jquery 1.x and 2.x use same api
http://lists.alioth.debian.org/pipermail/pkg-javascript-devel/2015-September/011230.html

Index: gitlab/app/assets/javascripts/application.js.coffee
===================================================================
--- gitlab.orig/app/assets/javascripts/application.js.coffee
+++ gitlab/app/assets/javascripts/application.js.coffee
@@ -4,7 +4,7 @@
 # It's not advisable to add code directly here, but if you do, it'll appear at the bottom of the
 # the compiled file.
 #
-#= require jquery2
+#= require jquery
 #= require jquery-ui/autocomplete
 #= require jquery-ui/datepicker
 #= require jquery-ui/draggable