ci: add code coverage tracking (#123)

Author: grant0417

.github/workflows/rust.yml

@@ -41,8 +41,12 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - run: sudo apt-get update && sudo apt-get install -y -qq build-essential pkg-config jq dpkg curl wget zstd cmake clang libssl-dev libgtk-3-dev libayatana-appindicator3-dev librsvg2-dev libdbus-1-dev libwebkit2gtk-4.1-dev libjavascriptcoregtk-4.1-dev valac libibus-1.0-dev libglib2.0-dev sqlite3 libxdo-dev protobuf-compiler libfuse2 bash fish zsh shellcheck
-      - uses: dtolnay/rust-toolchain@stable
+      - uses: dtolnay/rust-toolchain@nightly
         id: toolchain
+        with:
+          components: llvm-tools-preview
+      - name: Install cargo-llvm-cov
+        uses: taiki-e/install-action@cargo-llvm-cov
       - uses: actions/cache@v4
         with:
           path: |
@@ -51,8 +55,14 @@ jobs:
             ~/.cargo/git/db/
             target/
           key: cargo-test-${{ runner.os }}-${{ hashFiles('**/Cargo.lock') }}-${{ steps.toolchain.outputs.cachekey }}
-      - run: cargo build --locked --workspace --tests
-      - run: cargo test --locked --workspace
+      - name: Generate code coverage
+        run: cargo llvm-cov --locked --workspace --lcov --output-path lcov.info
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v5
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }} # not required for public repos
+          files: lcov.info
+          fail_ci_if_error: true
 
   cargo-fmt:
     name: Fmt