Add Nix flake for installation via nix run/profile install

.gitignore

@@ -22,3 +22,7 @@ site/
 # NPM packages
 npm-artifacts/
 npm/.output/
+
+# Nix build result symlinks
+/result
+/result-*

README.md

@@ -210,6 +210,19 @@ nix-env -iA nixos.prek
 nix profile install nixpkgs#prek
 ```
 
+For the latest release (Nixpkgs may lag behind), use the flake in this repo:
+
+```bash
+# Run without installing
+nix run github:j178/prek
+
+# Install into your profile
+nix profile install github:j178/prek
+
+# Pin a specific release
+nix run github:j178/prek/v0.4.5
+```
+
 <!-- --8<-- [end: nix-install] -->
 
 </details>

flake.nix

@@ -0,0 +1,89 @@
+{
+  description = "Better pre-commit, re-engineered in Rust";
+
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+
+  outputs = { self, nixpkgs }: let
+    version = "0.4.5";
+
+    # ponytail: only the 4 standard Nix systems are exposed; upstream also ships
+    # musl/arm/armv7/riscv64/s390x tarballs but those map to no stdenv system.
+    # Upgrade path: add entries here + bump version + refresh SRI hashes.
+    assets = {
+      "x86_64-linux" = {
+        file = "prek-x86_64-unknown-linux-gnu.tar.gz";
+        sha256 = "sha256-3IbhjlMlFt1inuYhq3a8TEdhBSIZsn468eR8v5pxonA=";
+      };
+      "aarch64-linux" = {
+        file = "prek-aarch64-unknown-linux-gnu.tar.gz";
+        sha256 = "sha256-akFDf9aGQd556qw9bdZmf6OFEsk6c/ZhombeKxJVexs=";
+      };
+      "x86_64-darwin" = {
+        file = "prek-x86_64-apple-darwin.tar.gz";
+        sha256 = "sha256-sK/Iu+pp1hu/5JEAOU35nu0VqcRnWwbJk2QX5lqoixY=";
+      };
+      "aarch64-darwin" = {
+        file = "prek-aarch64-apple-darwin.tar.gz";
+        sha256 = "sha256-7Ukgdi8OPbBxY8Q3r2IqHUkF4a1wU2kqSVVRuc6SVJ8=";
+      };
+    };
+
+    systems = builtins.attrNames assets;
+    forAllSystems = f: nixpkgs.lib.genAttrs systems (system: f system);
+
+    prekFor = system: let
+      pkgs = nixpkgs.legacyPackages.${system};
+      asset = assets.${system};
+    in pkgs.stdenv.mkDerivation {
+      pname = "prek";
+      inherit version;
+
+      src = pkgs.fetchurl {
+        url = "https://github.com/j178/prek/releases/download/v${version}/${asset.file}";
+        sha256 = asset.sha256;
+      };
+
+      sourceRoot = ".";
+
+      nativeBuildInputs = pkgs.lib.optionals pkgs.stdenv.isLinux [ pkgs.autoPatchelfHook ];
+      buildInputs = pkgs.lib.optionals pkgs.stdenv.isLinux [ pkgs.stdenv.cc.cc.lib ];
+
+      dontConfigure = true;
+      dontBuild = true;
+
+      installPhase = ''
+        runHook preInstall
+        mkdir -p "$out/bin"
+        cp prek-*/prek "$out/bin/prek"
+        chmod +x "$out/bin/prek"
+        runHook postInstall
+      '';
+
+      meta = with pkgs.lib; {
+        description = "Better pre-commit, re-engineered in Rust";
+        homepage = "https://github.com/j178/prek";
+        downloadPage = "https://github.com/j178/prek/releases";
+        license = licenses.mit;
+        mainProgram = "prek";
+        platforms = systems;
+        sourceProvenance = [ sourceTypes.binaryNativeCode ];
+      };
+    };
+  in {
+    packages = forAllSystems (system: rec {
+      prek = prekFor system;
+      default = prek;
+    });
+
+    apps = forAllSystems (system: {
+      prek = {
+        type = "app";
+        program = "${prekFor system}/bin/prek";
+      };
+      default = {
+        type = "app";
+        program = "${prekFor system}/bin/prek";
+      };
+    });
+  };
+}