Decide when the REPL should enter multi-line mode

[smarter]

Right now when pressing Enter, the REPL will add a new line instead of running the current input if:

• the input is incomplete (eg. "class Foo {")
• the cursor is in the middle of a line

But after experimenting with it, I think that usually when pressing enter in the middle of a line, I expect the input to be run. I suggest adding another shortcut (maybe Shift+Enter, Ctrl+Enter is not technically possible on most terminals) to signify "I want to add a new line and not run this command". (We might also need a shortcut for the opposite problem: "I want to run this command and not add a new line")

[allanrenucci]

I asked for this in the JLine mailing list

[smarter]

Looks like we can just use alt+enter to make a newline so we should just change enter to only check if the input is incomplete.

[allanrenucci]

You can make this work on the default Mac terminal by going to Terminal -> Preference -> Profiles -> Keyboard and then selecting Use Option as Meta key.

However this is not enabled by default. Do we want to move forward anyway?

[smarter]

Yes, I think so, as a fallback we can always implement Ammonite's behavior where you can force multi-line by wrapping your code in { ... }

[allanrenucci]

I played a bit with ammonite and it seems it submit the buffer, only if the cursor is on the last line. I think it makes sense and is a good compromise. Always submitting would make multi-line editing cumbersome

[smarter]

Sounds reasonable to me