Automatically add exercise links to sections. (mainmatter#52)

We use an mdbook preprocessor to automatically generate links to the relevant exercise for each section.
We remove all existing manual links and refactor the deploy process to push the rendered book to a branch.

Author: LukeMathWalker

.github/workflows/ci.yml

@@ -9,22 +9,20 @@ on:
       - main
 
 jobs:
-  formatter:
+  build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
-      - uses: dprint/[email protected]
-
-  check-links:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v4
+      - uses: actions/checkout@v4
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
+      - name: Install plugin
+        run: cargo install --path helpers/mdbook-exercise-linker
+      - uses: taiki-e/install-action@v2
+        with:
+          tool: mdbook
       - name: Build book
         run: |
           cd book
-          curl -sSL https://github.com/rust-lang/mdBook/releases/download/v0.4.40/mdbook-v0.4.40-x86_64-unknown-linux-gnu.tar.gz | tar -xz --directory=.
-          ./mdbook build
+          mdbook build
       - name: Link Checker
         uses: lycheeverse/lychee-action@v1
         with:
@@ -34,3 +32,25 @@ jobs:
             --require-https 
             --no-progress 
             book/book
+      # Upload the book as an artifact
+      - uses: actions/upload-artifact@v4
+        with:
+          name: book
+          path: book/book
+            # Commit and push all changed files.
+            # Must only affect files that are listed in "paths-ignore".
+      - name: Git commit build artifacts
+        # Only run on main branch push (e.g. pull request merge).
+        if: github.event_name == 'push'
+        run: |
+          git config --global user.name "${{ env.CI_COMMIT_AUTHOR }}"
+          git config --global user.email "[email protected]"
+          git add --force book/book
+          git commit -m "${{ env.CI_COMMIT_MESSAGE }}"
+          git push --set-upstream --force-with-lease origin deploy
+
+  formatter:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dprint/[email protected]