I'm sending a simple patch that should be considered 1st-try-only. I still need
to clarify some points in order to provide the final patch.

a) Does the original urpmi code changes the base url permanently on the config,
or does it read the reconfig.urpmi every time it needs to fetch something?

b) Is it possible to exist more than one reconfig.urpmi? I mean, if 'a'
redirects to 'a/b' then it have another redirection to 'a/b/c', or is this
redirection one-time-only?

While these questions are being clarified, I would like to ask anyone interested
to test the attached patch (smat-reconfig-urpmi-1.patch).