cargo fmt no longer accepts --write-mode overwrite after --

[shepmaster]

cargo fmt -- --write-mode overwrite

Invalid argument: `overwrite`.
usage: cargo fmt [options]

Options:
    -h, --help          show this message
    -q, --quiet         no output printed to stdout
    -v, --verbose       use verbose output
    -p, --package <package>
                        specify package to format (only usable in workspaces)
        --version       print rustfmt version and exit
        --all           format all packages (only usable in workspaces)

This utility formats all bin and lib files of the current crate using rustfmt. Arguments after `--` are passed to rustfmt.

This is preventing rustfmt from working in the Playground.

[shepmaster]

Can reproduce outside of the playground:

$ cargo +nightly fmt -- --version
0.3.8-nightly (346238f4 2018-02-04)

$ cargo +nightly fmt -- --write-mode overwrite
Invalid argument: `overwrite`.
usage: cargo fmt [options]

$ rustup run nightly -- rustfmt --help | grep write
        --write-mode [replace|overwrite|display|plain|diff|coverage|checkstyle]

[shepmaster]

It appears that cargo +nightly fmt -- --write-mode=overwrite works, so perhaps something is trying to be overly clever about whitespace parsing?

[sinkuu]

This is rust-lang/cargo#5208

[nrc]

So this should be fixed now? (Or at least when the Cargo change hits nightly). Please comment if not.