Current nixpkgs always wraps neovim with the "-u" which has sideeffects as explained in https://github.com/NixOS/nixpkgs/issues/55376 :
1. vim won't set the variable $MYVIMRC as explained #34215
2. vim skips loading folder-specific .vimrc / .nvimrc
I wanted to provide a way for users to better control what flags are used to wrap neovim. This is achived by introducing wrapNeovimUnstable et neovimUtils, utilities to help with that. We provide a compatibility layer so that wrapNeovim still works and to let us experiment with wrapNeovimUnstable to better control neovim configuration, plugin dependencies, haskell environment etc so that it becomes easier to generate per-project neovim config.
With this commit, it's possible for instance for home-manager to wrap neovim without the `-u` and just write the config in the
expected $XDG_CONFIG_HOME/nvim/init.vim .
Expect wrapNeovimUnstable interface to evolve in the upcoming months.
