message: nydusify: output nydus & oci manifest index for check
  In order to debug oci and nydus image more friendly when use
  `nydusify check` command, we'd better output `oci_index.json`
  and `nydus_index.json` file.
diff: @@ -32,12 +32,21 @@ func (checker *Checker) Output(
  ) error {
  logrus.Infof("Dumping OCI and Nydus manifests to %s", outputPath)
  + if sourceParsed.Index != nil {
  + if err := prettyDump(
  + sourceParsed.Index,
  + filepath.Join(outputPath, "oci_index.json"),
  + ); err != nil {
  + return errors.Wrap(err, "output oci index file")
  + }
  + }
  +
  if targetParsed.Index != nil {
  if err := prettyDump(
  targetParsed.Index,
  - filepath.Join(outputPath, "index.json"),
  + filepath.Join(outputPath, "nydus_index.json"),
  ); err != nil {
  - return errors.Wrap(err, "output index file")
  + return errors.Wrap(err, "output nydus index file")
  }
  }
  