[pmeunier]

I am one of the authors of Pijul. It is indeed a semilattice, but not exactly "commutative": the only operations that commute are operations that could be done in parallel. For example, adding a file doesn't commute with editing it.

But unlike in Darcs, where conflicts are messy and not super well-defined in all cases (and not to mention, sometimes cause Darcs to run for a time exponential in the size of the repo's history), two conflicting edits always commute in Pijul.

The main points of Pijul were (1) to solve the soundness issues with conflicts and (2) to fix the exponential problems.