use Gitlab::UserSettings directly as a singleton instead of including/extending it

app/controllers/admin/cohorts_controller.rb

 class Admin::CohortsController < Admin::ApplicationController
   def index
-    if current_application_settings.usage_ping_enabled
+    if Gitlab::CurrentSettings.usage_ping_enabled
       cohorts_results = Rails.cache.fetch('cohorts', expires_in: 1.day) do
         CohortsService.new.execute
       end

app/controllers/application_controller.rb

@@ -2,7 +2,6 @@ require 'gon'
 require 'fogbugz'
 class ApplicationController < ActionController::Base
-  include Gitlab::CurrentSettings
   include Gitlab::GonHelper
   include GitlabRoutingHelper
   include PageLayoutHelper
@@ -28,7 +27,7 @@ class ApplicationController < ActionController::Base
   protect_from_forgery with: :exception
-  helper_method :can?, :current_application_settings
+  helper_method :can?
   helper_method :import_sources_enabled?, :github_import_enabled?, :gitea_import_enabled?, :github_import_configured?, :gitlab_import_enabled?, :gitlab_import_configured?, :bitbucket_import_enabled?, :bitbucket_import_configured?, :google_code_import_enabled?, :fogbugz_import_enabled?, :git_import_enabled?, :gitlab_project_import_enabled?
   rescue_from Encoding::CompatibilityError do |exception|
@@ -120,7 +119,7 @@ class ApplicationController < ActionController::Base
   end
   def after_sign_out_path_for(resource)
-    current_application_settings.after_sign_out_path.presence || new_user_session_path
+    Gitlab::CurrentSettings.after_sign_out_path.presence || new_user_session_path
   end
   def can?(object, action, subject = :global)
@@ -268,15 +267,15 @@ class ApplicationController < ActionController::Base
   end
   def import_sources_enabled?
-    !current_application_settings.import_sources.empty?
+    !Gitlab::CurrentSettings.import_sources.empty?
   end
   def github_import_enabled?
-    current_application_settings.import_sources.include?('github')
+    Gitlab::CurrentSettings.import_sources.include?('github')
   end
   def gitea_import_enabled?
-    current_application_settings.import_sources.include?('gitea')
+    Gitlab::CurrentSettings.import_sources.include?('gitea')
   end
   def github_import_configured?
@@ -284,7 +283,7 @@ class ApplicationController < ActionController::Base
   end
   def gitlab_import_enabled?
-    request.host != 'gitlab.com' && current_application_settings.import_sources.include?('gitlab')
+    request.host != 'gitlab.com' && Gitlab::CurrentSettings.import_sources.include?('gitlab')
   end
   def gitlab_import_configured?
@@ -292,7 +291,7 @@ class ApplicationController < ActionController::Base
   end
   def bitbucket_import_enabled?
-    current_application_settings.import_sources.include?('bitbucket')
+    Gitlab::CurrentSettings.import_sources.include?('bitbucket')
   end
   def bitbucket_import_configured?
@@ -300,19 +299,19 @@ class ApplicationController < ActionController::Base
   end
   def google_code_import_enabled?
-    current_application_settings.import_sources.include?('google_code')
+    Gitlab::CurrentSettings.import_sources.include?('google_code')
   end
   def fogbugz_import_enabled?
-    current_application_settings.import_sources.include?('fogbugz')
+    Gitlab::CurrentSettings.import_sources.include?('fogbugz')
   end
   def git_import_enabled?
-    current_application_settings.import_sources.include?('git')
+    Gitlab::CurrentSettings.import_sources.include?('git')
   end
   def gitlab_project_import_enabled?
-    current_application_settings.import_sources.include?('gitlab_project')
+    Gitlab::CurrentSettings.import_sources.include?('gitlab_project')
   end
   # U2F (universal 2nd factor) devices need a unique identifier for the application

