Added documentation for 'alias' tag
diff --git a/flags.go b/flags.go
index de3aead..34adf1a 100644
--- a/flags.go
+++ b/flags.go
@@ -98,6 +98,10 @@
// field a (sub)command with the given name (optional)
// subcommands-optional: when specified on a command struct field, makes
// any subcommands of that command optional (optional)
+// alias: when specified on a command struct field, adds the
+// specified name as an alias for the command. Can be
+// be specified multiple times to add more than one
+// alias (optional)
//
// Either short: or long: must be specified to make the field eligible as an
// option.
