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
Index: gitlab/Gemfile
===================================================================
--- gitlab.orig/Gemfile
+++ gitlab/Gemfile
@@ -227,7 +227,7 @@ gem 'font-awesome-rails', '~> 4.6', '>=
 gem 'gemojione',          '~> 3.0'
 gem 'gon',                '~> 6.0', '>= 6.0.1'
 gem 'jquery-atwho-rails', '~> 1.3', '>= 1.3.2'
-gem 'jquery-rails',       '~> 4.1'
+gem 'jquery-rails',       '~> 4.0'
 gem 'jquery-ui-rails',    '~> 5.0'
 gem 'request_store',      '~> 1.3'
 gem 'select2-rails',      '~> 3.5', '>= 3.5.9'