#dirstat v1 specification

dirstat summarizes the files in a directory tree, grouped by format, with aggregate statistics (counts, sizes, lines of code) rendered as a colored terminal table or as JSON. It is a clean-slate Go redesign of an internal Python prototype, built for speed: no subprocesses, parallel scanning, single static binary.

This document is the authoritative spec for the initial implementation. Every requirement is numbered (R1, R2, ...) so audits can address them individually.

#1. Project shape

• R1. Go module github.com/smm-h/dirstat, Go directive go 1.25.7, flat

package main at the repo root (no cmd/), matching safegit/saferm layout.

• R2. CLI built on github.com/smm-h/strictcli/go/strictcli, unpinned latest.

.strictcli/schema.json committed.

• R3. rlsbl-managed: .rlsbl/config.json with targets: ["go"], pipeline

{"type": "go", "local": true, "install_paths": ["."]}, private: false, pre-release hooks running go vet ./..., go build -o /dev/null ., and go test ./... -race -count=1. JSONL changelog in use from the first commit.

• R4. selfdoc-managed root templates only: selfdoc.json with

root_files: [".stricttools/docs/_README.md", ".stricttools/docs/_CLAUDE.md"]; no docs site, no deploy config. Generated README.md/CLAUDE.md are committed and chmod 444.

• R5. Version 0.1.0 in VERSION; binary version via -X main.Version ldflags

with debug.ReadBuildInfo() fallback. The symbol name must match the one .goreleaser.yml injects: the linker silently ignores an -X naming a symbol that does not exist. MIT LICENSE, Copyright (c) 2026 smm-h.

• R6. Dependencies: strictcli, github.com/gabriel-vasile/mimetype (content

sniffing), go-git's plumbing/format/gitignore package (ignore matching), golang.org/x/term (terminal size), github.com/mattn/go-runewidth (display-cell width for table column measurement, R28). github.com/smm-h/go-toml-edit was added with §11 (scan config). No CGO (CGO_ENABLED=0 must work).

#2. CLI surface

• R7. Single command: dirstat scan [where]. where is an optional positional

argument, default ".", the directory to summarize. A missing or non-directory path is a hard error (exit code for usage/input error, message to stderr).

• R8. Flags (strictcli conventions: every flag and the positional argument

declares exactly one presence -- Required(), Optional() or Default(v); a closed set is declared as Choices(Ch(<value>, <help>) ...), one record per value, so --help describes each value beneath its flag; auto --no-* negation on bools; short names only where listed). scan is read_only, so a declared default is legal on it -- the mutating-default ban reaches only commands that write. The Default column below reads optional where the flag declares no value at all:

• R9. Flag semantics that the prototype got wrong and dirstat must define cleanly:

rendering-only flags (--show, --combined, --singletons, --legend, --colors, --human, --style, --top) have no effect on the machine payload. --sort-by/--sort-order order groups in both outputs. --stats limits which stats are computed and emitted in both outputs. --list-no-ext adds data to both outputs (a section in table mode, a field in the payload).

#3. Grouping methods

• R10. Extension normalization: last-dot suffix, lowercased, dot stripped

(Path.suffix semantics: archive.tar.gz → gz; dotfiles like .bashrc and bare names like Makefile have no extension).

• R11. ext: group name is the extension, or (no extension); text/binary decided

by the extension list only; no content sniffing ever.

• R12. type: every file is content-sniffed; group name is the detected MIME type

or (unknown) when detection fails; text/binary via the MIME rule (R15).

• R13. hybrid (default): a file whose extension is in the text-extensions list is

text without sniffing (the map is trusted on a hit). A file whose extension misses the list is content-sniffed: the group name stays the extension, and the MIME rule (R15) alone decides text/binary — a missing map entry never means binary. Extensionless files are sniffed and grouped by MIME type, falling back to (no extension) when sniffing yields nothing. A sniff that cannot read the file makes the file unreadable (R20).

Added after 0.4.0, and numbered from the end of the requirement list per the numbering convention: --formats decides how the group name chosen by R11–R13 is spelled, without changing which files are grouped together by method, which files are sniffed, or the text/binary verdict.

