LogDog: Implement prefix registration in Butler.

client/cmd/logdog_butler/subcommand_stream.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package main
 
 import (
         "os"
 
         "github.com/luci/luci-go/client/internal/logdog/butler"
@@ skipping 50 matching lines @@
                 if err != nil {
                         log.Fields{
                                 log.ErrorKey: err,
                                 "path":       cmd.path,
                         }.Errorf(a, "Failed to open input stream file.")
                         return runtimeErrorReturnCode
                 }
                 streamFile = file
         }
 
+        // We think everything should work. Configure our Output instance.
+        output, err := a.configOutput()
+        if err != nil {
+                log.WithError(err).Errorf(a, "Failed to create output instance.")
+                return runtimeErrorReturnCode
+        }
+        defer output.Close()
+
         // Instantiate our Processor.
-        err := a.Main(func(b *butler.Butler) error {
+        err = a.runWithButler(output, func(b *butler.Butler) error {
                 if err := b.AddStream(streamFile, cmd.stream.properties()); err != nil {
                         return err
                 }
 
                 b.Activate()
                 return nil
         })
         if err != nil {
                 log.Fields{
                         log.ErrorKey: err,
                 }.Errorf(a, "Failed to stream file.")
                 return runtimeErrorReturnCode
         }
 
         return 0
 }