mirror of
https://github.com/NixOS/nixpkgs.git
synced 2025-11-10 01:33:11 +01:00
87d9b08ffb
When a contributor mistakenly sets the wrong target branch for a Pull Request, this can lead to bad consequences for CI. Most prominent is the mass ping of codeowners, that is already handled in `ci/request-reviews/verify-base-branch.sh`. But there are other things that go wrong: - After eval, a mass ping of maintainers would still be possible, in theory. Practically, this doesn't happen, because we have a limit of 10 reviewer requests at the same time. - This will most often contain a change to `ci/pinned.json`, thus the full Eval matrix of all Lix/Nix versions will be run, burning a lot of resources. - The PR will be labelled with almost all labels that are available. We can improve on the current situation with some API calls to determine the "best" merge-base for the current PR. We then consider this as the "real base". If the current target is not the real base, we fail the prepare step, which is early enough to prevent all other CI from running.
231 lines
9.3 KiB
JavaScript
231 lines
9.3 KiB
JavaScript
const { classify } = require('../supportedBranches.js')
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const { postReview } = require('./reviews.js')
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module.exports = async ({ github, context, core, dry }) => {
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const pull_number = context.payload.pull_request.number
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for (const retryInterval of [5, 10, 20, 40, 80]) {
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core.info('Checking whether the pull request can be merged...')
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const prInfo = (
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await github.rest.pulls.get({
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...context.repo,
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pull_number,
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})
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).data
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if (prInfo.state !== 'open') throw new Error('PR is not open anymore.')
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if (prInfo.mergeable == null) {
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core.info(
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`GitHub is still computing whether this PR can be merged, waiting ${retryInterval} seconds before trying again...`,
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)
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await new Promise((resolve) => setTimeout(resolve, retryInterval * 1000))
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continue
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}
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const { base, head } = prInfo
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const baseClassification = classify(base.ref)
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core.setOutput('base', baseClassification)
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console.log('base classification:', baseClassification)
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const headClassification =
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base.repo.full_name === head.repo.full_name
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? classify(head.ref)
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: // PRs from forks are always considered WIP.
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{ type: ['wip'] }
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core.setOutput('head', headClassification)
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console.log('head classification:', headClassification)
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if (baseClassification.type.includes('channel')) {
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const { stable, version } = baseClassification
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const correctBranch = stable ? `release-${version}` : 'master'
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const body = [
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'The `nixos-*` and `nixpkgs-*` branches are pushed to by the channel release script and should not be merged into directly.',
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'',
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`Please target \`${correctBranch}\` instead.`,
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].join('\n')
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await postReview({ github, context, core, dry, body })
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throw new Error('The PR targets a channel branch.')
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}
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if (headClassification.type.includes('wip')) {
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// In the following, we look at the git history to determine the base branch that
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// this Pull Request branched off of. This is *supposed* to be the branch that it
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// merges into, but humans make mistakes. Once that happens we want to error out as
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// early as possible.
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// To determine the "real base", we are looking at the merge-base of primary development
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// branches and the head of the PR. The merge-base which results in the least number of
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// commits between that base and head is the real base. We can query for this via GitHub's
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// REST API. There can be multiple candidates for the real base with the same number of
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// commits. In this case we pick the "best" candidate by a fixed ordering of branches,
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// as defined in ci/supportedBranches.js.
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//
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// These requests take a while, when comparing against the wrong release - they need
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// to look at way more than 10k commits in that case. Thus, we try to minimize the
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// number of requests across releases:
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// - First, we look at the primary development branches only: master and release-xx.yy.
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// The branch with the fewest commits gives us the release this PR belongs to.
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// - We then compare this number against the relevant staging branches for this release
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// to find the exact branch that this belongs to.
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// All potential development branches
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const branches = (
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await github.paginate(github.rest.repos.listBranches, {
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...context.repo,
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per_page: 100,
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})
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).map(({ name }) => classify(name))
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// All stable primary development branches from latest to oldest.
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const releases = branches
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.filter(({ stable, type }) => type.includes('primary') && stable)
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.sort((a, b) => b.version.localeCompare(a.version))
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async function mergeBase({ branch, order, version }) {
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const { data } = await github.rest.repos.compareCommitsWithBasehead({
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...context.repo,
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basehead: `${branch}...${head.sha}`,
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// Pagination for this endpoint is about the commits listed, which we don't care about.
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per_page: 1,
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// Taking the second page skips the list of files of this changeset.
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page: 2,
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})
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return {
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branch,
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order,
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version,
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commits: data.total_commits,
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sha: data.merge_base_commit.sha,
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}
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}
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// Multiple branches can be OK at the same time, if the PR was created of a merge-base,
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// thus storing as array.
