Fix sticky diff header

app/assets/javascripts/diff.js.coffee

 class @Diff
   UNFOLD_COUNT = 20
   constructor: ->
+    $(document).off('click', '.js-unfold')
     $(document).on('click', '.js-unfold', (event) =>
       target = $(event.target)
       unfoldBottom = target.hasClass('js-unfold-bottom')
@@ -36,7 +37,7 @@ class @Diff
       )
     )
 
-    $('.diff-header').stick_in_parent(offset_top: $('.navbar').height())
+    $('.diff-header').stick_in_parent(recalc_every: 1, offset_top: $('.navbar').height())
 
   lineNumbers: (line) ->
     return ([0, 0]) unless line.children().length

app/assets/javascripts/merge_request.js.coffee

@@ -95,6 +95,7 @@ class @MergeRequest
         this.$('.merge-request-tabs .diffs-tab').addClass 'active'
         this.loadDiff() unless @diffs_loaded
         this.$('.diffs').show()
+        $(".diff-header").trigger("sticky_kit:recalc")
       when 'commits'
         this.$('.merge-request-tabs .commits-tab').addClass 'active'
         this.$('.commits').show()