rails/rails — pull request #6682 by acapilleri (2012-06-08 17:44:03+00:00)
Title: Dup validation fix backport for 1 9 3

At the end of initialize_dup was added the call to super if it exists,
so it also works with 1.8.7 where initialize_dup doesn't exist.
This issu was introduced with the pull request #6324