Add new endpoint and button to revert merge. #3409

app/controllers/projects/merge_requests_controller.rb

@@ -191,6 +191,10 @@ class Projects::MergeRequestsController < Projects::ApplicationController
     end
   end
 
+  def revert
+    redirect_to new_namespace_project_merge_request_url(@project.namespace, @project)
+  end
+
   def branch_from
     #This is always source
     @source_project = @merge_request.nil? ? @project : @merge_request.source_project

app/views/projects/merge_requests/show/_mr_title.html.haml

@@ -17,4 +17,6 @@
           %i.fa.fa-pencil-square-o
           Edit
       - if @merge_request.closed?
-        = link_to 'Reopen', merge_request_path(@merge_request, merge_request: {state_event: :reopen }), method: :put, class: 'btn btn-nr btn-grouped btn-reopen reopen-mr-link', title: 'Reopen merge request'
+        = link_to 'Reopen', merge_request_path(@merge_request, merge_request: {state_event: :reopen }), method: :put, class: 'btn btn-nr btn-grouped btn-reopen reopen-mr-link', title: "Reopen merge request"
+      - if @merge_request.merged?
+        = link_to 'Revert', revert_namespace_project_merge_request_path(@project.namespace, @project, @merge_request), method: :post, class: "btn btn-grouped btn-close", title: "Revert merge request"

config/routes.rb

@@ -590,6 +590,7 @@ Rails.application.routes.draw do
             post :cancel_merge_when_build_succeeds
             get :ci_status
             post :toggle_subscription
+            post :revert
           end
 
           collection do