aptly 1.2.0-3 (s390x binary) in ubuntu cosmic

 It offers several features making it easy to manage Debian package
 repositories:
 .
  - make mirrors of remote Debian/Ubuntu repositories, limiting by
    components/architectures
  - take snapshots of mirrors at any point in time, fixing state of
    repository at some moment of time
  - publish snapshot as Debian repository, ready to be consumed by apt
  - controlled update of one or more packages in snapshot from upstream
    mirror, tracking dependencies
  - merge two or more snapshots into one