GitHub Merge Queue

Update - disabled ~ Mar 17 2023

Issues found

still runs all the checks (including GHA) again even if the queue is empty https://github.com/orgs/community/discussions/46757?sort=top#discussioncomment-4912738
GH enforcing the max 20 runners at once limit, which they never did before
hence PRs were being silently removed from the queue (GHA not reporting status) and no benefit was being gained from the queue

Update - enabled on Mar 13 2023. DCO required adjusting as per https://github.com/hyperledger/besu/pull/5207.

Essentially this works the same as enabling auto-merge, except that any additional "merge from main" actions are automated.

Impacts on current workflow

once the merge queue is enabled, it's a requirement - so all PRs will be merged via the queue.
to add your PR to the merge queue, you need to click the green "merge when ready" button" just as you would click the "enable auto-merge" button
"squash merge commits" is done automatically
- with the commit message = PR title (full commit details still available in the PR)
- so if you want to edit the commit message, you'll need to do this locally on your branch prior to adding it to the merge queue - eg https://stackoverflow.com/questions/25356810/git-how-to-squash-all-commits-on-branch
avoiding unnecessary merge conflicts - think about inserting into a sensible place in the changelog, rather than appending to the end by default
when there's a merge conflict, the PR with the conflicts gets kicked out of the merge queue and manual intervention is required - same as if you had enabled "auto-merge"

Discussion in Feb 28 contributor call on enabling the merge queue 2023-02-28 Contributor Call - APAC Friendly Time after 23.1.1 release

Note - it's part of "branch protection" - so you turn it on for specific branch protection rules.

Link to Besu merge queue (when enabled) would be https://github.com/hyperledger/besu/queue/main