//
// The order of the remaining elements in the list is deterministic
// but arbitrary.
func (g *Graph) BuildList() []module.Version {
	seenRoot := make(map[string]bool, len(g.roots))

	var list []module.Version
	for _, r := range g.roots {
		if seenRoot[r.Path] {
			// Multiple copies of the same root, with the same or different versions,
			// are a bit of a degenerate case: we will take the transitive