SCons Mercurial Branching
The main SCons mercurial repository is kept at bitbucket, its URL is https://bitbucket.org/scons/scons. All the current development work is typically done on the "default" branch. To clone the repo to your local machine, the command line should look something like this:
hg clone https://bitbucket.org/scons/scons
If your goal is to actually contribute, you should fork the repo instead. Check out SconsMercurialWorkflows for a more detailed description of how to create pull requests for your code and documentation patches.