WIP add a nix flake to build just

.gitignore

@@ -15,3 +15,4 @@
 /test-utilities/Cargo.lock
 /test-utilities/target
 /tmp
+result

flake.nix

@@ -0,0 +1,147 @@
+{
+  description = "Just a command runner";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = { self, nixpkgs, flake-utils, rust-overlay }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        overlays = [ (import rust-overlay) ];
+        pkgs = import nixpkgs {
+          inherit system overlays;
+        };
+
+        # Read version from Cargo.toml
+        cargoToml = builtins.fromTOML (builtins.readFile ./Cargo.toml);
+        version = cargoToml.package.version;
+
+        # Common build inputs
+        buildInputs = with pkgs; [
+          libiconv
+        ] ++ lib.optionals stdenv.hostPlatform.isDarwin [
+          darwin.apple_sdk.frameworks.Security
+        ];
+
+        nativeBuildInputs = with pkgs; [
+          installShellFiles
+          pkg-config
+        ];
+
+        # The main just package
+        just = pkgs.rustPlatform.buildRustPackage {
+          pname = "just";
+          inherit version;
+
+          src = ./.;
+
+          cargoLock = {
+            lockFile = ./Cargo.lock;
+          };
+
+          inherit nativeBuildInputs buildInputs;
+
+          # Don't check during build since we run tests separately
+          doCheck = false;
+
+          # Generate shell completions and man pages
+          postInstall = ''
+            # Generate and install shell completions
+            for shell in bash fish zsh; do
+              $out/bin/just --completions $shell > just.$shell
+              installShellCompletion just.$shell
+            done
+
+            # Generate and install man page
+            $out/bin/just --man > just.1
+            installManPage just.1
+          '';
+
+          # Setup hook for runtime dependencies
+          setupHook = pkgs.writeText "setup-hook.sh" ''
+            export JUST_PATH_PREFIX="${pkgs.lib.makeBinPath [ pkgs.coreutils pkgs.bashInteractive ]}''${JUST_PATH_PREFIX:+:$JUST_PATH_PREFIX}"
+          '';
+
+          meta = with pkgs.lib; {
+            description = "Just a command runner";
+            homepage = "https://github.com/casey/just";
+            changelog = "https://github.com/casey/just/blob/master/CHANGELOG.md";
+            license = licenses.cc0;
+            mainProgram = "just";
+            maintainers = with maintainers; [ ];
+          };
+        };
+
+        # Development shell with additional tools
+        devShell = pkgs.mkShell {
+          inputsFrom = [ just ];
+
+          packages = with pkgs; [
+            # Rust toolchain with clippy and rustfmt
+            (rust-bin.stable.latest.default.override {
+              extensions = [ "rust-src" "rust-analyzer" "clippy" "rustfmt" ];
+            })
+            rust-bin.nightly.latest.default
+
+            # Development tools
+            cargo-watch
+            cargo-fuzz
+            cargo-outdated
+            cargo-udeps
+            mdbook
+            mdbook-linkcheck
+            shellcheck
+
+            # Runtime dependencies
+            bashInteractive
+            coreutils
+
+            # Additional utilities from justfile
+            python3
+            nodejs
+            perl
+            ruby
+          ];
+
+          shellHook = ''
+            echo "Just development environment"
+            echo "Version: ${version}"
+            echo ""
+            echo "Available commands:"
+            echo "  cargo build       - Build the project"
+            echo "  cargo test        - Run tests"
+            echo "  cargo clippy      - Run clippy lints"
+            echo "  just              - Run using the local justfile"
+            echo ""
+          '';
+
+          RUST_SRC_PATH = "${pkgs.rust-bin.stable.latest.rust-src}/lib/rustlib/src/rust/library";
+        };
+
+      in
+      {
+        packages = {
+          default = just;
+          just = just;
+        };
+
+        apps = {
+          default = flake-utils.lib.mkApp {
+            drv = just;
+            exePath = "/bin/just";
+          };
+        };
+
+        devShells.default = devShell;
+
+        # Formatter for `nix fmt`
+        formatter = pkgs.nixpkgs-fmt;
+      }
+    );
+}