Merge branch 'mr-widget-replace-body' into 'master'

Replace merge request widget body

See merge request !8697

app/assets/javascripts/merge_request_widget.js.es6

@@ -126,7 +126,9 @@
 
     MergeRequestWidget.prototype.getMergeStatus = function() {
       return $.get(this.opts.merge_check_url, function(data) {
-        return $('.mr-state-widget').replaceWith(data);
+        var $html = $(data);
+        $('.mr-state-body').replaceWith($html.find('.mr-state-body'));
+        $('.mr-state-footer').replaceWith($html.find('.mr-state-footer'));
       });
     };