code: func (h *DeployHandler) serveOldInstance(w http.ResponseWriter, br blob.Ref, depl *Deployer) (found bool) {
  	inst, err := depl.Get()
  	if err != nil {
  		// TODO(mpl,bradfitz): log or do something more
  		// drastic if the error is something other than
  		// instance not found.
  		return false
  	}
  	h.logger.Printf("Reusing existing instance for (%v, %v, %v)", depl.Conf.Project, depl.Conf.Name, depl.Conf.Zone)
  
  	if err := h.recordState(br, &creationState{
  		InstConf: br,
  		InstAddr: addr(inst),
  		Exists:   true,
  	}); err != nil {
  		h.logger.Printf("Could not record creation state for %v: %v", br, err)
  		h.serveErrorPage(w, fmt.Errorf("An error occurred while recording the state of your instance. %v", fileIssue(br.String())))
  		return true
  	}
  	h.serveProgress(w, br)
  	return true
  }
docs: // serveOldInstance looks on GCE for an instance such as defined in depl.Conf, and if
  // found, serves the appropriate page depending on whether the instance is usable. It does
  // not serve anything if the instance is not found.