code: func buildRevCache(c context.Context, b *buildbot.Build) memcache.Item {
  	item := memcache.NewItem(c, "buildbot_revision/"+b.ID().String())
  	if b.Sourcestamp != nil {
  		item.SetValue([]byte(b.Sourcestamp.Revision))
  	}
  	return item
  }
docs: // buildRevCache returns a memcache.Item for the build's revision.
  // Initializes the value with current revision.