Butler: export Coordinator host in environment.

logdog/client/cmd/logdog_butler/subcommand_run.go

Index: logdog/client/cmd/logdog_butler/subcommand_run.go
diff --git a/logdog/client/cmd/logdog_butler/subcommand_run.go b/logdog/client/cmd/logdog_butler/subcommand_run.go
index e3927b798f521e25e907aaefbc2d8334386bf380..01873c0f4c4911acfa2529c121f3247cffe1fbd6 100644
--- a/logdog/client/cmd/logdog_butler/subcommand_run.go
+++ b/logdog/client/cmd/logdog_butler/subcommand_run.go
@@ -162,12 +162,24 @@ func (cmd *runCommandRun) Run(app subcommands.Application, args []string) int {
 		cwd, _ = os.Getwd()
 	}
 
+	// Get our output factory.
+	of, err := a.getOutputFactory()
+	if err != nil {
+		log.WithError(err).Errorf(a, "Failed to get output factory instance.")
+		return runtimeErrorReturnCode
+	}
+
 	// Update our environment for the child process to inherit
 	bsEnv := bootstrap.Environment{
 		Project: a.project,
 		Prefix:  a.prefix,
 	}
 
+	// If our output factory has a Coordinator host, fill that in too.
+	if cho, ok := of.(coordinatorHostOutput); ok {
+		bsEnv.CoordinatorHost = cho.getCoordinatorHost()
+	}
+
 	// Configure stream server
 	streamServer := streamserver.StreamServer(nil)
 	streamServerOwned := true
@@ -269,7 +281,7 @@ func (cmd *runCommandRun) Run(app subcommands.Application, args []string) int {
 	// We're about ready to execute our command. Initialize our Output instance.
 	// We want to do this before we execute our subprocess so that if this fails,
 	// we don't have to interrupt an already-running process.
-	output, err := a.configOutput()
+	output, err := of.configOutput(a)
 	if err != nil {
 		log.WithError(err).Errorf(a, "Failed to create output instance.")
 		return runtimeErrorReturnCode