Allow WooCommerce variations to be added to cart via URL

gistfile1.txt

add_action( 'init', 'woo_add_to_cart_fixup' );
function woo_add_to_cart_fixup() {
    // Duplicate WooCommerce variation attributes from $_GET to $_POST because WC_Form_Handler->add_to_cart_handler_variable only looks in $_POST
	if ( isset( $_GET, $_GET['add-to-cart'] ) ) {
        foreach ( $_GET as $key => $value ) {
            if ( false !== strpos( $key, 'attribute' ) ) {
                $_POST[ $key ] = $value;
            }
        }
    }
}

Allows a HTTP GET request to add to cart like: http://woodev.local/cart/?add-to-cart=10&attribute_color=orange&attribute_size=large

This will be unnecessary with the next WooCommerce release. PR was just merged in woocommerce/woocommerce#16715