thinkwell/mongoid_nested_set — pull request #7 by asavartsov (2012-05-11 05:43:24+00:00)
Title: Order option on association and Mongoid 3

As far as mongoid 3 using Origin DSL, only this sorting options could be used: https://github.com/mongoid/origin/blob/master/lib/origin/optional.rb#L134

So, changed :order option for children, otherwise children will fail on new mongoid.

This syntax also does not fail on mongoid 2 according to my tests.