Fetch history.

.github/workflows/ci.yml

@@ -13,6 +13,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
       - uses: actions-rust-lang/setup-rust-toolchain@v1
       - name: Install plugin
         run: cargo install --path helpers/mdbook-exercise-linker