anchor.diff:  === Custom Help Subcommands
   Custom help subcommands should mark themselves as a <<Help Subcommands,help command>> to tell picocli not to throw a `MissingParameterException` when required options are missing.
   
  -[source,java]
  +.Java / Kotlin
  +[source,java,role="primary"]
   ----
   @Command(helpCommand = true)
   ----
  
positive.code: 
  === Printing Help Automatically
  
  From picocli 2.0, the <<Executing Commands,convenience methods>> will automatically print usage help and version information
  when a help option was specified on the command line (options annotated with the `versionHelp` or `usageHelp` attribute - but not the `help` attribute).
  
  The same holds for the `mixinStandardHelpOptions` attribute, the built-in `HelpCommand` and any custom help subcommands marked as a <<Help Subcommands,help command>>.
  
negative.code: ----
  
  === Built-in Help Subcommand
  As of version 3.0, picocli provides a `help` subcommand (`picocli.CommandLine.HelpCommand`) that can be installed as a subcommand
  on any application command. It prints usage help for the parent command or sibling subcommands. For example:
  
  .Java
  [source,java,role="primary"]
  ----
  import picocli.CommandLine.HelpCommand;
  
  