Packaging Touhou project and utilities into deterministic derivation.

• Wineprefix with Noto fonts and DXVK carefully bubblewrapped. All saves/config stored nice in ~/.config/touhou-on-nixos/. This effectively makes game root readonly.
• Nixified thcrap patches.
• Thprac and vpatch support.

1. Bring your own Touhou game, for example th06. Note that you should use a clean copy, e.g. the one you use for thcrap. Your Touhou game will not go into Nix store, but will be bind-mounted into bubblewrapped environment.
2. Switch to game root and nix run github:gjz010/touhou-on-nixos#zh_CN.th06.

• Wayland/X11 smart switching.

• thpatch.net does not provide permalinks/content-addresses links to patch assets, making it impossible to create a deterministic derivation.
• Mirrors of thpatch.net also have the same issue and are not always synced. For example, I get completely different hashes when switching from mirrors back and forth. Sometimes, some thpatch.net mirrors even host broken metadata.
• The repo discovery behaviour is also weird: repo discovery starts from thpatch.net to GitHub, only to find a mirror exists on thpatch.net, which totally defeating the purpose of mirroring. Therefore we only allow (probably auto-generated) downloading from thpatch.net and thpatch.rcopky.top by dirty hacking: providing an invalid http_proxy and a whitelist of no_proxy.
• Every user has to run thcrap2nix (which is a bad name since it does not produce Nix, but fixed output derivation) to download patches. The utility is dirtyly linked to thcrap itself and is therefore 32bit Wine only.

(20241011 notes: while lilywhite.cc provides fast downloading for Chinese users, some important metadata files like tpZHCNex/tsa/patch.js adds it as "first server of patch", which is then used to fetch patch.js. We have no way but to add lilywhite.cc to the whitelist.)

One possible solution to all the dirty issues above is to create and maintain a content-addressable mirror (e.g. like a git repository) by ourselves. We could even create our own metadata during sync with thpatch, such that thcrap2nix is only needed to be run by CI, and touhou-on-nixos users can use generated thcrap patch derivations.

Possible problems:

• Current dirty thcrap2nix is still too dirty. We may want to rollout our own thcrap patch downloader.
• thpatch.net repo is large. I once tried downloading entire mirrors.thpatch.net and it consumed ~20 GB of total size.
• Creating thpatch.net mirror may face legal issues like copyright infringement.