Merge branch 'add-gitlab-workhorse-version-to-admin-dashboard' into 'master'

Add gitlab-workhorse version to admin dashboard

## What does this MR do?
Add gitlab-workhorse version to admin dashboard.

## What are the relevant issue numbers?
Closes #15418 

## Screenshot
![Zrzut_ekranu_2016-07-20_o_23.20.55](/uploads/ba6761e2145d903ac87bc7198bc8b182/Zrzut_ekranu_2016-07-20_o_23.20.55.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] Add test - show Gitlab Workhorse version on Admin Dashboard
  - [x] All builds are passing
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)

cc @ubudzisz @yorickpeterse @grzesiek [@chastell](https://github.com/chastell) [@tomash](https://github.com/tomash)

See merge request !5321

CHANGELOG

@@ -5,6 +5,7 @@ v 8.11.0 (unreleased)
   - Limit git rev-list output count to one in forced push check
   - Retrieve rendered HTML from cache in one request
   - Load project invited groups and members eagerly in ProjectTeam#fetch_members
+  - Add GitLab Workhorse version to admin dashboard (Katarzyna Kobierska Ula Budziszewska)
 
 v 8.10.0
   - Fix profile activity heatmap to show correct day name (eanplatter)

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

@@ -79,6 +79,10 @@
           GitLab Shell
           %span.pull-right
             = Gitlab::Shell.new.version
+        %p
+          GitLab Workhorse
+          %span.pull-right
+            = Gitlab::Workhorse.version
         %p
           GitLab API
           %span.pull-right

lib/gitlab/workhorse.rb

@@ -4,6 +4,7 @@ require 'json'
 module Gitlab
   class Workhorse
     SEND_DATA_HEADER = 'Gitlab-Workhorse-Send-Data'
+    VERSION_FILE = 'GITLAB_WORKHORSE_VERSION'
 
     class << self
       def git_http_ok(repository, user)
@@ -75,6 +76,11 @@ module Gitlab
         ]
       end
 
+      def version
+        path = Rails.root.join(VERSION_FILE)
+        path.readable? ? path.read.chomp : 'unknown'
+      end
+
       protected
 
       def encode(hash)

spec/views/admin/dashboard/index.html.haml_spec.rb

+require 'spec_helper'
+
+describe 'admin/dashboard/index.html.haml' do
+  include Devise::TestHelpers
+
+  before do
+    assign(:projects, create_list(:empty_project, 1))
+    assign(:users, create_list(:user, 1))
+    assign(:groups, create_list(:group, 1))
+
+    allow(view).to receive(:admin?).and_return(true)
+  end
+
+  it "shows version of GitLab Workhorse" do
+    render
+
+    expect(rendered).to have_content 'GitLab Workhorse'
+    expect(rendered).to have_content Gitlab::Workhorse.version
+  end
+end