toYaml method
Returns the YAML-formatted source, using name as a key, for writing into
a pubspec 'dependencies' section.
Implementation
@override
String toYaml({required String name}) {
  var buffer = StringBuffer()
    ..writeln('  $name:')
    ..writeln('    git:')
    ..writeln('      url: $_url');
  if (_ref != null) {
    buffer.writeln('      ref: $_ref');
  }
  if (_path != null) {
    buffer.writeln('      path: $_path');
  }
  return buffer.toString();
}