Install

go-libfossil is a Go module and a command. Neither needs cgo, a C toolchain or an installed fossil.

The command

go install github.com/danmestas/go-libfossil/cmd/libfossil@latest
libfossil --help

This needs the Go toolchain named in go.mod (Go 1.26 or later). The binary is statically linked and runs on Linux, macOS and Windows. Every command is listed in the CLI reference.

The library

go get github.com/danmestas/go-libfossil@latest

The library talks to SQLite through database/sql and does not pick a driver for you. Blank-import exactly one of the two driver modules in your main package; importing both panics at start-up.

Each driver is its own module, so go get it too:

go get github.com/danmestas/go-libfossil/db/driver/modernc@latest

WebAssembly

With the ncruces driver the module builds for GOOS=js GOARCH=wasm (a browser) and GOOS=wasip1 GOARCH=wasm (any WASI Preview 1 host). CI builds the module’s packages for js/wasm on every change. The wasm example builds and runs a WASI module.

TinyGo

The whole public API, the HTTP sync client and signing included, also builds with TinyGo for the wasm target, which is what makes it small enough to ship with a page or an edge function:

tinygo build -target=wasm -no-debug -opt=z -stack-size=1MB -o libfossil.wasm ./examples/tinygo/
wasm-opt -Oz --detect-features --strip-debug --strip-producers libfossil.wasm -o libfossil.wasm

• Size: for examples/tinygo, about 1.3 MB gzipped as CI builds it, against about 4.1 MB from the standard toolchain. A program without sync is smaller.
• Driver: a TinyGo build imports no SQLite driver. The host registers a database/sql driver over its own SQLite; ncruces is for standard Go builds and modernc has no wasm build.
• Stack: -stack-size=1MB, because TinyGo’s default goroutine stack is too small for the deeper paths.
• Differences: under TinyGo a sync redirect ends the request with an error instead of being followed, and DNS failures are not classified as transient.
• Without HTTP: a program that serves sync through HandleSyncWithOpts and syncs, if at all, through a Transport its host supplies can build with -tags libfossil_nohttp. That leaves out NewHTTPTransport, WithHTTPClient, Repo.Pull, Repo.XferHandler and Repo.ServeHTTP, and with them net/http, whose TLS and X.509 dependencies are about 97 KB of a gzipped TinyGo binary. Everything else is unchanged. The tag is for library embedders: the cli package and examples/tinygo, which calls NewHTTPTransport, do not build with it. A tagged embedder supplies its own transport and serving, for example a Transport for Sync and its own request handling around HandleSyncWithOpts.
• Without slog: -tags libfossil_noslog leaves log/slog out, about 33 KB of a gzipped TinyGo binary. The check-in linker then writes its info and warning messages to stderr as plain LEVEL message key=value lines and drops its debug messages; nothing else changes. It combines with libfossil_nohttp.

CI builds examples/tinygo with TinyGo 0.43 on every change, and builds the library under both tags.

Smaller still

The html-artifact-publisher engine, which serves Fossil repositories from Cloudflare Durable Objects, uses both tags and goes further. It is 754,725 bytes gzipped with TinyGo 0.43 and Go 1.27.3, where the same program built as above is about 1.2 MB; in the publisher’s measurements on Go 1.26 it also ran its test workload about three times faster. Its fossil/build.sh is the worked example. Beyond the tags it:

• builds with -scheduler=none, which drops TinyGo’s asyncify pass, the largest single cost;
• builds as a reactor (-buildmode=c-shared) and exports its entry point with //go:wasmexport, because a js.FuncOf callback cannot run without a scheduler;
• adds -panic-unwind=explicit, so recover still works without asyncify;
• compiles against a patched copy of the Go standard library (fossil/goroot.patch) that removes the goroutines database/sql, context and time.AfterFunc start, since a build without a scheduler cannot run them. The patch changes behavior: database/sql opens connections on demand and does not watch contexts, a context derived from a custom parent does not inherit its cancellation, and an AfterFunc callback runs inline. It also leaves out the FIPS self-tests.

These steps are the publisher’s, not the library’s, and this repository’s CI does not build that way. They hold for a program that, like the publisher’s engine, opens repositories, commits and serves sync through HandleSyncWithOpts; other paths, such as the HTTP sync client, may start goroutines of their own that such a build cannot run.

Next

• Quickstart: the CLI
• Embed in Go