Merge Nix flake (#6)

README.md

@@ -10,14 +10,26 @@ the future.
 
 ## Running
 
-Run in an environment with all dependencies available with [Nix][nix] [2.3][nix-2.3]:
+GitHub access manager needs Python 3.11 or later (for TOML support) and has no
+dependencies outside of the standard library.
 
-    nix run --command ./main.py
+    ./main.py --help
+    ./main.py config.toml
 
-Alternatively, use Python 3.11 which has toml support in the standard library,
-or set up a virtualenv and `pip install tomli`.
+Optionally, a Nix flake is provided to run with a pinned Python version. You
+need [Nix 2.10 or later](https://nixos.org/download.html). Then run `nix`
+with either `--extra-experimental-features nix-command` and
+`--extra-experimental-features flakes`, or add them to your
+`~/.config/nix/nix.conf`:
 
-See the docstring in `main.py` for more information, or run with `--help`.
+    experimental-features = nix-command flakes
 
-[nix]:     https://nixos.org/
-[nix-2.3]: https://releases.nixos.org/?prefix=nix/nix-2.3/
+Then run with Nix:
+
+    nix run . -- --help
+    nix run . -- config.toml
+
+You can also enter a shell with the right Python version in the environment:
+
+    nix develop
+    ./main.py --help

flake.nix

@@ -0,0 +1,33 @@
+{
+  description = "GitHub Access Manager";
+
+  inputs.nixpkgs.url = "nixpkgs/nixos-unstable";
+
+  outputs = { self, nixpkgs }:
+    let
+      name = "github-access-manager";
+      version = builtins.substring 0 8 self.lastModifiedDate;
+      supportedSystems = [ "x86_64-linux" "x86_64-darwin" "aarch64-linux" "aarch64-darwin" ];
+      forAllSystems = nixpkgs.lib.genAttrs supportedSystems;
+    in
+      {
+        packages = forAllSystems (system:
+          let
+            pkgs = import nixpkgs { inherit system; };
+          in
+            {
+              default = pkgs.stdenv.mkDerivation {
+                inherit name version;
+                src = ./.;
+                buildInputs = [ pkgs.python311 ];
+                installPhase = ''
+                  mkdir --parents $out/bin
+                  echo "#!${pkgs.python311}/bin/python3" > preamble
+                  cat preamble main.py > $out/bin/github-access-manager
+                  chmod +x $out/bin/github-access-manager
+                '';
+              };
+            }
+        );
+      };
+}

main.py

@@ -124,7 +124,7 @@
 import os
 import sys
 import json
-import tomli
+import tomllib
 
 from typing import (
     Any,
@@ -412,8 +412,8 @@ def from_toml_dict(data: Dict[str, Any]) -> Configuration:
 
     @staticmethod
     def from_toml_file(fname: str) -> Configuration:
-        with open(fname, "r", encoding="utf-8") as f:
-            data = tomli.load(f)
+        with open(fname, "rb") as f:
+            data = tomllib.load(f)
             return Configuration.from_toml_dict(data)
 
     def get_repository_target(self, actual: Repository) -> Repository: