Support an external config file instead of just package.json config

This is somewhat of a similar ask to #250, but with a little different use context:

I’d like to put my XO configuration in a separate file (.xorc.*), just like how ESLint and Prettier do it.

Having all of those config options in a single file really clutters up my package.json, and I’d like to be able to more easily copy/symlink files from a central location, instead of having to copy/paste configurations into my package.json every time.

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Submitted pull Requests

• #425 Find XO config based on linted file path

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[pvdlg]

A reason to adopt cosmiconfig would be https://github.com/xojs/xo/pull/279#issuecomment-356021126

[sindresorhus]

and I’d like to be able to more easily copy/symlink files from a central location, instead of having to copy/paste configurations into my package.json every time.

Why are you copy-pasting the config each time? That sounds like a maintenance nightmare. Instead, just create a shareable ESLint config file and all you need in your package.json is:

{
	"xo": {
		"extends": "name-of-your-shareable-config"
	}
}