Only redirect to homepage url when its not the root url

It was possible to create an infi redirect when the user set up the
`home_page_url` to redirect to the main URL of the gitlab instance.

This fix makes sure this redirect is not possible.

Fixes !1020
Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

app/controllers/application_controller.rb

@@ -59,13 +59,8 @@ class ApplicationController < ActionController::Base
   end
 
   def authenticate_user!(*args)
-    # 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
-    if current_application_settings.home_page_url.present? &&
-        current_application_settings.home_page_url.chomp('/') != Gitlab.config.gitlab['url'].chomp('/')
-      if current_user.nil? && root_path == request.path
-        redirect_to current_application_settings.home_page_url and return
-      end
+    if redirect_to_home_page_url?
+      redirect_to current_application_settings.home_page_url and return
     end
 
     super(*args)
@@ -346,4 +341,17 @@ class ApplicationController < ActionController::Base
   def git_import_enabled?
     current_application_settings.import_sources.include?('git')
   end
+
+  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('/')
+    root_urls = [Gitlab.config.gitlab['url'].chomp('/'), root_url.chomp('/')]
+
+    return false if root_urls.include?(home_page_url)
+
+    current_user.nil? && root_path == request.path
+  end
 end