Log uses of isolate archive and exparchive when 'chromium' build tag is set.

client/cmd/isolate/common.go

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package main
 
 import (
         "errors"
         "flag"
         "fmt"
@@ skipping 117 matching lines @@
                 }
         }
         return nil
 }
 
 // loggingFlags configures eventlog logging.
 type loggingFlags struct {
         EventlogEndpoint string
 }
 
+const eventlogEndpointHelp = `The URL destination for eventlogs. The following special values are supported:
+\t"prod": use the prod eventlog endpoint
+\t"test": use the test eventlog endpoint
+\t"none": disable eventlogging
+\t"auto": use the prod endpoint if --isolate-server is set to the prod isolate server; otherwise disable eventlogging.`
+
 func (lf *loggingFlags) Init(f *flag.FlagSet) {
-        f.StringVar(&lf.EventlogEndpoint, "eventlog-endpoint", "", `The URL destination for eventlogs. The special values "prod" or "test" may be used to target the standard prod or test urls repspectively. An empty string disables eventlogging.`)
+        f.StringVar(&lf.EventlogEndpoint, "eventlog-endpoint", "auto", eventlogEndpointHelp)
 }