Validate username. Gitlab::Regex added

lib/gitlab/regex.rb

@@ -0,0 +1,19 @@
+module Gitlab
+  module Regex
+    extend self
+
+    def username_regex
+      default_regex
+    end
+
+    def path_regex
+      default_regex
+    end
+
+    protected
+
+    def default_regex
+      /\A[a-zA-Z][a-zA-Z0-9_\-\.]*\z/
+    end
+  end
+end