When shifting RWO to dune 2.0 and then to ocaml 4.08, we noticed that dune build errors out after failing the first promotion. Previously, it would continue on until all the promotions were attempted.

This means that we have to iteratively run dune build on RWO via for in in 1 2 3 4 5 6 7 8 9; do dune build || dune promote; done to get the complete diff. I believe the dune 1 behaviour is the right one here, since auto-promote also seems to fail with dune 2 in the current state.