Merge branch 'casecmp-cop' into 'master'

Enable Rubocop Casecmp Performance Cop.

Also fixes the errors caused by enabling the cop.

`casecmp` is more performant than `.downcase` and `==`.

See also: https://github.com/bbatsov/rubocop/blob/master/lib/rubocop/cop/performance/casecmp.rb

See merge request !3957

4 files changed, 5 insertions, 6 deletions

diff --git a/.rubocop.yml b/.rubocop.yml
index c96c7123c16..ccceea45963 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -937,10 +937,9 @@ Lint/Void:
 
 ##################### Performance ############################
 
-# TODO: Enable Casecmp Cop.
 # Use `casecmp` rather than `downcase ==`.
 Performance/Casecmp:
-  Enabled: false
+  Enabled: true
 
 # TODO: Enable DoubleStartEndWith Cop.
 # Use `str.{start,end}_with?(x, ..., y, ...)` instead of
diff --git a/app/models/repository.rb b/app/models/repository.rb
index a4b42d7226d..de7e163078d 100644
--- a/app/models/repository.rb
+++ b/app/models/repository.rb
@@ -453,7 +453,7 @@ class Repository
   def version
     cache.fetch(:version) do
       tree(:head).blobs.find do |file|
-        file.name.downcase == 'version'
+        file.name.casecmp('version').zero?
       end
     end
   end
diff --git a/lib/gitlab/database.rb b/lib/gitlab/database.rb
index 6f9da69983a..42bec913a45 100644
--- a/lib/gitlab/database.rb
+++ b/lib/gitlab/database.rb
@@ -5,11 +5,11 @@ module Gitlab
     end
 
     def self.mysql?
-      adapter_name.downcase == 'mysql2'
+      adapter_name.casecmp('mysql2').zero?
     end
 
     def self.postgresql?
-      adapter_name.downcase == 'postgresql'
+      adapter_name.casecmp('postgresql').zero?
     end
 
     def self.version
diff --git a/lib/gitlab/markup_helper.rb b/lib/gitlab/markup_helper.rb
index a5f767b134d..dda371e6554 100644
--- a/lib/gitlab/markup_helper.rb
+++ b/lib/gitlab/markup_helper.rb
@@ -40,7 +40,7 @@ module Gitlab
     # Returns boolean
     def plain?(filename)
       filename.downcase.end_with?('.txt') ||
-        filename.downcase == 'readme'
+        filename.casecmp('readme').zero?
     end
 
     def previewable?(filename)