SubCommand enum variant with fields duplicates parent attributes

[pfernie]

This example:

use structopt::StructOpt;

#[derive(Debug, StructOpt)]
struct Opts {
    #[structopt(subcommand)]
    /// The command to run
    command: Command,
}

#[derive(Debug, StructOpt)]
enum Command {
    /// Reticulate the splines
    #[structopt(visible_alias = "ret")]
    Reticulate {
        /// How many splines
        num_splines: u8,
    },
    /// Frobnicate the rest
    #[structopt(visible_alias = "frob")]
    Frobnicate,
}

fn main() {
    let opts = Opts::from_args();
    println!("{:?}", opts);
}

Produces this output:

$ cargo run -- -h
so_test 0.1.0

USAGE:
    so_test <SUBCOMMAND>

FLAGS:
    -h, --help       Prints help information
    -V, --version    Prints version information

SUBCOMMANDS:
    frobnicate    Frobnicate the rest [aliases: frob]
    help          Prints this message or the help of the given subcommand(s)
    reticulate    Reticulate the splines [aliases: ret, ret]

Where we see the reticulate command has the ret alias appear twice. Looking at the expanded code:

$ cargo expand
...
        let app = app.subcommand({
           let subcommand = ::structopt::clap::SubCommand::with_name("reticulate");
            let subcommand = {
                let subcommand = subcommand
                    .about("Reticulate the splines")
                    .visible_alias("ret");
                let subcommand = subcommand.arg(
                    ::structopt::clap::Arg::with_name("num-splines")
                        .takes_value(true)
                        .multiple(false)
                        .required(true)
                        .validator(|s| {
                            ::std::str::FromStr::from_str(s.as_str())
                                .map(|_: u8| ())
                                .map_err(|e| e.to_string())
                        })
                        .help("How many splines"),
                );
                subcommand.version("0.1.0")
            };
            subcommand
                .about("Reticulate the splines")
                .visible_alias("ret")
                .version("0.1.0")
        });
...

The about, visible_alias, and version functions on subcommand are called twice. In contrast, the Frobnicate case in the Command enum does not exhibit this behavior, as it does not contain any fields, so does not include a call subcommand.arg:

       let app = app.subcommand({
            let subcommand = ::structopt::clap::SubCommand::with_name("frobnicate");
            let subcommand = subcommand;
            subcommand
                .about("Frobnicate the rest")
                .visible_alias("frob")
                .version("0.1.0")
        });
        app.version("0.1.0")

I believe this duplication arises from this or this code, but I am not sure if simply removing would break other cases or not.

[0xazure]

I'm able to confirm the duplicate visible_alias in the help output. I'm upgrading from v0.2.15, and some quick tests show that the alias duplication starts appearing from v0.3.0 so I would consider this a regression.