app/controllers/concerns/enforces_two_factor_authentication.rb

@@ -20,13 +20,13 @@ module EnforcesTwoFactorAuthentication
   end
   def two_factor_authentication_required?
-    current_application_settings.require_two_factor_authentication? ||
+    Gitlab::CurrentSettings.require_two_factor_authentication? ||
       current_user.try(:require_two_factor_authentication_from_group?)
   end
   def two_factor_authentication_reason(global: -> {}, group: -> {})
     if two_factor_authentication_required?
-      if current_application_settings.require_two_factor_authentication?
+      if Gitlab::CurrentSettings.require_two_factor_authentication?
         global.call
       else
         groups = current_user.expanded_groups_requiring_two_factor_authentication.reorder(name: :asc)
@@ -36,7 +36,7 @@ module EnforcesTwoFactorAuthentication
   end
   def two_factor_grace_period
-    periods = [current_application_settings.two_factor_grace_period]
+    periods = [Gitlab::CurrentSettings.two_factor_grace_period]
     periods << current_user.two_factor_grace_period if current_user.try(:require_two_factor_authentication_from_group?)
     periods.min
   end

app/controllers/concerns/requires_whitelisted_monitoring_client.rb

 module RequiresWhitelistedMonitoringClient
   extend ActiveSupport::Concern
-  include Gitlab::CurrentSettings
-
   included do
     before_action :validate_ip_whitelisted_or_valid_token!
   end
@@ -26,7 +24,7 @@ module RequiresWhitelistedMonitoringClient
     token.present? &&
       ActiveSupport::SecurityUtils.variable_size_secure_compare(
         token,
-        current_application_settings.health_check_access_token
+        Gitlab::CurrentSettings.health_check_access_token
       )
   end

app/controllers/invites_controller.rb

@@ -51,7 +51,7 @@ class InvitesController < ApplicationController
     return if current_user
     notice = "To accept this invitation, sign in"
-    notice << " or create an account" if current_application_settings.allow_signup?
+    notice << " or create an account" if Gitlab::CurrentSettings.allow_signup?
     notice << "."
     store_location_for :user, request.fullpath

app/controllers/koding_controller.rb

@@ -10,6 +10,6 @@ class KodingController < ApplicationController
   private
   def check_integration!
-    render_404 unless current_application_settings.koding_enabled?
+    render_404 unless Gitlab::CurrentSettings.koding_enabled?
   end
 end

app/controllers/oauth/applications_controller.rb

 class Oauth::ApplicationsController < Doorkeeper::ApplicationsController
-  include Gitlab::CurrentSettings
   include Gitlab::GonHelper
   include PageLayoutHelper
   include OauthApplications
@@ -31,7 +30,7 @@ class Oauth::ApplicationsController < Doorkeeper::ApplicationsController
   private
   def verify_user_oauth_applications_enabled
-    return if current_application_settings.user_oauth_applications?
+    return if Gitlab::CurrentSettings.user_oauth_applications?
     redirect_to profile_path
   end

app/controllers/omniauth_callbacks_controller.rb

@@ -145,7 +145,7 @@ class OmniauthCallbacksController < Devise::OmniauthCallbacksController
     label = Gitlab::OAuth::Provider.label_for(oauth['provider'])
     message = "Signing in using your #{label} account without a pre-existing GitLab account is not allowed."
-    if current_application_settings.allow_signup?
+    if Gitlab::CurrentSettings.allow_signup?
       message << " Create a GitLab account first, and then connect it to your #{label} account."
     end

app/controllers/passwords_controller.rb

 class PasswordsController < Devise::PasswordsController
-  include Gitlab::CurrentSettings
-
   skip_before_action :require_no_authentication, only: [:edit, :update]
   before_action :resource_from_email, only: [:create]
@@ -46,7 +44,7 @@ class PasswordsController < Devise::PasswordsController
     if resource
       return if resource.allow_password_authentication?
     else
-      return if current_application_settings.password_authentication_enabled?
+      return if Gitlab::CurrentSettings.password_authentication_enabled?
     end
     redirect_to after_sending_reset_password_instructions_path_for(resource_name),

app/controllers/projects_controller.rb

@@ -394,7 +394,7 @@ class ProjectsController < Projects::ApplicationController
   end
   def project_export_enabled
-    render_404 unless current_application_settings.project_export_enabled?
+    render_404 unless Gitlab::CurrentSettings.project_export_enabled?
   end
   def redirect_git_extension

