Avoid writing prompt for multi-line input #801

Overview

There was a bug where the shell prompt was being written during multi-line input during interactive shell sessions.

Solution

Stop printing the shell prompt when quotes are open and instead print quote> .

Notes

I'm not sure is there is a good way to add some tests around this since it only applies to interactive shell sessions. If anyone has an idea of how to do this, I'll be happy to add some.