Merge branch 'edit-on-fork' into 'master'

Automatically fork a project when not allowed to edit a file.

Fixes #3215.

To do:

- [ ] Add tests

-----

## "Edit" button on file in a project the user does NOT have write access to

![edit_file](/uploads/7602157420768aef483a6586bba2d164/edit_file.png)

## Clicking will automatically create a fork

![during_fork](/uploads/32f4f5dff9f24ea99522000b0bf881c5/during_fork.png)

## When the fork has been created, the user is returned to the edit page on the original project with a notice

![edit_notice](/uploads/94ed1319404370ff1e9c0d672fb41e03/edit_notice.png)

## The user cannot change the target branch and is informed that editing will start an MR

![edit_footer](/uploads/4da68d4795c7177e575b7c434d16eeae/edit_footer.png)

## Hitting "Commit changes" will commit and start an MR from my fork to the origin project

![Screen_Shot_2015-12-17_at_23.38.08](/uploads/d777a4db6f38a5a1be84031694465bc1/Screen_Shot_2015-12-17_at_23.38.08.png)

-----

## "Create file, "Upload file" and "New directory" buttons in a project the user does NOT have write access to

![new_directory](/uploads/72f556248f30d6652523bbb4be01b3e0/new_directory.png)

## Clicking any of these options will automatically create a fork

![during_fork](/uploads/32f4f5dff9f24ea99522000b0bf881c5/during_fork.png)

## When the fork has been created, the user is returned to the tree page on the original project with a notice

![new_directory_notice](/uploads/a1a3e11308ae0e8f0913fae6813a37ed/new_directory_notice.png)

## Clicking "New directory" again will show the modal. The user cannot change the target branch and is informed that editing will start an MR

![new_dir](/uploads/99ca8cbfb2f70603e352b3fdf67b6281/new_dir.png)

## Hitting "Create directory" will commit and start an MR from my fork to the origin project

![Screen_Shot_2015-12-17_at_23.39.19](/uploads/3713d0235abf831361b803a6198c5bc1/Screen_Shot_2015-12-17_at_23.39.19.png)

cc @dzaporozhets @skyruler

See merge request !2145

1 files changed, 15 insertions, 2 deletions

diff --git a/app/services/create_branch_service.rb b/app/services/create_branch_service.rb
index a6844985c4e..f139872c728 100644
--- a/app/services/create_branch_service.rb
+++ b/app/services/create_branch_service.rb
@@ -1,7 +1,7 @@
 require_relative 'base_service'
 
 class CreateBranchService < BaseService
-  def execute(branch_name, ref)
+  def execute(branch_name, ref, source_project: @project)
     valid_branch = Gitlab::GitRefValidator.validate(branch_name)
     if valid_branch == false
       return error('Branch name is invalid')
@@ -13,7 +13,20 @@ class CreateBranchService < BaseService
       return error('Branch already exists')
     end
 
-    new_branch = repository.add_branch(current_user, branch_name, ref)
+    new_branch = nil
+    if source_project != @project
+      repository.with_tmp_ref do |tmp_ref|
+        repository.fetch_ref(
+          source_project.repository.path_to_repo,
+          "refs/heads/#{ref}",
+          tmp_ref
+        )
+
+        new_branch = repository.add_branch(current_user, branch_name, tmp_ref)
+      end
+    else
+      new_branch = repository.add_branch(current_user, branch_name, ref)
+    end
 
     if new_branch
       push_data = build_push_data(project, current_user, new_branch)