Visual states should set region-extract-function

[catern]

Issue type

• Enhancement request

Expected behavior

When in visual block state or visual line state, evil-mode should set region-extract-function so that Emacs functions which interact with the region behave correctly. This includes, but is not limited to:

• shell-command-on-region
• kill-region
• copy-region-as-kill
• various rectangle commands

Invoking region-extract-function is the correct way to deal with non-standard regions in Emacs, so this allows commands to support evil's nonstandard regions without actually depending on evil.

Actual behavior

There's no portable way to write a command which supports visual block/visual line, without depending on evil.