feat: Add flake.nix for nix users

Co-authored-by: Winter <[email protected]>

README.md

@@ -28,6 +28,19 @@ curl -L https://raw.githubusercontent.com/rust-lang/rustlings/main/install.sh |
 
 This will install Rustlings and give you access to the `rustlings` command. Run it to get started!
 
+### Nix
+Basically: Clone the repository at the latest tag, finally run `nix develop` or `nix-shell`.
+
+```bash
+# find out the latest version at https://github.com/rust-lang/rustlings/releases/latest (on edit 5.2.1)
+git clone -b 5.2.1 --depth 1 https://github.com/rust-lang/rustlings
+cd rustlings
+# if nix version > 2.3
+nix develop
+# if nix version <= 2.3
+nix-shell
+```
+
 ## Windows
 
 In PowerShell (Run as Administrator), set `ExecutionPolicy` to `RemoteSigned`:

flake.nix

@@ -0,0 +1,53 @@
+{
+  description = "Small exercises to get you used to reading and writing Rust code";
+
+  inputs = {
+    flake-compat = {
+      url = "github:edolstra/flake-compat";
+      flake = false;
+    };
+    flake-utils.url = "github:numtide/flake-utils";
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+  };
+
+  outputs = { self, flake-utils, nixpkgs, ... }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+        rustlings =
+          pkgs.rustPlatform.buildRustPackage {
+            name = "rustlings";
+            version = "5.2.1";
+
+            src = with pkgs.lib; cleanSourceWith {
+              src = self;
+              # a function that returns a bool determining if the path should be included in the cleaned source
+              filter = path: type:
+                let
+                  # filename
+                  baseName = builtins.baseNameOf (toString path);
+                  # path from root directory
+                  path' = builtins.replaceStrings [ "${self}/" ] [ "" ] path;
+                  # checks if path is in the directory
+                  inDirectory = directory: hasPrefix directory path';
+                in
+                inDirectory "src" ||
+                inDirectory "tests" ||
+                hasPrefix "Cargo" baseName ||
+                baseName == "info.toml";
+            };
+
+            cargoLock.lockFile = ./Cargo.lock;
+          };
+      in
+      {
+        devShell = pkgs.mkShell {
+          buildInputs = with pkgs; [
+            cargo
+            rustc
+            rust-analyzer
+            rustlings
+          ];
+        };
+      });
+}

shell.nix

@@ -0,0 +1,6 @@
+(import (let lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+in fetchTarball {
+  url =
+    "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+  sha256 = lock.nodes.flake-compat.locked.narHash;
+}) { src = ./.; }).shellNix