Error message quality regresssion from clap2 to clap3/4

[matklad]

Please complete the following tasks

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

Rust Version

rustc 1.64.0-beta.6 (25912c097 2022-09-09)

Clap Version

3.., 4..

Minimal reproducible code

// clap 2
use clap::{App, Arg, SubCommand};
fn main() {
    let matches = App::new("app")
        .arg(
            Arg::with_name("config")
                .short("c")
                .long("config")
                .value_name("FILE")
                .help("Sets a custom config file")
                .takes_value(true),
        )
        .subcommand(SubCommand::with_name("sub"))
        .get_matches();
    eprintln!("matches = {:?}", matches);
}

// clap 3
use clap::{App, Arg, SubCommand};
fn main() {
    let matches = App::new("app")
        .arg(
            Arg::with_name("config")
                .short('c')
                .long("config")
                .value_name("FILE")
                .help("Sets a custom config file")
                .takes_value(true),
        )
        .subcommand(SubCommand::with_name("sub"))
        .get_matches();
    eprintln!("matches = {:?}", matches);
}


// clap 4
use clap::{builder::{Arg, Command}, ArgAction};
fn main() {
    let matches = Command::new("app")
        .arg(
            Arg::new("config")
                .short('c')
                .long("config")
                .value_name("FILE")
                .help("Sets a custom config file")
                .action(ArgAction::Set),
        )
        .subcommand(Command::new("sub"))
        .get_matches();
    eprintln!("matches = {:?}", matches);
}

Steps to reproduce the bug with the above code

Run the above three binaries with sub -c foo args.

Clap2 gives correct, if not maximally helpful, error message:

error: Found argument '-c' which wasn't expected, or isn't valid in this context

USAGE:
    clap-repro sub

Clap3 and clap4 give actively misleading error messages:

error: Found argument '-c' which wasn't expected, or isn't valid in this context

	If you tried to supply `-c` as a value rather than a flag, use `-- -c`

USAGE:
    clap-repro sub

error: Found argument '-c' which wasn't expected, or isn't valid in this context

  If you tried to supply '-c' as a value rather than a flag, use '-- -c'

Usage: clap-repro sub

Actual Behaviour

Expected Behaviour

Additional Context

No response

Debug Output

No response

[epage]

This looks to be a duplicate of #2766. If I misunderstood, let me know and I can re-open this.

In #2766 could you clarify what you are not liking and why it caused confusion about the CLI in near/nearcore#7732?