ref(home-manager): don't use home-manager when building the host

When rebuilding the host (through `nixos-rebuild switch --flake`) I
don't want to rebuild also my home-manager configuration. I want these
to be two different steps.

I rebuild the home-manager configuration more frequently and it's a
waste of time and CPU to rebuild the world every time.

This is a pretty large refactoring:
- move checks back into the flake: if I modify a check, the
  configuration for `pre-commits` is not regenerated, as the file with the
  checks is not monitored with `direnv` (I could probably configure it for
  it, but not now)
- remove `home.nix` from the host level configuration
- introduce a `mkHomeManagerConfiguration` function to manage the
  different user@host
- fix a warning with the rust overlay

4 files changed, 32 insertions, 39 deletions

diff --git a/nix/checks.nix b/nix/checks.nix
deleted file mode 100644
index aadb170..0000000
--- a/nix/checks.nix
+++ /dev/null
@@ -1,31 +0,0 @@
-{ pkgs, pre-commit-hooks, ... }:
-
-with pkgs;
-
-{
-  pre-commit-check = pre-commit-hooks.lib.${system}.run {
-    src = lib.cleanSource ../.;
-    hooks = {
-      nix-linter.enable = true;
-      nixpkgs-fmt.enable = true;
-      trailing-whitespace = {
-        enable = true;
-        entry =
-          "${pkgs.python3Packages.pre-commit-hooks}/bin/trailing-whitespace-fixer";
-        types = [ "text" ];
-      };
-      end-of-file-fixer = {
-        enable = true;
-        entry =
-          "${pkgs.python3Packages.pre-commit-hooks}/bin/end-of-file-fixer";
-        types = [ "text" ];
-      };
-      terraform-format = { enable = true; };
-      shellcheck = {
-        enable = true;
-        files = "\\.sh$";
-        types_or = [ "file" ];
-      };
-    };
-  };
-}
diff --git a/nix/default.nix b/nix/default.nix
index 2dfd8a2..2e76200 100644
--- a/nix/default.nix
+++ b/nix/default.nix
@@ -1,5 +1,4 @@
-{ inputs }:
-
-{
+inputs: {
   mkSystem = import ./mkSystem.nix inputs;
+  mkHomeManagerConfiguration = import ./mkHomeManagerConfiguration.nix inputs;
 }
diff --git a/nix/mkHomeManagerConfiguration.nix b/nix/mkHomeManagerConfiguration.nix
new file mode 100644
index 0000000..bcf374a
--- /dev/null
+++ b/nix/mkHomeManagerConfiguration.nix
@@ -0,0 +1,28 @@
+inputs@{ self, ... }:
+{ system ? "x86_64-linux"
+, username ? "fcuny"
+, hostname
+, stateVersion ? "22.05"
+, extraModules ? [ ]
+,
+}:
+inputs.home-manager.lib.homeManagerConfiguration {
+  inherit system;
+  inherit username;
+  inherit stateVersion;
+
+  homeDirectory = "/home/${username}";
+
+  pkgs = import inputs.nixpkgs {
+    inherit system;
+    config.allowUnfree = true;
+    overlays = [
+      inputs.emacs-overlay.overlay
+      inputs.nur.overlay
+      inputs.rust.overlays.default
+      (final: prev: { tools = import "${self}/tools" { pkgs = prev; }; })
+    ];
+  };
+  configuration.imports =
+    [ "${self}/home" "${self}/hosts/${hostname}/home.nix" ];
+}
diff --git a/nix/mkSystem.nix b/nix/mkSystem.nix
index 1f7ccaf..00b5664 100644
--- a/nix/mkSystem.nix
+++ b/nix/mkSystem.nix
@@ -12,12 +12,9 @@ inputs.nixpkgs.lib.nixosSystem {
       nixpkgs = {
         config.allowUnfree = true;
         overlays = [
-          inputs.emacs-overlay.overlay
           inputs.nur.overlay
-          inputs.rust.overlay
-          (final: prev: {
-            tools = import "${self}/tools" { pkgs = prev; };
-          })
+          inputs.rust.overlays.default
+          (final: prev: { tools = import "${self}/tools" { pkgs = prev; }; })
         ];
       };
       # Add each input as a registry