Show long help message when defined
This fixes the help template so that if a command
includes a Long form help message that is displayed instead
of ignoring it and always showing the Short message.
@@ -104,7 +104,7 @@ var usageTemplate = `Usage:
{{- if not .HasSubCommands}} {{.UseLine}}{{end}}
{{- if .HasSubCommands}} {{ .CommandPath}} COMMAND{{end}}
-{{ .Short | trim }}
+{{if ne .Long ""}}{{ .Long | trim }}{{ else }}{{ .Short | trim }}{{end}}
{{- if gt .Aliases 0}}
