Remove --sources CLI flag

[novemberborn]

With #925 we've changed how test files are resolved. If file patterns are passed as CLI arguments they're resolved relative to the current working directory. Otherwise file patterns in package.json, or indeed default patterns, are resolved relative to the the directory that contains package.json.

Our management of source patterns is similarly affected. This may or may not be the reason why watch mode doesn't work correctly when AVA is called outside of the project root (see #936). However we should reconsider how sources works.

From @jamestalmage in #863 (comment):

If they are cded into a child directory and use the --sources flag, that should probably be resolved from cwd, right? But if they don't specify --sources, then we probably want to use whatever is in package.json, and resolve from that directory? That's getting complicated.

Should we eliminate the --sources flag? I have never used it, and I don't see why you really need it. Doesn't this qualify as a static config item that should live in package.json?

I'm 👍 on removing the sources flag. Patterns must then be specified in the package.json, which hopefully makes them easier to manage. Both for AVA users and maintainers.

[sindresorhus]

Let's do it.

[novemberborn]

Somewhat blocked by #1048.

[sotojuan]

Are we still doing this? Making a list of things to take care of this weekend!

[novemberborn]

@sotojuan yes.

[LasaleFamine]

Hi guys!
Can I take this one? Is there something more I should know?

[novemberborn]

@LasaleFamine go for it! 👍

[LasaleFamine]

Just to be sure, I can see a --source flag, not a --sources. Is right?

Another thing I can see is that the cli.flags.source is used within the Watcher constructor:

// lib/cli.js
if (cli.flags.watch) {
		try {
			const watcher = new Watcher(logger, api, files, arrify(cli.flags.source));
			watcher.observeStdin(process.stdin);
		} catch (err) {

...

We need to get that source prop from the pacakge.json?

[novemberborn]

Just to be sure, I can see a --source flag, not a --sources. Is right?

Yes.

We need to get that source prop from the pacakge.json?

I think you can get it from conf.source. See #1046 for context.