Implement the following plan:

Go REUSE parsing library

Parsing library for the REUSE specification v3.3 at github.com/git-pkgs/reuse. Extracts SPDX license and copyright information from files, REUSE.toml, .reuse/dep5, and .license sidecars. No CLI, no linting output, just parsing.

Context

git-pkgs needs to extract licensing information from repositories. The REUSE spec (fsfe.org) standardises where and how license/copyright info lives in a project. The Python reference implementation (fsfe/reuse-tool) is GPL-licensed and has complex dependencies. A focused Go parsing library lets git-pkgs consume REUSE data without shelling out to Python.

Test fixtures

Add fsfe/reuse-example as a git submodule at testdata/reuse-example for conformance testing. It has a compliant main branch with LICENSES/, SPDX headers in source, .license sidecars for images.

Also create testdata/fake_repository/ modelled on the reuse-tool's test fixtures, with various license files, source files with headers, and edge cases.

Dependencies

• github.com/BurntSushi/toml for REUSE.toml parsing (Go stdlib has no TOML parser)
• SPDX expressions stored as raw strings; no dependency on git-pkgs/spdx (consumers validate if needed)
• No dep5 library needed; write a minimal parser for the Debian copyright format

Files

All under /Users/andrew/code/git-pkgs/reuse/.

reuse.go - Package docs and top-level types

Core types that other files use:

extract.go - SPDX tag extraction from file contents

Port of Python's extract.py. The core parsing engine.

• ExtractReuseInfo(text string) ReuseInfo - find SPDX-License-Identifier, SPDX-FileCopyrightText, SPDX-FileContributor tags in text
• ExtractFromFile(path string) (ReuseInfo, error) - read a file and extract
• FilterIgnoreBlocks(text string) string - strip REUSE-IgnoreStart/End regions
• Regex patterns ported from Python: copyright notice pattern, license identifier pattern, contributor pattern

extract_test.go

• Tags in various comment styles (// # /* -- etc.)
• REUSE-IgnoreStart/End filtering
• Multiple copyright notices and licenses in one file
• SPDX-SnippetBegin/End handling
• Empty files, binary files (return empty ReuseInfo)
• Malformed tags

toml.go - REUSE.toml parsing

Port of Python's global_licensing.py (ReuseTOML parts).

• ParseReuseTOML(content string) (*ReuseTOML, error)
• ParseReuseTOMLFile(path string) (*ReuseTOML, error)
• (a *Annotation) Matches(path string) bool - glob matching with * and ** support
• (t *ReuseTOML) ReuseInfoOf(path string) (ReuseInfo, PrecedenceType, bool) - find matching annotation for a path

toml_test.go

• Valid REUSE.toml with single and multiple annotations
• Glob pattern matching (* vs ** vs escaped)
• Precedence values (closest, aggregate, override)
• Missing version field, invalid TOML, wrong version number
• Last-match-wins when multiple annotations match
• Copyright and license as string vs array

dep5.go - .reuse/dep5 parsing

Minimal Debian copyright format 1.0 parser (no external dep).

• ParseDep5(content string) (*Dep5, error)
• ParseDep5File(path string) (*Dep5, error)
• (d *Dep5) ReuseInfoOf(path string) (ReuseInfo, bool) - find matching paragraph for a path

dep5_test.go

• Valid dep5 with multiple file paragraphs
• Wildcard patterns (*, ?)
• Multi-line copyright fields
• Missing required fields
• Continuation lines

covered.go - Covered file logic

Determines which files need licensing info and which are excluded per the spec.

• IsCoveredFile(path string) bool - checks against exclusion patterns
• IsIgnoredDir(name string) bool - .git, .hg, LICENSES, .reuse
• IsIgnoredFile(name string) bool - LICENSE*, COPYING*, *.license, REUSE.toml, .spdx
• CoveredFiles(root string) ([]string, error) - walk directory returning covered files

covered_test.go

• Exclusion of LICENSE, COPYING, .git, LICENSES/, .reuse/
• .license sidecar files excluded
• REUSE.toml excluded
• SPDX documents excluded
• Zero-byte files excluded
• Symlinks excluded
• Normal source files included

project.go - Project-level parsing

Ties everything together. Given a project root, find and parse all licensing info.

• OpenProject(root string) (*Project, error) - discover REUSE.toml or dep5, scan LICENSES/
• (p *Project) ReuseInfoOf(path string) (ReuseInfo, error) - resolve all sources with precedence:
  1. Check for .license sidecar
  2. Check REUSE.toml override annotations
  3. Extract from file header
  4. Check REUSE.toml closest/aggregate annotations
  5. Check dep5
• (p *Project) AllReuseInfo() (map[string]ReuseInfo, error) - walk all covered files

project_test.go

• Uses testdata/reuse-example submodule for real-world conformance
• Uses testdata/fake_repository for edge cases
• Project with REUSE.toml
• Project with dep5
• Project with neither (header-only)
• Precedence resolution between sources
• .license sidecar overrides

glob.go - REUSE.toml glob matching

Custom glob implementation matching the REUSE.toml spec:

• * matches everything except /

• ** matches everything including /

• \\* is a literal asterisk

• Forward slashes only

• GlobMatch(pattern, path string) bool

glob_test.go

• *.go matches foo.go but not dir/foo.go
• **/*.go matches dir/foo.go and dir/sub/foo.go
• src/** matches everything under src/
• Escaped asterisks
• Edge cases

Infrastructure files

• go.mod - module github.com/git-pkgs/reuse, go 1.25.6, deps on BurntSushi/toml and git-pkgs/spdx
• LICENSE - MIT, copied from vers
• README.md - usage examples
• .gitignore - *.test, *.prof
• .gitmodules - testdata/reuse-example submodule
• .github/workflows/ci.yml - matching other modules (with submodules: true)
• .github/workflows/zizmor.yml - matching other modules

Build order

1. reuse.go - types
2. glob.go + tests - glob matching (no deps on other files)
3. extract.go + tests - SPDX tag extraction (no deps on other files)
4. dep5.go + tests - dep5 parsing
5. toml.go + tests - REUSE.toml parsing (depends on glob.go)
6. covered.go + tests - covered file logic
7. project.go + tests - ties it all together
8. Add submodule, infrastructure, README

Verification

1. go test -v -race ./... - all tests pass
2. go vet ./... - clean
3. Tests against reuse-example submodule confirm real-world parsing works

If you need specific details from before exiting plan mode (like exact code snippets, error messages, or content you generated), read the full transcript at: /Users/andrew/.claude/projects/-Users-andrew-code-git-pkgs/ced24506-3bc7-4de2-84fd-76adc53e1512.jsonl