nix: replace nix-filter with lib.fileset

Co-authored-by: sodiboo <git@sodi.boo>

flake.lock

@@ -1,20 +1,5 @@
 {
   "nodes": {
-    "nix-filter": {
-      "locked": {
-        "lastModified": 1731533336,
-        "narHash": "sha256-oRam5PS1vcrr5UPgALW0eo1m/5/pls27Z/pabHNy2Ms=",
-        "owner": "numtide",
-        "repo": "nix-filter",
-        "rev": "f7653272fd234696ae94229839a99b73c9ab7de0",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "nix-filter",
-        "type": "github"
-      }
-    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1742707865,
@@ -33,7 +18,6 @@
     },
     "root": {
       "inputs": {
-        "nix-filter": "nix-filter",
         "nixpkgs": "nixpkgs",
         "rust-overlay": "rust-overlay"
       }

flake.nix

@@ -4,7 +4,6 @@
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
-    nix-filter.url = "github:numtide/nix-filter";
 
     # NOTE: This is not necessary for end users
     # You can omit it with `inputs.rust-overlay.follows = ""`
@@ -18,7 +17,6 @@
     {
       self,
       nixpkgs,
-      nix-filter,
       rust-overlay,
     }:
     let
@@ -50,16 +48,16 @@
           pname = "niri";
           version = self.shortRev or self.dirtyShortRev or "unknown";
 
-          src = nix-filter.lib.filter {
-            root = self;
-            include = [
-              "niri-config"
-              "niri-ipc"
-              "niri-visual-tests"
-              "resources"
-              "src"
-              ./Cargo.lock
+          src = lib.fileset.toSource {
+            root = ./.;
+            fileset = lib.fileset.unions [
+              ./niri-config
+              ./niri-ipc
+              ./niri-visual-tests
+              ./resources
+              ./src
               ./Cargo.toml
+              ./Cargo.lock
             ];
           };