rails/rails — pull request #6936 by jfoley (2012-07-02 19:14:05+00:00)
Title: Fix collisions with before and after validation callbacks.

This commit allows a user to do something like:
```ruby
before_validation :do_stuff, :on => [ :create, :update ]
after_validation :do_more, :on => [ :create, :update ]
```

This addresses issue #6744.

This also uses the unit tests from mandrews/rails/@0f115f4012779ec8691d2c20ad3be8033861c1b0
(lightly modified)