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

1 files changed, 28 insertions, 0 deletions

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" ];
+}