src/server/pkg/dag/dag.go
func (d *DAG) Ghosts() []string {
	var result []string
	for id := range d.children {
		if _, ok := d.parents[id]; !ok {
			result = append(result, id)
		}
	}
	return result
}
func (d *DAG) Ghosts() []string {
	var result []string
	for id := range d.children {
		if _, ok := d.parents[id]; !ok {
			result = append(result, id)
		}
	}
	return result
}
// Ghosts returns nodes that were referenced as parents but never created.