Add Nix flake

.gitignore

@@ -1 +1,5 @@
 /target
+# created by `nix-direnv`
+.direnv
+# created by `nix build`
+/result

flake.nix

@@ -0,0 +1,166 @@
+{
+  description = "debugger for Hubris";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-23.11";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = { self, nixpkgs, rust-overlay }:
+    let
+      systems = [ "x86_64-linux" "aarch64-linux" "armv7l-linux" "x86_64-darwin" "aarch64-darwin" ];
+      overlays = [ (import rust-overlay) ];
+      forAllSystems = function:
+        nixpkgs.lib.genAttrs systems
+          (system:
+            let
+              pkgs = import nixpkgs {
+                inherit system overlays;
+              };
+            in
+            function pkgs);
+      pname = "humility";
+      build-humility =
+        (pkgs: with pkgs; let
+
+          udevFilename = "69-probe-rs.rules";
+          # fetch the probe-rs website to use their list of udev rules for all
+          # debug probes supported by probe-rs
+          probeRsWebsite = fetchFromGitHub
+            {
+              owner = "probe-rs";
+              repo = "webpage";
+              rev = "2617971b3584bae9c227cd026aaaabdc45a308a3";
+              hash = "sha256-ur5oGb6aypce6h0YPvCKc/8/X7FBfzOQS9zlkLP2UGY=";
+            };
+
+          # use the Rust toolchain specified in the project's rust-toolchain.toml
+          rustToolchain =
+            let
+              file = pkgsBuildHost.rust-bin.fromRustupToolchainFile
+                ./rust-toolchain.toml;
+            in
+            file.override {
+              extensions = [
+                "rust-src" # for rust-analyzer
+              ];
+            };
+
+          configuredRustPlatform = makeRustPlatform {
+            cargo = rustToolchain;
+            rustc = rustToolchain;
+          };
+
+          src = nix-gitignore.gitignoreSource [ ] ./.;
+          cargoTOML = lib.importTOML "${src}/Cargo.toml";
+        in
+        configuredRustPlatform.buildRustPackage {
+          inherit src pname;
+          inherit (cargoTOML.package) version;
+
+          buildInputs =
+            if stdenv.isLinux then [
+              libudev-zero
+            ] else [ ];
+          nativeBuildInputs = if stdenv.isLinux then [ pkg-config ] else [ ];
+
+          cargoLock.lockFile = ./Cargo.lock;
+          cargoLock.outputHashes = {
+            "capstone-0.10.0" = "sha256-x0p005W6u3QsTKRupj9HEg+dZB3xCXlKb9VCKv+LJ0U=";
+            "gimlet-inspector-protocol-0.1.0" = "sha256-NLKiYL1CMkQaaTP0ePwEK49Y9lckkOrzw7371SHHEWQ=";
+            "hidapi-1.4.1" = "sha256-2SBQu94ArGGwPU3wJYV0vwwVOXMCCq+jbeBHfKuE+pA=";
+            "hif-0.3.1" = "sha256-o3r1akaSARfqIzuP86SJc6/s0b2PIkaZENjYO3DPAUo=";
+            "humpty-0.1.3" = "sha256-efeb+RaAjQs9XU3KkfVo8mVK2dGyv+2xFKSVKS0vyTc=";
+            "idol-0.3.0" = "sha256-s6ZM/EyBE1eOySPah5GtT0/l7RIQKkeUPybMmqUpmt8=";
+            "idt8a3xxxx-0.1.0" = "sha256-S36fS9hYTIn57Tt9msRiM7OFfujJEf8ED+9R9p0zgK4=";
+            "libusb1-sys-0.5.0" = "sha256-7Bb1lpZvCb+OrKGYiD6NV+lMJuxFbukkRXsufaro5OQ=";
+            "pmbus-0.1.2" = "sha256-NFSrh4yD7PCqYhGuioRYWFmFIcpFvDO1qh6Lp9tsJ9E=";
+            "probe-rs-0.12.0" = "sha256-/L+85K6uxzUmz/TlLLFbMlyekoXC/ClO33EQ/yYjQKU=";
+            "spd-0.1.0" = "sha256-X6XUx+huQp77XF5EZDYYqRqaHsdDSbDMK8qcuSGob3E=";
+            "tlvc-0.2.0" = "sha256-HiqDRqmKOTxz6UQSXNMOZdWdc5W+cFGuKBkNrqFvIIE=";
+            "vsc7448-info-0.1.0" = "sha256-otNLdfGIzuyu03wEb7tzhZVVMdS0of2sU/AKSNSsoho=";
+          };
+
+          # Copy the probe-rs udev rules into `etc/udev/rules.d` so that this
+          # package can be added to `services.udev.packages` on NixOS.
+          postInstall = ''
+            mkdir -p $out/etc/udev/rules.d
+            cp ${probeRsWebsite}/src/static/files/${udevFilename} $out/etc/udev/rules.d/${udevFilename}
+          '';
+
+          meta = {
+            inherit (cargoTOML.package) homepage license;
+            description = "debugger for Hubris";
+            mainProgram = pname;
+          };
+        });
+    in
+    {
+      ########################################################################
+      #### Packages
+      ########################################################################
+      packages = forAllSystems (pkgs: with pkgs; {
+        humility = build-humility pkgs;
+        default = self.packages.${system}.humility;
+        humility-cross-armv7l-linux =
+          build-humility pkgsCross.armv7l-hf-multiplatform;
+        humility-cross-aarch64-linux =
+          build-humility pkgsCross.aarch64-multiplatform;
+      });
+
+      ########################################################################
+      #### Flake app (for `nix run`)
+      ########################################################################
+      apps = forAllSystems
+        (pkgs: with pkgs; {
+          humility = {
+            type = "app";
+            program = "${self.packages.${system}.humility}/bin/${pname}";
+          };
+          default = self.apps.${system}.humility;
+        });
+
+      ########################################################################
+      #### Dev shell (for `nix develop`)
+      ########################################################################
+      devShells = forAllSystems
+        (pkgs: with pkgs; let humilityPackage = self.packages.${system}.humility; in {
+          default = mkShell {
+            buildInputs = [ humilityPackage humilityPackage.buildInputs ];
+            nativeBuildInputs = [ humilityPackage.nativeBuildInputs ];
+          };
+        });
+
+      ########################################################################
+      #### NixOS module (`programs.humility`)
+      ########################################################################
+      nixosModules.default = { config, lib, pkgs, ... }: with lib; let
+        cfg = config.programs.humility;
+      in
+      {
+        options.programs.humility = {
+          enable = mkEnableOption "Humility, the debugger for Hubris";
+          users = mkOption {
+            type = types.listOf types.str;
+            default = [ ];
+            description = mdDoc ''
+              List of users added to the "plugdev" group,
+              allowing access to debug probes used by Humility.
+            '';
+          };
+        };
+
+        config = mkIf cfg.enable {
+          environment.systemPackages = [ pkgs.humility ];
+          services.udev.packages = [ pkgs.humility ];
+          users.groups.plugdev = {
+            members = cfg.users;
+          };
+        };
+      };
+
+    };
+}