if test ! -z "$cdup"
+	then
+		cd "$cdup" || {
+			echo >&2 "Cannot chdir to $cdup, the toplevel of the working tree"
+			exit 1
+		}
+	fi
+}
+
 require_work_tree () {
 	test $(is_bare_repository) = false ||
 	die "fatal: $0 cannot be used without a working tree."