func (l Label) Contains(other Label) bool {
	if l.Relative {
		log.Panicf("l must not be relative: %s", l)
	}
	if other.Relative {
		log.Panicf("other must not be relative: %s", other)
	}
	result := l.Repo == other.Repo && pathtools.HasPrefix(other.Pkg, l.Pkg)
	return result
}
func (l Label) Contains(other Label) bool {
	if l.Relative {
		log.Panicf("l must not be relative: %s", l)
	}
	if other.Relative {
		log.Panicf("other must not be relative: %s", other)
	}
	result := l.Repo == other.Repo && pathtools.HasPrefix(other.Pkg, l.Pkg)
	return result
}
// Contains returns whether other is contained by the package of l or a
// sub-package. Neither label may be relative.