code: func redirectLUCIBuild(c *router.Context) error {
  	idStr := c.Params.ByName("id")
  	// Verify it is an int64.
  	id, err := strconv.ParseInt(idStr, 10, 64)
  	if err != nil {
  		return errors.Annotate(err, "invalid id").Tag(grpcutil.InvalidArgumentTag).Err()
  	}
  	builder, number, err := buildbucket.GetBuilderID(c.Context, id)
  	if err != nil {
  		return err
  	}
  	numberOrID := fmt.Sprintf("%d", number)
  	if number == 0 {
  		numberOrID = fmt.Sprintf("b%d", id)
  	}
  
  	u := fmt.Sprintf("/p/%s/builders/%s/%s/%s", builder.Project, builder.Bucket, builder.Builder, numberOrID)
  	http.Redirect(c.Writer, c.Request, u, http.StatusMovedPermanently)
  	return nil
  }
docs: // redirectLUCIBuild redirects to a canonical build URL
  // e.g. to /p/{project}/builders/{bucket}/{builder}/{number or id}.