Add validation errors to Merge Request form

If source branch or target branch doesn't exist in the project, display
form validation errors. Previously, this caused a 500 error code.

1 files changed, 8 insertions, 0 deletions

diff --git a/spec/features/merge_requests/create_new_mr_spec.rb b/spec/features/merge_requests/create_new_mr_spec.rb
index b963d1305b5..c68e1ea4af9 100644
--- a/spec/features/merge_requests/create_new_mr_spec.rb
+++ b/spec/features/merge_requests/create_new_mr_spec.rb
@@ -59,4 +59,12 @@ feature 'Create New Merge Request', feature: true, js: true do
       expect(page).to have_css('a.btn.active', text: 'Side-by-side')
     end
   end
+
+  it 'does not allow non-existing branches' do
+    visit new_namespace_project_merge_request_path(project.namespace, project, merge_request: { target_branch: 'non-exist-target', source_branch: 'non-exist-source' })
+
+    expect(page).to have_content('The form contains the following errors')
+    expect(page).to have_content('Source branch "non-exist-source" does not exist')
+    expect(page).to have_content('Target branch "non-exist-target" does not exist')
+  end
 end