fix trailing <nil> on help output

command.go

@@ -176,6 +176,15 @@ func (c *Command) Usage() error {
 	return err
 }
 
+func (c *Command) UsageString() string {
+	tmpOutput := c.Commander().cmdr.output
+	bb := new(bytes.Buffer)
+	c.Commander().SetOutput(bb)
+	c.Usage()
+	c.Commander().cmdr.output = tmpOutput
+	return bb.String()
+}
+
 // The full path to this command
 func (c *Command) CommandPath() string {
 	str := c.Name()

commander.go

@@ -143,8 +143,7 @@ Additional help topics: {{if gt .Commands 0 }}{{range .Commands}}{{if not .Runna
 Use "{{.Commander.Name}} help [command]" for more information about that command.
 `
 
-	c.HelpTemplate = `{{.Name}}
-{{.Long | trim}}
-{{if .Runnable}}{{.Usage}}{{end}}
+	c.HelpTemplate = `{{.Long | trim}}
+{{if .Runnable}}{{.UsageString}}{{end}}
 `
 }