The devguide recommends using hg update to switch between branches in one repository.  This is only practical if you build Python in a custom (sub)directory, otherwise you’d need to either do the configure-make-test dance when merging/porting patches, or skip testing.  I’ve always used one clone per Python version, where I can keep the compiled artifacts; it makes it easy to see what a file looks like in any of the three versions, easy to work on different things in the different repos (like fixing something in 3.2 that you noticed while you were adding something to 3.3), it is cheap thanks to hardlinks, fast because you run hg pull instead of hg update to merge a patch from 3.2, and is just the simplest thing that works.  I don’t think anyone uses the one-clone-with-update approach, so I think we should rewrite the instructions to talk about one clone per version.