Add test demonstrating the problem

When there's a branch with the same name as the tag, the branch gets checked out
instead of the tag.

pkg/integration/tests/test_list.go

@@ -245,6 +245,7 @@ var tests = []*components.IntegrationTest{
 	sync.PushWithCredentialPrompt,
 	sync.RenameBranchAndPull,
 	tag.Checkout,
+	tag.CheckoutWhenBranchWithSameNameExists,
 	tag.CreateWhileCommitting,
 	tag.CrudAnnotated,
 	tag.CrudLightweight,