Use wireutil.reply() where possible.

lib/roles/device/plugins/shell.js

@@ -14,7 +14,7 @@ module.exports = syrup.serial()
     var log = logger.createLogger('device:plugins:shell')
 
     router.on(wire.ShellCommandMessage, function(channel, message) {
-      var seq = 0
+      var reply = wireutil.reply(options.serial)
 
       log.info('Running shell command "%s"', message.command)
 
@@ -34,11 +34,7 @@ module.exports = syrup.serial()
             while ((chunk = stream.read())) {
               push.send([
                 channel
-              , wireutil.envelope(new wire.TransactionProgressMessage(
-                  options.serial
-                , seq++
-                , chunk
-                ))
+              , reply.progress(chunk)
               ])
             }
           }
@@ -46,11 +42,7 @@ module.exports = syrup.serial()
           function endListener() {
             push.send([
               channel
-            , wireutil.envelope(new wire.TransactionDoneMessage(
-                options.serial
-              , seq++
-              , true
-              ))
+            , reply.okay()
             ])
             resolver.resolve()
           }
@@ -85,12 +77,7 @@ module.exports = syrup.serial()
           log.error('Shell command "%s" failed', message.command, err.stack)
           push.send([
             channel
-          , wireutil.envelope(new wire.TransactionDoneMessage(
-              options.serial
-            , seq++
-            , false
-            , err.message
-            ))
+          , reply.fail(err.message)
           ])
         })
     })