chore: add flake template

Author: dpc

.envrc

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+use flake

.gitignore

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+/target
+/.direnv
+/result

flake.lock

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+{
+  description = "dpc's basic flake template";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-22.05";
+    flake-utils.url = "github:numtide/flake-utils";
+    crane.url = "github:ipetkov/crane";
+    crane.inputs.nixpkgs.follows = "nixpkgs";
+    fenix = {
+      url = "github:nix-community/fenix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = { self, nixpkgs, flake-utils, crane, fenix }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+        };
+        lib = pkgs.lib;
+        fenixChannel = fenix.packages.${system}.stable;
+        fenixToolchain = (fenixChannel.withComponents [
+          "rustc"
+          "cargo"
+          "clippy"
+          "rust-analysis"
+          "rust-src"
+          "rustfmt"
+        ]);
+        craneLib = crane.lib.${system}.overrideToolchain fenixToolchain;
+
+        commonArgs = {
+          src = craneLib.cleanCargoSource ./.;
+
+          buildInputs = with pkgs; [
+          ];
+
+          nativeBuildInputs = with pkgs; [
+          ];
+        };
+      in
+      {
+        packages.default = craneLib.buildPackage ({ } // commonArgs);
+
+        devShells = {
+          default = pkgs.mkShell {
+
+            buildInputs = with pkgs; [ ] ++ commonArgs.buildInputs;
+            nativeBuildInputs = with pkgs; [
+              fenix.packages.${system}.rust-analyzer
+              fenixToolchain
+              cargo-udeps
+
+              # This is required to prevent a mangled bash shell in nix develop
+              # see: https://discourse.nixos.org/t/interactive-bash-with-nix-develop-flake/15486
+              (hiPrio pkgs.bashInteractive)
+
+              # Nix
+              pkgs.nixpkgs-fmt
+              pkgs.shellcheck
+              pkgs.rnix-lsp
+              pkgs.nodePackages.bash-language-server
+
+            ] ++ commonArgs.nativeBuildInputs;
+            shellHook = ''
+              dot_git="$(git rev-parse --git-common-dir)"
+              if [[ ! -d "$dot_git/hooks" ]]; then mkdir "$dot_git/hooks"; fi
+              for hook in misc/git-hooks/* ; do ln -sf "$(pwd)/$hook" "$dot_git/hooks/" ; done
+              ${pkgs.git}/bin/git config commit.template $(pwd)/misc/git-hooks/commit-template.txt
+            '';
+          };
+        };
+      }
+    );
+}

flake.nix

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+
+# Explain *why* this change is being made                width limit ->|

misc/git-hooks/commit-template.txt

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+#!/usr/bin/env bash
+
+set -eo pipefail
+
+# Revert `git stash` on exit
+function revert_git_stash {
+  >&2 echo "Unstashing uncommited changes..."
+  git stash pop -q
+}
+
+set +e
+git diff-files --quiet
+is_unclean=$?
+set -e
+
+# Stash pending changes and revert them when script ends
+if [ $is_unclean -ne 0 ]; then
+  >&2 echo "Stashing uncommited changes..."
+  git stash -q --keep-index
+  trap revert_git_stash EXIT
+fi
+
+# TODO: add checks below