This is the very first step to extending the commits job to do more than
just cherry-picks in the future: It could check reverts or merge
commits, but also the commit message format and more.
Of course, cherry-picks are still just checked on the stable branches as
before. For now, this allows us to run the part that dismisses automated
reviews automatically. This helps us when we do branch related checks in
the prepare step, which would also create such a review. To avoid
cluttering multiple reviews across a PR, we'll want all of these reviews
to be handled by the same code, thus this change.
This workflow runs the PR and Push workflow files on a `pull_request`
trigger. The intent is to test changes to the workflow files
immediately. Previously, these were run directly from the respective
workflow files.
The new approach allows us to move the logic to run this only when
workflow files changed from the pull_request trigger into a job. This
has the advantage that older jobs are cleaned up, when the PR changes
from a state of "workflow files changed" to "no workflow files changed".
This can happen when changing a PR's base from staging to master, in
which case changes from master would temporarily appear in the PR as
changes. When these include changes to workflow files, this would
trigger the PR workflow via `pull_request`. Once the base is changed,
the PR is closed and re-opened, so CI runs again - but since it's on the
same commit and the new run doesn't trigger `pull_request`, the results
of the previous run are still kept and displayed. These results may
include cancelled or failed jobs, which are impossible to recover from
without another force-push.
Checking this condition at run-time is only possible, because we move it
into a separate workflow, turning the `pr.yml` workflow into a re-usable
workflow. This will make sure to skip the whole workflow at once, when
no change was detected, which will prevent the "no PR failures" job from
appearing as skipped - which would imply "success" and make the PR
mergeable immediately. Instead the "no PR failures" job is not shown at
all for this trigger, which is generally what we want.
Do the same for `push.yml` for consistency.
This needs the multiline flags, which enables `^` and `$` to match line
start and line end, not start and end of the whole string.
Not sure how this got past testing when initially merged.
This change allows giving a reason via footer of the commit message for
why this commit is not cherry-picked. This avoids having to "explain"
the automated review comment afterwards - instead, this explanation can
be given immediately when writing that commit.
For example, for an update of `xen` on the stable branch, this could be:
```
xen: 4.19.3-unstable-2025-07-09 -> 4.19.3
[... commit message ...]
Not-cherry-picked-because: unstable is on a different minor version
```
This would then be shown as part of the automated review. The severity
of this will be downgraded from "warning" to "important". We still treat
the review as "changes requested", because it would be very complicated
and noisy to handle two different categories of reviews, some with
requested changes and some with comments only.
An alternative would be to not show this review at all. However, given
that the reviewers expectation on backports should already be "if it's
not a clean backport, the automated review will tell me what to look
at", it seems better to show these and have the committer confirm by
dismissing the review. Otherwise we risk merging actually unreviewed
commits.
The filtered checkout we used before was a nice idea, but only worked
for small numbers of commits in a PR. It would fetch the whole history
initially, but only fetch objects on demand. This turns out to be much
too slow in a PR with 18 commits, regularly hitting the 10 minute
timeout, even when running it locally.
The new approach uses regular checkouts again. In contrast to the old
style, before we switched to the filtered checkout, this only fetches
exactly the commits we need - and all of them at once. This is
significantly faster than both other approaches, and scales much better.
A bigger number of commits doesn't have much of an effect, if any at
all.
This broke when we moved the check-cherry-picks workflow into the bigger
PR workflow. At this time, the "workflow run" became the whole PR
workflow, which includes many more than just 1 job, thus the assumption
in `jobs[0]` doesn't hold anymore.
Most of the checks we do for cherry-picks are dismissable warnings, with
one exception: When a commit hash has been found, but this hash is not
available in any of the pickable branches, we raise this with
severity=error. This should also *block* the merge and not be
dismissable. That's because this is a fixable issue in every case.
Previously, when the diff contained a context line with ```, this would
end the code block and entirely break the markdown rendering.
Now we use the html code blocks provided by `core.summary` and properly
escape the content, so that it never escapes via html tags.
This reduces noise that the cherry-pick reviews produce when formatting
related conflicts had to be resolved. We only do this in the
length-limited review comment, though. All changes, including
whitespace, can still be double-checked in the job log if needed.
This turns the check-cherry-pick script into a github-script based
JavaScript program. This makes it much easier to extend to check reverts
or merge commits later on.
