Which repo should I clone?

Hello, I've been able to figure out from all the various HOWTOs about the different kernel trees (main development, -next, -stable, the subsystem trees, etc.) and I see where the files and patches are archived on kernel.org, but I haven't been able to find the actual git repos that I need to clone to work on the main kernel, or any of the others. Can someone please elaborate on exactly where each of these are stored so that I can more easily translate this conceptual knowledge into the actual git commands I have to run to make it work? Thanks, Dolan