in pkg/archive/spec.go [86:96]
func (s *Spec) NameTagRevision() string {
pkg := s.Pkg
tag := s.Tag
rev := s.Revision
for _, ptr := range []*string{&pkg, &tag, &rev} {
*ptr = nonAlnum.ReplaceAllString(*ptr, "_")
}
return fmt.Sprintf("%s.%s.%s", pkg, tag, rev)
}