yum question

[Neal D. Becker]

I run yum update nightly.

I like to check 
[updates-testing]
name=Fedora Core $releasever - $basearch - Unreleased Updates
baseurl=http://download.fedora.us/fedora/fedora/$releasever/$basearch/yum/updates-testing

manually from time to time.

I don't want updates-testing automatically installed by the nightly run!

What's the easiest way to arrange for this?  I guess I could have 2 different 
configs.

What I'd like even more, is to have 1 config that specifies the locations of 
all packages, but have yum automatic update only pick up some.