Rename field in Snapshot: Tree -> TreeID

cmd/khepri/cmd_backup.go

@@ -125,7 +125,7 @@ func commandBackup(repo *khepri.Repository, args []string) error {
 	}
 
 	sn := khepri.NewSnapshot(target)
-	sn.Tree = id
+	sn.TreeID = id
 	snid, err := sn.Save(repo)
 
 	if err != nil {

cmd/khepri/cmd_restore.go

@@ -127,7 +127,7 @@ func commandRestore(repo *khepri.Repository, args []string) error {
 		log.Fatalf("error loading snapshot %s", id)
 	}
 
-	err = restore_dir(repo, sn.Tree, target)
+	err = restore_dir(repo, sn.TreeID, target)
 	if err != nil {
 		return err
 	}