Hooks on Simon Shine

A gallery of hk-nix git hooks

Thu, 05 Nov 2026 11:19:29 +0200

I’ve been obsessed with git commit hooks this year. Since discovering lefthook.nix this year, and later replacing it with my own hk-nix wrapper around hk, I’ve been enjoying faster and less buggy commit hooks with support for git 2.54’s config-based hooks.

This is a walkthrough of all the git hooks I’ve made this year. 36 of my repositories have a nix/hooks.nix. Every one of them started as a copy of the previous one, and then grew whatever that project turned out to need.

hk-nix + ast-grep: Remove all comments

Wed, 21 Oct 2026 14:10:00 +0200

Here’s a git pre-commit hook for removing all comments that relies on hk-nix.

It enforces the removal of all source code comments besides certain doc comments, plus the one YAML exception described below.

In Rust, comments that begin with /// or //!, for example.

For a particular project, this addresses source code in Rust, Nix, YAML and shell scripts.

The reason is that recent AI coding models obnoxiously litter all source code with excessive thinking. One may wonder: Are these comments here to improve the context for when the coding agent comes around another time, or do they only serve watermarking mandated by the EU AI Act?

hk-nix and mdformat gotchas

Sun, 27 Sep 2026 21:31:10 +0200

I run mdformat as a pre-commit hook via hk-nix and treefmt-nix. treefmt-nix runs over every markdown file in the tree and applies mdformat when it encounters .md files.

This is a collection of small gotchas.

So far I’ve just got two.

mdformat destroys YAML frontmatter by default ¶

Both SKILL.md files and Hugo static website content open with YAML frontmatter.

It might look like:

---
name: email-admin
description: >-
 Administers MXroute email hosting through the mxroute MCP tools. [...]
allowed-tools:
 - mcp__plugin_mxroute_mxroute__mxroute_list_domains
 - mcp__plugin_mxroute_mxroute__mxroute_get_domain
license: MIT OR Apache-2.0
---

Or like:

Git config-based hooks with hk-nix

Sat, 01 Aug 2026 00:00:00 +0100

hk is a fast, modern git hook manager and project linter configured in Pkl. hk-nix is to hk what lefthook-nix is to lefthook: you install hk with Nixpkgs, declare your hooks in Nix, pin every tool with Nix, and the hooks install themselves whenever you enter the devshell. It is the same stack I previously built with lefthook, with a nicer configuration language and one fewer workaround.

Synergies ¶

Nix + direnv: You only ever need to install these two manually: Nix being the package manager, and direnv being the thing that activates the Nix devshell. All other tooling is derived, pinned and installed for you.

Using lefthook and treefmt with Nix

Sat, 07 Mar 2026 21:47:14 +0100

In my recent attempts to modernize my CI pipelines, I’ve experimented with and subsequently let go of pre-commit. The reason why I didn’t stick with pre-commit is that pre-commit drags in several software runtimes and toolchains when building it from scratch. When Nix fails to build something from nixpkgs, it’s an omen of too many chefs.

Alternatives I’m aware of:

lefthook: A generic tool written in Go; defines hooks in a lefthook.yml file.
husky: A generic tool written in JavaScript; enough said.
cargo-husky: A tool specialized to Rust/Cargo; very nice, but not generic enough.

I initially disregarded lefthook because of its special lefthook.yml.