cargo-llvm-cov is a Cargo subcommand to easily use LLVM source-based code
coverage.

This is a wrapper around rustc instrument-coverage command and provides:
- Generate very precise coverage data. (line, region, and branch coverage.
  branch coverage is currently optional and requires nightly, etc)
- Support `cargo test`, `cargo run`, and `cargo nextest` with command-line
  interface compatible with cargo.
- Support for proc-macro, including coverage of UI tests.
- Support for doc tests. (this is currently optional and requires nightly.
- Fast because it does not introduce extra layers between rustc, cargo, and
  llvm-tools.
