Function cache_root 

pub fn cache_root() -> PathBuf

The module artifact cache root: IGNITION_CLI_CACHE env override first, else the platform cache dir (directories::ProjectDirs:: from("", "", "ignition-cli").cache_dir()) — mirrors crate::config::config_path’s IGNITION_CLI_CONFIG shape exactly, including its expect on a missing home directory. The env override is what lets tests point at a tempfile::TempDir instead of the developer’s real cache.