Preserve Unknown User Options Across Down-/Upgrades

[SimonN]

Lix 0.10.21

1. Have two different versions of the Lix executable in the same Lix tree: Lix version A and Lix version B, with A older than B.
2. Run version B and exit B. This will generate an options file lixdir/user/options.sdl.
3. Look in the file for options that B recognizes, but A doesn't.
4. Run version A and exit A. This will overwrite the options file.
5. Run version B and look in the options menu.

Expected: After step 4, all options from step 3 are still visible in the file. In step 5, the user options in version B are identical to how they were in step 2.

Observed instead: In step 4, version A has removed options unknown to A. In step 5, those options default; in general, they're not what they were in step 2.

[SimonN]

I'm testing a fix for this:

• During option loading, Lix will collect unknown options. Lix will parse them (and will reject invalid SDLang) but will not interpret them; they're kept as SDLang tags.
• During saving, Lix will tack those unknown options to the bottom of the options file. This will let you preserve options during downgrades, as long as all versions have this option-preserving feature.
• We accept that, over the years, the option files will accumulate a handful of unknown options.

@geoo89, you suggested preserving options across down-/upgrades. Do you have a better idea than this planned fix?

The fix is already in unstable Lix. If this has no bugs, it will go into 0.10.22 later this week.