Currently, archive.debian.org suites are imported manually into Debsources
(using bin/debsources-suite-archive), and not watched periodically by the cron
job using bin/debsources-update.

This poses a problem at release time: when oldstable is removed from the mirror
network (more precisely: when stable becomes the new oldstable),
debsources-update will notice and remove all (old) oldstable packages from its
database. Those packages will have to be reimported manually using
debsources-suite-archive, when the archive suite shows up on archive.d.o.

A proper solution for the underlying problem requires automating the watching
of archive.d.o suites, which might need a separate bug report.

In the meantime, we should add an import command to debsources-suite-archive,
that allows to import manually, before the next stable->oldstable->archive
rotation, a currently live suite as an archive.d.o suite (AKA sticky suite),
inhibiting its deletion. To implement that, it might be enough to simply set
sticky=True on all packages belonging to that suite. But some reflection is
needed about what might happen during debsources-update runs, in the interim
between the import and the disappearing of the imported suite from the mirror
network.

Cheers.