func managerOrUserAgent(manager, userAgent string) string {
	if manager != "" {
		return manager
	}
	return prefixFromUserAgent(userAgent)
}

// prefixFromUserAgent takes the characters preceding the first /, quote
// unprintable character and then trim what's beyond the
// FieldManagerMaxLength limit.
func prefixFromUserAgent(u string) string {
	m := strings.Split(u, "/")[0]
	buf := bytes.NewBuffer(nil)
	for _, r := range m {