One of the features I miss most from Magit/Fugitive/Tig is to
apply/revert/stage/unstage individual hunks or even exactly the
selected line(s). This provides a much more convenient way of
splitting changes than "git add/restore -p".
Implement a "patch" command that applies the selected lines within
a diff by piping them to the "patch" program.
It can also feed other programs like "git apply" (see the next commit).
Original discussion: https://discuss.kakoune.com/t/atomic-commits-in-kakoune/1446
Interestingly, :patch is defined outside the "patch" module. This is
to make it readily available for interactive use.
Putting it into the module does not save any work.
I tentatively added a patch module anyway so we can explicitly declare
this dependency.. although there is the argument that this is not
really needed?
