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Skip merge queue for GHA CI (#4687)
* Move .buildkite/pipeline.yml to full_pipeline.yml * Add dispatch pipeline.yml and merge-queue skip scripts * Skip merge queue for GHA CI
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‎.github/should_skip_merge_queue.sh‎

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#!/bin/bash
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# GitHub Actions merge-queue fast path. Companion to
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# .buildkite/should_skip_merge_queue.sh, applying the same reasoning to the
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# GitHub-hosted checks: the unit-test matrix (.github/workflows/ci.yml) and the
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# doc build (.github/workflows/docs.yml).
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#
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# Exit 0 => the merge group is provably identical to an already-green PR head,
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# so this workflow's real jobs can be skipped and a trivial gate job
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# reports the required check green.
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# Exit non-zero => run the real jobs.
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#
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# Usage: should_skip_merge_queue.sh <check-name-prefix>
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# <check-name-prefix> selects which of the PR's checks must already be green
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# for this workflow, e.g. "ci " for the ci matrix or "docbuild" for the docs.
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#
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# All of the following must hold to skip. ANY uncertainty (not a merge-queue
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# build, unparseable ref, failed fetch/API call, missing or non-green check)
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# exits non-zero and runs the full jobs, so a wrong guess can never merge
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# untested code:
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#
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# 1. This is a GitHub merge-queue build: GITHUB_EVENT_NAME == "merge_group"
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# and the head ref has the form
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# gh-readonly-queue/main/pr-<pr_number>-<base_sha>
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#
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# 2. <base_sha> (from the merge_group payload) is a real commit on `main`
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# (git merge-base --is-ancestor), i.e. the merge group stacks exactly one
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# PR on `main`. Groups combining multiple PRs stack on a synthetic
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# gh-readonly-queue commit that never reaches `main` and fail this check.
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# (Same argument as the Buildkite script; see its header for detail.)
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#
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# 3. The merge group's tree equals the PR head's tree, i.e. the merged code is
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# byte-identical to what the PR already tested. This is the "up to date
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# with origin/main" condition: it holds only when `main` has not advanced
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# past what the PR contains. Compares tree content, so it holds for the
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# squash, rebase, and merge-commit queue methods alike.
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#
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# 4. Every one of the PR's own checks whose name starts with <prefix> already
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# concluded successfully (queried with `gh pr checks`, which reports the
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# checks GitHub shows for the PR head and is agnostic to how Actions
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# associates runs). This is the GitHub analogue of the Buildkite
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# "staged bundle exists" condition: it confirms the PR build actually ran
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# these checks to green on the identical code.
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set -euo pipefail
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prefix="${1:?usage: should_skip_merge_queue.sh <check-name-prefix>}"
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# (1) merge-queue build + parse the PR number from the head ref.
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[[ "${GITHUB_EVENT_NAME:-}" == "merge_group" ]] || exit 1
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head_ref="${MERGE_GROUP_HEAD_REF:-}"
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base_sha="${MERGE_GROUP_BASE_SHA:-}"
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[[ "$head_ref" =~ pr-([0-9]+)-[0-9a-fA-F]+$ ]] || exit 1
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pr_number="${BASH_REMATCH[1]}"
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[[ -n "$base_sha" ]] || exit 1
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# (2) <base_sha> must be a real commit on `main` (single-PR delta).
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git fetch -q origin main || exit 1
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git merge-base --is-ancestor "$base_sha" FETCH_HEAD || exit 1
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# (3) merge-group tree must equal the PR head tree (up to date, nothing new to
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# test). HEAD is the merge-group commit checked out by actions/checkout.
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git fetch -q origin "refs/pull/${pr_number}/head" || exit 1
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pr_head="$(git rev-parse FETCH_HEAD)" || exit 1
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git diff --quiet "$pr_head" HEAD || exit 1
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# (4) every matching check on the PR already concluded success. `gh pr checks`
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# exits non-zero when checks are pending/failing, so read the JSON (still
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# emitted) and evaluate it ourselves; require >=1 match, all buckets "pass".
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checks="$(gh pr checks "$pr_number" --repo "$GITHUB_REPOSITORY" \
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--json name,bucket 2>/dev/null || true)"
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[[ -n "$checks" ]] || exit 1
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echo "$checks" | jq -e --arg p "$prefix" \
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'[.[] | select(.name | startswith($p))] as $m
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| ($m | length) > 0 and ($m | all(.bucket == "pass"))' >/dev/null || exit 1
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exit 0