• R48. --formats raw (default) counts every file under the group name R11–R13

produced, verbatim: the normalized extension, the sniffed MIME type, or (no extension)/(unknown). --formats canonical maps that name through an embedded alias table (internal/config/data/canonical_formats.txt, old new pairs, one per line, # comments) before the file is counted, so alias formats merge into one group: mjs/cjs into js, mts/cts into ts, h into c, hh/hpp into cpp, and the script MIME types the sniffer emits (text/x-python, text/x-shellscript, text/x-perl, text/x-ruby, text/x-php, text/x-lua, text/x-tcl) into their format names. A name the table does not list is unchanged. A malformed line in the table is a hard error when the table is read, never a skipped line. formats is also a scan config key (R42), with the flag/file conflict rule of R43 applying to it.

• R49. Under --formats canonical, an extensionless file whose first line is a

shebang is named by its interpreter, before the MIME sniff gets a say: the sniffer has no signature for most scripts and answers text/plain, which names nothing. An env wrapper is stripped (its options, its -S and --split-string forms, and any NAME=value assignments), the uv run X and uvx X runner forms resolve to X, and a trailing version suffix is dropped (python3.12 reads as python). The mapping is python* → py, bash/sh/zsh/dash/ksh → sh, node/deno/bun → js, perl → pl, ruby → rb, php → php, fish → fish, awk/gawk → awk, Rscript → r, lua → lua. An interpreter outside the mapping falls through to the sniff, whose result still goes through the alias table (R48). The sniff still runs either way: it decides text/binary (R15) and counts toward Files sniffed, and the shebang only names the group. ext, which reads no content at all (R11), is untouched.

• R50. The payload shape is unchanged by --formats (R34): only group names,

their counts and unique_formats differ, so raw output stays byte-identical to what pre---formats versions produced. Tests: table-driven unit tests for the alias-table parser and the shebang parser (env forms, runner forms, version stripping, unknown-interpreter fallthrough), a config-key test, and integration tests pinning the merged groups and a shebang-named group against the real embedded table.

#4. Text/binary classification

• R14. Extension-classified files are text iff the extension is in the embedded

text-extensions list. A zero-byte file is text under every method, whatever its extension: an empty file has no bytes that could make it binary, and it contributes 0 LOC. Where the extension decides the verdict, the size short-circuits it and no content is read; where the method groups by MIME type (R12, and R13's extensionless path) the sniff still runs to name the group but cannot override emptiness.

• R15. MIME-classified files are text iff the MIME type starts with text/ or is in

the embedded text-mimetypes list. The result is a strict bool.

• R16. Both lists are embedded via go:embed, seeded from the prototype's

lists and extended since (about 210 extensions incl. svg, Godot's text formats, mod/sum and the shader languages, but deliberately not lock, which is text for some tools and binary for others and must therefore be sniffed per file; about 45 mimetypes incl. image/svg+xml, application/json, application/x-empty, inode/x-empty). No runtime config files, no lookup in cwd/HOME/XDG. Changing the lists means a rebuild.

#5. Traversal

• R17. Walk with filepath.WalkDir-level efficiency (DirEntry, no redundant stat).

Root is depth 0. Directories beyond --depth, matching --exclude, hidden (when excluded), or gitignored (when excluded) are pruned: not counted, not descended into.

• R18. Gitignore handling is fully in-process using go-git's gitignore package:

patterns from every .gitignore in the tree, .git/info/exclude, and the global core.excludesFile. Modes: include = no matching at all; exclude = drop ignored paths; only = keep only ignored paths (only prunes ignored dirs' contents from exclusion — files under an ignored dir count as ignored). When the target is not inside a git work tree, exclude and only behave as if no patterns exist; this must be documented in the flag help.

• R19. Symlinks are never followed — neither file nor directory symlinks — but every

symlink encountered in any traversed directory is counted, so the symlink count does not depend on traversal order (fixes a prototype bug where symlinks under pruned dirs were missed; symlinks under pruned dirs are legitimately out of scope, but all symlinks in traversed dirs must be counted even when they would be filtered by name rules).

• R20. Unreadable directories and files (permission errors, stat failures) are

skipped and counted in a summary stat Unreadable (skipped). Never a warning spew; never a crash.

• R21. Per-file work (LOC counting, content sniffing) runs in a worker pool sized to

runtime.GOMAXPROCS(0). Results must be deterministic regardless of scheduling.

