Feature-request: Allow usage of local mirrors in migrate2rocky.sh

[jdeamicis]

With the release of RockyLinux 8.5, using migrate2rocky.sh on a CentOS 8.4 installation will automatically migrate it to a Rocky 8.5.

If one has access to local mirrors for different Rocky minor releases, one could edit the repos before the package_swaps phase in order to control the resulting minor release for the migration (by picking the right mirror for the desired minor release).

[jdeamicis]

It's actually easier than expected: one must just use the local mirrors in repo_urls for both rockybaseos and rockyappstream, instead of the default ones.

I wonder if it makes sense to make it a command line option for the users.

[m41kc0d3]

please see #92
and my fork https://github.com/m41kc0d3/rocky-tools/tree/set-mirror-url

we used it internally for many migrations