Add button for sorting

app/views/shared/_sort_dropdown.html.haml

@@ -2,19 +2,19 @@
 - viewing_issues = controller.controller_name == 'issues' || controller.action_name == 'issues'
 
 .dropdown.inline.prepend-left-10
-  %button.dropdown-menu-toggle{ type: 'button', data: { toggle: 'dropdown', display: 'static' } }
-    = sorted_by
-    = icon('chevron-down')
-  %ul.dropdown-menu.dropdown-menu-right.dropdown-menu-selectable.dropdown-menu-sort
-    %li
-      = sortable_item(sort_title_priority,         page_filter_path(sort: sort_value_priority,         label: true), sorted_by)
-      = sortable_item(sort_title_created_date,     page_filter_path(sort: sort_value_created_date,     label: true), sorted_by)
-      = sortable_item(sort_title_recently_updated, page_filter_path(sort: sort_value_recently_updated, label: true), sorted_by)
-
-      - if viewing_issues && (@project || @group)&.feature_available?(:issue_weights)
-        = sortable_item(sort_title_weight, page_filter_path(sort: sort_value_weight, label: true), sorted_by)
-
-      = sortable_item(sort_title_milestone,        page_filter_path(sort: sort_value_milestone,        label: true), sorted_by)
-      = sortable_item(sort_title_due_date,         page_filter_path(sort: sort_value_due_date,         label: true), sorted_by) if viewing_issues
-      = sortable_item(sort_title_popularity,       page_filter_path(sort: sort_value_popularity,       label: true), sorted_by)
-      = sortable_item(sort_title_label_priority,   page_filter_path(sort: sort_value_label_priority,   label: true), sorted_by)
+  .btn-group{ role: 'group' }
+    .btn-group{ role: 'group' }
+      %button.dropdown-toggle{ type: 'button', data: { toggle: 'dropdown', display: 'static' }, class: 'btn btn-default' }
+        = sorted_by
+        = icon('chevron-down')
+      %ul.dropdown-menu.dropdown-menu-right.dropdown-menu-selectable.dropdown-menu-sort
+        %li
+          = sortable_item(sort_title_priority,         page_filter_path(sort: sort_value_priority,         label: true), sorted_by)
+          = sortable_item(sort_title_created_date,     page_filter_path(sort: sort_value_created_date,     label: true), sorted_by)
+          = sortable_item(sort_title_recently_updated, page_filter_path(sort: sort_value_recently_updated, label: true), sorted_by)
+          = sortable_item(sort_title_milestone,        page_filter_path(sort: sort_value_milestone,        label: true), sorted_by)
+          = sortable_item(sort_title_due_date,         page_filter_path(sort: sort_value_due_date,         label: true), sorted_by) if viewing_issues
+          = sortable_item(sort_title_popularity,       page_filter_path(sort: sort_value_popularity,       label: true), sorted_by)
+          = sortable_item(sort_title_label_priority,   page_filter_path(sort: sort_value_label_priority,   label: true), sorted_by)
+    %a{ type: 'button', href: '#', class: 'btn btn-default' }
+      = sprite_icon('sort-lowest', size: 16)