Add code coverage as PR comment (#1162)

* Add code coverage as PR comment

* Workaround for test coverage permission issue

.github/workflows/coverage-comment.yml

@@ -0,0 +1,37 @@
+name: coverage-comment
+
+on:
+  workflow_run:
+    workflows: [test]
+    types: [completed]
+
+jobs:
+  comment:
+    if: >
+      github.event.workflow_run.event == 'pull_request' &&
+      github.event.workflow_run.conclusion == 'success'
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+    steps:
+    - name: Download coverage artifact
+      uses: actions/download-artifact@v4
+      with:
+        name: coverage
+        run-id: ${{ github.event.workflow_run.id }}
+        github-token: ${{ github.token }}
+
+    - name: Post coverage comment
+      env:
+        GH_TOKEN: ${{ github.token }}
+        GH_REPO: ${{ github.repository }}
+      run: |
+        PR=$(cat pr_number.txt)
+        {
+          echo "## Test Coverage"
+          echo ""
+          echo '```'
+          cat coverage_summary.txt
+          echo '```'
+        } > comment_body.md
+        gh pr comment "$PR" --body-file comment_body.md

.github/workflows/test.yml

@@ -17,11 +17,11 @@ jobs:
     - name: Install build dependencies from debian/control
       run: |
         sudo apt-get update
-        sudo apt-get install --yes devscripts equivs ninja-build
+        sudo apt-get install --yes devscripts equivs ninja-build lcov
         sudo mk-build-deps -i -r -t "apt-get --yes" debian/control
 
     - name: Configure
-      run: cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Debug -DUSE_STATIC_MPVQT=ON
+      run: cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Debug -DUSE_STATIC_MPVQT=ON -DCOVERAGE=ON
 
     - name: Build
       run: cmake --build build
@@ -30,3 +30,26 @@ jobs:
       run: |
         cd build
         ctest --output-on-failure
+
+    - name: Collect coverage
+      run: |
+        lcov --capture --directory build --output-file coverage.info \
+          --ignore-errors mismatch
+        lcov --remove coverage.info \
+          '/usr/*' '*/external/*' '*/tests/*' '*/build/*' \
+          --output-file coverage.info \
+          --ignore-errors unused
+        lcov --summary coverage.info 2>&1 | grep -v 'no data found' > coverage_summary.txt
+
+    - name: Save PR number
+      if: github.event_name == 'pull_request'
+      run: echo "${{ github.event.pull_request.number }}" > pr_number.txt
+
+    - name: Upload coverage artifact
+      if: github.event_name == 'pull_request'
+      uses: actions/upload-artifact@v4
+      with:
+        name: coverage
+        path: |
+          coverage_summary.txt
+          pr_number.txt