md-orphan

Detect markdown files not reachable from a given entry point by crawling links recursively. Also flags broken links, ambiguous basenames, broken anchors, and link-style violations — including cross-repo references resolved through a global config.

Install

Pre-built macOS binary in dist/. Build and symlink to ~/.local/bin:

just install

Or build only:

just build

Usage

md-orphan <entry-point...> [flags]

md-orphan CLAUDE.md
md-orphan CLAUDE.md README.md
md-orphan --verbose CLAUDE.md
md-orphan --fix CLAUDE.md

The root directory is the parent of the entry point. All .md files under that directory are scanned. Silent on success by default — only outputs issues on failure (exit 1).

Flag	Description
--exclude <pattern>	Exclude paths by prefix or glob (comma-separated, repeatable)
--verbose, -v	Show success message when all files are reachable
--fix	Rewrite link style issues in place (atomic write)
--config <path>	Override global config (default $XDG_CONFIG_HOME/md-orphan/md-orphan.json)
--no-default-excludes	Disable built-in defaults (.git, node_modules, Library, .build, ...)
--no-cache	Disable both the walk-result cache and the per-file extraction cache
--orient	Print md-orphan's own CLAUDE.md (usage guide for this tool)

Link styles

The tool recognizes four link forms in markdown. Style violations are flagged when a link could be expressed in a more canonical form, where canonical = bare basename when the basename is unique within its target repo, or root-relative path when not.

Form	Example	Style-checked?
Wiki	[[guide.md]], [[guide.md#sec|alias]]	yes (any extension)
Standard md link	[text](path.md)	broken/ambiguous/anchor only — no style rewrite
Cross-repo backtick	`bar.md` (meow-toolbox), `bar.md#sec` (repo)	yes
Inline code	`path.ext` (no repo suffix)	deferred — see [[TODO.md]]

Standard md links ([text](path)) get broken-link / ambiguity / anchor checks, but are not rewritten — most renderers (GitHub, etc.) interpret them as filesystem-relative, so basename-magic would silently break them.

Cross-repo annotation filter: the `path.ext` (name) syntax is only treated as a cross-repo ref when name matches a configured repo. Patterns like `view.name` (GridView), `Unity.Analytics` (Runtime), `UISortingOrder.Activity` (10) are silently treated as inline-code annotations. Trade-off: typos to a known-repo name are caught at file-resolution (CrossRepoBroken); typos to a wrong-repo name are silent.

Fenced code blocks (```) are skipped during scanning — content inside fences is never parsed as a link or cross-repo ref.

Style examples

[[../system/foo.md]]               → [[foo.md]]                  (basename unique in repo)
[[docs/system/foo.md]]             → [[foo.md]]                  (basename unique in repo)
[[a/foo.md]] (with b/foo.md)       → unchanged (basename duplicated; root-relative is canonical)

`docs/foo.md` (meow-toolbox)        → `foo.md` (meow-toolbox)     (basename unique in target repo)
`../docs/foo.md` (meow-tower)       → `foo.md` (meow-tower)       (path escape; basename fallback)

Pass --fix to rewrite the source bytes in place. The replacement is scoped to the path bytes only — fragments, aliases, and the (repo) suffix are preserved.

Cross-repo configuration

Cross-repo refs `path.ext` (repo-name) are resolved by looking up the repo name in a global config file. Two equivalent JSON shapes are accepted:

{
  "repos": {
    "meow-tower":   "$HOME/Develop/meow-tower",
    "meow-toolbox": "$HOME/Develop/meow-toolbox"
  }
}

{
  "meow-tower":   "$HOME/Develop/meow-tower",
  "meow-toolbox": "$HOME/Develop/meow-toolbox"
}

$VAR / ${VAR} and a leading ~/ are expanded against the environment. Default location: $XDG_CONFIG_HOME/md-orphan/md-orphan.json, falling back to ~/.config/md-orphan/md-orphan.json. Override with --config <path>.

Failure modes (all exit 1): file doesn't exist in target repo, style violation, broken anchor. A `…` (name) whose name isn't in the config is treated as an inline-code annotation, not a cross-repo ref — see the parser filter note in Link styles.

The crawl visits each cross-repo target file the entry repo directly references — to verify the file exists and its anchors resolve — but does not recurse into the cross-repo file's own outgoing links. Cross-repo internal rot is the responsibility of that repo's own md-orphan run, not yours. Orphan detection is also scoped to the entry repo only.

Per-repo ignore (.md-orphan)

Required. Every entry repo must have a .md-orphan file at its root listing project-specific ignore patterns. Running md-orphan against a repo without one exits 1 with a clear error message. If you have nothing to add beyond the built-in defaults, an empty file (touch .md-orphan) satisfies the requirement.

Loaded automatically for the entry repo and every cross-repo target visited during recursion. Cross-repo targets without their own .md-orphan fall back to defaults only — no hard-fail on cross-repo absence.

