func (dmf *DefaultMirrorFinder) ClearMirrors(original RemoteRef) {
	dmf.Lock()
	defer dmf.Unlock()
	delete(dmf.underlyer, original)
}
ClearMirrors removes the association between a particular `RemoteRef` and all mirrored copies.
package mirrorcat
import (
	"context"
	"sync"
)
type RemoteRef struct {
	Repository string `json:"repo"`
	Ref        string `json:"ref"`
}
type MirrorFinder interface {
	FindMirrors(context.Context, RemoteRef, chan<- RemoteRef) error
}
type DefaultMirrorFinder struct {
	sync.RWMutex
	underlyer map[RemoteRef][]RemoteRef
}
func NewDefaultMirrorFinder() *DefaultMirrorFinder {
	return &DefaultMirrorFinder{
		underlyer: make(map[RemoteRef][]RemoteRef),
	}
}
func (dmf *DefaultMirrorFinder) AddMirrors(original RemoteRef, branches ...RemoteRef) {
	dmf.Lock()
	defer dmf.Unlock()
	dmf.underlyer[original] = append(dmf.underlyer[original], branches...)
}