Function mergePullRequest

src/utils/github.ts:516–569

(
  token: string,
  owner: string,
  repo: string,
  pullNumber: number,
  mergeMethod: MergeMethod = 'merge',
  maxRetries = 3
)

 * Merge a PR with retries.
 */
export async function mergePullRequest(
  token: string,
  owner: string,
  repo: string,
  pullNumber: number,
  mergeMethod: MergeMethod = 'merge',
  maxRetries = 3
): Promise<{ merged: boolean; sha?: string; message?: string }> {
  let lastError: Error | null = null;

  for (let attempt = 0; attempt < maxRetries; attempt++) {
    try {
      const res = await ghFetch(`/repos/${owner}/${repo}/pulls/${pullNumber}/merge`, token, {
        method: 'PUT',
        body: JSON.stringify({ merge_method: mergeMethod }),
        headers: { 'Content-Type': 'application/json' },
      });

      if (res.ok) {
        const data = await res.json();
        return { merged: true, sha: data.sha, message: data.message };
      }

      const err = await res.json().catch(() => ({ message: res.statusText }));

      if (res.status === 405) {
        if (attempt < maxRetries - 1) { await sleep(2000); continue; }
        throw new Error(`Cannot merge PR #${pullNumber}: ${err.message || 'Method not allowed. Check branch protection rules.'}`);
      }
      if (res.status === 409) {
        if (attempt < maxRetries - 1) { await sleep(1500); continue; }
        throw new Error(`Merge conflict on PR #${pullNumber}: ${err.message}`);
      }
      if (res.status === 403) {
        if (err.message?.includes('Resource not accessible'))
          throw new Error(`PERMISSION_DENIED: ${err.message}`);
        if (err.message?.includes('rate limit') || err.message?.includes('abuse'))
          throw new Error(`RATE_LIMITED: ${err.message}`);
        throw new Error(`Forbidden: ${err.message}`);
      }
      if (res.status === 401) {
        throw new Error(`PERMISSION_DENIED: Token expired or invalid (401 Unauthorized)`);
      }
      throw new Error(`Merge failed (HTTP ${res.status}): ${err.message || res.statusText}`);
    } catch (err) {
      lastError = err instanceof Error ? err : new Error(String(err));
      if (lastError.message.includes('PERMISSION_DENIED') || lastError.message.includes('RATE_LIMITED')) {
        throw lastError;
      }
      if (attempt < maxRetries - 1) { await sleep(1500); }
    }
  }
  throw lastError || new Error(`Failed to merge PR #${pullNumber} after ${maxRetries} attempts`);
}

/**
 * Delete a branch after merge (cleanup).