smart-reconfig-urpmi-2.patch
This is my proposal for the final solution to this problem. After the first
reading of reconfig.urpmi it changes permanently the channel 'baseurl'. The
recursion also works, i.e. it will look for reconfig.urpmi in each executed
reconfig, allowing for (possibly) unlimited recursion and (proably) completely
URL rewriting.

Please test before I commit into trunk. Thanks.