home: fish: use real .fish files for functions

home/fish/default.nix

@@ -0,0 +1,15 @@
+{ config, lib, ... }:
+let
+  cfg = config.my.home.fish;
+in
+{
+  options.my.home.fish.enable = lib.mkEnableOption "Fish shell";
+
+  config = lib.mkIf cfg.enable {
+    programs.fish = {
+      enable = true;
+    };
+
+    xdg.configFile."fish/functions" = { source = ./. + "/functions"; };
+  };
+}

home/fish/functions/nfl.fish

@@ -0,0 +1,7 @@
+function nfl
+    set -l flags "--commit-lock-file"
+    for flake in $argv
+        set -a flags "--update-input" "$flake"
+    end
+    nix flake lock $flags
+end