‎.github/workflows/ci.yml‎

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contents: read
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jobs:
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# Merge-queue fast path: decide whether the matrix below can be reused from an
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# already-green PR head (see .github/should_skip_merge_queue.sh). Always runs;
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# only ever returns skip=true for a merge_group build that is provably
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# identical to a PR whose "ci " checks already passed.
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decide:
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name: decide
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runs-on: ubuntu-latest
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permissions:
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contents: read
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checks: read
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pull-requests: read
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statuses: read
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outputs:
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skip: ${{ steps.decide.outputs.skip }}
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steps:
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- uses: actions/checkout@v7
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with:
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fetch-depth: 0
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- id: decide
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env:
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GH_TOKEN: ${{ github.token }}
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MERGE_GROUP_HEAD_REF: ${{ github.event.merge_group.head_ref }}
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MERGE_GROUP_BASE_SHA: ${{ github.event.merge_group.base_sha }}
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run: |
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if .github/should_skip_merge_queue.sh "ci "; then
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echo "Merge-queue CI skipped: reusing this PR's green checks."
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echo "skip=true" >> "$GITHUB_OUTPUT"
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else
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echo "skip=false" >> "$GITHUB_OUTPUT"
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fi
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test:
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name: ci ${{ matrix.version }} - ${{ matrix.os }} - ${{ matrix.test_group }}
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needs: decide
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if: needs.decide.outputs.skip != 'true'
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runs-on: ${{ matrix.os }}
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timeout-minutes: 60
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with:
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file: lcov.info
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token: ${{secrets.CODECOV_TOKEN}}
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# Single required status check for branch protection / the merge queue. Set
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# THIS ("ci-required") as the required check instead of the individual matrix
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# jobs, so a reused merge-queue build (matrix skipped) still reports green.
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ci-required:
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name: ci-required
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needs: [decide, test]
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if: always()
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runs-on: ubuntu-latest
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steps:
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- run: |
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if [[ "${{ needs.decide.result }}" != "success" ]]; then
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echo "decide job did not succeed"; exit 1
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fi
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if [[ "${{ needs.test.result }}" == "success" ]]; then
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echo "ci matrix passed"; exit 0
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fi
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if [[ "${{ needs.test.result }}" == "skipped" && \
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"${{ needs.decide.outputs.skip }}" == "true" ]]; then
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echo "ci matrix reused from an already-green PR head"; exit 0
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fi
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echo "ci matrix did not pass (result=${{ needs.test.result }})"
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exit 1

‎.github/workflows/docs.yml‎

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cancel-in-progress: true
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jobs:
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# Merge-queue fast path: reuse the doc build from an already-green PR head
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# when the merge group is byte-identical to it (see
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# .github/should_skip_merge_queue.sh).
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decide:
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name: decide
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runs-on: ubuntu-latest
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permissions:
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contents: read
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checks: read
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pull-requests: read
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statuses: read
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outputs:
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skip: ${{ steps.decide.outputs.skip }}
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steps:
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- uses: actions/checkout@v7
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with:
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fetch-depth: 0
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- id: decide
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env:
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GH_TOKEN: ${{ github.token }}
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MERGE_GROUP_HEAD_REF: ${{ github.event.merge_group.head_ref }}
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MERGE_GROUP_BASE_SHA: ${{ github.event.merge_group.base_sha }}
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run: |
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if .github/should_skip_merge_queue.sh "docbuild"; then
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echo "Merge-queue doc build skipped: reusing this PR's green check."
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echo "skip=true" >> "$GITHUB_OUTPUT"
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else
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echo "skip=false" >> "$GITHUB_OUTPUT"
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fi
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docbuild:
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needs: decide
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if: needs.decide.outputs.skip != 'true'
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runs-on: ubuntu-latest
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timeout-minutes: 30
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steps:
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} else {
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await github.rest.issues.createComment({ owner, repo, issue_number: pr, body });
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}
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# Single required status check for the doc build. Set THIS ("docs-required")
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# as the required check instead of "docbuild", so a reused merge-queue build
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# (docbuild skipped) still reports green.
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docs-required:
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name: docs-required
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needs: [decide, docbuild]
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if: always()
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runs-on: ubuntu-latest
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steps:
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- run: |
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if [[ "${{ needs.decide.result }}" != "success" ]]; then
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echo "decide job did not succeed"; exit 1
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fi
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if [[ "${{ needs.docbuild.result }}" == "success" ]]; then
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echo "doc build passed"; exit 0
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fi
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if [[ "${{ needs.docbuild.result }}" == "skipped" && \
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"${{ needs.decide.outputs.skip }}" == "true" ]]; then
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echo "doc build reused from an already-green PR head"; exit 0
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fi
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echo "doc build did not pass (result=${{ needs.docbuild.result }})"
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exit 1

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