[https://github.com/remkop/picocli/issues/1696] Fix asciidoc output for nested ArgGroups

[rsenden]

As described in #1696, this fix utilizes the ArgGroupSpec#allOptionsNested() and ArgGroupSpec#allPositionalParametersNested() to list options under the proper group in the asciidoc output.

Note that this fix may cause an option to be shown multiple times in the output when nesting multiple ArgGroups with headings. For example, if an ArgGroup with heading Top contains another ArgGroup with heading Nested, then any options defined in the Nested group will be listed under both Top and Nested groups in the asciidoc output. Not sure whether this is a valid/common use case though, and functionally both ArgGroups contain that option (directly or indirectly), so it's not even really wrong.

For reference, following is a sample command class and corresponding asciidoc output when using this fix.

Test class:

import picocli.CommandLine.ArgGroup;
import picocli.CommandLine.Command;
import picocli.CommandLine.Option;
import picocli.CommandLine.Parameters;
import picocli.CommandLine.Help.Visibility;

@Command(name="test")
public class TestCommand {
	@Option(names={"option0"}, required = false, defaultValue = "option0", showDefaultValue = Visibility.ALWAYS) 
	private String option1;
	@Parameters(index="0") 
	private String param0;
	@ArgGroup(exclusive = false, multiplicity = "1", heading = "Top")
	private ArgGroup1 argGroup1;
	 
	
	static class ArgGroup1 {
		@Option(names={"option1"}, required = false, defaultValue = "option1", showDefaultValue = Visibility.ALWAYS) 
		private String option1;
		@Parameters(index="1") 
		private String param1;
		@ArgGroup(exclusive = false, multiplicity = "1", heading = "Nested")
		private ArgGroup2 argGroup2;
		@ArgGroup(exclusive = false, multiplicity = "1")
		private ArgGroup3 argGroup3;
	}
	
	public static class ArgGroup2 {
		@Option(names={"option2"}, required = false, defaultValue = "option2", showDefaultValue = Visibility.ALWAYS) 
		private String option2;
		@Parameters(index="2") 
		private String param2;
	}
	
	public static class ArgGroup3 {
		@Option(names={"option3"}, required = false, defaultValue = "option3", showDefaultValue = Visibility.ALWAYS) 
		private String option3;
		@Parameters(index="3") 
		private String param3;
	}
}

Asciidoc output:

// tag::picocli-generated-full-manpage[]
// tag::picocli-generated-man-section-header[]
:doctype: manpage
:revnumber: 
:manmanual: Test Manual
:mansource: 
:man-linkstyle: pass:[blue R < >]
= test(1)

// end::picocli-generated-man-section-header[]

// tag::picocli-generated-man-section-name[]
== Name

test - 

// end::picocli-generated-man-section-name[]

// tag::picocli-generated-man-section-synopsis[]
== Synopsis

*test* [*option0*=_<option1>_] ([*option1*=_<option1>_] _<param1>_ ([*option2*=_<option2>_]
     _<param2>_) ([*option3*=_<option3>_] _<param3>_)) _<param0>_

// end::picocli-generated-man-section-synopsis[]

// tag::picocli-generated-man-section-description[]
== Description



// end::picocli-generated-man-section-description[]

// tag::picocli-generated-man-section-options[]
== Options

*option0*=_<option1>_::
    Default: option0

== Nested

_<param2>_::
  

*option2*=_<option2>_::
    Default: option2

== Top

_<param1>_::
  

_<param2>_::
  

_<param3>_::
  

*option1*=_<option1>_::
    Default: option1

*option2*=_<option2>_::
    Default: option2

*option3*=_<option3>_::
    Default: option3

// end::picocli-generated-man-section-options[]

// tag::picocli-generated-man-section-arguments[]
== Arguments

_<param0>_::
  

_<param3>_::
  

// end::picocli-generated-man-section-arguments[]

// tag::picocli-generated-man-section-commands[]
// end::picocli-generated-man-section-commands[]

// tag::picocli-generated-man-section-exit-status[]
// end::picocli-generated-man-section-exit-status[]

// tag::picocli-generated-man-section-footer[]
// end::picocli-generated-man-section-footer[]

// end::picocli-generated-full-manpage[]

[remkop]

@rsenden Thank you for the contribution, that was very fast! I hope I will be able to review the PR this weekend.