defer func(prev *Engine) { s.engine = prev }(s.engine)
	s.engine = e

	var sectionStart time.Time
	// endSection flushes the logs for the current section from s.log to log.
	// ok indicates whether all commands in the section succeeded.
	endSection := func(ok bool) error {
		var err error
		if sectionStart.IsZero() {
			// We didn't write a section header or record a timestamp, so just dump the