Reducing CI load with automerge and rebaseWhen

[adam-moss]

What would you like help with?

I would like help with my configuration

How are you running Renovate?

Self-hosted

If you're self-hosting Renovate, tell us which platform (GitHub, GitLab, etc) and which version of Renovate.

latest official via docker

Please tell us more about your question or problem

When a repository is configured for fast-forward merges and thus renovate with rebaseWhen: "behind-base-branch" and automergeType: branch what would be the preferred configuration to reduce CI load without unduly impacting flow?

For example say a repository has the default max of 10 concurrent and they're all eligible for automerge.

At the moment what happens is renovate merges 1 and rebases 9, so 10 pipelines. Of these 8 are effectively redundant.

On next run (assuming no other changes) it'll merge 1, rebase 8, so 9 pipelines of which 7 are redundant.

From an operational point of view only 2 pipelines are actually required in this scenario, the one being merged and the one being rebased to merge next, the others could conceivably be pushed with --push-option=ci.skip so they're updated but not "passing".

I'd be interested in ideas for minimising this overhead whilst not impacting non-automerge flows?

Thanks.

Logs (if relevant)

n/a