sync-devel.yaml

# Keeps the long-lived devel branches at master plus their own work.
#
# A push to master merges into each devel branch and pushes the result. On a
# conflict the branch is left untouched and an issue names it and the files,
# because a merge that needs judgement is not one a job should force.
name: sync-devel

on:
  push:
    branches: [master]
  workflow_dispatch:

permissions:
  contents: write
  issues: write

jobs:
  merge:
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false
      matrix:
        branch: [devel-EM, devel-bayes]

    steps:
      # GITHUB_TOKEN, not DMODVERSE_PAT: the PAT grants Contents:read only, so a
      # push with it is refused. A GITHUB_TOKEN push triggers no further workflow.
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Merge master into ${{ matrix.branch }}
        id: merge
        run: |
          set +e
          git config user.name  "github-actions[bot]"
          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
          git checkout "${{ matrix.branch }}" || { echo "missing=1" >> "$GITHUB_OUTPUT"; exit 0; }

          if git merge-base --is-ancestor master HEAD; then
            echo "Already contains master."
            exit 0
          fi

          git merge --no-edit master
          if [ $? -ne 0 ]; then
            {
              echo "conflicts<<EOT"
              git diff --name-only --diff-filter=U
              echo "EOT"
            } >> "$GITHUB_OUTPUT"
            git merge --abort
            exit 0
          fi
          git push origin "${{ matrix.branch }}"

      - name: Report a conflict
        if: steps.merge.outputs.conflicts != ''
        uses: actions/github-script@v7
        with:
          script: |
            const branch = '${{ matrix.branch }}';
            const files = `${{ steps.merge.outputs.conflicts }}`.trim();
            const title = `sync-devel: ${branch} needs a manual merge`;
            const body = [
              `\`git merge master\` into \`${branch}\` stopped on conflicts, so the branch is unchanged.`,
              '',
              'Conflicting paths:',
              '```', files, '```',
              '',
              'Generated files (`man/`, `NAMESPACE`, `RcppExports`, `README.md`) are resolved by',
              'regenerating after the merge, not by hand. Watch for changes that conflict without',
              'a marker: a deletion on master the branch still calls, or a signature the branch',
              'still passes the old arguments to.',
            ].join('\n');
            const open = await github.rest.issues.listForRepo({
              owner: context.repo.owner, repo: context.repo.repo,
              state: 'open', labels: 'sync-devel',
            });
            const hit = open.data.find(i => i.title === title);
            if (hit) {
              await github.rest.issues.createComment({
                owner: context.repo.owner, repo: context.repo.repo,
                issue_number: hit.number, body,
              });
            } else {
              await github.rest.issues.create({
                owner: context.repo.owner, repo: context.repo.repo,
                title, body, labels: ['sync-devel'],
              });
            }