help_short() allows conflict option

[maicallist]

Rust Version

rustc 1.37.0 (eae3437df 2019-08-13)C

Affected Version of clap

2.33.0

Bug or Feature Request Summary

help_short() allows conflict option.

Expected Behavior Summary

when setting arg with short(h) and help_short(h)
Clap should give an error about the conflict.

Actual Behavior Summary

Under App
pre-condition, App has a -h arg.

1. when not setting help_short(), clap works as expected.
2. when help_short("h") is set, -h option prints help info and lists -h is for two options.

Under Subcommand
pre-condition, subcommand has -h arg.

1. when not setting help_short(), clap works as expected.
2. when help_short("h") is set, -h option prints nothing and --help lists that -h is for two options.

[pksunkara]

NOTE: .help_short() has been changed to .mut_arg()

.mut_arg("help", |h| {
    h.short('H').long("help").help("Print help information")
})