code: func ReplaceOrAppendEnvValues(defaults, overrides []string) []string {
  	cache := make(map[string]int, len(defaults))
  	for i, e := range defaults {
  		parts := strings.SplitN(e, "=", 2)
  		cache[parts[0]] = i
  	}
  
  	for _, value := range overrides {
  		// Values w/o = means they want this env to be removed/unset.
  		if !strings.Contains(value, "=") {
  			if i, exists := cache[value]; exists {
  				defaults[i] = "" // Used to indicate it should be removed
  			}
  			continue
  		}
  
  		// Just do a normal set/update
  		parts := strings.SplitN(value, "=", 2)
  		if i, exists := cache[parts[0]]; exists {
  			defaults[i] = value
  		} else {
  			defaults = append(defaults, value)
  		}
  	}
  
  	// Now remove all entries that we want to "unset"
  	for i := 0; i < len(defaults); i++ {
  		if defaults[i] == "" {
  			defaults = append(defaults[:i], defaults[i+1:]...)
  			i--
  		}
  	}
  
  	return defaults
  }
docs: // ReplaceOrAppendEnvValues returns the defaults with the overrides either
  // replaced by env key or appended to the list