Add version check badge to admin area

app/helpers/version_check_helper.rb

+module VersionCheckHelper
+  def version_status_badge
+    image_tag VersionCheck.new.url
+  end
+end

app/views/admin/dashboard/index.html.haml

@@ -56,7 +56,11 @@
         %span.light.pull-right
           = boolean_to_icon Gitlab.config.omniauth.enabled
     .col-md-4
-      %h4 Components
+      %h4
+        Components
+        .pull-right
+          = version_status_badge
+
       %hr
       %p
         GitLab

lib/version_check.rb

+# This class is used to encrypt GitLab version and URL
+# with public key when we send it to version.gitlab.com to
+# check if it is a new version for update
+class VersionCheck
+  include SimpleEncrypt
+
+  def public_key
+    public_key_file = Rails.root.join('safe', 'public.pem').to_s
+    File.read(public_key_file)
+  end
+
+  def data
+    {
+      version: Gitlab::VERSION,
+      url: Gitlab.config.gitlab.url
+    }
+  end
+
+  def encrypt(string)
+    encrypt_with_public_key(string, public_key)
+  end
+
+  def url
+    "#{host}?gitlab_info=#{encrypt(data.to_json)}"
+  end
+
+  def host
+    'http://localhost:9090/check.png'
+  end
+end