wp-e-commerce/WP-e-Commerce — pull request #276 by 1bigidea (2013-03-09 17:42:30+00:00)
Title: Filter provided parameters in Add to Cart

Add new filter 'wpsc_add_to_cart_parameters' to provided_parameters
during add_to_cart ajax action

This allows a external plugin to set additional information re: product being added to cart. In this case, my bakery client is setting a "pickup" date. I can't find anywhere else in the logic to affect the shopping cart item.