take an optional argument for the server directory

gen-stats.rb

@@ -3,6 +3,9 @@
 require "json"
 require "set"
 
+# Run with gen-stats.rb <server_directory>
+SERVER_DIR = ARGV[0] || "."
+
 ADVENTURE_BIOMES = [
   "Beach",
   "Birch Forest",
@@ -48,7 +51,7 @@ class GenStats
   end
 
   def run
-    user_cache = JSON.load(File.read("usercache.json"))
+    user_cache = JSON.load(File.read("#{SERVER_DIR}/usercache.json"))
     @users_by_uuid = user_cache.reduce({}) do |result, user|
       result[user["uuid"]] = user
       result
@@ -64,7 +67,7 @@ class GenStats
       "Killed By" => {},
       "Items Broken" => {},
     }
-    Dir["world/stats/*.json"].each do |stats_fname|
+    Dir["#{SERVER_DIR}/world/stats/*.json"].each do |stats_fname|
       load_stats(stats_fname)
     end