Options shown in Global section can include unreachable alternatives.

Hello 👋🏼

The CLI for Unison has one very common use-case (launching the unison shell) and several other 'utility' commands. The way we have things set up right now is as follows:

• ucm without any subcommand runs the 'launch' behaviour
• ucm run defers to the run subcommand.

The way we've implemented this is by using our launch option parser as a fallback for our subcommand parser:

topLevelParser =
  hsubparser subcommands <|> launchCommand

Meaning that if the user doesn't provide a command, we interpret it as a 'launch'.

The issue is that currently optparse-applicative interprets all of the options of launch as global options, even though all of those options will fail if passed to the run subcommand for example.

Is there any way to indicate options as being only relevant if no subcommand is provided, rather than showing them as global?

Effectively I want the empty command to just be treated as another subcommand.

This may not be the most common setup, but if you can think of a way to make this work I'd love to hear it 😄

Thank you for maintaining such an awesome tool, it saves us a lot of time :D

Start by examining the topLevelParser expression in the issue, especially how hsubparser combines subcommands with launchCommand as a fallback. Read the parser-combinator implementation and existing parser tests to determine whether an empty command can be represented separately from global options. Done means launch options are shown only for the no-subcommand path and are rejected or absent for commands such as run.