What's the option/method to do this, and are there limits to what it will take?

(We should probably define a schema we intend to support, if it's completely free-form.)

Free form.

createrepo --distro and --content
or mdconf.distro_tags = [] and mdconf.content_tags = []

cpeid strings for distro tags are probably a good idea - like in /etc/system-release-cpe

Adding to Fedora 12 Alpha tag, feature freeze.

This didn't happen, punting to Beta.

Ok, after IRC discussion we've reached some conclusions.

distro-tag should be the CPE tag, and whatever else helps distinguish the repos, so for rawhide it could be "cpe:/o:fedoraproject:fedora:11.92" "rawhide"

content-tag should be (auto) generated from the type of content in the repo, eg:

SRPMS get a content-tag of 'source'
x86_64 gets a content-tag of 'binary-x86_64'
debuginfo for i386 gets a content-tag of 'debuginfo-i386'

The important thing is to be consistent and the other repos will follow our example.

I'm working on some mash patches to be able to provide this data at mash time.

Further, the distro tag should have some data about whether or not a repo is "updates" or "updates-testing"

Patches sent to mash upstream to add these flags for repo generation.

The patches didn't work out so well, so punting this for F13.

Repo IDs are now getting in, although we made it wrong somehow for F13. See ticket #3759