execution.rb

module Capistrano
  class Configuration
    module Extensions
      module Execution
        def transaction(&blk)
          super do
            self.rollback_requests = [] unless transaction?
            blk.call
          end
        end

        def on_rollback(&block)
          self.rollback_requests ||= [] if transaction?
          super
        end

        def rollback!
          return if rollback_requests.nil?
          super
          Thread.current[:rolled_back] = true
        end
      end
    end
  end
end