with_scope merges create conditions incorrectly

To make chained named scopes work, with_scope was changed to do a reverse merge of create conditions. This breaks normal use of with_scope for create conditions. For example:

comment = nil
Comment.with_scope(:create => {:conditions => {:approved => true}}) do
  Comment.with_scope(:create => {:conditions => {:approved => false}}) do
    comment = Comment.new
  end
end
comment.approved? #=> true

My solution is to add a new action to with_scope: the reverse_merge. If you want, you can pull the change from http://github.com/Manfred/rails/...