ci(github): Rewrite the Docker build job

Replace the `docker-ort` workflow with the new `docker-build` workflow.
Instead of the old approach to build separate Docker images for the
different package managers, the new workflow uses the Docker registry
cache [1] to cache the layers in the GitHub container registry. This
dramatically simplifies the build process, as no additional logic for
building the Docker images is required anymore.

The workflow first builds the full Docker image and caches it to the
registry. The minimal image is built afterwards and can reuse all layers
but the last one from the previously populated cache.

This commit also slightly changes the way that Docker images are tagged:

* All published images are now tagged with the Git revision. Previously,
  the revision was only visible as part of the ORT version tag, which
  does not include the revision for release builds.
* The latest build from the main branch is now tagged with the `main`
  tag.

[1]: https://docs.docker.com/build/cache/backends/registry/

Signed-off-by: Martin Nonnenmacher <[email protected]>

.github/workflows/docker-build.yml

@@ -0,0 +1,90 @@
+name: Docker Build
+
+on:
+  pull_request:
+    branches:
+      - main
+  push:
+    branches:
+      - main
+    tags:
+      - '*'
+  workflow_dispatch:
+
+env:
+  GRADLE_OPTS: -Dorg.gradle.daemon=false
+  REGISTRY: ghcr.io
+  IMAGE_CACHE_TAG: ghcr.io/mnonnenmacher/ort:cache
+  IMAGE_NAME: ghcr.io/mnonnenmacher/ort
+
+jobs:
+  disk_space:
+    name: Disk Space
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Checkout Repository
+        uses: actions/checkout@v4
+      - name: Free Disk Space
+        uses: ./.github/actions/free-disk-space
+      - name: Setup Gradle
+        uses: gradle/actions/setup-gradle@v3
+        with:
+          gradle-home-cache-cleanup: true
+      - name: Get ORT version
+        run: |
+          ORT_VERSION=$(./gradlew -q properties --property version | sed -nr "s/version: (.+)/\1/p")
+          echo "ORT_VERSION=${ORT_VERSION}" >> $GITHUB_ENV
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Extract Docker Metadata for ort Image
+        id: meta-ort
+        uses: docker/metadata-action@v5
+        with:
+          images: |
+            ${{ env.REGISTRY }}/${{ github.repository_owner }}/ort
+          tags: |
+            type=pep440,pattern={{version}}
+            type=raw,value=${{ env.ORT_VERSION }}
+            type=ref,event=branch
+            type=ref,event=tag
+            type=sha
+      - name: Build & Push ort Docker Image
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta-ort.outputs.tags }}
+          labels: ${{ steps.meta-ort.outputs.labels }}
+          cache-from: type=registry,ref=${{ env.REGISTRY }}/${{ github.repository_owner }}/ort:cache
+          cache-to: type=registry,ref=${{ env.REGISTRY }}/${{ github.repository_owner }}/ort:cache,mode=max
+          build-args: ORT_VERSION=${{ env.ORT_VERSION }}
+      - name: Extract Docker Metadata for ort-minimal Image
+        id: meta-ort-minimal
+        uses: docker/metadata-action@v5
+        with:
+          images: |
+            ${{ env.REGISTRY }}/${{ github.repository_owner }}/ort-minimal
+          tags: |
+            type=pep440,pattern={{version}}
+            type=raw,value=${{ env.ORT_VERSION }}
+            type=ref,event=branch
+            type=ref,event=tag
+            type=sha
+      - name: Build & Push ort-minimal Docker Image
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta-ort-minimal.outputs.tags }}
+          labels: ${{ steps.meta-ort-minimal.outputs.labels }}
+          target: minimal
+          cache-from: type=registry,ref=${{ env.REGISTRY }}/${{ github.repository_owner }}/ort:cache
+          build-args: ORT_VERSION=${{ env.ORT_VERSION }}
+      - name: Print Disk Space
+        run: df -h