Just extend main, rather than include to Kernel

Unfortunately rake doesn't have nested context,
everything just runs on a main rake object.
This is probably due to compatibility issue,
but anyway, we could just extend the object.

lib/tasks/gitlab/check.rake

@@ -41,8 +41,6 @@ namespace :gitlab do
   end
 
   namespace :gitlab_shell do
-    include SystemCheck::Helpers
-
     desc "GitLab | Check the configuration of GitLab Shell"
     task check: :environment  do
       warn_user_is_not_gitlab
@@ -249,8 +247,6 @@ namespace :gitlab do
   end
 
   namespace :sidekiq do
-    include SystemCheck::Helpers
-
     desc "GitLab | Check the configuration of Sidekiq"
     task check: :environment  do
       warn_user_is_not_gitlab
@@ -309,8 +305,6 @@ namespace :gitlab do
   end
 
   namespace :incoming_email do
-    include SystemCheck::Helpers
-
     desc "GitLab | Check the configuration of Reply by email"
     task check: :environment  do
       warn_user_is_not_gitlab
@@ -444,8 +438,6 @@ namespace :gitlab do
   end
 
   namespace :ldap do
-    include SystemCheck::Helpers
-
     task :check, [:limit] => :environment do |_, args|
       # Only show up to 100 results because LDAP directories can be very big.
       # This setting only affects the `rake gitlab:check` script.
@@ -501,8 +493,6 @@ namespace :gitlab do
   end
 
   namespace :repo do
-    include SystemCheck::Helpers
-
     desc "GitLab | Check the integrity of the repositories managed by GitLab"
     task check: :environment do
       Gitlab.config.repositories.storages.each do |name, repository_storage|
@@ -517,8 +507,6 @@ namespace :gitlab do
   end
 
   namespace :user do
-    include SystemCheck::Helpers
-
     desc "GitLab | Check the integrity of a specific user's repositories"
     task :check_repos, [:username] => :environment do |t, args|
       username = args[:username] || prompt("Check repository integrity for fsername? ".color(:blue))

lib/tasks/gitlab/helpers.rake

@@ -4,5 +4,5 @@ require 'tasks/gitlab/task_helpers'
 StateMachines::Machine.ignore_method_conflicts = true if ENV['CRON']
 
 namespace :gitlab do
-  include Gitlab::TaskHelpers
+  extend SystemCheck::Helpers
 end