spree/spree — pull request #3816 by huoxito (2013-10-03 00:44:13+00:00)
Title: Reload rules select2 box after picking a PromotionRule

So that the chosen rule no longer is displayed on the select2 box, users
can associate each rule only once with the promotion

Fixes #3572

This should apply cleanly to 2-1-stable and 2-0-stable