Option not to reorder possible values for an argument

[rzumer]

Affected Version of clap

2.33.0

Bug or Feature Request Summary

I have a list of possible numeric values for a given argument, but clap reorders them in alphabetical (non-numeric) order.

Expected Behavior Summary

Being able to tell clap not to reorder my argument list.

Actual Behavior Summary

A list of numbers (e.g. ["0", "1", "2", "12"]) is reordered in non-numeric order (e.g. ["0", "1", "12", "2"]).

Sample Code or Link to Sample Code

let number_strings = ["0", "1", "2", "12"];

(boilerplate)
.arg(
    Arg::with_name("my_arg")
    .short("m")
    .long("my_arg")
    .value_name("MY_ARG")
    .possible_values(&number_strings)
)
(boilerplate)

Example Output

error: 'blah' isn't a valid value for '--my_arg <MY_ARG>'

[possible values: 0, 1, 12, 2]

[rzumer]

Actually, it looks like --help displays options as ordered in the input list, but when passing an invalid argument value, the list of possible values displayed is reordered. So it is only an issue in the latter situation for me.