prow/cmd/build/controller.go
func defaultArguments(t *buildv1alpha1.TemplateInstantiationSpec, rawEnv map[string]string) {
	keys := sets.String{}
	for _, arg := range t.Arguments {
		keys.Insert(arg.Name)
	}
	for _, k := range sets.StringKeySet(rawEnv).List() { // deterministic ordering
		if keys.Has(k) {
			continue
		}
		t.Arguments = append(t.Arguments, buildv1alpha1.ArgumentSpec{Name: k, Value: rawEnv[k]})
	}
}
func defaultArguments(t *buildv1alpha1.TemplateInstantiationSpec, rawEnv map[string]string) {
	keys := sets.String{}
	for _, arg := range t.Arguments {
		keys.Insert(arg.Name)
	}
	for _, k := range sets.StringKeySet(rawEnv).List() { // deterministic ordering
		if keys.Has(k) {
			continue
		}
		t.Arguments = append(t.Arguments, buildv1alpha1.ArgumentSpec{Name: k, Value: rawEnv[k]})
	}
}
// defaultArguments will append each arg to the template, except where the argument name is already defined.