Add a Dockerfile that allows efficient local builds

.gitignore

@@ -1 +1,2 @@
 *~
+*.uf2

Dockerfile

@@ -0,0 +1,44 @@
+FROM nixpkgs/nix:nixos-23.11
+
+ENV PATH=/root/.nix-profile/bin:/usr/bin:/bin
+
+RUN <<EOF
+    set -euo pipefail
+    nix-env -iA cachix -f https://cachix.org/api/v1/install
+    cachix use moergo-glove80-zmk-dev
+    mkdir /config
+    # Mirror ZMK repository to make it easier to reference both branches and
+    # tags without remote namespacing
+    git clone --mirror https://github.com/moergo-sc/zmk /zmk
+    GIT_DIR=/zmk git worktree add --detach /src
+EOF
+
+# Prepopulate the container's nix store with the build dependencies for the main
+# branch and the most recent three tags
+RUN <<EOF
+    cd /src
+    for tag in main $(git tag -l --sort=committerdate | tail -n 3); do
+      git checkout -q --detach $tag
+      nix-shell --run true -A zmk ./default.nix
+    done
+EOF
+
+COPY --chmod=755 <<EOF /bin/entrypoint.sh
+#!/usr/bin/env bash
+    set -euo pipefail
+    : "\${BRANCH:=main}"
+
+    echo "Checking out \$BRANCH from moergo-sc/zmk" >&2
+    cd /src
+    git fetch origin
+    git checkout -q --detach "\$BRANCH"
+
+    echo 'Building Glove80 firmware' >&2
+    cd /config
+    nix-build ./config --arg firmware 'import /src/default.nix {}' -j2 -o /tmp/combined --show-trace
+    install -o "\$UID" -g "\$GID" /tmp/combined/glove80.uf2 ./glove80.uf2
+EOF
+
+ENTRYPOINT ["/bin/entrypoint.sh"]
+
+# Run build.sh to use this file

build.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+
+set -euo pipefail
+
+IMAGE=glove80-zmk-config-docker
+BRANCH="${1:-main}"
+
+docker build -t "$IMAGE" .
+docker run --rm -v "$PWD:/config" -e UID="$(id -u)" -e GID="$(id -g)" -e BRANCH="$BRANCH" "$IMAGE"

config/default.nix

@@ -1,7 +1,8 @@
-{ pkgs ?  import <nixpkgs> {} }:
+{ pkgs ?  import <nixpkgs> {}
+, firmware ? import ../src {}
+}:
 
 let
-  firmware = import ../src {};
   config = ./.;
 
   glove80_left  = firmware.zmk.override { board = "glove80_lh"; keymap = "${config}/glove80.keymap"; kconfig = "${config}/glove80.conf"; };