Issues tracker settings enableds/disableds without page reloading now

app/assets/javascripts/projects.js.coffee

@@ -18,3 +18,18 @@ $ ->
   # Ref switcher
   $('.project-refs-select').on 'change', ->
     $(@).parents('form').submit()
+
+  $('#project_issues_enabled').change ->
+    if ($(this).is(':checked') == true)
+      $('#project_issues_tracker').removeAttr('disabled')
+    else
+      $('#project_issues_tracker').attr('disabled', 'disabled')
+
+    $('#project_issues_tracker').change()
+
+  $('#project_issues_tracker').change ->
+    if ($(this).val() == gon.default_issues_tracker || $(this).is(':disabled'))
+      $('#project_issues_tracker_id').attr('disabled', 'disabled')
+    else
+      $('#project_issues_tracker_id').removeAttr('disabled')
+