Render stages in valid order

CHANGELOG

@@ -18,6 +18,7 @@ v 8.12.0 (unreleased)
   - API: Ensure invitees are not returned in Members API.
   - Add two-factor recovery endpoint to internal API !5510
   - Pass the "Remember me" value to the U2F authentication form
+  - Display stages in valid order in stages dropdown on build page
   - Only update projects.last_activity_at once per hour when creating a new event
   - Remove vendor prefixes for linear-gradient CSS (ClemMakesApps)
   - Move pushes_since_gc from the database to Redis

app/views/projects/builds/_sidebar.html.haml

@@ -112,14 +112,14 @@
           %span.label.label-primary
             = tag
-    - if builds.size > 1
+    - if @build.pipeline.stages.many?
       .dropdown.build-dropdown
         .title Stage
         %button.dropdown-menu-toggle{type: 'button', 'data-toggle' => 'dropdown'}
           %span.stage-selection More
           = icon('caret-down')
         %ul.dropdown-menu
-          - builds.map(&:stage).uniq.each do |stage|
+          - @build.pipeline.stages.each do |stage|
             %li
               %a.stage-item= stage