resolve confilts

app/views/exercises/_editor.html.slim

@@ -1,7 +1,7 @@
 #editor.row data-exercise-id=exercise.id data-message-depleted=t('exercises.editor.depleted') data-message-timeout=t('exercises.editor.timeout', permitted_execution_time: @exercise.execution_environment.permitted_execution_time) data-errors-url=execution_environment_errors_path(exercise.execution_environment) data-submissions-url=submissions_path data-user-id=@current_user.id
   div class=(@exercise.hide_file_tree ? 'hidden col-sm-3' : 'col-sm-3') = render('editor_file_tree', files: @files)
   div id='frames' class=(@exercise.hide_file_tree ? 'col-sm-12' : 'col-sm-9')
-    - @files.sort{ |a,b| a[:group][:name] <=> b[:group][:name] }.each do |file|
+    - @files.each do |file|
       = render('editor_frame', exercise: exercise, file: file)
     #autosave-label
       = t('exercises.editor.lastsaved')

app/views/exercises/_file_form.html.slim

@@ -4,7 +4,7 @@ li.panel.panel-default
     div.clearfix role="button"
       span = f.object.name
       a.pull-right data-toggle="collapse" data-parent="#files" href="#collapse#{id}" collapse
-  .panel-collapse.collapse id="collapse#{id}" role="tabpanel"
+  .panel-collapse.collapse.in id="collapse#{id}" role="tabpanel"
     .panel-body
       .clearfix = link_to(t('shared.destroy'), '#', class:'btn btn-warning btn-sm discard-file pull-right')
       .form-group

app/views/exercises/show.html.slim

@@ -23,13 +23,13 @@ h1
 h2 = t('activerecord.attributes.exercise.files')
 
 ul.list-unstyled.panel-group#files
-  - @exercise.files.order('name').each do |file|
+  - @exercise.files.each do |file|
     li.panel.panel-default
       .panel-heading role="tab" id="heading"
         div.clearfix role="button"
           span.panel-title = file.name_with_extension
           a.pull-right data-toggle="collapse" data-parent="#files" href="#collapse#{file.id}" collapse
-      .panel-collapse.collapse id="collapse#{file.id}" role="tabpanel"
+      .panel-collapse.collapse.in id="collapse#{file.id}" role="tabpanel"
         .panel-body
           - if policy(file).destroy?
             .clearfix = link_to(t('shared.destroy'), file, class:'btn btn-warning btn-sm pull-right', data: {confirm: t('shared.confirm_destroy')}, method: :delete)