'stack upload' should require confirmation before uploading

[borsboom]

I was originally going to title this "'stack upload' should be harder to use."

Uploading a package to hackage is irrevocable and it's a too easy now to accidentally upload without intending to do so (which I did in the last stack release, so now there's a weird version of stack on Hackage that can't be deleted). stack upload could default to just telling you what it would do plus a message saying something like "use stack upload -y to actually upload". Alternatively, it could prompt the user interactively, and also provide a -y option to have it skip the prompt.

[snoyberg]

I hadn't thought of going in this direction to be honest. What I'd thought of was simply removing the ability of stack upload without arguments to do an upload.

[borsboom]

Ah, so you'd have to specify the directory/tarball. Yeah, that'd work too. Just something more than stack upload on its own.

[snoyberg]

@manny-fp Confirmed?