Support TOML and env vars parsing

[bestouff]

Hi,
Structopt is really nice, but to have a complete solution what would be good is to also support TOML and env vars parsing (think 12-factor apps).

[TeXitoi]

That's not the scope of StructOpt. StructOpt is an interface for clap. If clap implement such functionality, StructOpt will, but StructOpt can't support such a functionality without support from clap.

[TeXitoi]

I think it's a very interesting feature, but the feature request is for https://github.com/kbknapp/clap-rs, not StructOpt

[TeXitoi]

Related issues: clap-rs/clap#748

[bestouff]

Thanks, I'll have a look at that issue.

[colemickens]

Clap supports sourcing values from env vars now. Could this be reconsidered for structopt? https://docs.rs/clap/2.32.0/clap/struct.Arg.html#method.env

[TeXitoi]

Yes, you can use it using env = "FOO"