In a saucepan set over moderate heat, warm the oil until it is hot, add the onion and garlic and cook, stirring, until golden. Add the gingerroot, cinnamon stick, and cardamom, and cook, stirring, 1 minute. Add the rice and cook, stirring, until rice is coated with oil. Add the water and salt, bring to a boil, and simmer, covered, 20 minutes. Stir in raisins and let stand, covered, 5 minutes. Remove cinnamon stick before serving.