config: add create_on_announce option

This option allows the user to specify whether or not to create a new
swarm for torrents that do not previously exist within the tracker's
storage.

config/config.go

@@ -75,6 +75,7 @@ type WhitelistConfig struct {
 
 // TrackerConfig is the configuration for tracker functionality.
 type TrackerConfig struct {
+	CreateOnAnnounce      bool     `json:"create_on_announce"`
 	PrivateEnabled        bool     `json:"private_enabled"`
 	FreeleechEnabled      bool     `json:"freeleech_enabled"`
 	PurgeInactiveTorrents bool     `json:"purge_inactive_torrents"`
@@ -107,6 +108,7 @@ type Config struct {
 // DefaultConfig is a configuration that can be used as a fallback value.
 var DefaultConfig = Config{
 	TrackerConfig: TrackerConfig{
+		CreateOnAnnounce:      true,
 		PrivateEnabled:        false,
 		FreeleechEnabled:      false,
 		PurgeInactiveTorrents: true,

example_config.json

@@ -1,4 +1,5 @@
 {
+  "create_on_announce": true,
   "private_enabled": false,
   "freeleech_enabled": false,
   "purge_inactive_torrents": true,

tracker/announce.go

@@ -27,7 +27,7 @@ func (tkr *Tracker) HandleAnnounce(ann *models.Announce, w Writer) (err error) {
 
 	torrent, err := tkr.FindTorrent(ann.Infohash)
 
-	if err == models.ErrTorrentDNE && !tkr.Config.PrivateEnabled {
+	if err == models.ErrTorrentDNE && cfg.CreateOnAnnounce {
 		torrent = &models.Torrent{
 			Infohash: ann.Infohash,
 			Seeders:  models.NewPeerMap(true, tkr.Config),