add-trailer.yml

# SPDX-License-Identifier: BSD-3-Clause
# Copyright (c) 2025 Robin Jarry
---
name: Add Trailer

on:
  issue_comment:
    types: [created]
  workflow_run:
    workflows: ["Review"]
    types: [completed]

permissions:
  contents: read
  pull-requests: read
  actions: read

jobs:
  add-trailer:
    if: >-
      ${{ (github.event_name == 'issue_comment' && github.event.issue.pull_request
          && (contains(github.event.comment.body, 'Acked-by:') || contains(github.event.comment.body, 'Tested-by:')))
      || (github.event_name == 'workflow_run' && github.event.workflow_run.conclusion == 'success') }}
    runs-on: ubuntu-latest
    steps:
      - name: Get PR info and trailer
        id: info
        uses: actions/github-script@v7
        with:
          github-token: ${{ secrets.TRAILER_BOT_TOKEN }}
          script: |
            let pr, trailer;

            if (context.eventName === 'issue_comment') {
              const body = context.payload.comment.body;
              const regexp = /(acked|tested)-by:\s+(\w[^<]+\w)(?:\s+<([a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,})>)?/i;
              const match = body.match(regexp);
              if (!match) {
                throw new Error(`No valid trailer found in comment: ${body}`)
              }

              const { data: prData } = await github.rest.pulls.get({
                owner: context.repo.owner,
                repo: context.repo.repo,
                pull_number: context.payload.issue.number
              });

              pr = prData;
              trailer = `${match[1]}-by: ${match[2]} <${match[3] || 'UNKNOWN_EMAIL'}>`;

            } else if (context.eventName === 'workflow_run') {
              const headBranch = context.payload.workflow_run.head_branch;

              const { data: allPRs } = await github.rest.pulls.list({
                owner: context.repo.owner,
                repo: context.repo.repo,
                state: 'open',
              });

              const matchingPRs = allPRs.filter(p => p.head.ref === headBranch);

              if (matchingPRs.length === 0) {
                throw new Error(`No open PR found for ${headBranch}`)
              }
              const { data: prData } = await github.rest.pulls.get({
                owner: context.repo.owner,
                repo: context.repo.repo,
                pull_number: matchingPRs[0].number
              });
              pr = prData;

              const actor = context.payload.workflow_run.triggering_actor.login;
              const { data: user } = await github.rest.users.getByUsername({
                username: actor
              });

              if (!user.name) {
                throw new Error(`User ${actor} does not expose their full name`);
              }

              trailer = `Reviewed-by: ${user.name} <${user.email || 'UNKNOWN_EMAIL'}>`;
            }

            return {
              commits: pr.commits,
              head_repo: pr.head.repo.full_name,
              head_ref: pr.head.ref,
              trailer: trailer,
            };

      - uses: actions/checkout@v4
        with:
          token: ${{ secrets.TRAILER_BOT_TOKEN }}
          repository: ${{ fromJSON(steps.info.outputs.result).head_repo }}
          ref: ${{ fromJSON(steps.info.outputs.result).head_ref }}
          fetch-depth: 0
          persist-credentials: true

      - name: Amend all pull request commits with the trailer
        env:
          GIT_TRAILER_DEBUG: 1
          COMMITS: ${{ fromJSON(steps.info.outputs.result).commits }}
          HEAD_REF: ${{ fromJSON(steps.info.outputs.result).head_ref }}
          TRAILER: ${{ fromJSON(steps.info.outputs.result).trailer }}
        run: |
          set -xe

          if echo "$TRAILER" | grep -qw 'UNKNOWN_EMAIL'; then
            NAME=$(echo "$TRAILER" | sed -En 's/.+-by:[[:blank:]]+([^<]+)[[:blank:]]<.+/\1/p')
            EMAIL=$(git log --pretty=%aE --author="$NAME" | head -n1)

            if [ -z "$EMAIL" ]; then
              EMAIL=$(git shortlog -se -w0 --group=author --group=committer \
                --group=trailer:acked-by --group=trailer:reviewed-by \
                --group=trailer:reported-by --group=trailer:signed-off-by \
                --group=trailer:tested-by HEAD | \
                sed -En "s/^[[:space:]]+[0-9]+[[:space:]]+$NAME <([^@]+@[^>]+)>$/\\1/p" | head -n1)
            fi

            if [ -z "$EMAIL" ]; then
              echo "Error: Could not find email for $NAME"
              exit 1
            fi

            TRAILER=$(echo "$TRAILER" | sed "s/\\<UNKNOWN_EMAIL\\>/$EMAIL/")
          fi

          GIT_COMMITTER_NAME=$(git log -1 --pretty=%cN)
          GIT_COMMITTER_EMAIL=$(git log -1 --pretty=%cE)
          git config set user.name "$GIT_COMMITTER_NAME"
          git config set user.email "$GIT_COMMITTER_EMAIL"
          export GIT_COMMITTER_NAME GIT_COMMITTER_EMAIL

          rm -f .git/hooks/commit-msg
          ln -s ../../devtools/commit-msg .git/hooks/commit-msg

          git rebase "HEAD~$COMMITS" \
            --exec "git commit -C HEAD --no-edit --amend --trailer='$TRAILER'"

          git push --force origin "$HEAD_REF"