refactor: rename tag struct for clarity

include/program_args/arguments.h

@@ -21,8 +21,8 @@ struct LongArg {
   std::string str;
 };
 
-constexpr struct usage_on_error_t {
-} usage_on_error;
+constexpr struct require_action_t {
+} require_action;
 
 template <typename Impl> class Arguments {
 private:
@@ -271,7 +271,7 @@ int typed_main(Args const &, Actions const &...);
   using Arguments::Arguments
 
 #define PROGRAM_ARGS_INVOKE(...)                                               \
-  PROGRAM_ARGS_INVOKE_WITH_DEFAULT(program::usage_on_error, ##__VA_ARGS__)
+  PROGRAM_ARGS_INVOKE_WITH_DEFAULT(program::require_action, __VA_ARGS__)
 
 #define PROGRAM_ARGS_MAIN(tname)                                               \
   int main(int argc, char const * const * const argv) try {                    \