}

func initFromJSON(overlayJSON OverlayJSON) error {
	// Canonicalize the paths in the overlay map.
	// Use reverseCanonicalized to check for collisions:
	// no two 'from' paths should canonicalize to the same path.
	overlay = make(map[string]*node)
	reverseCanonicalized := make(map[string]string) // inverse of canonicalize operation, to check for duplicates