Fix up list datacenters to build help string in constructor

command/catlistdc/catalog_list_datacenters.go

@@ -10,7 +10,7 @@ import (
 
 func New(ui cli.Ui) *cmd {
 	c := &cmd{UI: ui}
-	c.initFlags()
+	c.init()
 	return c
 }
 
@@ -18,13 +18,15 @@ type cmd struct {
 	UI    cli.Ui
 	flags *flag.FlagSet
 	http  *flags.HTTPFlags
+	usage string
 }
 
-func (c *cmd) initFlags() {
+func (c *cmd) init() {
 	c.flags = flag.NewFlagSet("", flag.ContinueOnError)
 	c.http = &flags.HTTPFlags{}
 	flags.Merge(c.flags, c.http.ClientFlags())
 	flags.Merge(c.flags, c.http.ServerFlags())
+	c.usage = flags.Usage(usage, c.flags, c.http.ClientFlags(), c.http.ServerFlags())
 }
 
 func (c *cmd) Run(args []string) int {
@@ -61,7 +63,10 @@ func (c *cmd) Synopsis() string {
 }
 
 func (c *cmd) Help() string {
-	s := `Usage: consul catalog datacenters [options]
+	return c.usage
+}
+
+const usage = `Usage: consul catalog datacenters [options]
 
   Retrieves the list of all known datacenters. This datacenters are sorted in
   ascending order based on the estimated median round trip time from the servers
@@ -72,5 +77,3 @@ func (c *cmd) Help() string {
       $ consul catalog datacenters
 
   For a full list of options and examples, please see the Consul documentation.`
-	return flags.Usage(s, c.flags, c.http.ClientFlags(), c.http.ServerFlags())
-}