Add cat tree snapshot:subpath command

This command prints the tree for the given path.

cmd/restic/cmd_cat.go

@@ -13,7 +13,7 @@ import (
 )
 
 var cmdCat = &cobra.Command{
-	Use:   "cat [flags] [pack|blob|snapshot|index|key|masterkey|config|lock] ID",
+	Use:   "cat [flags] [masterkey|config|pack ID|blob ID|snapshot ID|index ID|key ID|lock ID|tree snapshot:path]",
 	Short: "Print internal objects to stdout",
 	Long: `
 The "cat" command is used to print internal objects to stdout.
@@ -55,7 +55,7 @@ func runCat(ctx context.Context, gopts GlobalOptions, args []string) error {
 	tpe := args[0]
 
 	var id restic.ID
-	if tpe != "masterkey" && tpe != "config" && tpe != "snapshot" {
+	if tpe != "masterkey" && tpe != "config" && tpe != "snapshot" && tpe != "tree" {
 		id, err = restic.ParseID(args[1])
 		if err != nil {
 			return errors.Fatalf("unable to parse ID: %v\n", err)
@@ -165,6 +165,29 @@ func runCat(ctx context.Context, gopts GlobalOptions, args []string) error {
 
 		return errors.Fatal("blob not found")
 
+	case "tree":
+		sn, subpath, err := restic.FindSnapshot(ctx, repo.Backend(), repo, args[1])
+		if err != nil {
+			return errors.Fatalf("could not find snapshot: %v\n", err)
+		}
+
+		err = repo.LoadIndex(ctx)
+		if err != nil {
+			return err
+		}
+
+		sn.Tree, err = restic.FindTreeDirectory(ctx, repo, sn.Tree, subpath)
+		if err != nil {
+			return err
+		}
+
+		buf, err := repo.LoadBlob(ctx, restic.TreeBlob, *sn.Tree, nil)
+		if err != nil {
+			return err
+		}
+		_, err = globalOptions.stdout.Write(buf)
+		return err
+
 	default:
 		return errors.Fatal("invalid type")
 	}