Separate changed and untracked files

[wookayin]

A feature request!

Some git GUI tools like Fork has two separate sections, one for changes and one for untracked files. Currently diffview.nvim treats untracked files as if tracked files; consequently it would open an untracked file (if it is lexicographically first) when diff-ing. A more sensible default would be showing tracked and changed files and show untracked files afterwards.

Ideally, the layout would look like:

/some/repository
Changes (2)
  somedir
...
Untracked files (10)
   somefile
``

Note that the option `-uno` completely ignores and hides untracked files.