src/Cart/ShoppingCartController.php
public static function direct($status = true)
    {
        if (Director::is_ajax()) {
            return (string)$status;
        }
        if (self::config()->direct_to_cart_page && ($cartlink = CartPage::find_link())) {
            return Controller::curr()->redirect($cartlink);
        } else {
            return Controller::curr()->redirectBack();
        }
    }
public static function direct($status = true)
    {
        if (Director::is_ajax()) {
            return (string)$status;
        }
        if (self::config()->direct_to_cart_page && ($cartlink = CartPage::find_link())) {
            return Controller::curr()->redirect($cartlink);
        } else {
            return Controller::curr()->redirectBack();
        }
    }
This is used here and in VariationForm and AddProductForm

@param bool|string $status

@return string|HTTPResponse