Merge #285

285: Swap to GHA r=therealprof a=adamgreig

First go at GHA. I think the other books will be significantly harder due to more extensive CI, so this one first seems like a good starting point. 🤞 

Co-authored-by: Adam Greig <adam@adamgreig.com>

.github/workflows/ci.yml

@@ -0,0 +1,57 @@
+name: CI
+
+on:
+  push:
+    branches: [ staging, trying, master ]
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+
+      - name: Install Python dependencies
+        run: |
+          pip3 install --user python-dateutil linkchecker
+      - name: Put pip binary directory into path
+        run: echo "~/.local/bin" >> $GITHUB_PATH
+
+      - name: Cache Cargo installed binaries
+        uses: actions/cache@v1
+        id: cache-cargo
+        with:
+          path: ~/cargo-bin
+          key: cache-cargo
+      - name: Install mdbook
+        if: steps.cache-cargo.outputs.cache-hit != 'true'
+        uses: actions-rs/install@v0.1
+        with:
+          crate: mdbook
+          version: latest
+      - name: Copy mdbook to cache directory
+        if: steps.cache-cargo.outputs.cache-hit != 'true'
+        run: |
+          mkdir ~/cargo-bin
+          cp ~/.cargo/bin/mdbook ~/cargo-bin
+      - name: Put new cargo binary directory into path
+        run: echo "~/cargo-bin" >> $GITHUB_PATH
+
+      - name: Build book
+        run: mdbook build
+      - name: Test book
+        run: mdbook test
+      - name: Check links
+        run: linkchecker book
+
+      - name: Deploy book
+        if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/master' }}
+        uses: peaceiris/actions-gh-pages@v3
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: book
+          force_orphan: true