[Cooker] Variables in urpmi media urls

[Rafael Garcia-Suarez]

The latest version of urpmi (4.6.16-2mdk) implements (after
the suggestion of Buchan Milne and a patch by Michael Scherer)
the ability to put variables in media URLs (thus giving
industrial-strength deployment features to this tool :)

For example you could define a media with this URL :

    # urpmi.addmedia main /mnt/mandrake/$RELEASE/$ARCH/media/main \
        with ../media_info/hdlist_main.cz

and it will replace $RELEASE and $ARCH with the relevant current values.

The recognized variables are currently :

    RELEASE : current mdk version (or "cooker" on a cooker system)
    ARCH : rpm architecture
    HOST : current canonical hostname

ARCH and RELEASE are taken from /etc/mandrakelinux-release.

If you think about other variables that might be useful, let me know.