Comment 6 for bug 783503

I've implemented a basic version of this feature in the lp:~arand/hydrazine/lp-promote-ppa branch doing a minor tweak of the lp-promote-ppa script

It allows passing a -i / --packageversion option to narrow down the origin set of packages to a specified version.
This allows the feature I requested here, i.e going from this state:
foo_0.2 oneiric
foo_0.1 natty
foor_0.1 lucid

to this state:
foo_0.2 oneiric
foo_0.2 natty
foo_0.2 lucid

possibly in the same PPA, by using

~$ lp-promote-ppa user/ppa user/ppa -s foo -i 0.2

Possible improvement are:
* per-package version (as of now it only accepts one version argument, which is applied to filter all packages), I guess it could use some apt-like syntax: "-s foo=0.2"
* copying to distroseries with no prior version of the package