Adding action for deleting image (#209)

* Adding action for deleting image

* Only trigger when deleting

.github/workflows/delete-container-tag.yaml

@@ -0,0 +1,37 @@
+name: Delete tag from container registry
+
+on:
+  delete:
+
+env:
+  REGISTRY: cfaprdbatchcr.azurecr.io
+  IMAGE_NAME: pyrenew-hew
+
+jobs:
+  delete-container:
+    runs-on: cfa-cdcgov
+    name: Deleting the container
+
+    steps:
+      - name : Checkout code
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+
+      - name: Extract branch name
+        shell: bash
+        run: echo "branch=${GITHUB_HEAD_REF:-${GITHUB_REF#refs/heads/}}" >> $GITHUB_OUTPUT
+        id: branch-name
+
+      - name: Login to the Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: "cfaprdbatchcr.azurecr.io"
+          username: "cfaprdbatchcr"
+          password: ${{ secrets.CFAPRDBATCHCR_REGISTRY_PASSWORD }}
+
+      - name: Deleting the image
+        run: |
+          az acr repository delete \
+            --name ${{ env.REGISTRY }} \
+            --image ${{ env.IMAGE_NAME }}:${{ steps.branch-name.outputs.branch}}

README.md

@@ -38,6 +38,12 @@ and [code of conduct](https://github.com/CDCgov/template/blob/master/code-of-con
 
 Describe the purpose of your project. Add additional sections as necessary to help collaborators and potential collaborators understand and use your project.
 
+## Containers
+
+The project uses GitHub Actions for automatically building container images based on the project's [Containerfile](Containerfile) and [Containerfile.dependencies](Containerfile.dependencies) files. The images are currently hosted on Azure Container Registry and are built and pushed via the [containers.yaml](.github/workflows/containers.yaml) GitHub Actions workflow.
+
+Container images pushed to the Azure Container Registry are automatically tagged as either `latest` (if the commit is on the `main` branch) or with the branch name (if the commit is on a different branch). After a branch is deleted, the image tag is remove from the registry via the [delete-container-tag.yaml](.github/workflows/delete-container-tag.yaml) GitHub Actions workflow.
+
 ## Project Admin
 
 Name, Degrees, e-mail, CDC org (e.g., CDC/IOD/ORR/CFA)