I was going to say that they already had started their own successor to Mercurial called Eden, but it seems like Sapling is just a renaming of Eden. Maybe anyway. It's a bit unclear.
> The Sapling CLI, sl, was originally based on Mercurial, and shares various aspects of the UI and features of Mercurial.
It's a pet peeve of mine folks that use python subprocess as a replacement for bash because it takes special discipline to not eat stdout and stderr, or to correctly try:finally: to show the Proc details before the raise eats the variable