stefankroes/ancestry — pull request #189 by brocktimus (2014-05-05 13:01:27+00:00)
Title: Only propagating updated_at if records have been changed with touch option

This is a sister PR to the main rails one I've written rails/rails#14979.

Basically, just adjusting the callback to only run if the record has actually changed. This brings it into line with updated_at on the main record itself which only updates if the record changed.