Function crate_dir 

pub fn crate_dir(root: &Path) -> Option<PathBuf>

The crate directory of a repository, when it has one.

use majordomus_cli::capability::builtin::quality::crate_dir;
let dir = tempfile::tempdir().unwrap();
assert_eq!(crate_dir(dir.path()), None, "a repository with no crate has none");
std::fs::create_dir_all(dir.path().join("apps/majordomus-cli/src")).unwrap();
std::fs::write(dir.path().join("apps/majordomus-cli/Cargo.toml"), "").unwrap();
std::fs::write(dir.path().join("apps/majordomus-cli/src/lib.rs"), "//! x\n").unwrap();
assert!(crate_dir(dir.path()).is_some());