ActiveRecord::Rollback Does Not Work In Nested Transactions

While I was working on the latest SQL Server adapter for rails 2.3 I noticed this in the docs and that it does not work at all in all DBs/core.

   # == Nested transactions
    #
    # #transaction calls can be nested. By default, this makes all database
    # statements in the nested transaction block become part of the parent
    # transaction. For example:
    #
    #   User.transaction do
    #     User.create(:username => 'Kotori')
    #     User.transaction do
    #       User.create(:username => 'Nemu')
    #       raise ActiveRecord::Rollback
    #     end
    #   end
    #   
    #   User.find(:all)  # => empty

I can totally see the issue but can not think of a good way to fix #transaction to let one block let another know this was set and hence all the block that finally answers true to transaction_open to do the work. I would love for some feedback for a way I might be able to patch this and/or if the docs should be changed to say that that exception class can only be used in the first transaction block.

BTW, there is a test in transaction_test.rb called #test_manually_rolling_back_a_transaction that I had copied but could never make it pass.

  def test_manually_rolling_back_a_nested_transaction
    Topic.transaction do
      @first.approved  = true
      @first.save
      Topic.transaction do
        @second.approved = false
        @second.save
        raise ActiveRecord::Rollback
      end
    end
    assert !Topic.find(1).approved?, "First shouldn't have been approved"
    assert Topic.find(2).approved?, "Second should still be approved"
  end

I believe Michael added this exception class, so I assigned him the ticket?