I'll start by quoting google's blog
Project owners can now create multiple repositories for their project, and they can choose to make any of those new repositories a clone of any of the project's other repositories. These project clones share the same commit access permissions as the original project and make it easier for project members to work together on new features. A common pattern in the Mercurial world is to place each "official" branch into a separate repository with naming conventions like "project-crew", "project-stable", and so on.
I've done exactly this. I have my default repository and then I've cloned that repository to a repo named "dev". I intend to use the default repository as my stable repo and then the dev repo as my primary development repo. Now I'm just wondering how on earth I should go about to pull and push between the default and the dev repositories?