Make flake inputs available as module argument

This moves a bunch of stuff out of flake.nix into the modules they
belong to. This removes complexity from flake.nix and gives the project
a more organised structure.

Sadly, it is not possible to import modules from a flake outside of
flake.nix, since that leads to an infinite recursion (`config` has to be
evaluated before `config._modules.args.inputs` is available but `config`
depends on an import from `config._modules.args.inputs`). Therefore, the
`extraModules` argument in `machines/default.nix` has to be used for
that (it now has access to all flake inputs).

flake.nix

@@ -46,20 +46,12 @@
 
   outputs =
     { self
-    , AriaNg
-    , aria2_exporter
-    , bang-evaluator
     , flake-utils
-    , home-manager
-    , infinisilSystem
     , krops
     , nix-pre-commit-hooks
-    , nixos-hardware
     , nixpkgs
-    , nixpkgs-overlay
-    , nixpkgs-unstable
-    , sops-nix
-    }: flake-utils.lib.eachDefaultSystem
+    , ...
+    }@inputs: flake-utils.lib.eachDefaultSystem
       (system:
       let
         pkgs = nixpkgs.legacyPackages.${system};
@@ -164,42 +156,10 @@
           modules = [
             (./machines + "/${hostname}/configuration.nix")
 
-            home-manager.nixosModules.home-manager
-            sops-nix.nixosModules.sops
-
-            aria2_exporter.nixosModules.aria2_exporter
-            bang-evaluator.nixosModules.bang-evaluator
-
-            # NIX_PATH for legacy tooling and flake registry pinning
             {
-              nix = {
-                nixPath = [
-                  "nixpkgs=${nixpkgs}"
-                ];
-                registry = {
-                  nixpkgs.flake = nixpkgs;
-                  nixpkgs-unstable.flake = nixpkgs-unstable;
-                };
-              };
+              _module.args.inputs = inputs;
             }
 
-            # overlays
-            ({ config, ... }: {
-              nixpkgs.overlays = [
-                self.overlay
-                nixpkgs-overlay.overlay
-                (final: prev: {
-                  unstable = import nixpkgs-unstable {
-                    inherit system;
-                    config = config.nixpkgs.config;
-                    overlays = config.nixpkgs.overlays;
-                  };
-                })
-
-                AriaNg.overlay
-              ];
-            })
-
             # deployment settings
             ({ lib, ... }: {
               options.deployment = {
@@ -221,12 +181,14 @@
                   unlockOverV4;
               };
             })
-          ] ++ extraModules;
+          ] ++ (with inputs; [
+            home-manager.nixosModules.home-manager
+            sops-nix.nixosModules.sops
+
+            aria2_exporter.nixosModules.aria2_exporter
+            bang-evaluator.nixosModules.bang-evaluator
+          ]) ++ extraModules;
         })
-        (import ./machines {
-          inherit
-            infinisilSystem
-            nixos-hardware;
-        });
+        (import ./machines inputs);
     };
 }

machines/default.nix

@@ -1,8 +1,6 @@
-{ infinisilSystem
-, nixos-hardware
-}:
+{ ... }@inputs:
 let
-  hardware = nixos-hardware.nixosModules;
+  hardware = inputs.nixos-hardware.nixosModules;
 in
 {
   nunotaba = {
@@ -22,7 +20,7 @@ in
   vueko = {
     system = "x86_64-linux";
     extraModules = [
-      "${infinisilSystem}/config/new-modules/murmur.nix"
+      "${inputs.infinisilSystem}/config/new-modules/murmur.nix"
     ];
 
     targetHost = "vueko.sbruder.de";

modules/nix.nix

@@ -1,4 +1,4 @@
-{ config, lib, pkgs, ... }:
+{ config, inputs, lib, pkgs, ... }:
 let
   # Adapted from https://nixos.wiki/wiki/Overlays
   overlaysCompat = pkgs.writeTextFile {
@@ -30,7 +30,13 @@ in
     # nix with flake support
     package = pkgs.nixUnstable;
 
+    registry = with inputs; {
+      nixpkgs.flake = nixpkgs;
+      nixpkgs-unstable.flake = nixpkgs-unstable;
+    };
+
     nixPath = [
+      "nixpkgs=${inputs.nixpkgs}"
       "nixpkgs-overlays=${overlaysCompat}"
     ];
     # Make sudoers trusted nix users
@@ -61,4 +67,19 @@ in
     daemonNiceLevel = 10;
     daemonIONiceLevel = 5; # 0-7
   };
+
+  nixpkgs.overlays = with inputs; [
+    self.overlay
+    nixpkgs-overlay.overlay
+    (final: prev: {
+      unstable = import nixpkgs-unstable {
+        inherit (config.nixpkgs)
+          config
+          overlays
+          system;
+      };
+    })
+
+    AriaNg.overlay
+  ];
 }