Add prompt_force_push option

[fmbarina]

Solves #1673.

A quick and simple addition, but I think I changed everything needed. Tested ok. Default true, no surprises. People who dislike it can find the option on their own. Though, I'll be honest, this still feels like a bit of a weird feature to have enabled by default. Spooked me a little.

If there's anything you'd like changed, be it code, names, or even the commit message, feel free to say so. Not sure I got the coding style, so I'm a little scared of introducing stuff that doesn't fit in.

[fmbarina]

That's odd. Sorry about that, could someone help me understand this test suite? Seems there's an issue with the branch popup rendering/view, but some tests haven't been written yet. I can't tell if failure is expected or not.

[CKolkey]

Don't worry about that; its not you, it's some CI runner issue that I've had no time to investigate. Currently at home with four month old twins, so... CI failures has been low priority.

Thanks for taking the time to do this. I'll try to have it merged soon.

Oh, but to answer your question, for fun I wrote an e2e test runner in ruby, but haven't finished writing all the tests I wanted because writing the infrastructure code was more fun than the tests themselves. So what you're seeing is a test failure, and some todos.

[fmbarina]

Don't worry, take however long you need! Hope you're having a great time with them.