[Yum] centralized metadata for security

[Muayyad AlSadi]

hi,
I have a silly suggestion
it's to allow both baseurl and mirrorlist to be used together
and in this case yum should download repomd.xml from the baseurl
(which is a very small file) and use the mirrorlist for other files

this way we avoid having messages like this

Not using downloaded repomd.xml because it is older than what we have:
(01:43:55 AM) alsadi:   Current   : Wed Nov  5 10:31:08 2008
(01:43:55 AM) alsadi:   Downloaded: Tue Nov  4 11:12:35 2008

what do you think ?