The shipped default named one private, internet-unreachable host, so an
unconfigured install failed against a server it could never reach rather
than saying what to set.
- drop the registry default and make the option required
- reject a non-string, empty, or non-http(s) registry with the option name
and how to set it
- ask for a registry only when a run has to resolve one, so clean, list,
and specs with an explicit url keep working without it
unkin-agent
c75a866c02