Enabling UNION_SLOTS today would break every client on an R minor we do
not publish. contribPath() redirects on any minor the User-Agent carries,
without checking that the target exists and without a fallback, and only
4.4, 4.5 and 4.6 are published: a 4.3 client would be sent to a 404 and
see no packages at all.
- Gate routing on KNOWN_MINORS, falling back to the flat index otherwise.
- Honour EXTRA_PUBLIC_HOSTS so the same script can run on a staging zone
and redirect within itself instead of into production.
- Add the cran-rpkgs-test pull zone with UNION_SLOTS pre-enabled, served
on the bunny default hostname so it needs no DNS record.
- Add scripts/verify-r-minor-routing.sh, covering all 16 slots: index
reachability, the union property against flat, Path: target
resolution, coverage parity across minors, and (--live) real
User-Agent routing.
- Cover the fallback in the edge test suite.
