trigger (Capistrano::Configuration::Callbacks)

    # File lib/capistrano/configuration/callbacks.rb, line 122
          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