update readme and add check if images already exist

README.md

@@ -1,7 +1,10 @@
 # Docker Official Images
 
-We are moving away from Docker Hub to GitHub Container Registry because of rate limiting issues. There may be certain images however, that officially available on Docker Hub so this is a small script to port those images to GHCR. You can then pull them using:
+We are moving away from Docker Hub to GitHub Container Registry because of rate limiting issues.
 
+There may be certain images however, that are officially available on Docker Hub so this is a small script to port those images to GHCR. You can add more images [here](./port-images-to-ghcr).
+
+You can then pull them using:
 ```bash
 docker pull ghcr.io/mrc-ide/docker-official-images/<image-name>:<tag>
 ```

port-images-to-ghcr

@@ -1,14 +1,22 @@
 #!/usr/bin/env bash
 set -ex
 
+# add more images here
 declare -a docker_images=(
     "redis:6"
     "redis:5"
 )
 
 for image in "${docker_images[@]}"
 do
-    docker pull "$image"
-    docker image tag "$image" ghcr.io/mrc-ide/docker-official-images/"$image"
-    docker image push ghcr.io/mrc-ide/docker-official-images/"$image"
+    docker manifest inspect ghcr.io/mrc-ide/docker-official-images/"$image" > /dev/null 2>&1
+    exit_code=$?
+
+    if [ $exit_code -eq 0 ]; then
+        echo "Not porting over $image because it already exists in the GHCR"
+    else
+        docker pull "$image"
+        docker image tag "$image" ghcr.io/mrc-ide/docker-official-images/"$image"
+        docker image push ghcr.io/mrc-ide/docker-official-images/"$image"
+    fi
 done