Allow to disable importing

[jbruechert]

I haven't thoroughly tested this yet

[felixguendling]

This will not work this way as most modules initialize data in the import method.

At least this needs to run for the nigiri module to work:

motis/modules/nigiri/src/nigiri.cc

Lines 473 to 481 in 092abec

	impl_->tt_ = std::make_shared<cista::wrapped<n::timetable>>(
	n::timetable::read(cista::memory_holder{
	cista::file{dump_file_path.string().c_str(), "r"}
	.content()}));
	(**impl_->tt_).locations_.resolve_timezones();
	if (!gtfsrt_urls_.empty() || !gtfsrt_paths_.empty()) {
	impl_->update_rtt(std::make_shared<n::rt_timetable>(
	n::rt::create_rt_timetable(**impl_->tt_, today)));
	}

motis/modules/nigiri/src/nigiri.cc

Lines 500 to 522 in 092abec

	if (lookup_) {
	impl_->station_lookup_ = std::make_shared<nigiri_station_lookup>(
	impl_->tags_, **impl_->tt_);
	auto copy = impl_->station_lookup_;
	add_shared_data(to_res_id(mm::global_res_id::STATION_LOOKUP),
	std::move(copy));
	}
	if (guesser_) {
	impl_->guesser_ =
	std::make_unique<guesser>(impl_->tags_, (**impl_->tt_));
	}
	if (railviz_) {
	impl_->initial_permalink_ = get_initial_permalink(**impl_->tt_);
	impl_->railviz_ =
	std::make_unique<railviz>(impl_->tags_, (**impl_->tt_));
	}
	add_shared_data(to_res_id(mm::global_res_id::NIGIRI_TIMETABLE),
	impl_->tt_->get());
	add_shared_data(to_res_id(mm::global_res_id::NIGIRI_TAGS),
	&impl_->tags_);

Same for the osr module:

motis/modules/osr/src/osr.cc

Lines 347 to 352 in 092abec

	auto w = std::make_unique<o::ways>(dir, cista::mmap::protection::READ);
	if (lock_) {
	w->lock();
	}
	auto l = std::make_unique<o::lookup>(*w);
	impl_ = std::make_unique<impl>(std::move(w), std::move(l));

I guess the only option is to have a additional parameter to the import() function that indicates if it's allowed to do preprocessing if the hash does not match.

[felixguendling]

I guess another option would be to split the import functionality into preprocessing the data and actually loading the data. My plan is to address this and many other issues mentioned in #452 (such as a stable API + versioning, running MOTIS without the input folder, etc.) in one go by creating something like "MOTIS 2.0". My plan is to start working on this big refactoring in one month.