can you please mention it in the cli docs too - otherwise people will wonder, and some won't even try it

And they would be better off without! Humph! :)

Ok ok, I'll see about adding a blurb to the docs. :P

LGTM

for the code

LGTM

ping @SvenDowideit

Ok, I improved the test slightly to cover our edge case better, and added some documentation to explain that this works and how it works. As always, let me know what needs to be improved. :)

Doh, my test is failing for me now, give me a minute to figure out why.

Ok, the test should be fixed now. My machine is taking forever to download "docker-test-image" this evening, so I haven't verified it for sure, but will verify as soon as it finishes.

Ok, test looks good now. 👍

Docs LGTM

(I wonder what happens now if someone does ADD file ./ - yes, don't add that to this PR)

I wondered about relative ADD myself, but agree that it's a separate issue. :)