chore: add grcov-coverage as an alternate report generation recipe

justfile

@@ -21,3 +21,17 @@ start-ngrok:
 coverage-update:
   cargo tarpaulin --lib --out html
   echo "Now:\n\topen tarpaulin-report.html"
+
+grcov-coverage:
+  #!/usr/bin/env bash
+  set -e
+  # an alternate coverage report
+  rustup component add llvm-tools-preview
+  export RUSTFLAGS="-Cinstrument-coverage"
+  cargo build
+  export LLVM_PROFILE_FILE="git-next-%p-%m.profraw"
+  cargo test
+  echo "Building report..."
+  grcov . -s . --binary-path ./target/debug/ -t html --branch --ignore-not-existing -o ./target/debug/coverage/
+  find . -name '*.profraw' -exec rm "{}" \;
+  echo "Now:\n\topen target/debug/coverage/index.html"