Feature request: Style/NonNilCheck to check unless

[madwort]

---

Expected behavior

$ cat test.rb 
puts 'OMG' if !myvar.nil?
puts 'WTF' unless myvar.nil?

$ rubocop test.rb
Inspecting 1 file
C

Offenses:

test.rb:1:1: C: Favor unless over if for negative conditions.
puts 'OMG' if !myvar.nil?
^^^^^^^^^^^^^^^^^^^^^^^^^
test.rb:1:15: C: Explicit non-nil checks are usually redundant.
puts 'OMG' if !myvar.nil?
              ^^^^^^^^^^^
test.rb:2:15: C: Explicit non-nil checks are usually redundant.
puts 'WTF' unless myvar.nil?
           ^^^^^^^^^^^^^^^^^

1 file inspected, 3 offenses detected

Actual behavior

$ cat test.rb 
puts 'OMG' if !myvar.nil?
puts 'WTF' unless myvar.nil?

$ rubocop test.rb
Inspecting 1 file
C

Offenses:

test.rb:1:1: C: Favor unless over if for negative conditions.
puts 'OMG' if !myvar.nil?
^^^^^^^^^^^^^^^^^^^^^^^^^
test.rb:1:15: C: Explicit non-nil checks are usually redundant.
puts 'OMG' if !myvar.nil?
              ^^^^^^^^^^^

1 file inspected, 2 offenses detected

RuboCop version

$ bundle exec rubocop -V
0.42.0 (using Parser 2.3.1.2, running on ruby 2.2.2 x86_64-linux)

[madwort]

Awesome! Thanks @jonas054 !