feat: Add tag_with_latest option for tagging with latest additionally

When skipping the push on unchanged digests, it's not enough to push the current tag,
which is probably semver, we also need to push the latest, so we can later check if
the latest digest equals the currently built image

README.md

@@ -54,6 +54,7 @@ the most used values. So, technically there is a single required argument
 | strip_tag_prefix      | Prefix to be stripped from the tag                              | false    |                 |
 | skip_unchanged_digest | Avoids pushing the image if the build generated the same digest | false    |                 |
 | path                  | Path to the build context. Defaults to `.`                      | false    | .               |
+| tag_with_latest       | Tags the built image with additional latest tag                 | false    |                 |
 
 **Here is where it gets specific, as the optional arguments become required depending on the registry targeted**
 

action.yml

@@ -48,6 +48,9 @@ inputs:
   skip_unchanged_digest:
     description: "Avoids pushing the image if the build generated the same digest"
     required: false
+  tag_with_latest:
+    description: "Tags the built image with additional latest tag"
+    required: false
 runs:
   using: "docker"
   image: "Dockerfile"

entrypoint.sh

@@ -10,6 +10,7 @@ export TAG=${TAG#$INPUT_STRIP_TAG_PREFIX}
 export USERNAME=${INPUT_USERNAME:-$GITHUB_ACTOR}
 export PASSWORD=${INPUT_PASSWORD:-$GITHUB_TOKEN}
 export REPOSITORY=$IMAGE
+export IMAGE_LATEST=${INPUT_TAG_WITH_LATEST:+"$IMAGE:latest"}
 export IMAGE=$IMAGE:$TAG
 export CONTEXT_PATH=${INPUT_PATH}
 
@@ -32,6 +33,10 @@ if [ "$REGISTRY" == "docker.pkg.github.com" ]; then
     export IMAGE="$IMAGE_NAMESPACE/$IMAGE"
     export REPOSITORY="$IMAGE_NAMESPACE/$REPOSITORY"
 
+    if [ ! -z $IMAGE_LATEST ]; then
+        export IMAGE_LATEST="$IMAGE_NAMESPACE/$IMAGE_LATEST"
+    fi
+
     if [ ! -z $INPUT_CACHE_REGISTRY ]; then
         export INPUT_CACHE_REGISTRY="$REGISTRY/$IMAGE_NAMESPACE/$INPUT_CACHE_REGISTRY"
     fi
@@ -41,6 +46,10 @@ if [ "$REGISTRY" == "docker.io" ]; then
     export REGISTRY="index.${REGISTRY}/v1/"
 else
     export IMAGE="$REGISTRY/$IMAGE"
+
+    if [ ! -z $IMAGE_LATEST ]; then
+        export IMAGE_LATEST="$REGISTRY/$IMAGE_LATEST"
+    fi
 fi
 
 export CACHE=${INPUT_CACHE:+"--cache=true"}
@@ -54,6 +63,9 @@ if [ ! -z $INPUT_SKIP_UNCHANGED_DIGEST ]; then
     export DESTINATION="--no-push --digest-file digest"
 else
     export DESTINATION="--destination $IMAGE"
+    if [ ! -z $IMAGE_LATEST ]; then
+        export DESTINATION="$DESTINATION --destination $IMAGE_LATEST"  
+    fi
 fi
 
 export ARGS="$CACHE $CONTEXT $DOCKERFILE $DESTINATION $INPUT_EXTRA_ARGS"
@@ -88,6 +100,10 @@ if [ ! -z $INPUT_SKIP_UNCHANGED_DIGEST ]; then
     fi
 
     export DESTINATION="--destination $IMAGE"
+    if [ ! -z $IMAGE_LATEST ]; then
+        export DESTINATION="$DESTINATION --destination $IMAGE_LATEST"  
+    fi
+    
     export ARGS="$CACHE $CONTEXT $DOCKERFILE $DESTINATION $INPUT_EXTRA_ARGS"
 
     echo "Pushing image..."