Cache mdbook build as it takes 5min

Author: adamgreig

.github/workflows/ci.yml

@@ -14,22 +14,40 @@ jobs:
         with:
           profile: minimal
           toolchain: stable
-      - uses: actions-rs/install@v0.1
-        with:
-          crate: mdbook
-          version: latest
-          use-tool-cache: true
+
       - 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-bni" >> $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