Add source-based coverage workflow

.github/workflows/coverage.yaml

@@ -0,0 +1,58 @@
+name: CI
+
+on:
+  pull_request:
+    branches:
+      - main
+  push:
+    branches:
+      - main
+
+jobs:
+
+  coverage:
+    name: Coverage
+    timeout-minutes: 30
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v2
+
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: nightly
+          override: true
+          profile: minimal
+          components: llvm-tools-preview
+
+      - name: Install rustfilt symbol demangler
+        run: |
+          cargo install rustfilt
+
+      - name: Rerun tests for coverage
+        env:
+          RUSTFLAGS: -Zinstrument-coverage -C link-dead-code -C debuginfo=2
+          LLVM_PROFILE_FILE: "${{ github.workspace }}/test.%p.profraw"
+          ZEBRA_SKIP_NETWORK_TESTS: 1
+        run: |
+          cargo test
+          cargo test --no-run --message-format=json | jq -r "select(.profile.test == true) | .filenames[]" | grep -v dSYM - > filenames.txt
+
+      - name: Merge coverage data
+        run: |
+          $(rustc --print target-libdir)/../bin/llvm-profdata merge test.*.profraw -o test.profdata
+
+      - name: Generate detailed html coverage report for github artifact
+        run: |
+          $(rustc --print target-libdir)/../bin/llvm-cov show -format=html -ignore-filename-regex=".*/.cargo/registry/.*" -ignore-filename-regex=".*/.cargo/git/.*" -ignore-filename-regex=".*/.rustup/.*" -Xdemangler=rustfilt -show-instantiations -output-dir=./coverage -instr-profile=./test.profdata $(printf -- "-object %s " $(cat filenames.txt))
+
+      - uses: actions/upload-artifact@v2
+        with:
+          name: coverage
+          path: ./coverage
+
+      - name: Generate lcov coverage report for codecov
+        run: |
+          $(rustc --print target-libdir)/../bin/llvm-cov export -format=lcov -instr-profile=test.profdata $(printf -- "-object %s " $(cat filenames.txt)) > "lcov.info"
+
+      - name: Upload coverage report to Codecov
+        uses: codecov/codecov-action@v1