Note

indexable-inc/build-version is a read-only mirror, generated from packages/build-version in indexable-inc/index at commit 4c5f3e7e2d40. The monorepo is the source of truth: please open issues and pull requests there. This mirror is regenerated automatically; anything pushed directly here will be overwritten.

build-version

A tiny Rust library that formats a binary's --version line from build metadata a Nix wrapper stamps into the environment, so every tool reports its revision, commit date, and how long ago it was built in one consistent shape:

$ nwm --version
nix-web-monitor 0.1.0 (7e42ccdb1882, 2026-06-07, 2 days ago)

A reproducible build has no wall-clock compile time, so the "when" is the flake's commit time (IX_BUILD_EPOCH, from self.lastModified), and "how long ago" is computed at run time against the current clock — which is why the metadata rides the wrapper environment (IX_BUILD_REV, IX_BUILD_EPOCH) instead of being baked into the binary: a new commit re-stamps a tiny wrapper without rebuilding the Rust unit.

Quickstart

Hand the interned &'static str straight to clap:

let cmd = clap::Command::new("mytool")
    .version(build_version::version_static(env!("CARGO_PKG_VERSION")));

With the two env vars set, --version prints 0.1.0 (7e42ccdb1882, 2026-06-07, 2 days ago); without them (a dev cargo run), it degrades to the bare crate version. In the monorepo the wrapper sets them from ix.rev / ix.revEpoch (see packages/nix/nix-web-monitor/server/default.nix for a real example).

Pointers

• doc/build-version/overview.md — from-source documentation.

Install

build-version is not on crates.io; add it as a git dependency:

[dependencies]
build-version = { git = "https://github.com/indexable-inc/build-version" }

Changes: CHANGELOG.md, derived from the monorepo history of the package.