The Pijul maintainer has opinions that I don't understand about how we
mention Pijul (they consider the current mentions offensive as
"bashing Pijul"). Let's just remove the references so we don't have to
deal with it. I think the references to Darcs we already had in most
of these places are sufficient.
Sturdy came up a while ago on lobste.rs when [jj was being discussed](https://lobste.rs/s/47zztj/jujutsu_dvcs). I'm not sure if I described it well, or if it's something you want as related-work, especially since the sturdy founder claims to be solving different problems in the very thread. But it does seem to be doing some similar things to removing the idea of an index/staging area.
