Merge branch '22773-add-comparison-link-to-system-note' into 'master'

Add link to comparison from system note, update changelog

## What does this MR do?
Adds a link to the comparison between the previous and latest version.

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

## Screenshots (if relevant)

![Screen_Shot_2016-10-01_at_3.37.03_AM](/uploads/89b48dc1b2ed868cf5dd85300e6b37a0/Screen_Shot_2016-10-01_at_3.37.03_AM.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] ~~[Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- [ ] ~~API support added~~
- Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Closes #22773

See merge request !6607

1 files changed, 6 insertions, 0 deletions

diff --git a/spec/services/system_note_service_spec.rb b/spec/services/system_note_service_spec.rb
index 3d854a959f3..b16840a1238 100644
--- a/spec/services/system_note_service_spec.rb
+++ b/spec/services/system_note_service_spec.rb
@@ -40,6 +40,12 @@ describe SystemNoteService, services: true do
     describe 'note body' do
       let(:note_lines) { subject.note.split("\n").reject(&:blank?) }
 
+      describe 'comparison diff link line' do
+        it 'adds the comparison text' do
+          expect(note_lines[2]).to match "[Compare with previous version]"
+        end
+      end
+
       context 'without existing commits' do
         it 'adds a message header' do
           expect(note_lines[0]).to eq "Added #{new_commits.size} commits:"