docs: def marvcli_comment_add(user, message, datasets):
      """Add comment as user for one or more datasets"""
      app = create_app()
      try:
          db.session.query(User).filter(User.name==user).one()
      except NoResultFound:
          click.echo("ERROR: No such user '{}'".format(user), err=True)
          sys.exit(1)
      ids = parse_setids(datasets, dbids=True)
      app.site.comment(user, message, ids)