Contributing to libfossil

Thanks for your interest in libfossil, a pure-Go implementation of Fossil SCM. This document covers everything you need to get a working checkout, run the tests, and submit changes.

Development setup

Requires Go 1.26 or newer.

git clone https://github.com/danmestas/libfossil
cd libfossil
make setup-hooks

The repository ships with a go.work file at the root, so the main module and the submodules (db/driver/modernc, db/driver/ncruces, observer/otel) resolve each other locally without any extra configuration. make setup-hooks points core.hooksPath at .githooks/ so the pre-commit hook runs on every commit. The hook runs both SQLite drivers, go vet, the OTel submodule, and the CLI build in roughly 45 seconds; skip it with --no-verify only in emergencies.

Running tests

The main targets are:

• make test runs go test ./... against the default modernc SQLite driver.
• make test-drivers runs the full suite twice: once with modernc and once with ncruces via go test -tags test_ncruces ./.... Any change that touches the database layer should pass both.
• make test-otel runs the OTel observer submodule in isolation with GOWORK=off so it resolves against its own go.mod rather than the workspace.
• make test-all chains test-drivers, test-otel, and the CLI build. This is the target CI uses and the one to run before opening a pull request.

Deterministic simulation tests live under ./dst/.... They are not excluded from the default run but are slow - roughly a minute per driver - so expect make test-drivers to take a few minutes end to end.

Code layout

• Root module (github.com/danmestas/libfossil) holds the public API: Repo, checkout, sync, merge, and history helpers. See fossil.go, repo.go, and the repo_*.go files.
• cli/ hosts the Kong-based command-line surface; the libfossil binary is assembled in cmd/libfossil/.
• internal/ contains the implementation packages that back the public API - sync, merge, checkout, manifest, content, and friends. These are not part of the stable surface.
• db/ is the SQLite abstraction plus two driver submodules: db/driver/modernc (the default, pure-Go) and db/driver/ncruces (WASM-based, selected with the test_ncruces build tag).
• observer/otel/ is a separate Go module providing an optional OpenTelemetry observer; it lives out of the workspace path so apps can take it as a narrow dependency.
• dst/ contains the deterministic simulation test harness and scenarios.

Submitting changes

Keep pull requests small and focused on a single change. Before opening one:

• Make sure the pre-commit hook passes (equivalent to make test-all).
• If your change touches the database layer, verify it runs under both the modernc and ncruces drivers.
• New behavior needs tests. Bug fixes should include a regression test that fails without the fix.
• If you are touching fault-sensitive code (sync, merge, checkout, or anything that writes to disk), consider whether a BUGGIFY site is appropriate so DST can exercise the new path. See docs/testing.md for the conventions.

Commit messages should explain the "why" as well as the "what". Reference issue numbers where relevant.

Reporting issues

Please open issues on GitHub. Include your Go version (go version), operating system, and minimal reproduction steps. If a specific .fossil repository triggers the bug and it is not sensitive, attach a sample - it speeds up triage considerably.