chore: add build workflow

.github/workflows/build.yml

@@ -0,0 +1,166 @@
+name: build-ublue
+on:
+  pull_request:
+  merge_group:
+  schedule:
+    - cron: '0 6 * * *'  # 6am everyday (1h after 'config')
+  workflow_dispatch:
+env:
+    IMAGE_NAME: ucore-kmods
+    IMAGE_REGISTRY: ghcr.io/${{ github.repository_owner }}
+    SOURCE_IMAGE: fedora-coreos
+
+jobs:
+  push-ghcr:
+    name: Build and push ucore-kmods image
+    runs-on: ubuntu-22.04
+    permissions:
+      contents: read
+      packages: write
+      id-token: write
+    strategy:
+      fail-fast: false
+      matrix:
+        coreos_version: [stable, latest]
+    steps:
+      # Checkout push-to-registry action GitHub repository
+      - name: Checkout Push to Registry action
+        uses: actions/checkout@v3
+
+      - name: Generate tags
+        id: generate-tags
+        shell: bash
+        run: |
+          # Generate a timestamp for creating an image version history
+          TIMESTAMP="$(date +%Y%m%d)"
+          VARIANT="${{ matrix.coreos_version }}"
+
+          COMMIT_TAGS=()
+          BUILD_TAGS=()
+
+          # Have tags for tracking builds during pull request
+          SHA_SHORT="${GITHUB_SHA::7}"
+          COMMIT_TAGS+=("pr-${{ github.event.number }}-${VARIANT}")
+          COMMIT_TAGS+=("${SHA_SHORT}-${VARIANT}")
+
+          BUILD_TAGS=("${VARIANT}" "${VARIANT}-${TIMESTAMP}")
+
+          if [[ "${{ github.event_name }}" == "pull_request" ]]; then
+              echo "Generated the following commit tags: "
+              for TAG in "${COMMIT_TAGS[@]}"; do
+                  echo "${TAG}"
+              done
+
+              alias_tags=("${COMMIT_TAGS[@]}")
+          else
+              alias_tags=("${BUILD_TAGS[@]}")
+          fi
+
+          echo "Generated the following build tags: "
+          for TAG in "${BUILD_TAGS[@]}"; do
+              echo "${TAG}"
+          done
+
+          echo "alias_tags=${alias_tags[*]}" >> $GITHUB_OUTPUT
+
+      - name: Retrieve akmods signing key
+        run: |
+          mkdir -p certs
+          if [[ "${{ github.event_name }}" == "pull_request" ]]; then
+              echo "Using test signing key"
+          else
+              echo "${{ secrets.AKMOD_PRIVKEY_20230518 }}" > certs/private_key.priv
+          fi
+          # DEBUG: get character count of key
+          wc -c certs/private_key.priv
+
+      - name: Get current versions
+        id: labels
+        run: |
+          skopeo inspect docker://quay.io/fedora-ostree-desktops/${{ env.SOURCE_IMAGE }}:${{ matrix.coreos_version }} > inspect.json
+          version=$(jq -r '.Labels["org.opencontainers.image.version"]' inspect.json)
+          linux=$(jq -r '.Labels["ostree.linux"]' inspect.json)
+          echo "VERSION=$version" >> $GITHUB_OUTPUT
+          echo "LINUX=$linux" >> $GITHUB_OUTPUT
+
+      # Build metadata
+      - name: Image Metadata
+        uses: docker/metadata-action@v4
+        id: meta
+        with:
+          images: |
+            ${{ env.IMAGE_NAME }}
+          labels: |
+            org.opencontainers.image.title=${{ env.IMAGE_NAME }}
+            org.opencontainers.image.description=A caching layer for pre-built akmod RPMs
+            org.opencontainers.image.version=${{ steps.labels.outputs.VERSION }}
+            ostree.linux=${{ steps.labels.outputs.LINUX }}
+            io.artifacthub.package.readme-url=https://raw.githubusercontent.com/${{ github.repository }}/main/README.md
+            io.artifacthub.package.logo-url=https://avatars.githubusercontent.com/u/1728152?s=200&v=4
+
+      # Build image using Buildah action
+      - name: Build Image
+        id: build_image
+        uses: redhat-actions/buildah-build@v2
+        with:
+          containerfiles: |
+            ./Containerfile
+          image: ${{ env.IMAGE_NAME }}
+          tags: |
+            ${{ steps.generate-tags.outputs.alias_tags }}
+          build-args: |
+            SOURCE_IMAGE=${{ env.SOURCE_IMAGE }}
+            COREOS_VERSION=${{ matrix.coreos_version }}
+          labels: ${{ steps.meta.outputs.labels }}
+          oci: false
+
+      # Workaround bug where capital letters in your GitHub username make it impossible to push to GHCR.
+      # https://github.com/macbre/push-to-ghcr/issues/12
+      - name: Lowercase Registry
+        id: registry_case
+        uses: ASzc/change-string-case-action@v5
+        with:
+          string: ${{ env.IMAGE_REGISTRY }}
+
+      # Push the image to GHCR (Image Registry)
+      - name: Push To GHCR
+        uses: redhat-actions/push-to-registry@v2
+        id: push
+        if: github.event_name != 'pull_request'
+        env:
+          REGISTRY_USER: ${{ github.actor }}
+          REGISTRY_PASSWORD: ${{ github.token }}
+        with:
+          image: ${{ steps.build_image.outputs.image }}
+          tags: ${{ steps.build_image.outputs.tags }}
+          registry: ${{ steps.registry_case.outputs.lowercase }}
+          username: ${{ env.REGISTRY_USER }}
+          password: ${{ env.REGISTRY_PASSWORD }}
+          extra-args: |
+            --disable-content-trust
+
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v2
+        if: github.event_name != 'pull_request'
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      # Sign container
+      - uses: sigstore/[email protected]
+        if: github.event_name != 'pull_request'
+
+      - name: Sign container image
+        if: github.event_name != 'pull_request'
+        run: |
+          cosign sign -y --key env://COSIGN_PRIVATE_KEY ${{ steps.registry_case.outputs.lowercase }}/${{ env.IMAGE_NAME }}@${TAGS}
+        env:
+          TAGS: ${{ steps.push.outputs.digest }}
+          COSIGN_EXPERIMENTAL: false
+          COSIGN_PRIVATE_KEY: ${{ secrets.SIGNING_SECRET }}
+
+      - name: Echo outputs
+        if: github.event_name != 'pull_request'
+        run: |
+          echo "${{ toJSON(steps.push.outputs) }}"