anchor.diff:  ----
   
   === Mixins
  -Picocli 3.0 introduced the concept of "mixins". Mixins are a convenient alternative to subclassing:
  -picocli annotations from _any_ class can be added to ("mixed in" with) another command.
  +Picocli 3.0 introduced the concept of "mixins".
  +Mixins allow reuse without subclassing:
  +picocli annotations from _any_ class can be added to ("mixed in" with) a command.
   Picocli's <<Mixin Standard Help Options,mixinStandardHelpOptions>> internally uses a mixin.
   
   A mixin is a separate class with options, positional parameters, subcommands and command attributes that you want to reuse in one or more other commands.
   A command receiving these mixed in options, positional parameters, and command attributes is called a "mixee".
   
   Mixins can be installed declaratively with a `@Mixin`-annotated field (or a `@Mixin`-annotated method parameter for command methods).
  -Mixins can be installed programmatically by calling the `CommandLine.addMixin` method with an instance of the mixin class.
  +Alternatively, mixins can be installed programmatically by calling the `CommandLine.addMixin` method with an instance of the mixin class.
   
   The examples below again use the sample `ReusableOptions` class as the mixin:
   
  
positive.code: 
  == Reuse
  You may find yourself defining the same options, parameters or command attributes in many command line applications.
  To reduce duplication, picocli supports both subclassing and mixins as ways to reuse such options and attributes.
  
  === Subclassing
  One way to reuse the above option and attributes is to extend the class.
  Picocli will walk the class hierarchy to check for annotations, so `@Options`, `@Parameters` and `@Command` attributes declared on a superclass are available in all subclasses.
  
  Below is an example class, `ReusableOptions`, that defines some usage help attributes and a `--verbose` option that we want to reuse.
  
negative.code:     private ReusableOptions myMixin;
  
      @Command
      void subcmd(@Mixin ReusableOptions opts) {
          // ...
      }
  }
  