Fish has wrong config files inside of Neovim

[marcuswhybrow]

:!mkdir templates
error: can not save universal variables or functions
warning-path: Unable to locate config directory derived from $XDG_CONFIG_HOME: '/nix/store/xabd1qazk33n780qanahmxyqmgb1n83r-neovim-config/fish'.
warning-path: The error was 'Read-only file system'.
warning-path: Please set $XDG_CONFIG_HOME to a directory where you have write access.

When I ask Neovim to run a command in the shell with the :! Neovim command, fish complains it has no write access to it's XDG_CONFIG_HOME. That's correct, because I'm hoisting it to a nix store derivation when Neovim starts up:

https://github.com/marcuswhybrow/.nixos/blob/4d44fa8001dc2dbcfd86a7dc8a70e12f89be1fa1/pkgs/neovim/default.nix#L104-L105

Proposed solution: Add to XDG_CONFIG_DIRS, instead of overriding XDG_CONFIG_HOME.

[marcuswhybrow]

• I belive this no longer an issue.
• These day's I wrap Neovim with -u /path/to/init.lua rather than XDG_CONFIG_... stuf.
• Before I used to have multiple lua files, and I couldn't figure out how to include them all without using XDG.
• Now I have a single init.lua with my entire config in one place.

This is how I'm doing it now:
https://github.com/marcuswhybrow/neovim/blob/750f299cf5b63c4e176076e7bf19b7d7d42e2d4e/flake.nix#L137