Add a devshell and CI

.github/workflows/ci.yml

@@ -0,0 +1,23 @@
+name: nix-flake-check
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2.3.2
+
+      - name: "Install Nix️"
+        uses: cachix/install-nix-action@v16
+
+
+      - name: "Why am I dirty?"
+        run: git status
+
+      - name: "Nix Flake Check"
+        run: nix -L flake check

README.md

@@ -26,10 +26,12 @@ You can also use `tut` in posts. See `posts/2016-09-30-subtype-typeclasses.md` f
 
 ### Previewing your changes
 
+#### Bundler
+
 To preview your changes, you have to install [Bundler](https://bundler.io/) first.
 To download and set up all necessary dependencies, run
 
-```bash
+```console
 $ bundle install
 ... lots of text ...
 Bundle complete! 1 Gemfile dependency, 81 gems now installed.
@@ -38,12 +40,55 @@ Bundled gems are installed into `./vendor/bundle`
 
 Then, you can generate the site by running
 
-```
+```console
 $ bundle exec jekyll serve -wl --baseurl ''
 ```
 
 The generated site will end up in the `_site` directory.
 
+#### Nix
+
+A fully configured Jekyll is available as a Nix app.  Flakes required:
+
+```console
+$ nix run github:typelevel/typelevel.github.com#jekyll build
+warning: Git tree '/Users/ross.baker/src/typelevel.github.com' is dirty
+Configuration file: /Users/ross.baker/src/typelevel.github.com/_config.yml
+            Source: /Users/ross.baker/src/typelevel.github.com
+       Destination: /Users/ross.baker/src/typelevel.github.com/_site
+ Incremental build: disabled. Enable with --incremental
+      Generating...
+                    done in 3.635 seconds.
+ Auto-regeneration: disabled. Use --watch to enable.
+```
+
+There is also a devshell for direct invocation, and a convenient alias:
+
+```console
+$ nix develop github:typelevel/typelevel.github.com
+🔨 Welcome to typelevel-org-shell
+
+[general commands]
+
+  jekyll     - a jekyll bundled with this site's dependencies
+  menu       - prints this menu
+  tl-preview - preview the Jekyll site
+
+$ tl-preview
+Configuration file: /home/you/src/typelevel.github.com/_config.yml
+            Source: /home/you/src/typelevel.github.com
+       Destination: /home/you/src/typelevel.github.com/_site
+ Incremental build: disabled. Enable with --incremental
+      Generating...
+                    done in 3.336 seconds.
+ Auto-regeneration: enabled for '/home/you/src/typelevel.github.com'
+LiveReload address: http://127.0.0.1:35729
+    Server address: http://127.0.0.1:4000/
+  Server running... press ctrl-c to stop.
+```
+
+
+
 ## License
 
 Unless otherwise noted, all website content is licensed under a [Creative Commons Attribution 3.0 Unported License](https://creativecommons.org/licenses/by/3.0/deed.en_US).

flake.nix

@@ -0,0 +1,63 @@
+{
+  description = "Virtual environment for typelevel.org site";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
+    devshell.url = "github:numtide/devshell";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils, devshell, ... }:
+    let
+      forSystem = system:
+        let
+          pkgs = import nixpkgs {
+            inherit system;
+            overlays = [ devshell.overlay ];
+          };
+
+          gems = pkgs.bundlerEnv {
+            name = "typelevel-org-bundler-env";
+            inherit (pkgs) ruby;
+            gemdir = ./.;
+          };
+        in
+        {
+          apps.jekyll = {
+            type = "app";
+            program = "${gems}/bin/jekyll";
+          };
+
+          checks = {
+            build-site = pkgs.stdenv.mkDerivation {
+              name = "build-site";
+              buildInputs = [ gems pkgs.glibcLocales ];
+              src = ./.;
+              buildPhase = ''
+                export LANG=en_US.UTF-8
+                ${gems}/bin/jekyll build
+                cp -a _site $out
+              '';
+              dontInstall = true;
+            };
+          };
+
+          devShell = pkgs.devshell.mkShell {
+            name = "typelevel-org-shell";
+            commands = [
+              {
+                name = "jekyll";
+                help = "a jekyll bundled with this site's dependencies";
+                command = "${gems}/bin/jekyll $@";
+              }
+              {
+                name = "tl-preview";
+                help = "preview the Jekyll site";
+                command = "${gems}/bin/jekyll serve -wl --baseurl ''";
+              }
+            ];
+          };
+        };
+    in
+    flake-utils.lib.eachDefaultSystem forSystem;
+}