code: func (d *Discovery) shouldWatchFromTags(tags []string) bool {
  	// If there's no fixed set of watched tags, we watch everything.
  	if len(d.watchedTags) == 0 {
  		return true
  	}
  
  tagOuter:
  	for _, wtag := range d.watchedTags {
  		for _, tag := range tags {
  			if wtag == tag {
  				continue tagOuter
  			}
  		}
  		return false
  	}
  	return true
  }
docs: // shouldWatch returns whether the service of the given name should be watched based on its tags.
  // This gets called when the user doesn't specify a list of services in order to avoid watching
  // *all* services. Details in https://github.com/prometheus/prometheus/pull/3814