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let candidates = [await mergeBase(classify('master'))]
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for (const release of releases) {
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const nextCandidate = await mergeBase(release)
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if (candidates[0].commits === nextCandidate.commits)
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candidates.push(nextCandidate)
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if (candidates[0].commits > nextCandidate.commits)
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candidates = [nextCandidate]
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// The number 10000 is principally arbitrary, but the GitHub API returns this value
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// when the number of commits exceeds it in reality. The difference between two stable releases
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// is certainly more than 10k commits, thus this works for us as well: If we're targeting
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// a wrong release, the number *will* be 10000.
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if (candidates[0].commits < 10000) break
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}
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core.info(`This PR is for NixOS ${candidates[0].version}.`)
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// Secondary development branches for the selected version only.
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const secondary = branches.filter(
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({ branch, type, version }) =>
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type.includes('secondary') && version === candidates[0].version,
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)
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// Make sure that we always check the current target as well, even if its a WIP branch.
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// If it's not a WIP branch, it was already included in either releases or secondary.
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if (classify(base.ref).type.includes('wip')) {
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secondary.push(classify(base.ref))
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}
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for (const branch of secondary) {
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const nextCandidate = await mergeBase(branch)
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if (candidates[0].commits === nextCandidate.commits)
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candidates.push(nextCandidate)
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if (candidates[0].commits > nextCandidate.commits)
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candidates = [nextCandidate]
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}
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// If the current branch is among the candidates, this is always better than any other,
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// thus sorting at -1.
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candidates = candidates
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.map((candidate) =>
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candidate.branch === base.ref
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? { ...candidate, order: -1 }
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: candidate,
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)
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.sort((a, b) => a.order - b.order)
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const best = candidates.at(0)
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core.info('The base branches for this PR are:')
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core.info(`github: ${base.ref}`)
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core.info(
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`candidates: ${candidates.map(({ branch }) => branch).join(',')}`,
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)
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core.info(`best candidate: ${best.branch}`)
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if (best.branch !== base.ref) {
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const current = await mergeBase(classify(base.ref))
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const body = [
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`The PR's base branch is set to \`${current.branch}\`, but ${current.commits === 10000 ? 'at least 10000' : current.commits - best.commits} commits from the \`${best.branch}\` branch are included. Make sure you know the [right base branch for your changes](https://github.com/NixOS/nixpkgs/blob/master/CONTRIBUTING.md#branch-conventions), then:`,
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`- If the changes should go to the \`${best.branch}\` branch, [change the base branch](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/changing-the-base-branch-of-a-pull-request).`,
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`- If the changes should go to the \`${current.branch}\` branch, rebase your PR onto the correct merge-base:`,
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' ```bash',
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` # git rebase --onto $(git merge-base upstream/${current.branch} HEAD) $(git merge-base upstream/${best.branch} HEAD)`,
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` git rebase --onto ${current.sha} ${best.sha}`,
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` git push --force-with-lease`,
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' ```',
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].join('\n')
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await postReview({ github, context, core, dry, body })
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throw new Error(`The PR contains commits from a different base.`)
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}
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}
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let mergedSha, targetSha
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if (prInfo.mergeable) {
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core.info('The PR can be merged.')
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mergedSha = prInfo.merge_commit_sha
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targetSha = (
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await github.rest.repos.getCommit({
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...context.repo,
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ref: prInfo.merge_commit_sha,
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})
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).data.parents[0].sha
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} else {
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core.warning('The PR has a merge conflict.')
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mergedSha = head.sha
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targetSha = (
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await github.rest.repos.compareCommitsWithBasehead({
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...context.repo,
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basehead: `${base.sha}...${head.sha}`,
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})
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).data.merge_base_commit.sha
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}
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core.info(
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`Checking the commits:\nmerged: ${mergedSha}\ntarget: ${targetSha}`,
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)
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core.setOutput('mergedSha', mergedSha)
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core.setOutput('targetSha', targetSha)
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core.setOutput('systems', require('../supportedSystems.json'))
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const files = (
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await github.paginate(github.rest.pulls.listFiles, {
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...context.repo,
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pull_number: context.payload.pull_request.number,
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per_page: 100,
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})
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).map((file) => file.filename)
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if (files.includes('ci/pinned.json')) core.setOutput('touched', ['pinned'])
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else core.setOutput('touched', [])
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return
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}
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throw new Error(
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"Not retrying anymore. It's likely that GitHub is having internal issues: check https://www.githubstatus.com.",
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)
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}
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