code: func NewAdvRefs() *AdvRefs {
  	return &AdvRefs{
  		Prefix:       [][]byte{},
  		Capabilities: capability.NewList(),
  		References:   make(map[string]plumbing.Hash),
  		Peeled:       make(map[string]plumbing.Hash),
  		Shallows:     []plumbing.Hash{},
  	}
  }
docs: // NewAdvRefs returns a pointer to a new AdvRefs value, ready to be used.