markCreated method
Records that the CLI created file from scratch, so cleanup can remove
it instead of restoring a backup.
Implementation
Future<void> markCreated(File file) async {
final relativePath = p.relative(file.path, from: projectDir);
final marker = File(p.join(_createdRoot.path, relativePath));
await marker.parent.create(recursive: true);
await marker.writeAsString('created=true');
}