Pass arguments after -- through to the script

[deanrad]

Since npm/npm#3494, if I want to pass args to the script run by npm run (as distinct from passing args to npm), I pass them after a --.

npm run test -- --grep 'specific test' #<- these are args for mocha, not for npm

[deanrad]

npm run test -- --foo bar # test command is `scripty` in package.json

> project@1.0.0 test /Users/deanius/src/project
> scripty "--foo" "bar"

Executing "/project/scripts/test.sh":

> #!/bin/bash
> echo $@
>

Nothing is echoed - scripty should pass its arguments through, and docs should
show that this use case is supported.

[searls]

It looks like what's happening is that npm is indeed passing those args to scripty and then scripty is dutifully doing nothing with them, since it doesn't look at ARGV. I suspect the fix is to just pass whatever args it receives on to the script it invokes via spawn