Merge branch '17932-move-to-project-dropdown' into 'master'

Move to project dropdown with infinite scroll for better performance

## What does this MR do?

On the Move dropdown on the edit issue page we introduced infinite scrolling to just return a limited number of projects, 50 items. So if the user can move the issue to 50 or more items when scroll down on the list a new set of projects will be requested to the server.

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

## Why was this MR needed?

See #17932

## What are the relevant issue numbers?

Closes #17932

## Screenshots (if relevant)

## 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
  - [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 !5686

1 files changed, 6 insertions, 0 deletions

diff --git a/app/finders/move_to_project_finder.rb b/app/finders/move_to_project_finder.rb
index 3334b8556df..79eb45568be 100644
--- a/app/finders/move_to_project_finder.rb
+++ b/app/finders/move_to_project_finder.rb
@@ -1,4 +1,6 @@
 class MoveToProjectFinder
+  PAGE_SIZE = 50
+
   def initialize(user)
     @user = user
   end
@@ -8,6 +10,10 @@ class MoveToProjectFinder
     projects = projects.search(search) if search.present?
     projects = projects.excluding_project(from_project)
 
+    # infinite scroll using offset
+    projects = projects.where('projects.id < ?', offset_id) if offset_id.present?
+    projects = projects.limit(PAGE_SIZE)
+
     # to ask for Project#name_with_namespace
     projects.includes(namespace: :owner)
   end