add alias when fork

modules/repository/fork.go

@@ -33,6 +33,7 @@ func ForkRepository(doer, owner *models.User, oldRepo *models.Repository, name,
 		Owner:         owner,
 		OwnerName:     owner.Name,
 		Name:          name,
+		Alias:         oldRepo.Alias,
 		LowerName:     strings.ToLower(name),
 		Description:   desc,
 		DefaultBranch: oldRepo.DefaultBranch,