fix: return error when --format and --pretty are both used (oras-proj…

…ect#1359)

Signed-off-by: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>

cmd/oras/root/manifest/fetch.go

@@ -74,11 +74,15 @@ Example - Fetch raw manifest from an OCI layout archive file 'layout.tar':
 			switch {
 			case opts.outputPath == "-" && opts.Template != "":
 				return fmt.Errorf("`--output -` cannot be used with `--format %s` at the same time", opts.Template)
-			case opts.OutputDescriptor && opts.Template != "":
-				return fmt.Errorf("`--descriptor` cannot be used with `--format %s` at the same time", opts.Template)
 			case opts.OutputDescriptor && opts.outputPath == "-":
 				return fmt.Errorf("`--descriptor` cannot be used with `--output -` at the same time")
 			}
+			if err := oerrors.CheckMutuallyExclusiveFlags(cmd.Flags(), "format", "pretty"); err != nil {
+				return err
+			}
+			if err := oerrors.CheckMutuallyExclusiveFlags(cmd.Flags(), "format", "descriptor"); err != nil {
+				return err
+			}
 			opts.RawReference = args[0]
 			return option.Parse(cmd, &opts)
 		},

test/e2e/suite/command/manifest.go

@@ -112,6 +112,8 @@ var _ = Describe("ORAS beginners:", func() {
 					ExpectFailure().Exec()
 				ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, foobar.Tag), "--output", "-", "--descriptor").
 					ExpectFailure().Exec()
+				ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, foobar.Tag), "--format", "test", "--pretty").
+					ExpectFailure().Exec()
 			})
 		})