godoc: initialize vars depending on flags after parsing the flags.

R=rsc
CC=golang-dev
https://golang.org/cl/206109

src/cmd/godoc/godoc.go

@@ -111,10 +111,12 @@ func init() {
 	flag.StringVar(&cmdroot, "cmdroot", pathutil.Join(goroot, "src/cmd"), "command source directory")
 	flag.StringVar(&pkgroot, "pkgroot", pathutil.Join(goroot, "src/pkg"), "package source directory")
 	flag.StringVar(&tmplroot, "tmplroot", pathutil.Join(goroot, "lib/godoc"), "template directory")
+}
+
 
+func initHandlers() {
 	fsMap.Init(*path)
 	fileServer = http.FileServer(goroot, "")
-
 	cmdHandler = httpHandler{"/cmd/", cmdroot, false}
 	pkgHandler = httpHandler{"/pkg/", pkgroot, true}
 }

src/cmd/godoc/main.go

@@ -152,6 +152,7 @@ func main() {
 		log.Exitf("negative tabwidth %d", *tabwidth)
 	}
 
+	initHandlers()
 	readTemplates()
 
 	if *httpaddr != "" {