final HashMap<NodeState, String> addedNodes = new HashMap<NodeState, String>();
final HashMap<NodeState, String> removedNodes = new HashMap<NodeState, String>();
if (before == null) {
if (after != null) {
buff.tag('+').key(path).object();
toJson(buff, after);
return buff.endObject().newline().toString();
} else {
throw new Exception("path doesn't exist in the specified revisions: " + path);
}