#6. Statistics

• R22. Per group: count, total-size, min-size, max-size, avg-size, and for

text groups total-loc, min-loc, max-loc, avg-loc. Binary groups have no LOC values (rendered -, JSON null). Averages are rounded to nearest integer, not floored. Stats not requested via --stats are neither computed nor shown (LOC is expensive; skipping it must actually skip the file reads), with one exception: sorting by a LOC key via --sort-by forces LOC computation even when LOC stats are not displayed.

• R23. LOC = number of \n bytes, plus 1 if the file is non-empty and does not end

with \n. Counted with buffered bytes.Count-style reads (no line decoding, no size cap). Read errors count the file as unreadable (R20), not LOC 0.

• R24. Summary stats: Directories, Files, Files without extension,

Max depth, Symlinks (skipped), Executables, Unique formats, Files sniffed, Unreadable (skipped). Files without extension counts only files that passed all filters including --type (fixes prototype bug). Executables = regular files with any execute permission bit. Files sniffed = number of content-sniff operations performed.

#7. Table output

• R25. Section order: summary (heading Summary, a rule line, label: value

lines), then table(s), then optional extensionless-file list, respecting --show.

• R26. Combined mode: one table Files by Format with text rows and binary rows

distinguished by color. Split mode (--no-combined): Text Files by Format and Binary Files by Format; the binary table omits LOC columns. Row-building logic must be shared, not duplicated per table (prototype wart).

• R27. Columns in fixed order: Format, Count, Total Size, Min Size,

Max Size, Avg Size, Total LOC, Min LOC, Max LOC, Avg LOC — each present only if its stat is selected. Sizes humanized in 1024-based units with one decimal (except bare bytes) when --human; raw integers otherwise. Counts get thousands separators when --human.

• R28. Width adaptation: query terminal width (x/term; fallback 80 when not a

TTY). If the table overflows, shrink only the Format column down to a floor of 10, truncating cells with a .. marker. Column widths are measured in terminal display cells (runewidth), not bytes, and truncation never splits a UTF-8 rune. MIME-type group names (any name containing a /) truncate from the left, keeping the subtype and prefixing ..: their prefix is shared and uninformative, so tail truncation would render every application/* group as the same indistinguishable applicat... All other names keep their prefix and take the marker as a suffix. Whenever colors are inactive (non-TTY or --no-colors), width is pinned to 80 so that --no-colors output is byte-identical to non-TTY output (R30).

• R29. Border styles: unicode (light box-drawing, the prototype's look) and

ascii (+ - |). One shared renderer parameterized by charset.

• R30. Colors: ANSI 256-color themes (dark and light) embedded as data; theme keys:

text/binary/header fg+bg, stat label, stat value, error, border. Dark unless COLORFGBG clearly indicates a light background. Colors apply only when --colors is true AND stdout is a TTY. --no-colors output must be byte-identical to non-TTY output. The theme's error color is applied to the error: prefix of stderr error messages when stderr is a TTY and --colors is true (stderr coloring is independent of machine mode).

• R31. Legend (■ Text files ■ Binary files) renders only when --legend,

--combined, --type both, and colors are active (it is meaningless without color).

• R32. --singletons collapse: groups with exactly one file are merged into a

single (singletons) pseudo-row (count = number of merged groups, sizes and text-only LOC aggregated); the row participates in sorting by its aggregate values and renders in a neutral (header) color. In split mode the collapse happens within each table independently.

• R33. Empty result → No files found. instead of an empty table.

#8. Machine output

• R34. Machine output is strictcli's --json mode, and dirstat declares no

output-format flag of its own. Under --json, stdout carries exactly one document -- the framework's envelope -- and no table; the scan document is the envelope's payload member. No ANSI codes ever, raw integer values (no humanization). The payload is a consumer contract (external tools will parse it): field names are stable, evolution is additive-only.

• R35. Payload shape, declared to the framework as a JSON Schema on the scan

command and validated at emission, so a deviating document fails the run instead of reaching a consumer:

json { "root": "/abs/path", "method": "hybrid", "summary": { "directories": 0, "files": 0, "files_without_extension": 0, "max_depth": 0, "symlinks": 0, "executables": 0, "unique_formats": 0, "files_sniffed": 0, "unreadable": 0 }, "groups": [ { "format": "go", "text": true, "count": 0, "total_size": 0, "min_size": 0, "max_size": 0, "avg_size": 0, "total_loc": 0, "min_loc": 0, "max_loc": 0, "avg_loc": 0 } ], "no_extension_files": ["relative/path"] }

The binary's version is the envelope's app_version and is not restated in the payload. Groups are ordered per --sort-by/--sort-order. Stats absent from --stats are omitted from group objects; LOC fields are null for binary groups. no_extension_files (paths relative to root, sorted) present only with --list-no-ext. --top and --singletons do not affect the payload (R9).

