Fixes #1400, #612, #1632, #1634, #1531, #1458: Tab isn't handled properly for insert and visualblockinsert modes

[Chillee]

So really, what I was doing in these commits was refactoring Visual Block Mode to use multicursors instead, where I also added my own code for handling Insert Mode Tab.

http://vimdoc.sourceforge.net/htmldoc/visual.html#blockwise-operators

Thus, this PR fixes (some of) #776, fixes #1400, fixes #612, fixes #1458, and fixes #1634.

I also added fixing #1531 into this one since its editing is a similar concept to visualblock.

[johnfn]

Wow, this is great! Is it ready to go?

[Chillee]

@johnfn Should be. I just realized that this PR actually also contains this PR: #1659, but that PR should also be fairly uncontroversial.

Lemme add a couple of tests for the new o/O functionality, and then I'd be fine with this being merged.

[Chillee]

@johnfn Alright just added tests. It should be ready to merge.

[Chillee]

This is a very bizarre bug.

This is the test that's failing:

|foo

with the keys yyO<esc>p.
This results in

foo
|foo

(this is because of the cursor position; it's not skipping a line when it pastes. For example, if bar was in the register, it would be

bar
|foo

).

The bizarre part about this is that if the cursor is like this before the O:

f|oo

it works fine. Looking at the returned vimState between the two cases, they look identical.

[Chillee]

I feel like it has to be an upstream issue, with how weird this bug is. It has nothing to do with O itself: If you enter a line above with ctrl+shift+enter, it still has the same bug.

[Chillee]

I ended up fixing it by moving the cursor to the right before calling editor.action.insertLineBefore

[jpoon]

typo

[johnfn]

Is this good to go now? 😁

[Chillee]

Except for that typo...

[johnfn]

The cool thing is that as a contributor I can fix that directly from GitHub. Here we gooo

[Chillee]

The reason I didn't say I completely fixed that refactor issue is that there's some visual block code I still haven't touched, related to visual block mode not in insert.