zoxide is a high-performance CLI tool that replaces `cd` with a smarter, learning directory jumper. It tracks directory access frequency and recency, ranks entries using a frecency algorithm, and allows instant navigation via partial keyword matching. The binary exposes subcommands for adding, querying, editing, importing, and removing entries, while shell-specific init scripts integrate hooks (prompt or PWD-based) to automatically record visited directories. Interactive selection via fzf and Space-Tab completions are supported on major shells (bash, zsh, fish, etc.). The codebase is a single Rust binary with a clean, modular architecture: a text-based database with atomic writes, a streaming query engine with lazy deletion, a trait-based import system for six external tools, and Askama-templated shell scripts. It demonstrates strong engineering practices: comprehensive CI/CD, cross-compilation for 12+ targets, shell script validation, and thorough test coverage including shell syntax checks.
asdf is a command-line application that manages multiple runtime versions (Node.js, Python, Ruby, etc.) per project using a plugin architecture. The Go binary dispatches commands like install, set, current, exec, and reshim; it reads `.tool-versions` files searched from the current directory upward, resolves versions via environment variables, plugin callbacks, and legacy version files, then invokes plugin-provided Bash scripts for listing, downloading, and installing tools. It generates shim executables that proxy to `asdf exec` at runtime, and supports shell completions, hooks, and extension commands. Architecturally, asdf is a modular single-binary Go application with internal packages for plugins, versions, shims, resolution, configuration, Git operations, execution, and plugin index lookups. Key external runtime dependencies are bash (plugin callbacks and hooks), git (plugin repository cloning/updating), and the asdf-plugins index. The codebase reflects a rewrite from Bash to Go (v0.16+), preserving the plugin extension model while introducing typed errors, interfaces, and more maintainable package boundaries. Some legacy BATS integration tests and in-progress cleanup comments remain, but the core implementation is clean and well-organized.