I think I know the thing you mean, but I can't find it either.
I did find 'flippers' from Flickr[1] which sounds like a very similar "keep it all in master and turn stuff on and off" methodology.
Here we go:
I think you might be looking for this: http://www.youtube.com/watch?v=dxk8b9rSKOo
I can't find it right now, but I know someone gave a talk on Apollo, which is how Amazon does deployments.