add test for \C-w using prefix arg

[matsl]

What

• Add test for hui-kill-region
• Refactored and simplified
• Use prefix arg for interactive call
• Refactor to have base behavior as kill-region
• Fix non-interactive behavior

Why

Tests.

Note

The inspiration for using an argument for identification of
interactive call or not comes from the comment in

{C-hf called-interactively-p RET}

It says:

Instead of using this function, it is cleaner and more reliable to
give your function an extra optional argument whose ‘interactive’ spec
specifies non-nil unconditionally ("p" is a good way to do this), or
via (not (or executing-kbd-macro noninteractive)).

[rswgnu]

Be sure to test for 2 kills in a row that they append as one kill properly:
case 1: kill based on matching pair at point followed by a regular C-k line kill
case 2: regular C-k line kill followed by a matching pair at point kill.

[rswgnu]

And we'll review this when we chat.

[matsl]

Be sure to test for 2 kills in a row that they append as one kill properly: case 1: kill based on matching pair at point followed by a regular C-k line kill

There is no validation of what is actually saved in the current tests so will add that in one or more separate tests I think.

case 2: regular C-k line kill followed by a matching pair at point kill.

That is an interesting case. Will take a look.

[rswgnu]

I think the signature of our overriding kill-region command should match the signature of kill-region as best as possible as well.

[matsl]

Added some tests for kill-region-type of functionality.