Function getOldFileContent

scripts/update/gitUtils.ts:126–163

(gitPath: string)

 * @returns A promise resolving to the raw string content, or an empty string on error.
 */
export async function getOldFileContent(gitPath: string): Promise<string> {
  const fromRef = process.env.GIT_FROM_REF || 'HEAD~1';
  return new Promise((resolve, reject) => {
    const gitShow = spawn('git', ['show', `${fromRef}:${gitPath}`]);
    let oldFileContent = '';
    let errorOutput = '';

    gitShow.stdout.on('data', (data: Buffer) => {
      oldFileContent += data.toString();
    });

    gitShow.stderr.on('data', (data: Buffer) => {
      errorOutput += data.toString();
    });

    gitShow.on('error', (err: Error) => {
      // Handle errors spawning the process itself
      console.error(`Error spawning git show for ${fromRef}:${gitPath}:`, err);
      resolve(''); // Resolve with empty string on spawn error
    });

    gitShow.on('close', (code: number | null) => {
      if (code === 0) {
        resolve(oldFileContent);
      } else {
        // Handle errors reported by git show (like file not found)
        if (errorOutput.includes('exists on disk, but not in')) {
          console.warn(`Previous version not found in git history (${fromRef}:${gitPath}).`);
        } else {
          console.error(
            `Error running git show for ${fromRef}:${gitPath} (code ${code}): ${errorOutput}`
          );
        }
        resolve(''); // Resolve with empty string if git show fails
      }
    });
  });
}