bug#36594: No hint for missing argument

["Ludovic Courtès" <ludo@gnu.org>]

Julien Lepiller <julien@lepiller.eu> skribis:

> When you type an option that requires an argument, but don't provide one, you get an error message that says there is a missing argument. There should brobably be a hint on what values are acceptable. For instance, there is no way to know from "guix package -v" or "guix package --help" what values are accepted. In other cases, there is a --list-something option.
>
> Maybe -v is the only case where it would be useful to do something, because you could guess its existence and not use a verbosity level. Maybe fixing the help message to say --verbosity=[0-5] is enough?

Currently it says:

--8<---------------cut here---------------start------------->8---
$ guix build --help | grep -e -verbo
  -v, --verbosity=LEVEL  use the given verbosity LEVEL
--8<---------------cut here---------------end--------------->8---

We could add “an integer between 0 and 2”, but this was left
non-explicit in case we eventually extend it to -7 to +42.

Maybe there’s a limit on what we can do to help users?  :-)

Ludo’.