Enable Style/NegatedIf Rubocop cop

Favor `unless` over `if` for negative conditions
(or control flow ||).

See #17478

.rubocop.yml

@@ -394,7 +394,7 @@ Style/MutableConstant:
 
 # Favor unless over if for negative conditions (or control flow or).
 Style/NegatedIf:
-  Enabled: false
+  Enabled: true
 
 # Favor until over while for negative conditions.
 Style/NegatedWhile:

app/models/ci/runner.rb

@@ -60,7 +60,7 @@ module Ci
     end
 
     def display_name
-      return short_sha unless !description.blank?
+      return short_sha if description.blank?
 
       description
     end

app/services/git_tag_push_service.rb

@@ -23,7 +23,7 @@ class GitTagPushService < BaseService
     commits = []
     message = nil
 
-    if !Gitlab::Git.blank_ref?(params[:newrev])
+    unless Gitlab::Git.blank_ref?(params[:newrev])
       tag_name = Gitlab::Git.ref_name(params[:ref])
       tag = project.repository.find_tag(tag_name)
       if tag && tag.target == params[:newrev]

app/services/projects/housekeeping_service.rb

@@ -22,7 +22,7 @@ module Projects
     end
 
     def execute
-      raise LeaseTaken if !try_obtain_lease
+      raise LeaseTaken unless try_obtain_lease
 
       GitlabShellOneShotWorker.perform_async(:gc, @project.path_with_namespace)
     ensure

config/initializers/1_settings.rb

@@ -52,7 +52,7 @@ class Settings < Settingslogic
     # check that values in `current` (string or integer) is a contant in `modul`.
     def verify_constant_array(modul, current, default)
       values = default || []
-      if !current.nil?
+      unless current.nil?
         values = []
         current.each do |constant|
           values.push(verify_constant(modul, constant, nil))

lib/ci/gitlab_ci_yaml_processor.rb

@@ -265,7 +265,7 @@ module Ci
     end
 
     def validate_job_dependencies!(name, job)
-      if !validate_array_of_strings(job[:dependencies])
+      unless validate_array_of_strings(job[:dependencies])
         raise ValidationError, "#{name} job: dependencies parameter should be an array of strings"
       end