checkout: count and print -m paths separately

checkout: count and print -m paths separately

Since 0f086e6dca (checkout: print something when checking out paths -
2018-11-13), this command reports how many paths have been updated
from what source (either from a tree, or from the index). I forget
that there's a third source: when -m is used, the merge conflict is
re-created (granted, also from the index, but it's not a straight copy
from the index).

Count and report unmerged paths separately. There's a bit more update
to avoid reporting:

   Recreated X merge conflicts
   Updated 0 paths from the index

The second line is unnecessary. Though if there's no conflict
recreation, we still report

   Updated 0 paths from the index

to make it clear we're not really doing anything.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>