Implement dry run mode

lib/producer/core/env.rb

@@ -2,13 +2,14 @@ module Producer
   module Core
     class Env
       attr_reader   :input, :output, :registry, :logger
-      attr_accessor :target
+      attr_accessor :target, :dry_run
 
       def initialize(input: $stdin, output: $stdout, remote: nil, registry: {})
         @input    = input
         @output   = output
         @registry = registry
         @remote   = remote
+        @dry_run  = false
       end
 
       def remote
@@ -43,6 +44,10 @@ module Producer
       def log_level=(level)
         logger.level = level
       end
+
+      def dry_run?
+        @dry_run
+      end
     end
   end
 end