Pre-release workflows: only force-push PR when needed

[tidoust]

Pre-release workflows currently re-create the PR commit over and over again, using force-push to update the PR. That should only be done when needed, meaning when the bumped version to commit actually changes!

[tidoust]

That bugged me because notifications get send each time the workflows run, but the behavior is by design. The goal is to rebase the PR on the default branch whenever the default branch gets updated, because the PR's base.sha property is what gets released when the PR is merged.

When there have been no change made to packages/xxx/package.json, the rebase could perhaps be done differently without a force-push, for instance through the new API endpoint to update a pull request branch, exposed in Octokit as pulls.update(). To be tested (in particular I'm not clear whether this updates the base.sha property, or whether this adds a merge commit to the PR)

[tidoust]

The goal is to rebase the PR on the default branch whenever the default branch gets updated, because the PR's base.sha property is what gets released when the PR is merged.

Replying to myself...

Presented differently, the goal is to tag the last commit on the default branch that creates the diff to release. We could instead be content with tagging the first commit on the default branch that creates the diff, and ignore commits that touch other bits and do not change the diff.

In other words, we could only update the base.sha property when the diff changes, and and leave it unchanged otherwise. The only caveat is that we also need to update the property when files under packages/xxx have changed too, e.g. if someone did a manual bump in packages/xxx/package.json or changed the README.md.

The PR would then only be updated when the diff changes. That would remove all unnecessary push notifications. One drawback is that, looking at a release tag, it is tempting to assert "x.y.z is on commit foo, pushed on date D, and so does not take into account changes made since date D", whereas it may simply be that changes made since date D had been considered but did not impact the contents of the package.