Merge branch 'jc/add-ignore-removal'

Introduce "--ignore-removal" as a synonym to "--no-all" for "git
add", and improve the 2.0 migration warning with it.

* jc/add-ignore-removal:
git add: rephrase -A/--no-all warning
git add: --ignore-removal is a better named --no-all

diff --cc builtin/add.c
Simple merge