Merge branch '19493-fork-does-not-protect-default-branch' into 'master'

Make forking protect default branch on completion

Closes #19493

See merge request gitlab-org/gitlab-ce!16449

app/workers/repository_fork_worker.rb

@@ -17,10 +17,7 @@ class RepositoryForkWorker
                                           project.repository_storage_path, project.disk_path)
     raise "Unable to fork project #{project_id} for repository #{source_disk_path} -> #{project.disk_path}" unless result
 
-    project.repository.after_import
-    raise "Project #{project_id} had an invalid repository after fork" unless project.valid_repo?
-
-    project.import_finish
+    project.after_import
   end
 
   private

changelogs/unreleased/19493-fork-does-not-protect-default-branch.yml

@@ -0,0 +1,5 @@
+---
+title: Makes forking protect default branch on completion
+merge_request:
+author:
+type: fixed

spec/workers/repository_fork_worker_spec.rb

@@ -47,6 +47,14 @@ describe RepositoryForkWorker do
       perform!
     end
 
+    it 'protects the default branch' do
+      expect_fork_repository.and_return(true)
+
+      perform!
+
+      expect(fork_project.protected_branches.first.name).to eq(fork_project.default_branch)
+    end
+
     it 'flushes various caches' do
       expect_fork_repository.and_return(true)