func (i *images) resolveStaleImages() {
	i.lastTarget = nil
	for img := range i.images {
		img.resolveStale()
	}
}
func (i *images) resolveStaleImages() {
	i.lastTarget = nil
	for img := range i.images {
		img.resolveStale()
	}
}
// resolveStaleImages resolves stale images.