Add support for ruleset alt_dir definition.
The ruleset can define alt_dir for itself. That definition about current ruleset is saved to savegames (along the main rulesetdir definition). When the savegame is loaded and loading of the ruleset as defined by main rulesetdir definition fails, server tries to load ruleset from the alt_dir.
Purpose of this is to provide a way, though slow - migration happens over a version boundary -, to rename ruleset directory. Older ruleset version, in the old path, has future path as alt_dir, so future version can load from that path.
#2 Updated by Marko Lindqvist about 1 month ago
- Handle alt directory loading in load_rulesets(), so that there's no unnecessary loading of fallback ruleset when attempt to load ruleset from the main rulesetdir fails