Merge branch 'lock_for_issuable' into 'master'

Optimistic locking for Issue and Merge Requests

## What does this MR do?

It implements Optimistic Locking http://api.rubyonrails.org/classes/ActiveRecord/Locking/Optimistic.html for Issues and MRs but in a bit custom way. We use it for cases when either title or description field is involved in the change.

## Why was this MR needed?

We have to prevent data losing.

## What are the relevant issue numbers?
https://gitlab.com/gitlab-org/gitlab-ce/issues/12940

## Screenshots (if relevant)

![Screen_Shot_2016-07-09_at_15.33.02](/uploads/2efbe547a12fda93bce347fa711438d7/Screen_Shot_2016-07-09_at_15.33.02.png)


See merge request !5146

2 files changed, 9 insertions, 2 deletions

diff --git a/app/controllers/projects/issues_controller.rb b/app/controllers/projects/issues_controller.rb
index b6e80762e3c..f7ada5cfee4 100644
--- a/app/controllers/projects/issues_controller.rb
+++ b/app/controllers/projects/issues_controller.rb
@@ -119,6 +119,10 @@ class Projects::IssuesController < Projects::ApplicationController
         render json: @issue.to_json(include: { milestone: {}, assignee: { methods: :avatar_url }, labels: { methods: :text_color } })
       end
     end
+
+  rescue ActiveRecord::StaleObjectError
+    @conflict = true
+    render :edit
   end
 
   def referenced_merge_requests
@@ -216,7 +220,7 @@ class Projects::IssuesController < Projects::ApplicationController
   def issue_params
     params.require(:issue).permit(
       :title, :assignee_id, :position, :description, :confidential,
-      :milestone_id, :due_date, :state_event, :task_num, label_ids: []
+      :milestone_id, :due_date, :state_event, :task_num, :lock_version, label_ids: []
     )
   end
 
diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index df659bb8c3b..2deb7959700 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -196,6 +196,9 @@ class Projects::MergeRequestsController < Projects::ApplicationController
     else
       render "edit"
     end
+  rescue ActiveRecord::StaleObjectError
+    @conflict = true
+    render :edit
   end
 
   def remove_wip
@@ -424,7 +427,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
       :title, :assignee_id, :source_project_id, :source_branch,
       :target_project_id, :target_branch, :milestone_id,
       :state_event, :description, :task_num, :force_remove_source_branch,
-      label_ids: []
+      :lock_version, label_ids: []
     )
   end