Git repo choices

I'm a little unclear on which repo is which and for what intended uses. And other than #1, their descriptions on the hubs are minimal. I'm not the best with git, but getting there. Are these the right way to think of them? And that #1 and #3 are what most builders and hacks should be tracking?

#1 https://github.com/bitcoin/bitcoin.git

The current development tree. As such, HEAD/master/origin may at times not be exactly reliable/usable.

#2 https://git.gitorious.org/bitcoin/bitcoind.git

A copy of some chunk of #1 that then died off around v0.4.0. Purposed similar to #3?

#3 https://git.gitorious.org/bitcoin/bitcoind-stable.git

Another copy of #1. For development along stable branches and making release cuts from same? Releases get pulled back to #1 for keeping? The HEAD/master/origin should be reliable.

Why is this functoin not a part of #1?

Thanks.