save cart for anonymous user after registration I know drupal commerce let anonymous user create cart and in billing or shipping step create a user according  billing or shipping information,But I want implement another policy,user can add product to his/her cart,then when he/she want checkout I want redirect him/her to registration form I provided then after he/she fill information(registration) then he/she can keep on shipping.
I have idea I save cart information in temp variables,after he/she create user add that cart information to him/her,But I don't sure this is the only and best way,anybody has idea about how can I achieve this task?
There is a module called Commerce Checkout Redirect, which redirects an anonymous user to Register or Login page and redirects to checkout on filling of either form, that would come handy for you.