anchor.diff:  
   Annotate a field or method with `@ArgGroup(validate = false)` to create a group for display purposes only. For example:
   
  -[source, java]
  +.Java
  +[source, java,role="primary"]
   ----
   @Command(name = "sectiondemo", description = "Section demo")
   public class OptionSectionDemo {
  
positive.code: }
  ----
  
  The above example defines a command with dependent options `-a`, `-b` and `-c` that must co-occur.
  
  The group itself has a `multiplicity` attribute that defines how many times the group may be specified within the command.
  
negative.code: Picocli will not be able to retrieve the default values that are defined by assigning a value in the declaration of an `@Option`-annotated field in a group. For example:
  
  .This does not work correctly: usage help shows `null` as the default value.
  
  .Java
  [source,java,role="primary"]
  ----
  class BadGroup {
      @Option(names = "-x", description = "Default: ${DEFAULT-VALUE}")
      int x = 123; // value not found until `BadGroup` is instantiated
  }
  
  @Command(name = "bad", description = "usage help shows the wrong default value")
  class BadExample {
      @ArgGroup BadGroup badGroup;
  