Detect if we didn't create the ref sooner

app/models/repository.rb

@@ -999,7 +999,7 @@ class Repository
     yield(commit(branch_name_or_sha))
 
   ensure
-    rugged.references.delete(tmp_ref) if tmp_ref
+    rugged.references.delete(tmp_ref) if tmp_ref && ref_exists?(tmp_ref)
   end
 
   def add_remote(name, url)
@@ -1022,6 +1022,9 @@ class Repository
   def fetch_ref(source_path, source_ref, target_ref)
     args = %W(fetch --no-tags -f #{source_path} #{source_ref}:#{target_ref})
     run_git(args)
+
+    # Make sure ref was created, and raise Rugged::ReferenceError when not
+    raise Rugged::ReferenceError unless ref_exists?(target_ref)
   end
 
   def create_ref(ref, ref_path)

spec/models/repository_spec.rb

@@ -961,6 +961,27 @@ describe Repository, models: true do
       end
     end
 
+    context 'when temporary ref failed to be created from other project' do
+      let(:target_project) { create(:project, :empty_repo) }
+
+      before do
+        expect(target_project.repository).to receive(:run_git)
+      end
+
+      it 'raises Rugged::ReferenceError' do
+        raise_reference_error = raise_error(Rugged::ReferenceError) do |err|
+          expect(err.cause).to be_nil
+        end
+
+        expect do
+          GitOperationService.new(user, target_project.repository)
+            .with_branch('feature',
+                         start_project: project,
+                         &:itself)
+        end.to raise_reference_error
+      end
+    end
+
     context 'when the update adds more than one commit' do
       let(:old_rev) { '33f3729a45c02fc67d00adb1b8bca394b0e761d9' }