fa8f081af3 ci: Checkout latest merged pulls (MarcoFalke)
Pull request description:
Currently, the `actions/checkout@v5` checks out pull requests merged against master, which is what we want.
However, it checks out ancient/stale merge commits on a re-run. This is documented (https://docs.github.com/en/actions/how-tos/manage-workflow-runs/re-run-workflows-and-jobs):
> Re-run workflows [...] will also use the same GITHUB_SHA (commit SHA) and GITHUB_REF (git ref) of the original event that triggered the workflow run.
For example:
* https://github.com/bitcoin/bitcoin/actions/runs/17458152407/job/49579638898?pr=29641#step:9:914 compiles with IPC=ON, even though latest master is at ed2ff3c63d
* https://github.com/bitcoin/bitcoin/pull/32989#issuecomment-3133536724 (example explained in comment)
This is problematic, because:
* Unrelated CI failures and intermittent issues, which are fixed or worked around in latest master can not be cleaned by re-running the task. The author has to actively go out and (force-)push the branch, invalidating review.
* It is odd to have a recent CI run, but it uses code and config from the past.
* Detecting silent merge conflicts by re-running the CI task is impossible.
Fix all issues by checking out the latest merged state of the pull request. The behavior is unchanged for non-pull-request actions. This patch changes the "re-run" default behaviour. Forcing it to use the new state instead of running the old state again.
ACKs for top commit:
janb84:
re ACK fa8f081af3
hebasto:
ACK fa8f081af3.
Tree-SHA512: c22c6f837402f61ec46be46817473e1946424b5312e36ed0e246cadb1ca89c04163bb471f71c309765a3d327f198a83cd83679d231f03828a99a97562a622fdd