app/controllers/root_controller.rb

@@ -23,7 +23,7 @@ class RootController < Dashboard::ProjectsController
   def redirect_unlogged_user
     if redirect_to_home_page_url?
-      redirect_to(current_application_settings.home_page_url)
+      redirect_to(Gitlab::CurrentSettings.home_page_url)
     else
       redirect_to(new_user_session_path)
     end
@@ -48,9 +48,9 @@ class RootController < Dashboard::ProjectsController
   def redirect_to_home_page_url?
     # If user is not signed-in and tries to access root_path - redirect him to landing page
     # Don't redirect to the default URL to prevent endless redirections
-    return false unless current_application_settings.home_page_url.present?
-    home_page_url = current_application_settings.home_page_url.chomp('/')
+    return false unless Gitlab::CurrentSettings.home_page_url.present?
+    home_page_url = Gitlab::CurrentSettings.home_page_url.chomp('/')
     root_urls = [Gitlab.config.gitlab['url'].chomp('/'), root_url.chomp('/')]
     root_urls.exclude?(home_page_url)

app/helpers/application_settings_helper.rb

 module ApplicationSettingsHelper
   extend self
-  include Gitlab::CurrentSettings
-
   delegate  :allow_signup?,
             :gravatar_enabled?,
             :password_authentication_enabled_for_web?,
             :akismet_enabled?,
             :koding_enabled?,
-            to: :current_application_settings
+            to: :'Gitlab::CurrentSettings.current_application_settings'
   def user_oauth_applications?
-    current_application_settings.user_oauth_applications
+    Gitlab::CurrentSettings.user_oauth_applications
   end
   def allowed_protocols_present?
-    current_application_settings.enabled_git_access_protocol.present?
+    Gitlab::CurrentSettings.enabled_git_access_protocol.present?
   end
   def enabled_protocol
-    case current_application_settings.enabled_git_access_protocol
+    case Gitlab::CurrentSettings.enabled_git_access_protocol
     when 'http'
       gitlab_config.protocol
     when 'ssh'
@@ -57,7 +55,7 @@ module ApplicationSettingsHelper
   # toggle button effect.
   def import_sources_checkboxes(help_block_id)
     Gitlab::ImportSources.options.map do |name, source|
-      checked = current_application_settings.import_sources.include?(source)
+      checked = Gitlab::CurrentSettings.import_sources.include?(source)
       css_class = checked ? 'active' : ''
       checkbox_name = 'application_setting[import_sources][]'
@@ -72,7 +70,7 @@ module ApplicationSettingsHelper
   def oauth_providers_checkboxes
     button_based_providers.map do |source|
-      disabled = current_application_settings.disabled_oauth_sign_in_sources.include?(source.to_s)
+      disabled = Gitlab::CurrentSettings.disabled_oauth_sign_in_sources.include?(source.to_s)
       css_class = 'btn'
       css_class << ' active' unless disabled
       checkbox_name = 'application_setting[enabled_oauth_sign_in_sources][]'

app/helpers/auth_helper.rb

 module AuthHelper
-  include Gitlab::CurrentSettings
-
   PROVIDERS_WITH_ICONS = %w(twitter github gitlab bitbucket google_oauth2 facebook azure_oauth2 authentiq).freeze
   FORM_BASED_PROVIDERS = [/\Aldap/, 'crowd'].freeze
@@ -41,7 +39,7 @@ module AuthHelper
   end
   def enabled_button_based_providers
-    disabled_providers = current_application_settings.disabled_oauth_sign_in_sources || []
+    disabled_providers = Gitlab::CurrentSettings.disabled_oauth_sign_in_sources || []
     button_based_providers.map(&:to_s) - disabled_providers
   end

