Update default command usage to show optional brackets

[DannyBen]

cc #526, #527

This PR updates the usage string for commands that are set as default.

# Before
$ ./cli src
missing required argument: TARGET
usage: cli download SOURCE TARGET

# After
$ ./cli src
missing required argument: TARGET
usage: cli [download] SOURCE TARGET

[codevogel]

I cloned master and built it with ruby 3.3.3.

This seems to work as expected on my end.

with bashly.yml

name: pls
help: "Project Level Shortcuts - A simple tool to manage project specific aliases."
version: 0.1.0

environment_variables:
- name: pls_default
  help: Path to the root configuration file (The fallback .pls file if is is not found in the current working directory or any of its parents)
  default: $HOME/.pls

commands:
  - name: do
    help: Executes the command associated with the given alias
    default: force
    args:
      - name: alias
        help: The alias to execute
        required: true
    examples:
      - pls open
      - pls do open

The help message shows

❯ ./pls --help
pls - Project Level Shortcuts - A simple tool to manage project specific aliases.

Usage:
  pls [COMMAND]
  pls [COMMAND] --help | -h
  pls --version | -v

Commands:
  do   Executes the command associated with the given alias (default)

Options:
  --help, -h
    Show this help

  --version, -v
    Show version number

Environment Variables:
  PLS_DEFAULT
    Path to the root configuration file (The fallback .pls file if is is not
    found in the current working directory or any of its parents)
    Default: /home/codevogel/.pls

and

❯ ./pls do --help
pls do - Executes the command associated with the given alias

Usage:
  pls [do] ALIAS
  pls do --help | -h

Options:
  --help, -h
    Show this help

Arguments:
  ALIAS
    The alias to execute

Examples:
  pls open
  pls do open

So it shows that do is the default, and it also shows that that means do is optional.

Great work 🥳

[DannyBen]

Notice that this also changed:

$ ./pls
missing required argument: ALIAS
usage: pls [do] ALIAS

[codevogel]

Notice that this also changed:

$ ./pls
missing required argument: ALIAS
usage: pls [do] ALIAS

Forgot to mention that. It perfectly addresses my original issue!