One problem remains: jj makes it a breeze to parallelize work, but descendant changes will then end up with multiple parents. But PRs cannot target multiple target branches at once - so you cannot point them at both at once.

cf. https://jj-vcs.github.io/jj/latest/cli-reference/#jj-paralle...

I mostly solve this by putting a branch on the merge commit M, then the “real” change R is a child of that. The PR is targeted to merge R into M.

As the parents of M are merged, I rebase the whole stack. When M has a single parent left, I abandon M and retarget the PR to merge R into that parent.

It requires a little babysitting, but the PR shows the diff I want it to.