Merge branch 'assign-issues-for-merge-request-18876' into 'master'

Ability to bulk assign issues to author of merge request

## What does this MR do?
Provides a link to auto-assign issues to the author of a merge request, when they are mentioned as being closed by the MR.

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


## Why was this MR needed?
To help avoid working on a MR without having assigned related issues to self

## What are the relevant issue numbers?
Fixes #18876 

## Screenshots (if relevant)
![ScreenShot-P216](/uploads/1af5e71a0a0ff0a60c5d7b54c0e09d9c/ScreenShot-P216.png)

## Tasks
- [x] Refactor or move away from using `BulkUpdateService`
- [x] ~~Consider alternate link message when only a subset of issues will be assigned~~
- [x] Minimize repeated calls to expensive `closes_issues` method
- [x] Move away from using inflector for pluralization and fix flash message
- [x] Change auth `before_action` and fallback to error flash message
- [x] Shouldn't overwrite current assignee if one exists

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] ~~[Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- [x] ~~API support added~~
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [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)

See merge request !5725

1 files changed, 22 insertions, 1 deletions

diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index ffd9833e3b1..869d96b86f4 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -10,7 +10,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
   before_action :module_enabled
   before_action :merge_request, only: [
     :edit, :update, :show, :diffs, :commits, :conflicts, :builds, :pipelines, :merge, :merge_check,
-    :ci_status, :toggle_subscription, :cancel_merge_when_build_succeeds, :remove_wip, :resolve_conflicts
+    :ci_status, :toggle_subscription, :cancel_merge_when_build_succeeds, :remove_wip, :resolve_conflicts, :assign_related_issues
   ]
   before_action :validates_merge_request, only: [:show, :diffs, :commits, :builds, :pipelines]
   before_action :define_show_vars, only: [:show, :diffs, :commits, :conflicts, :builds, :pipelines]
@@ -31,6 +31,8 @@ class Projects::MergeRequestsController < Projects::ApplicationController
   # Allow modify merge_request
   before_action :authorize_update_merge_request!, only: [:close, :edit, :update, :remove_wip, :sort]
 
+  before_action :authenticate_user!, only: [:assign_related_issues]
+
   before_action :authorize_can_resolve_conflicts!, only: [:conflicts, :resolve_conflicts]
 
   def index
@@ -354,6 +356,25 @@ class Projects::MergeRequestsController < Projects::ApplicationController
     render layout: false
   end
 
+  def assign_related_issues
+    result = MergeRequests::AssignIssuesService.new(project, current_user, merge_request: @merge_request).execute
+
+    respond_to do |format|
+      format.html do
+        case result[:count]
+        when 0
+          flash[:error] = "Failed to assign you issues related to the merge request"
+        when 1
+          flash[:notice] = "1 issue has been assigned to you"
+        else
+          flash[:notice] = "#{result[:count]} issues have been assigned to you"
+        end
+
+        redirect_to(merge_request_path(@merge_request))
+      end
+    end
+  end
+
   def ci_status
     pipeline = @merge_request.pipeline
     if pipeline