Add help message

Author: satotake

Diff for: cmd/compose/pull.go

@@ -65,8 +65,8 @@ func pullCommand(p *projectOptions, backend api.Service) *cobra.Command {
 	cmd.Flags().BoolVar(&opts.parallel, "no-parallel", true, "DEPRECATED disable parallel pulling.")
 	flags.MarkHidden("no-parallel") //nolint:errcheck
 	cmd.Flags().BoolVar(&opts.ignorePullFailures, "ignore-pull-failures", false, "Pull what it can and ignores images with pull failures")
-	cmd.Flags().BoolVar(&opts.dryRun, "dry-run", false, "TODO")
-	cmd.Flags().StringVar(&opts.format, "format", "", "TODO")
+	cmd.Flags().BoolVar(&opts.dryRun, "dry-run", false, "Calc and print effects of execution of pull command without any actual effects")
+	cmd.Flags().StringVar(&opts.format, "format", "", `Format the output. Only compatible with "--dry-run". Values: [pretty | json]. (Default: pretty)`)
 	return cmd
 }