feat: Hook the code only when APPMAP=true

If the appmap gem is loaded, but APPMAP enabled, the process initializes
as normal.
With APPMAP=true, all the hooking is performed, with its advantages and
disadvantages.

Author: kgilpin

lib/appmap.rb

@@ -98,4 +98,4 @@ def detect_metadata
 end
 
 require 'appmap/railtie' if defined?(::Rails::Railtie)
-AppMap.initialize unless ENV['APPMAP_INITIALIZE'] == 'false'
+AppMap.initialize if ENV['APPMAP'] == 'true'

lib/appmap/railtie.rb

@@ -3,8 +3,6 @@
 module AppMap
   # Railtie connects the AppMap recorder to Rails-specific features.
   class Railtie < ::Rails::Railtie
-    config.appmap = ActiveSupport::OrderedOptions.new
-
     # appmap.subscribe subscribes to ActiveSupport Notifications so that they can be recorded as
     # AppMap events.
     initializer 'appmap.subscribe' do |_| # params: app
@@ -15,25 +13,5 @@ class Railtie < ::Rails::Railtie
 
       AppMap::Handler::Rails::RequestHandler::HookMethod.new.activate
     end
-
-    # appmap.trace begins recording an AppMap trace and writes it to appmap.json.
-    # This behavior is only activated if the configuration setting app.config.appmap.enabled
-    # is truthy.
-    initializer 'appmap.trace', after: 'appmap.subscribe' do |app|
-      lambda do
-        return unless app.config.appmap.enabled
-
-        require 'appmap/command/record'
-        require 'json'
-        AppMap::Command::Record.new(AppMap.configuration).perform do |version, metadata, class_map, events|
-          appmap = JSON.generate \
-            version: version,
-            metadata: metadata,
-            classMap: class_map,
-            events: events
-          File.open('appmap.json', 'w').write(appmap)
-        end
-      end.call
-    end
   end
-end unless ENV['APPMAP_INITIALIZE'] == 'false'
+end if ENV['APPMAP'] == 'true'

lib/appmap/version.rb

@@ -5,5 +5,5 @@ module AppMap
 
   VERSION = '0.47.1'
 
-  APPMAP_FORMAT_VERSION = '1.5.0'
+  APPMAP_FORMAT_VERSION = '1.5.1'
 end