Custom help for subcommands

[htngr]

Please complete the following tasks

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

Clap Version

4.5.19

Describe your use case

I'm currently trying to implement Canop/clap-help#1 (showing a custom help message for subcommands). Without subcommands I can catch if --help was requested (Parser::try_parse and ErrorKind::DisplayHelp). But with subcommands, I couldn't find a way (without manually reparsing the arguments) to check if help for a subcommand was issued.

Did I miss something?

Describe the solution you'd like

A solution might be to attach the current clap::Command to the clap_builder::error::Error.

Manually adding help flags is tedious and doesn't work if there are required arguments:

#[derive(Parser, Debug)]
#[command(
    name = "subcommand",
    author,
    version,
    about,
    disable_help_subcommand = true,
    disable_help_flag = true
)]
struct Args {
    /// Print help
    #[arg(long)]
    help: bool,

    /// A subcommand
    #[command(subcommand)]
    pub command: Option<Subcmd>,
}

#[derive(Subcommand, Clone, Debug)]
enum Subcmd {
    /// Some info for A
    #[clap(disable_help_flag = true)]
    A {
        /// Print help
        #[arg(long)]
        help: bool,
    },
    
    /// Some info for B
    #[clap(disable_help_flag = true)]
    B {
        /// Print help
        #[arg(long)]
        help: bool,

        /// An arg
        x: u8,
    },
}

For example, this does not work:

> cargo run -- -- b --help
error: the following required arguments were not provided:
  <X>

Usage: subcommands b --help <X>

Alternatives, if applicable

No response

Additional Context

No response