case funcMode:
		op = makeDumpOp(funcMode)
	case pkglistMode:
		op = makeDumpOp(pkglistMode)
	case subtractMode:
		op = makeSubtractIntersectOp(subtractMode)
	case intersectMode:
		op = makeSubtractIntersectOp(intersectMode)
	default:
		usage(fmt.Sprintf("unknown command selector %q", cmd))
	}

	// Edit out command selector, then parse flags.
	os.Args = append(os.Args[:1], os.Args[2:]...)