Use Nix flakes, use built-in tomllib

Flakes are said to be the future ... the convenient "nix run" command
from Nix 2.3 has been repurposed in later versions and there is no
direct replacement. 2.3 is quite old by now, so jump on the flakes
bandwagon.

This also changes the Python script to no longer use the external
"tomli" package, but to use the built-in "tomllib" instead (which is the
former "tomli" brought into the stdlib).

Author: ruuda

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

default.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
+                '';
+              };
+            }
+        );
+      };
+}

flake.lock

@@ -118,7 +118,7 @@
 import os
 import sys
 import json
-import tomli
+import tomllib
 
 from typing import (
     Any,
@@ -406,8 +406,8 @@ 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: