Update repositories for .gentoo directories

[TheChymera]

I notice that persistent testing is somewhat difficult given the current gebuilder features. Since the repo containing the .gentoo file remains static between updates, this means that new e.g. deps, even if correctly specified in the .gentoo ebuild, will be lacking in the image unless the repo is manually updated.

Most immediately this can be addressed by creating a cron script at a higher frequency than the gebuilder ... update script.

@Doeme, what do you think about - in stead - adding this as an optional feature in the gebuilder update subcommand?

I'm a bit unfamiliar with your subcommand management - how would one best add optional parameterization?

[Doeme]

The thing is: a changed dependency yields a new .gentoo-ID, hence we need to instanciate a new root image.
But: We could make the stemgentoo configurable, and save some time installing all the dependencies by basing the new image on the old one.

The parametrization on the command-line level is an unsolved problem, But I would introduce it into the already standing config-chain, i.e.

1. The global-config in '/gebuilder/root/config` is loaded
2. The per-Image config roots/<ID>/config is loaded and overrides 1.
3. The command-line config is evaluated, and overrides 1. and 2.

[TheChymera]

1. You mean /usr/share/gebuilder/config/generic.conf, right?

About that, it might be a good idea to harmonize gebuilder with the filesystem hierarchy standard (which Gentoo is particularly fond of enforcing). As such, we should instead install the config files to /etc/gebuilder/. What would be a prefix-robust way to do this?