Add version check badge to admin area

lib/version_check.rb

@@ -0,0 +1,30 @@
+# 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