redshift didn't properly work because it couldn't read the DISPLAY environment
variable. I can fix this ad-hoc with `systemctl --user import-environment
DISPLAY`, but home-manager will do this automatically if I allow it to manage my
xsession.
If you haven't noticed, home-manager is managing increasingly more of my
configuration.
- Migrate session variables to home.nix
- Drop support for unused session variables like TERMINAL, VISUAL
I patched home-manager locally to support fzf keybindings for fish. I will PR
this into home-manager, but I haven't yet, which means that my home.nix file
depends on my local ~/home-manager.