The "root" is the parent directory of the first entry point. When that parent has no .md-orphan but a strict ancestor does, the missing-file error reframes as "wrong-scoped entry point — pass an entry point inside <ancestor> instead" rather than suggesting you create a phantom mini-root at the subdirectory. Create .md-orphan at the subdirectory only when it's genuinely a separate repo with its own scope.

# Comments and blank lines are ignored.
Pods/                       # bare basename — matches at ANY depth (proj-ios/Pods/ etc.)
Packages/
docs/draft-*.md
docs/internal/              # path-anchored — only matches at root

Pattern syntax (gitignore-flavored):

• Trailing / makes it a directory pattern.
• Bare basename + trailing / (Pods/, Library/) — matches that directory at any depth in the tree.
• Path-containing + trailing / (docs/internal/) — anchored at the repo root.
• Patterns with *, ?, […] are matched as fnmatch(3) globs (PATHNAME mode — * doesn't cross /).
• Plain patterns (no /, no glob) match as path prefix at root.
• No negation. Use CLI --exclude to add CLI-time patterns.

Built-in defaults (.git, .svn, .hg, node_modules, .build, DerivedData, Library, Pods, target, vendor, .venv, __pycache__) apply on top and use the same nested-matching semantics. Disable with --no-default-excludes.

Caches

Two layers, both keyed by fnv1a64(canonical_root) — two repos with the same basename in different parents don't collide. Both use atomic writes (tempfile + rename), schema-versioned, last-writer-wins on concurrent invocations.

Walk-result cache at $XDG_CONFIG_HOME/md-orphan/walk-cache/<hash>.json — persists RepoIndex (md_files + by_name + effective excludes). Validation: per-dir mtime stat (APFS bumps dir mtime on entry add/remove/rename, not file content edits). Flags-keyed: changes to --exclude, .md-orphan, --no-default-excludes invalidate. On hit, skips the entire index_repo walk (~99 ms cold → ~40 ms warm on Unity-scale repos).

Per-file extraction cache at $XDG_CONFIG_HOME/md-orphan/cache/<hash>.json — caches links + headings per .md file. Per-entry validation: (mtime_ns, size, fnv1a64(content)) all match. Per-cache-file validation: repo_set_hash (fnv1a64 of sorted configured repo names) — invalidates the whole cache when the user's repo config changes, since cross-repo refs are filtered against that set at extract time. Catches the post---fix byte-equal-output edge case via content hash. Entries for vanished files auto-pruned each run.

Load errors silently fall through to fresh extraction; corrupted files are treated as misses and overwritten next run.

Disable both with --no-cache.

Structure

• src/path.rs — path helpers (real_path, dir_name, base_name, rel_path) + read_file
• src/exclude.rs — ExcludeMatcher with bare-basename hash-set fast path + DEFAULT_EXCLUDES
• src/extract.rs — Link type + byte-level link/heading/fence scanners + grapheme-aware anchor_id
• src/crawl.rs — bfs_crawl, CrawlState, LinkIssue, CrawlOptions, resolve_link, apply_style_fixes
• src/discovery.rs — index_repo + RepoIndex (ignore::WalkParallel-based)
• src/config.rs — global JSON config + per-repo .md-orphan parsing + expand_path
• src/cache.rs — per-file extraction cache (mtime + size + fnv1a64 content-hash keyed)
• src/walk_cache.rs — walk-result cache: persisted RepoIndex, per-dir-mtime validated
• src/main.rs — clap-derive CLI entry + output rendering + --fix wiring
• tests/fixtures/ — anchor-id parity TSV captured during the Swift→Rust port
• dist/md-orphan — pre-built release binary (committed to repo for fast just install)
• See [[architecture.md]] for module layout + design rationale, [[performance.md]] for benchmarks, and [[rust-migration.md]] for the historical Swift→Rust migration record

Algorithm

1. Discover — ignore::WalkParallel traversal under the entry root with per-thread visitor pruning excluded subtrees (work-stealing across num_cpus threads). .md filenames enter the basename map for style/ambiguity checks. (Non-.md extensions in the basename map costs ~30× more on Unity-sized repos and is off by default — see [[TODO.md]].)
2. Crawl — BFS from entry points. For each visited entry-repo file: extract links (cached when source unchanged), resolve each link, check broken/ambiguous/anchor/style. Cross-repo refs trigger lazy index of the target repo. The target file is visited (heading extraction for anchor checks) but its outgoing links are NOT followed — cross-repo recursion stops at depth 1. Two visited sets, both keyed by canonical path.
3. Diff — .md files in the entry repo whose canonical path is not in the reachable set are orphans.

Edge cases: missing entry point → exit 1; broken link → exit 1; circular links → visited set; symlinks → std::fs::canonicalize (handles macOS /var/folders → /private/var/folders); multiple entry points → reachability union.

Performance

~5 ms self-check; ~63 ms cold / ~29 ms warm on a Unity-scale 51k-file repo (post-prune). Numbers, per-phase breakdown, and what the walk-cache and per-file cache actually buy: [[performance.md]].