Managing breaking changes upstream

[ehildenb]

Currently, when we have breaking changes in upstream repos, it can cause blockages in merging things downstream. Here we are recording the issues: #4090

There are three proposed solutions to this:

• Monorepo: K Monorepo Planning #4063.
• Auto-revert: When an _update-deps job fails, automatically open a PR into the upstream repo that reverts the given change there, and allow any developer to approve it so that it rolls the upstream repo back to a prior state.
• Downstream testing: When a PR is approved for merge in an upstream repo, move it into a staging area and automatically open a PR downstream running the test-suite there. If that test-suite doesn't pass, kick the PR out of the staging area.

The monorepo for all of K solves this issue for dependencies of any depth, but the other ones only solve it for depth 1.

• Auto-revert approach: on test-pr.yml, anything that should trigger auto-revert upstream adds a failure block which:
  • Checks the branch. If it's _update-deps/runtimeverification/..., then it figures out which repo sent that update, and tags the devops repo to open a PR into that repo with the revert of that latest commit.

[Baltoli]

Blocked on merging:

• Haskell backend + booster
• Pyk + K

This may also be of limited usefulness for deeper dependency chains.