- conflicts: the object is there but is not handled yet.
- properties: (hold) still unimplemented.
- properties: (update-first) still unimplemented.
- A configuration file? I think we can survive without it...
- xbps-repo: a way to change the order of registered repos (push/pop enough?)
- xbps-bin: a target to clean outdated binpkgs in cachedir
  (like apt-get autoclean).
- xbps-repo: support to verify PGP signed pkg-index.plist repo files
  (I have some preliminar code but need to clean it up, thanks to
   NetBSD's netpgp).