soft-deprecate --reporter-options and replace with --reporter-option

[boneskull]

This assumes #3556 lands. This issue came out of code review there.

Yargs has great support for "array"-type options. Generally, any option can be specified multiple times. In addition, options can accept multiple, space-delimited values, e.g., --foo bar baz quux.

This issue has two parts:

1. Soft-deprecate (using utils.deprecate()) --reporter-options
2. Implement --reporter-option which can be repeated multiple times.

It'd be cool to be able to specify a minimum of one value and a maximum of two, e.g.:

--reporter-option someBooleanFlag --reporter-option someString stringValue

Not sure if Yargs can to that, but if it can't, then require a single value and split the result on =:

--reporter-option someBooleanFlag --reporter-option someString=stringValue

[plroebuck]

See discussion from #3487. @johanblumenberg provided the PR's implementation.

Would strongly prefer that reporter name be prefixed to key in --reporter-option key=value.
For example, if specifying "xunit" reporter output file, then:
--reporter-option xunit.output=mocha-xunit.xml

We should decide how to address these potential problems first.

[boneskull]

I'm closing this; I've since gotten some backchannel feedback that comma-sep is useful, and it's really not much trouble to support both styles. as of v6, --reporter-option and --reporter-options are the same thing, and can be described using commas (--reporter-option foo=bar,baz=quux) or repetition (--reporter-option foo=bar --reporter-option baz=quux)

[plroebuck]

Wait. I don't care whether --reporterOptions is deprecated or not.

But need --reporterOption to be able to process comma-separated arguments as the value
(e.g., --reporterOption meta=foo,bar,baz) which cannot currently be done if using exact same code.

[boneskull]

mm, I think all it needs is a coerce: list in lib/cli/run.js.

[boneskull]

let's keep this closed and just make a new issue, nevermind.