add support for rustc's --error-format short

[QuietMisdreavus]

As implemented in rust-lang/rust#44636, this exposes the --error-format short in Cargo's --message-format flag.

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[matklad]

implementation looks good to me!

One thing I am not certain about is that names human and short don't really fit together. Should we rename (with deprecation) human to long?

Am I correct that current human should be preserved as a default?

cc @rust-lang/cargo

[QuietMisdreavus]

That makes sense, but may also require intervention in rustc as well, since human is also used there.

As for being default, human is still the default in rustc, so i codified that here. The Default impl was needed to bring it into BuildConfig, so its #[derive(Default)] would work.

[alexcrichton]

I think this option to rustc was supposed to be unstable? If so I'm somewhat wary of landing this now...

[QuietMisdreavus]

Since rust-lang/rust#46005 was merged, making that parameter unstable, should i just close this?

[alexcrichton]

Ah yes, let's do that for now.

[matklad]

should i just close this?

Hm, I think it would be beneficial to expose this feature to Cargo users somehow: I am afraid rustc only option wouldn't get much testing without being able to enable it with Cargo. Or will it be possible to add RUST_FLAGS=["--message-format", "short"] to .cargo/config to achieve this effect? Will it work with tools which want to pass --message-format=json?

[alexcrichton]

We could consider adding an unstable cargo option?

[pickfire]

Any update on this after rust-lang/rust#49546 was merged?

[sanmai-NL]

@matklad: ping, see preceding post. Seems like low-hanging fruit? Since #5879 it’s supported with at least the check and doc subcommands it seems, but with run nor check it works yet with cargo 1.29.0-nightly (0ec7281b9 2018-08-20):

error: Found argument '--error-format' which wasn't expected, or isn't valid in this context

USAGE:
    cargo run [OPTIONS] [--] [args]..

Update: Argh, they named the option differently between rustc and cargo --error-format vs. --message-format.

On the bright side, this issue can be closed.

[pickfire]

Maybe we should change the arguments to be the same?