···44repo. Generally:
5566* Pipelines are defined in YAML.
77-* Dependencies can be specified from
88-[Nixpkgs](https://search.nixos.org) or custom registries.
99-* Environment variables can be set globally or per-step.
77+* Workflows can run using different *engines*.
88+99+The most barebones workflow looks like this:
1010+1111+```yaml
1212+when:
1313+ - event: ["push"]
1414+ branch: ["main"]
1515+1616+engine: "nixery"
1717+1818+# optional
1919+clone:
2020+ skip: false
2121+ depth: 50
2222+ submodules: true
2323+```
2424+2525+The `when` and `engine` fields are required, while every other aspect
2626+of how the definition is parsed is up to the engine. Currently, a spindle
2727+provides at least one of these built-in engines:
2828+2929+## `nixery`
3030+3131+The Nixery engine uses an instance of [Nixery](https://nixery.dev) to run
3232+steps that use dependencies from [Nixpkgs](https://github.com/NixOS/nixpkgs).
10331134Here's an example that uses all fields:
1235