Adds '--clear-screen' option to clear screen between watch runs

[colinta]

This is very slapped together, but I wanted it for myself and figured I'd start the conversation. If you are even open to mergin it let me know of any changes.

Usage:

npm test ava --watch --clear-scren 

What does this PR change?

Between test runs, it sends this.lineWriter.write(ansiEscapes.clearTerminal), which clears the screen and scrollback buffer on all the terminal apps I have handy.

I promoted this same behaviour in TypeScript, I guess it's my hill to die on 🤣 (in that case, --watch was already clearing the screen, this just changed/improved the behaviour).

Jest also clears the screen when using --watch. I prefer it, FWIW, but I've read the argument for keeping all those logs... I'm not convinced, but hey that's just me. I'd be happy w/ --clear-screen though it isn't exactly very discoverable atm.

WDYT?

[colinta]

When I first wrote this, I used process.stderr.write('\x1b[2J\x1b[H\x1b[3J');, but that felt wrong given the use of this.lineWriter.write so I switched to that... but now it doesn't work, so I switched it back to process.stderr.write. 🤷‍♂️

Correction: it works fine using lineWriter.

[sindresorhus]

I have no opinion whether this should be added, but the flag should be --clear-screen.

[colinta]

I'm not personally a fan of the more verbose --clear-screen – I chose cls for what I thought was a good reason – but I won't quibble. 🙂 (edit: that article points out that in *nix, the equivalent command would be clear, but I like --clear even less than --clear-screen, so --clear-screen is a decent compromise at the end of the day, and in the absence of other arguments, verbose/clarity beats all)

I gave this a short alias of -C, btw. Like/dislike? I'm not stuck on it.