A rebuild script that commits on a successful build

configuration.nix

{
  config,
  pkgs,
  options,
  ...
}: let
  hostname = "oatman-pc"; # to alllow per-machine config
in {
  networking.hostName = hostname;

  imports = [
    /etc/nixos/hardware-configuration.nix
    (/home/oatman/dotfiles/nixos + "/${hostname}.nix")
  ];
}

nixos-rebuild.sh

#!/usr/bin/env bash
#
# I believe there are a few ways to do this:
#
#    1. My current way, using a minimal /etc/nixos/configuration.nix that just imports my config from my home directory (see it in the gist)
#    2. Symlinking to your own configuration.nix in your home directory (I think I tried and abandoned this and links made relative paths weird)
#    3. My new favourite way: as @clot27 says, you can provide nixos-rebuild with a path to the config, allowing it to be entirely inside your dotfies, with zero bootstrapping of files required.
#       `nixos-rebuild switch -I nixos-config=path/to/configuration.nix`
#    4. If you uses a flake as your primary config, you can specify a path to `configuration.nix` in it and then `nixos-rebuild switch —flake` path/to/directory
# As I hope was clear from the video, I am new to nixos, and there may be other, better, options, in which case I'd love to know them! (I'll update the gist if so)

# A rebuild script that commits on a successful build
set -e

# Edit your config
$EDITOR configuration.nix

# cd to your config dir
pushd ~/dotfiles/nixos/

# Early return if no changes were detected (thanks @singiamtel!)
if git diff --quiet '*.nix'; then
    echo "No changes detected, exiting."
    popd
    exit 0
fi

# Autoformat your nix files
alejandra . &>/dev/null \
  || ( alejandra . ; echo "formatting failed!" && exit 1)

# Shows your changes
git diff -U0 '*.nix'

echo "NixOS Rebuilding..."

# Rebuild, output simplified errors, log trackebacks
sudo nixos-rebuild switch &>nixos-switch.log || (cat nixos-switch.log | grep --color error && exit 1)

# Get current generation metadata
current=$(nixos-rebuild list-generations | grep current)

# Commit all changes witih the generation metadata
git commit -am "$current"

# Back to where you were
popd

# Notify all OK!
notify-send -e "NixOS Rebuilt OK!" --icon=software-update-available

I have made a script that handles all initialization logic, and post+pre git hooks. See here

I've been playing with changing the automatic commit message from just the nixos version metadata to also include a local llm summary of the changes. lumen is a good tool for this (though aichat probably works too), and I've found that mevatron/diffsense:0.5b is a good, small model for this that runs in ~3s on my mid-range i5 laptop with no GPU:

echo "Summarising diff with ollama..."
summary=$(lumen -p ollama -m"mevatron/diffsense:0.5b" draft)
echo $summary
sudo echo "installing..."
nh os switch ~/dotfiles/nixos/ -Hdefault -- --impure
current=$(nixos-rebuild list-generations --json | jq '.[] | select (.current == true) | "\(.generation)"')
git commit -am "$current - llm summary: $summary" && true
git push

The output seems to be a single-line summary, then a blank line, then some semi-useful detail. Better than nothing!

Whatever you use will require an ollama server running, which I've found to be quite light on resources when not in use. Trivial to install with nixos, of course:
configuration.nix

services.ollama.enable = true;