Merge branch 'mr-fetch-command' into 'master'

merge_requests: add fetch command to the MR page

In our instance, users asked for an easy way to get the contents of the MR into their local clone. This adds a command line which can be used to fetch the contents of the MR.

Screenshot:

![fetch-command](https://gitlab.com/gitlab-org/gitlab-ce/uploads/d83acfbdb69f023d13b45dff5d583ac1/fetch-command.png)

See merge request !678

CHANGELOG

@@ -8,6 +8,7 @@ v 7.14.0 (unreleased)
   - Set OmniAuth full_host parameter to ensure redirect URIs are correct (Stan Hu)
   - Expire Rails cache entries after two weeks to prevent endless Redis growth
   - Add support for destroying project milestones (Stan Hu)
+  - Add fetch command to the MR page.
 
 v 7.13.0 (unreleased)
   - Only enable HSTS header for HTTPS and port 443 (Stan Hu)

app/views/projects/merge_requests/_show.html.haml

@@ -31,6 +31,16 @@
               %li= link_to "Email Patches", merge_request_path(@merge_request, format: :patch)
               %li= link_to "Plain Diff",    merge_request_path(@merge_request, format: :diff)
 
+    - if @merge_request.open? and @merge_request.source_branch_exists?
+      .append-bottom-20
+        .slead
+          %span
+            Fetch the branch with
+            %strong.label-branch<
+              git fetch
+              \ #{@merge_request.source_project.http_url_to_repo}
+              \ #{@merge_request.source_branch}
+
     = render "projects/merge_requests/show/how_to_merge"
     = render "projects/merge_requests/widget/show.html.haml"