1  /**
 2   * Build a base URL for linking to files on GitHub at a specific commit.
 3   * Returns null when headSha is missing (e.g. loaded reviews without SHA).
 4   */
 5  export function buildFileUrlBase(prUrl: string, headSha?: string): string | null {
 6    if (!headSha) return null;
 7    const match = prUrl.match(/^(https:\/\/github\.com\/[^/]+\/[^/]+)\//);
 8    if (!match) return null;
 9    return `${match[1]}/blob/${headSha}/`;
10  }