How It Works

Storage layout

.lhi/
├── index.jsonl    Append-only event log (one JSON line per change)
└── blobs/         Content-addressed file storage (SHA-256, zstd-compressed)
    ├── a1b2c3...
    └── d4e5f6...

Blob store

Files are stored by their SHA-256 hash. Identical content is automatically deduplicated. Blobs are zstd-compressed on write; old uncompressed blobs are read transparently (magic byte detection). Writes are atomic (temp file + rename). Short hash prefixes are resolved by scanning the blobs directory.

Index

JSONL format — each line records timestamp, event type, file path, content hash, size, and git branch. Append-only during normal operation; compact rewrites it.

Watcher

Uses OS-native filesystem notifications (notify crate) with 100ms debouncing. On first run, captures a baseline snapshot of all existing files. Respects .gitignore. Ignores .lhi/ directories at any nesting depth. Files over 10MB are skipped. Symlinks are ignored.

Git integration

Automatically records the current git branch with each event (captured at watcher startup and snapshot time via git rev-parse --abbrev-ref HEAD). Stored as Option<String> — None when not in a git repo.

Terminal output

cat, diff, and search use bat as a library (PrettyPrinter) for syntax-highlighted output when stdout is a terminal. When piped, they emit plain/raw output for composability.

diff additionally tries piping to delta if installed before falling back to bat. The bat dependency uses default-features = false with regex-fancy (pure Rust, no C dependencies). Filenames for syntax auto-detection are resolved from the index via hash lookup.

Architecture

bin/lhi  →  commands  →  core (index, store, event)
                │                    ▲
                └──►  watcher  ──────┘

• core/ — Data layer. Index manages the JSONL index, BlobStore handles content-addressed blobs, event defines serializable types. Core types return io::Result.
• commands/ — One file per CLI subcommand. All return anyhow::Result. cat.rs, diff.rs, and search.rs use bat for syntax-highlighted output, with diff.rs also piping to delta if available.
• watcher/ — Real-time filesystem monitoring. Debounces events, respects .gitignore, stores blobs and index entries.
• util.rs — Shared hex_sha256, get_file_mode, and current_git_branch.
• bin/lhi/ — Thin CLI layer using clap.