Actions: Add build action

.forgejo/workflows/publish.yaml

@@ -0,0 +1,37 @@
+name: build and publish containers
+
+on:
+  push:
+    branches:
+      - main
+  schedule:
+    - cron: "0 0 * * 1,3,5"
+  workflow_dispatch: {}
+
+jobs:
+  build:
+    runs-on: nixos-latest
+    strategy: &strategy
+      matrix:
+        container: [ nixos ]
+        version: [ "24.11", "unstable" ]
+    steps:
+      - name: pre-requisites
+        run: |
+          nix-env -iA nixpkgs.docker nixpkgs.nodejs_20 nixpkgs.gnused nixpkgs.coreutils && mkdir -p ~/.config/nix && echo "experimental-features = nix-command flakes" > ~/.config/nix/nix.conf
+      - name: checkout
+        uses: actions/checkout@v4
+        with:
+          ref: 'main'
+      - name: nix package names
+        id: pkgs
+        run: |
+          echo "pkgs-name=${{ matrix.container }}-${{ matrix.version }}" | tr -d . >>"${GITHUB_OUTPUT}""
+      - name: build
+        uses: actions/nix/build@main
+        with:
+          package: ${{ steps.pkgs.outputs.pkgs-name }}
+          out-link: ${{ steps.pkgs.outputs.pkgs-name }}
+      - name: load image into docker
+        run: |
+          docker load < ${{ steps.pkg.outputs.pkg-name }}