We often ask people for their openttd.cfg, which now includes their
passwords, usernames, etc. It is easy for people to overlook this,
unwillingly sharing information they shouldn't.
By splitting this information over either private.cfg or secrets.cfg,
we make it more obvious they shouldn't be sharing those files, and
hint to what is inside them.
With std::variant all memory can be figured out at compile time, so the compiler needs to keep track of fewer elements. It also saves out a unique_ptr and its memory management, over a slight impact for resolving a setting.
One UpdateServiceInterval has two parameters to update the service interval for a vehicle type, the other for all vehicle types at once. Rename the latter to help with function resolution for the introduction of variants.
This means that during loading we can validate that what is saved
is also that what is expected. Additionally, this makes all list
types similar to how they are stored on disk:
First a gamma to indicate length, followed by the data.
The size still depends on the type.
It was rather confusing which one was for what, especially as some
SaveLoad flags were settings-only. Clean up this mess a bit by
having only Setting flags.
It is a lovely organicly grown enum, where it started off with
GUI-only flags, and after that a few flags got added that can be
considered GUI-only (the GUI disables/enables based on them), to
only have flags added that has nothing to do with the GUI.
So be less confusing, and rename them to what they do.
Additionally, I took this opportunity to rename 0ISDISABLED to
reflect what it really does.
This is mostly done as there are now constraints on settings.ini you might not
expected. For example, conditional settings always have to come last, as otherwise
they would influence the index.
