Document and add GHCR example

Signed-off-by: divyansh42 <diagrawa@redhat.com>

.github/workflows/verify-push.yaml

@@ -9,16 +9,16 @@ on:
     - cron: '0 0 * * *'  # every day at midnight
 
 env:
-  IMAGE_REGISTRY: quay.io
-  IMAGE_NAMESPACE: redhat-github-actions
   IMAGE_NAME: ptr-test
   IMAGE_TAGS: v1 ${{ github.sha }}
-  MVN_REPO_DIR: ~/.m2/repository
 
 jobs:
-  build-and-push:
+  push-quay:
     name: Build and push image to Quay.io
     runs-on: ubuntu-20.04
+    env:
+      IMAGE_REGISTRY: quay.io
+      IMAGE_NAMESPACE: redhat-github-actions
     strategy:
       fail-fast: false
       matrix:
@@ -64,3 +64,56 @@ jobs:
       - name: Echo outputs
         run: |
           echo "${{ toJSON(steps.push.outputs) }}"
+
+  push-ghcr:
+    name: Build and push image to GHCR
+    runs-on: ubuntu-20.04
+    env:
+      IMAGE_REGISTRY: ghcr.io/${{ github.repository_owner }}
+      REGISTRY_USER: ${{ github.actor }}
+      REGISTRY_PASSWORD: ${{ github.token }}
+    strategy:
+      fail-fast: false
+      matrix:
+        install_latest: [ true, false ]
+
+    steps:
+      # Checkout push-to-registry action github repository
+      - name: Checkout Push to Registry action
+        uses: actions/checkout@v2
+
+      - name: Install latest podman
+        if: matrix.install_latest
+        run: |
+          bash .github/install_latest_podman.sh
+
+      # Build image using Buildah action
+      - name: Build Image
+        id: build_image
+        uses: redhat-actions/buildah-build@v2
+        with:
+          image: ${{ env.IMAGE_NAME }}
+          tags: ${{ env.IMAGE_TAGS }}
+          base-image: busybox:latest
+          entrypoint: |
+            bash
+            -c
+            echo 'hello world'
+          oci: true
+
+      # Push the image to GHCR (Image Registry)
+      - name: Push To GHCR
+        uses: ./
+        id: push
+        with:
+          image: ${{ steps.build_image.outputs.image }}
+          tags: ${{ steps.build_image.outputs.tags }}
+          registry: ${{ env.IMAGE_REGISTRY }}
+          username: ${{ env.REGISTRY_USER }}
+          password: ${{ env.REGISTRY_PASSWORD }}
+          extra-args: |
+            --disable-content-trust
+
+      - name: Echo outputs
+        run: |
+          echo "${{ toJSON(steps.push.outputs) }}"

README.md

@@ -94,6 +94,8 @@ jobs:
       run: echo "Image pushed to ${{ steps.push-to-quay.outputs.registry-paths }}"
 ```
 
+Refer to [examples](./.github/workflows/verify-push.yaml) for complete example of push to [GitHub Container Registry (GHCR)](https://docs.github.com/en/packages/working-with-a-github-packages-registry/working-with-the-container-registry).
+
 ## Note about images built with Docker
 
 This action uses `Podman` to push, but can also push images built with `Docker`. However, Docker and Podman store their images in different locations, and Podman can only push images in its own storage.