Allow global args in top-level multicall

[jaskij]

Please complete the following tasks

• I have searched the discussions
• I have searched the open and rejected issues

Clap Version

4.0.27

Describe your use case

When writing a multicall program, I have some options that I'd like to be available to all commands. In addition, to reduce boilerplate, I would like them to be in the top-level struct.

A prime example of this would be log level, which is set once, just after parsing the commandline, before entering a specific subcommand.

Describe the solution you'd like

This looks good enough - as is, this is rejected by debug asserts.

#[derive(Debug, clap::Parser)]
#[command(multicall(true))]
struct Cli {
    #[command(subcommand)]
    command: Command,

    #[arg(global = true)]
    log_level: LogLevel,
}

Alternatives, if applicable

A workaround would be to add the log level enum as an option on all subcommands - doable, but seems to require some amount of repetitive code, which is always an issue when it comes to later changes.

The amount of repetition could perhaps be eased by using a declarative macro, but those are somewhat annoying to write and not everyone is comfortable with them.

Additional Context

No response

[epage]

When I prevented arguments on the multicall command, I was trying to balance

• Correct parsing behavior (ie disallowing $ --verbose cmd)
• Correct $ help behavior (not showing arguments)
• Minimal binary size impact
  • At the moment, I would classify this a small scope feature (few people would use it) which means we prioritize binary size over conveniences.

It would be nice to support global arguments but any solution should maintain the above balance unless we find a reason to re-evaluate our priorities for this feature.