rails/rails — pull request #7267 by yalab (2012-08-05 10:48:10+00:00)
Title: Fix a bug that has_many dependent: destroy not delete child records 

Hi.
I have found a bug that has_many dependant destroy don't destroy all child records.

```ruby
class Post < ActiveRecord::Base
has_many :comments, :dependent => :destroy
end

class Comment < ActiveRecord::Base
belongs_to :post
before_destroy do
false
end
end

post = Post.create(title: "new post")
post.comments << Comment.create(body: "hello")
post.destroy
p Post.all #=> []
p Comment.all #=> [#]
```

I add a judge all records is deleted into has_many dependent callback.

Thanks.