Function derivePrHeadRef

actions/setup/js/apply_samples.cjs:217–256

* Derive the pull request head ref for the triggering event. * * Resolution order: * 1. `pull_request.head.ref` from the event payload (pull_request and * pull_request_target events). * 2. PR API lookup using `issue.number` when the payload describes an * issue_comment on a pull

(entry)

 * @returns {Promise<string|null>}
 */
async function derivePrHeadRef(entry) {
  const payload = readEventPayload();

  // 1. pull_request* events expose the head ref directly.
  const directRef = payload?.pull_request?.head?.ref;
  if (typeof directRef === "string" && directRef.trim()) {
    return directRef.trim();
  }

  // Determine the target repo for any API lookups.
  // Resolution order:
  //   a. entry.arguments.repo — explicit per-sample override (cross-repo workflows).
  //   b. target-repo from the safe-outputs config file (GH_AW_SAFE_OUTPUTS_CONFIG_PATH)
  //      for the tool — covers siderepo workflow_dispatch where the sample arguments
  //      carry `pull_request_number` but not a `repo` override (issue #41292).
  //   c. GITHUB_REPOSITORY — host repo fallback.
  let repoSlug = "";
  if (typeof entry.arguments.repo === "string" && entry.arguments.repo.trim()) {
    repoSlug = entry.arguments.repo.trim();
  } else {
    repoSlug = readConfiguredTargetRepo(entry.tool) || process.env.GITHUB_REPOSITORY || "";
  }
  const [owner, repo] = repoSlug.split("/");
  if (!owner || !repo) return null;

  // 2. issue_comment / pull_request_review_comment with a PR-linked issue.
  if (payload?.issue?.pull_request && typeof payload.issue.number === "number") {
    const ref = await fetchPullRequestHeadRef({ owner, repo, pullNumber: payload.issue.number });
    if (ref) return ref;
  }

  // 3. Explicit pull_request_number on the sample arguments.
  const argNumber = Number(entry.arguments.pull_request_number);
  if (Number.isFinite(argNumber) && argNumber > 0) {
    const ref = await fetchPullRequestHeadRef({ owner, repo, pullNumber: argNumber });
    if (ref) return ref;
  }

  return null;
}

/**
 * Read the configured `target-repo` for a given safe-output tool from the