In a heavy saucepan toss together gently the tomatoes, the onion, and the sugar and let the mixture stand for 2 hours. Stir in the vinegar, the ginger root, the jalapeno, the coriander seeds, the mustard seeds, and the salt and simmer the mixture for 10 minutes. Transfer the solids with a slotted spoon to a bowl, pouring any accumulated liquid back into the pan, and boil the liquid until it is reduced to about 1/2 cup. Stir in the rosemary or the mint and pour the liquid over the tomato mixture. Stir the chutney gently and chill it, covered, for 2 hours, or until it is cold. The chutney may be made 5 days in advance and kept covered and chilled. Serve the chutney chilled or at room temperature. Makes about 2 cups. veg