repo staging implementation
currently, when rebuilding things in multiple repositories, main/community/testing all upload separately.
when doing large rebuilds where e.g. an soname changes, this breaks the repositories until the're all finished building; e.g. main uploads a new icu
and community becomes uninstallable, because none of the packages can find the old icu (it was deleted after upload of new).
it would be nice if main/community/testing did not upload individually.
that would have the downside of 'failing testing/ blocks upgrades for everything else', but we generally don't allow the builders to be blocked very long (e.g. disable things to get other things to upload if there's no way for something to build, ..) , but imo that is fine. it's better for the repos to be generally consistent with upgrades rather than 'main/ uploads a bit faster and saves a tiny bit of time'. consistency makes much more sense than this minor speed gain for higher-priority repos.
the harder implementation is to have a 'switch' that can be toggled, to temporarily swap between the two behaviours, for big rebuilds only. but this would need the people making the changes to have access to that switch, e.g. usually that would be me for large rebuilds. i don't mind manual staging, but it is more complex (and needs more design, etc) than just making everything upload at once.