app/helpers/projects_helper.rb

 module ProjectsHelper
-  include Gitlab::CurrentSettings
-
   def link_to_project(project)
     link_to [project.namespace.becomes(Namespace), project], title: h(project.name) do
       title = content_tag(:span, project.name, class: 'project-name')
@@ -214,7 +212,7 @@ module ProjectsHelper
       project.cache_key,
       controller.controller_name,
       controller.action_name,
-      current_application_settings.cache_key,
+      Gitlab::CurrentSettings.cache_key,
       'v2.5'
     ]
@@ -447,10 +445,10 @@ module ProjectsHelper
       path = "#{import_path}?repo=#{repo}&branch=#{branch}&sha=#{sha}"
-      return URI.join(current_application_settings.koding_url, path).to_s
+      return URI.join(Gitlab::CurrentSettings.koding_url, path).to_s
     end
-    current_application_settings.koding_url
+    Gitlab::CurrentSettings.koding_url
   end
   def contribution_guide_path(project)
@@ -559,7 +557,7 @@ module ProjectsHelper
   def restricted_levels
     return [] if current_user.admin?
-    current_application_settings.restricted_visibility_levels || []
+    Gitlab::CurrentSettings.restricted_visibility_levels || []
   end
   def project_permissions_settings(project)

app/helpers/version_check_helper.rb

 module VersionCheckHelper
   def version_status_badge
-    if Rails.env.production? && current_application_settings.version_check_enabled
+    if Rails.env.production? && Gitlab::CurrentSettings.version_check_enabled
       image_url = VersionCheck.new.url
       image_tag image_url, class: 'js-version-status-badge'
     end

app/helpers/visibility_level_helper.rb

@@ -151,12 +151,12 @@ module VisibilityLevelHelper
   def restricted_visibility_levels(show_all = false)
     return [] if current_user.admin? && !show_all
-    current_application_settings.restricted_visibility_levels || []
+    Gitlab::CurrentSettings.restricted_visibility_levels || []
   end
   delegate  :default_project_visibility,
             :default_group_visibility,
-            to: :current_application_settings
+            to: :'Gitlab::CurrentSettings.current_application_settings'
   def disallowed_visibility_level?(form_model, level)
     return false unless form_model.respond_to?(:visibility_level_allowed?)

app/mailers/abuse_report_mailer.rb

 class AbuseReportMailer < BaseMailer
-  include Gitlab::CurrentSettings
-
   def notify(abuse_report_id)
     return unless deliverable?
     @abuse_report = AbuseReport.find(abuse_report_id)
     mail(
-      to:       current_application_settings.admin_notification_email,
+      to:       Gitlab::CurrentSettings.admin_notification_email,
       subject:  "#{@abuse_report.user.name} (#{@abuse_report.user.username}) was reported for abuse"
     )
   end
@@ -15,6 +13,6 @@ class AbuseReportMailer < BaseMailer
   private
   def deliverable?
-    current_application_settings.admin_notification_email.present?
+    Gitlab::CurrentSettings.admin_notification_email.present?
   end
 end

app/mailers/base_mailer.rb

 class BaseMailer < ActionMailer::Base
-  include Gitlab::CurrentSettings
-
   around_action :render_with_default_locale
   helper ApplicationHelper
   helper MarkupHelper
   attr_accessor :current_user
-  helper_method :current_user, :can?, :current_application_settings
+  helper_method :current_user, :can?
   default from:     proc { default_sender_address.format }
   default reply_to: proc { default_reply_to_address.format }

app/models/clusters/platforms/kubernetes.rb

 module Clusters
   module Platforms
     class Kubernetes < ActiveRecord::Base
-      include Gitlab::CurrentSettings
       include Gitlab::Kubernetes
       include ReactiveCaching
@@ -169,7 +168,7 @@ module Clusters
         {
           token: token,
           ca_pem: ca_pem,
-          max_session_time: current_application_settings.terminal_max_session_time
+          max_session_time: Gitlab::CurrentSettings.terminal_max_session_time
         }
       end

app/models/issue_assignee.rb

 class IssueAssignee < ActiveRecord::Base
-  extend Gitlab::CurrentSettings
-
   belongs_to :issue
   belongs_to :assignee, class_name: "User", foreign_key: :user_id
 end