message: replace meta option to bootstrap
diff: @@ -375,10 +375,11 @@ func main() {
  EnvVars: []string{"BACKEND_TYPE"},
  },
  &cli.StringFlag{
  - Name: "meta",
  + Name: "bootstrap",
  + Aliases: []string{"meta"}, // for compatibility
  Required: true,
  Usage: "Specify Nydus meta file name",
  - EnvVars: []string{"META"},
  + EnvVars: []string{"BOOTSTRAP"},
  },
  &cli.StringFlag{
  Name: "backend-config-file",
  @@ -423,7 +424,7 @@ func main() {
  }
  cfg, err := packer.ParseBackendConfig(backendConfigFile)
  if err != nil {
  - return errors.Errorf("failed to parse backend-config-file %s", backendConfigFile)
  + return errors.Errorf("failed to parse backend-config-file %s, err = %v", backendConfigFile, err)
  }
  backendConfig = &cfg
  }
  @@ -439,7 +440,7 @@ func main() {
  if res, err = p.Pack(context.Background(), packer.PackRequest{
  TargetDir: c.String("target-dir"),
  - Meta: c.String("meta"),
  + Meta: c.String("bootstrap"),
  PushBlob: c.Bool("backend-push"),
  }); err != nil {
  return err
  