Pijul handles all merges predictably, by design, because it doesn't actually merge anything, it just applies changes to a CRDT, and CRDTs work.
CRDTs aren't common in real-world distributed applications because they are hard to design. But when the problem is important enough (like in this case) I think the approach is worth it.
One way for Git to do what you said would be to import the repos in Pijul, commit by commit since the last common ancestor, instead of doing a 3-way merge. Technically feasible, but the performance would be terrible.