#9. Sorting

• R36. Multi-key sort over --sort-by columns with a single --sort-order

direction. format compares case-insensitively. For LOC keys, binary groups sort as 0. Ties broken by format name ascending so output is deterministic.

#10. Testing

• R37. Unit tests colocated per package, table-driven. Integration tests in

internal/test/ build the real binary once (TestMain pattern from saferm) and run it against fixture trees created with t.TempDir() (including: nested gitignore, hidden files, symlinks, permission-denied entries where the platform allows, extensionless files, empty dirs).

• R38. Golden-file tests for machine output: fixture tree in, committed golden

envelope compared byte-for-byte (after normalizing the absolute root path and the app version, and re-indenting the one-line document). Golden files live in internal/test/testdata/.

• R39. Determinism test: two runs over the same fixture tree produce identical

output despite the parallel worker pool.

• R40. go vet ./... clean, gofmt clean, go test ./... -race passes.

#11. Scan config file

Added after 0.1.0. A TOML file supplying scan defaults, loaded and fully validated before scanning begins. The file is used only when explicitly requested via --config <path> — dirstat never auto-discovers config from XDG, HOME, the current directory, or the scanned tree. Only scan-semantic keys are allowed; rendering and output options are rejected with a hard error naming the key.

• R41. --config <path>: when set, the file MUST exist and parse as TOML; a

missing, unreadable, or malformed file is a hard error (exit 2) reporting the path and, for parse errors, line/column (go-toml-edit ParseError). Loaded and fully validated before any scanning starts.

• R42. Allowed keys (flag names with underscores), exactly the scan-semantic set:

exclude (string array), method, formats, depth (integer), ignored, hidden, type, stats (string array), sort_by (string array), sort_order. Values are validated with the same rules as the corresponding flags (choices, valid stat names, uniqueness). Any unknown key, rendering/output key (e.g. colors, style, output, top), wrong type, or invalid value is a hard error (exit 2) naming the key and the allowed key set. where cannot be set from config.

• R43. Conflict rule (no silent override): if a key is present in the config file

AND its flag was explicitly passed on the command line, that is a hard error (exit 2) naming the key. Explicit passing is detected from raw os.Args (matching --flag value and --flag=value forms for the R42 flag set). CLI flags for keys the file does not set remain usable alongside --config.

• R44. Effective settings: registered flag defaults, overlaid by config-file

values, overlaid by CLI values only for keys absent from the file (R43 makes the file/CLI overlap impossible). Rendering flags are unaffected by config.

• R45. Built-in default excludes: --exclude registers a curated default list:

.git, node_modules, .venv, vendor, build, dist, target, zig-out, zig-pkg, .next, .svelte-kit, __pycache__, .mypy_cache, .ruff_cache, .pytest_cache, .hypothesis, .gradle, .idea, .wrangler, .vscode. The list is visible in --help. An explicit exclude = [] in the config file (or any CLI --exclude) replaces it entirely; there is no additive merging anywhere.

• R46. Visibility: when a config file is in effect, the table summary gains a

Config: <path> line (first summary line, absolute path), and the machine payload gains an additive optional field "config" (absolute path) after "method". Absent entirely when --config is not used (additive schema evolution, R34).

• R47. Tests: unit tests for the TOML loader/validator and the argv explicitness

scanner; integration tests covering happy path, missing file, malformed TOML, unknown key, rendering key, wrong type, file/CLI conflict, exclude = [], and a golden JSON fixture exercising the config field. The default-exclude behavior change is covered by updated integration expectations (e.g. .git no longer scanned by default; --exclude "" style overrides still honored).

#12. Non-goals for v1

• No result caching (measure first; the subprocess elimination and parallel scan

are expected to make it unnecessary).

• No interactive/TUI mode.
• No symlink following.
• No auto-discovered config and no runtime classification/theme data: extension

lists, mimetype lists, and themes are embedded-only, and dirstat never picks up config from XDG, HOME, cwd, or the scanned tree. (The explicit --config scan file of §11 is the sole, opt-in file input.)

• Never bump to 1.0.0 (stays 0.x until explicitly authorized).