dotenv: enable overriding rails secret token / session key.

config/initializers/secret_token.rb

@@ -1,9 +1,9 @@
 require File.expand_path('../../state_checker', __FILE__)
 
-StateChecker.new.check!
+StateChecker.check!
 
 Rails.application.config.action_dispatch.session = {
   :key    => '_danbooru2_session',
-  :secret => File.read(File.expand_path("~/.danbooru/session_secret_key"))
+  :secret => StateChecker.session_secret_key
 }
-Rails.application.config.secret_token = File.read(File.expand_path("~/.danbooru/secret_token"))
+Rails.application.config.secret_token = StateChecker.secret_token

config/state_checker.rb

@@ -1,7 +1,17 @@
-class StateChecker
+module StateChecker
+  module_function
+
   def check!
-    check_secret_token
-    check_session_secret_key
+    ENV["SECRET_TOKEN"].present? || check_secret_token
+    ENV["SESSION_SECRET_KEY"].present? || check_session_secret_key
+  end
+
+  def secret_token
+    ENV["SECRET_TOKEN"] || File.read(secret_token_path)
+  end
+
+  def session_secret_key
+    ENV["SESSION_SECRET_KEY"] || File.read(session_secret_key_path)
   end
 
 private