Update check: version feed from the git server's releases, title-screen banner, clearer version refusals

scripts/net/net.gd

@@ -167,6 +167,18 @@ func _start_dedicated() -> void:
 	if not err.is_empty():
 		printerr("[server] ", err)
 		get_tree().quit(1)
+		return
+	# A real dedicated server (not one a test or Host Game started) says in
+	# its log when there's a newer version; server.json "check_updates".
+	if not _args.has("exit-with") and bool(config.v("check_updates")):
+		Updates.checked.connect(_on_update_checked, CONNECT_ONE_SHOT)
+		Updates.check(true)
+
+func _on_update_checked(s: String) -> void:
+	if s == "available":
+		print("[server] Emberwild %s is out (protocol %d); this server runs %s (protocol %d). %s" % [
+			Updates.latest_version(), Updates.latest_protocol(), Updates.version, PROTOCOL,
+			"Players with the new version can't join until it's updated." if Updates.latest_protocol() != PROTOCOL else ""])
 
 ## Opens the server. Returns "" on success, otherwise what went wrong.
 func start_server(config_path: String, overrides: Dictionary = {}) -> String:
@@ -577,7 +589,9 @@ func _c2s_hello(d: Dictionary) -> void:
 	if not is_server() or not _pending.has(peer) or _pending[peer].has("hello"):
 		return
 	if int(d.get("protocol", 0)) != PROTOCOL:
-		_reject(peer, "Different game version (server %d, you %d): update the game" % [PROTOCOL, int(d.get("protocol", 0))])
+		var theirs := int(d.get("protocol", 0))
+		_reject(peer, "Different game version: this server runs Emberwild %s (protocol %d), you have protocol %d. %s" % [
+			Updates.version, PROTOCOL, theirs, "Update the game to join." if theirs < PROTOCOL else "The server needs updating."])
 		return
 	var pw := String(config.v("password"))
 	if not pw.is_empty() and String(d.get("password", "")) != pw:

scripts/net/server_config.gd

@@ -27,6 +27,7 @@ const DEFAULTS := {
 	"autosave_minutes": 2,
 	"backups_kept": 10,
 	"backup_hours": 6,
+	"check_updates": true,
 	"admins": [],
 	"allowlist": [],
 	"banned": [],