When encountered, report [ErrorKind::UnknownArgument][crate::error::ErrorKind::UnknownArgument]

Useful to help users migrate, either from old versions or similar tools.

Examples

# use clap_builder as clap;
# use clap::Command;
# use clap::Arg;
let cmd = Command::new("mycmd")
    .args([
        Arg::new("current-dir")
            .short('C'),
        Arg::new("current-dir-unknown")
            .long("cwd")
            .aliases(["current-dir", "directory", "working-directory", "root"])
            .value_parser(clap::builder::UnknownArgumentValueParser::suggest_arg("-C"))
            .hide(true),
    ]);

// Use a supported version of the argument
let matches = cmd.clone().try_get_matches_from(["mycmd", "-C", ".."]).unwrap();
assert!(matches.contains_id("current-dir"));
assert_eq!(
    matches.get_many::<String>("current-dir").unwrap_or_default().map(|v| v.as_str()).collect::<Vec<_>>(),
    vec![".."]
);

// Use one of the invalid versions
let err = cmd.try_get_matches_from(["mycmd", "--cwd", ".."]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::UnknownArgument);