Make the revision on the `/help` page clickable

For quicker access, add hyperlink to the gitlab.com commits page for the current
REVISION of GitLab.

app/views/help/index.html.haml

@@ -4,7 +4,7 @@
     Community Edition
     - if user_signed_in?
       %span= Gitlab::VERSION
-      %small= Gitlab::REVISION
+      %small= link_to Gitlab::REVISION, Gitlab::COM_URL + namespace_project_commits_path('gitlab-org', 'gitlab-ce', Gitlab::REVISION)
       = version_status_badge
   %p.slead
     GitLab is open source software to collaborate on code.

changelogs/unreleased/tc-link-to-commit-on-help-page.yml

+---
+title: Make the revision on the `/help` page clickable
+merge_request: 12016
+author:

lib/gitlab.rb

 require_dependency 'gitlab/git'
 module Gitlab
+  COM_URL = 'https://gitlab.com'.freeze
+
   def self.com?
     # Check `staging?` as well to keep parity with gitlab.com
-    Gitlab.config.gitlab.url == 'https://gitlab.com' || staging?
+    Gitlab.config.gitlab.url == COM_URL || staging?
   end
   def self.staging?

spec/views/help/index.html.haml_spec.rb

@@ -21,7 +21,7 @@ describe 'help/index' do
       render
       expect(rendered).to match '8.0.2'
-      expect(rendered).to match 'abcdefg'
+      expect(rendered).to have_link('abcdefg', 'https://gitlab.com/gitlab-org/gitlab-ce/commits/abcdefg')
     end
   end