Function updateChangelog

scripts/changes/version.ts:204–242

* Updates CHANGELOG.md with new content

(packageDirName: string, newContent: string)

 * Updates CHANGELOG.md with new content
 */
function updateChangelog(packageDirName: string, newContent: string) {
  let changelogPath =
    packageDirName === "/"
      ? path.join(getRootDir(), "CHANGELOG.md")
      : getPackageFile(packageDirName, "CHANGELOG.md");

  if (preview) {
    console.log(
      `  • Would update ${path.relative(process.cwd(), changelogPath)}:\n`,
    );
    console.log(
      newContent
        .split("\n")
        .map((line) => `    ${line}`)
        .join("\n"),
    );
    return;
  }

  let existingChangelog = readFile(changelogPath);

  let lines = existingChangelog.split("\n");

  // Find the first ## version entry
  let firstVersionIndex = lines.findIndex((line) => line.startsWith("## "));

  let updatedChangelog: string;
  if (firstVersionIndex !== -1) {
    // Insert before the first version entry
    lines.splice(firstVersionIndex, 0, newContent);
    updatedChangelog = lines.join("\n");
  } else {
    // No version entries yet - append to the end
    updatedChangelog = existingChangelog.trimEnd() + "\n\n" + newContent + "\n";
  }

  writeFile(changelogPath, updatedChangelog);
  console.log(`  ✓ Updated CHANGELOG.md`);
}

/**
 * Deletes all change files (except README.md)