Revert "no need to show the help about Github or the other authentication sources"

app/helpers/application_settings_helper.rb

@@ -71,8 +71,15 @@ module ApplicationSettingsHelper
       label_tag(checkbox_name, class: css_class) do
         check_box_tag(checkbox_name, source, !disabled,
                       autocomplete: 'off',
-                      'aria-describedby' => help_block_id) + Gitlab::OAuth::Provider.label_for(source)
+                      aria: { describedby: help_block_id }) + Gitlab::OAuth::Provider.label_for(source)
       end
     end
   end
+
+  def oauth_providers_with_help_links
+    button_based_providers.map do |provider|
+      Gitlab::OAuth::Provider.label_for(provider) + ' ' +
+        link_to("(?)", help_page_path("integration", provider))
+    end
+  end
 end

app/views/admin/application_settings/_form.html.haml

@@ -116,6 +116,9 @@
           .btn-group{ data: { toggle: 'buttons' } }
             - oauth_providers_checkboxes('oauth-providers-help').each do |source|
               = source
+          %span.help-block#oauth-providers-help
+            Enabled OmniAuth must be configured for
+            = oauth_providers_with_help_links.to_sentence.html_safe
     .form-group
       = f.label :two_factor_authentication, 'Two-factor authentication', class: 'control-label col-sm-2'
       .col-sm-10