feat: add initial GitHub Actions workflow for building and pushing development images

Author: Simen Andrè Vikestrand Skogum

.github/workflows/dev-image-build.yml

@@ -0,0 +1,80 @@
+name: Build & Push Dev Images
+
+on:
+  push:
+    branches: [ dev ]
+
+permissions:
+  contents: read
+  packages: write
+
+jobs:
+  detect:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.set.outputs.matrix }}
+    steps:
+      - uses: actions/checkout@v4
+        with: { fetch-depth: 0 }
+      - id: set
+        shell: bash
+        run: |
+          set -euo pipefail
+          base="${{ github.event.before }}"
+          head="${{ github.sha }}"
+
+          # Find changed Dockerfiles or VERSION files; build all if first push
+          if [ -z "$base" ] || [ "$base" = "0000000000000000000000000000000000000000" ]; then
+            paths="$(git ls-files 'salamicontainers/**/Dockerfile')"
+          else
+            paths="$(git diff --name-only "$base" "$head" -- 'salamicontainers/**/Dockerfile' 'salamicontainers/**/VERSION' || true)"
+            [ -n "$paths" ] || paths="$(git ls-files 'salamicontainers/**/Dockerfile')"
+          fi
+
+          # Collect app dirs that contain a Dockerfile
+          dirs="$(for p in $paths; do d="$(dirname "$p")"; [ -f "$d/Dockerfile" ] && echo "$d"; done | sort -u)"
+
+          includes="[]"
+          for d in $dirs; do
+            # Expect: salamicontainers/salami/<app>/<major>/Dockerfile
+            major="$(basename "$d")"
+            app="$(basename "$(dirname "$d")")"
+            ver="$(tr -d '\n\r\t ' < "$d/VERSION")"
+            image="ghcr.io/${{ github.repository_owner }}/salami-${app}-${major}"
+            tags="${image}:${ver}-dev,${image}:dev"
+            includes="$(jq -c --arg dir "$d" --arg img "$image" --arg ver "$ver" --arg tags "$tags" \
+              '. + [{dir:$dir,image:$img,version:$ver,tags:$tags}]' <<<"$includes")"
+          done
+
+          echo "matrix=$(jq -c '{include: .}' <<<"$includes")" >> "$GITHUB_OUTPUT"
+
+      - name: Show matrix
+        run: echo '${{ steps.set.outputs.matrix }}' | jq .
+
+  build-and-push:
+    needs: detect
+    if: ${{ needs.detect.outputs.matrix != '' }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix: ${{ fromJson(needs.detect.outputs.matrix) }}
+    steps:
+      - uses: actions/checkout@v4
+        with: { fetch-depth: 0 }
+      - uses: docker/setup-buildx-action@v3
+
+      - name: Login to GHCR
+        run: echo "${{ github.token }}" | docker login ghcr.io -u ${{ github.actor }} --password-stdin
+
+      - name: Build and push ${{ matrix.image }}
+        shell: bash
+        run: |
+          set -euo pipefail
+          IFS=, read -r TAG1 TAG2 <<<"${{ matrix.tags }}"
+          docker buildx build \
+            --platform linux/amd64,linux/arm64 \
+            -f "${{ matrix.dir }}/Dockerfile" \
+            --build-arg APP_VERSION="${{ matrix.version }}" \
+            -t "$TAG1" -t "$TAG2" \
+            --push \
+            "${{ matrix.dir }}"