Use the Gitlab Workhorse HTTP header in the admin dashboard

Signed-off-by: Rémy Coutable <remy@rymai.me>

app/helpers/components_helper.rb

+module ComponentsHelper
+  def gitlab_workhorse_version
+    if request.headers['Gitlab-Workhorse'].present?
+      request.headers['Gitlab-Workhorse'].split('-').first
+    else
+      Gitlab::Workhorse.version
+    end
+  end
+end

app/views/admin/dashboard/index.html.haml

@@ -87,7 +87,7 @@
         %p
           GitLab Workhorse
           %span.pull-right
-            = Gitlab::Workhorse.version
+            = gitlab_workhorse_version
         %p
           GitLab API
           %span.pull-right

changelogs/unreleased/21664-incorrect-workhorse-version-number-displayed.yml

+---
+title: Use the Gitlab Workhorse HTTP header in the admin dashboard
+merge_request:
+author: Chris Wright

spec/helpers/components_helper_spec.rb

+require 'spec_helper'
+
+describe ComponentsHelper do
+  describe '#gitlab_workhorse_version' do
+    context 'without a Gitlab-Workhorse header' do
+      it 'shows the version from Gitlab::Workhorse.version' do
+        expect(helper.gitlab_workhorse_version).to eq Gitlab::Workhorse.version
+      end
+    end
+
+    context 'with a Gitlab-Workhorse header' do
+      before do
+        helper.request.headers['Gitlab-Workhorse'] = '42.42.0-rc3'
+      end
+
+      it 'shows the actual GitLab Workhorse version currently in use' do
+        expect(helper.gitlab_workhorse_version).to eq '42.42.0'
+      end
+    end
+  end
+end