anchor.diff:  ----
   
   For argument groups, use the `headingKey` to specify a resource bundle key. For example:
  -```java
  +[source,java]
  +----
   @ArgGroup(headingKey = "myBundleKey") MyArgGroup myGroup;
  -```
  +----
   The matching entry in the resource bundle could look like this:
   ----
   myBundleKey = The localized heading for this argument group%n
  
positive.code: 
  It is recommended that custom factories should fall back to the default factory. Something like this:
  
  ```java
  @Override
  public <K> K create(Class<K> clazz) throws Exception {
      try {
  
negative.code:         return CommandLine.defaultFactory().create(clazz); // fallback if missing
      }
  }
  ----
  
  
  === Automatic Parameter Indexes
  