# File lib/capistrano/configuration/callbacks.rb, line 135
      def trigger(event, task=nil)
        pending = Array(callbacks[event]).select { |c| c.applies_to?(task) }
        if pending.any?
          msg = "triggering #{event} callbacks"
          msg << " for `#{task.fully_qualified_name}'" if task
          logger.trace(msg)
          pending.each { |callback| callback.call }
        end
      end