Add thor help command to view all subcommands simultaneously

[hlascelles]

I would like to be able to see all thor commands and subcommands in one go.

ie not:

❯ myapp --help
Commands:
  myapp foo            # Foo commands
  myapp qux            # Qux commands

❯ myapp foo --help
Commands:
  myapp foo baz        # Baz!
  myapp foo bar        # Bar!

I would like:

❯ myapp --tree-help
Commands:
  myapp foo            # Foo commands
  myapp foo baz        # Baz!
  myapp foo bar        # Bar!
  myapp qux            # Qux commands
  myapp qux pop        # Pop!

The switch could be one of:

myapp --tree-help
myapp  --help-tree
myapp --help --tree
myapp --tree
....

If you think this would be useful I could have a go... Or does something like it exist?