clap usage explains the "exclusive argument mode" for one-time program setup

[jtmoon79]

I want my program --help message Usage: section to look something like this:

Usage:
  program --setup
  program [OPTIONS] <PATHS>

My program must run --setup once after installation. After that, it can be run many times with varied required PATHS and optional OPTIONS.

So to install and run my program, the user would run these shell commands:

# run once
$ cargo install program

# run once
$ program --setup

# run many times

$ program --opt1 path1

$ program path2 path3

$ program ...  # etc.

So --setup must be run once and should not have other arguments or options. After that, all other arguments and options may be used. So program --setup a would cause clap to print an error that --setup and -a should not be intermixed.

What is a good way to have something like this one-time use "exclusive mode" or "setup mode"?
It's okay if the user runs --setup more than once. More importantly, how to succinctly communicate that --setup is a distinct "mode" apart from the normal "mode" that may use other arguments and options?

In my case, I'm using #[derive(Parser)] struct CLI_Args { .. } to create the argument structure. Hopefully it's possible with Derive.

[epage]

While I hadn't considered exclusive for it, we've been talking about something like this in #4191.