Function fetchPullRequestHeadRef

actions/setup/js/apply_samples.cjs:176–201

* Fetch a pull request via the REST API and return its head ref. Uses the * per-repo token from GH_AW_REPO_TOKENS when present, falling back to * GITHUB_TOKEN; falls back to anonymous (works for public repositories) when * no token is available. Returns null on any failure so the caller can decid

({ owner, repo, pullNumber })

 * @returns {Promise<string|null>}
 */
async function fetchPullRequestHeadRef({ owner, repo, pullNumber }) {
  const apiUrl = process.env.GITHUB_API_URL || "https://api.github.com";
  const url = `${apiUrl}/repos/${owner}/${repo}/pulls/${pullNumber}`;
  /** @type {Record<string, string>} */
  const headers = {
    Accept: "application/vnd.github+json",
    "X-GitHub-Api-Version": "2022-11-28",
    "User-Agent": "gh-aw-apply-samples",
  };
  const token = selectTokenForRepo(owner, repo);
  if (token) headers["Authorization"] = `Bearer ${token}`;
  try {
    const resp = await fetch(url, { headers });
    if (!resp.ok) {
      core.warning(`apply_samples: GET ${url} returned HTTP ${resp.status}`);
      return null;
    }
    const body = await resp.json();
    // @ts-ignore - REST API response shape is well-defined; trust GitHub PR endpoint contract
    const ref = body && body.head && typeof body.head.ref === "string" ? body.head.ref : null;
    return ref || null;
  } catch (err) {
    core.warning(`apply_samples: failed to fetch PR ${owner}/${repo}#${pullNumber}: ${getErrorMessage(err)}`);
    return null;
  }
}

/**
 * Derive the pull request head ref for the triggering event.