Add OCI labels to Docker images (#361)

* ✨ add OCI labels, rework tagging

Signed-off-by: Achim Krämer <39946364+pxlfrk@users.noreply.github.com>

* re-implement existing tagging system

Signed-off-by: Achim Krämer <39946364+pxlfrk@users.noreply.github.com>

---------

Signed-off-by: Achim Krämer <39946364+pxlfrk@users.noreply.github.com>

.github/workflows/release.yml

@@ -15,6 +15,38 @@ jobs:
       - name: Check out the repo
         uses: actions/checkout@v4
 
+      - name: set Environment Variables
+        id: env
+        run: |
+          echo "NOW=$(date +'%F %Z %T')" >> $GITHUB_ENV
+
+      - name: Docker meta
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          # list of Docker images to use as base name for tags
+          images: |
+            offen/docker-volume-backup
+            ghcr.io/offen/docker-volume-backup
+          # define global behaviour for tags
+          flavor: |
+            latest=false
+          # specify one tag which never gets set, to prevent the tag-attribute being empty, as it will fallback to a default
+          tags: |
+            # output v2.42.1-alpha.1 (incl. pre-releases)
+            type=semver,pattern=v{{version}},enable=false
+          labels: |
+            org.opencontainers.image.title=${{github.event.repository.name}}
+            org.opencontainers.image.description="Backup Docker volumes locally or to any S3, WebDAV, Azure Blob Storage, Dropbox or SSH compatible storage"
+            org.opencontainers.image.vendor=${{github.repository_owner}}
+            org.opencontainers.image.licenses="MPL-2.0"
+            org.opencontainers.image.version=${{github.ref_name}}
+            org.opencontainers.image.created=${{ env.NOW }}
+            org.opencontainers.image.source=${{github.server_url}}/${{github.repository}}
+            org.opencontainers.image.revision=${{github.sha}}
+            org.opencontainers.image.url="https://offen.github.io/docker-volume-backup/"
+            org.opencontainers.image.documentation="https://offen.github.io/docker-volume-backup/"
+
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v2
 
@@ -35,7 +67,7 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Extract Docker tags
-        id: meta
+        id: tags
         run: |
           version_tag="${{github.ref_name}}"
           tags=($version_tag)
@@ -51,9 +83,10 @@ jobs:
           echo "releases=$releases" >> "$GITHUB_OUTPUT"
 
       - name: Build and push Docker images
-        uses: docker/build-push-action@v4
+        uses: docker/build-push-action@v5
         with:
           context: .
           push: true
           platforms: linux/amd64,linux/arm64,linux/arm/v7
-          tags: ${{ steps.meta.outputs.releases }}
+          tags: ${{ steps.tags.outputs.releases }}
+          labels: ${{ steps.meta.outputs.labels }}