anchor.diff:  /// Writes the mapping to a [StringSink].
   ///
   /// If [comment] is provided, the output will contain this comment
  -/// with `#` in front of each line.
  +/// with `# ` in front of each line.
  +/// Lines are defined as ending in line feed (`'\n'`). If the final
  +/// line of the comment doesn't end in a line feed, one will be added.
   ///
   /// If [baseUri] is provided, package locations will be made relative
   /// to the base URI, if possible, before writing.
  
positive.code:   }
  
    if (comment != null) {
      for (var commentLine in comment.split('\n')) {
        output.write('#');
        output.writeln(commentLine);
      }
    } else {
  
negative.code: }
  
  // TODO: inline to uri.normalizePath() when we move to 1.11
  Uri _normalizePath(Uri uri) => new Uri().resolveUri(uri);
  