Add option to clear the console

[stoeffel]

We are running elm-test --watch with https://github.com/DarthSim/overmind Unfortunately, it doesn't only clear the output for elm-test, but everything else that is running through overmind. This PR adds an option to preserve the output and printing a separate between reruns. Let me know if this makes sense to you or if you want me to change anything. Thanks!

[lydell]

Here are some thoughts:

• Thanks for providing the use case! And thanks for sharing overmind – that’s very interesting to me personally given that I’ve written run-pty 😄
• elm-test-rs never clears the screen. I like that the separator in elm-test-rs and this PR are very similar!
• I’d like to bikeshed the flag name later. Maybe --no-clear-screen is more obvious?
• We plan to release elm-test 0.19.1-revision10 tonight (https://github.com/rtfeldman/node-test-runner/pull/614). So the timing of this PR is … either perfect or unfortunate.
  • It is tempting to merge this and get it out immediately, since it’s a simple feature that makes sense. But it’s often dangerous to push things out so quickly 😅
  • elm-test 0.19.1-revision10 is going to be compatible only with elm-explorations/test 2.x. So if you’re not ready to upgrade to 2.x right now, getting this feature into that release won’t help you. We could make 0.19.1-revision10 only contain this PR, and then do 0.19.1-revision11 with the breaking stuff, but I’m not sure… (Also you could potentially use elm-test-rs instead until upgrading to 2.x?) 🤔

[stoeffel]

@lydell Thanks for your feedback. I committed some changes to address it. I think we are going to be able to upgrade to elm-explorations/test v2 so would be awesome to have this change in the release today, but it's not a big deal if it isn't, because as a work around we temporarily switched to elm-test-rs.

[lydell]

Thanks! This is perfect, I’m adding it to the release! 🎉