fix: unbreak docker image version tagging

Author: themightychris

.github/workflows/dockerpublish.yml

@@ -58,10 +58,10 @@ jobs:
           IMAGE_ID="docker.pkg.github.com/${GITHUB_REPOSITORY,,}/${IMAGE_NAME}"
 
           # Strip git ref prefix from version
-          VERSION=$(echo "${GITHUB_SHA}" | sed -e 's,.*/\(.*\),\1,')
+          VERSION=$(echo "${{ github.ref }}" | sed -e 's,.*/\(.*\),\1,')
 
           # Strip "v" prefix from tag name
-          [[ "${GITHUB_SHA}" == "refs/tags/"* ]] && VERSION=$(echo $VERSION | sed -e 's/^v//')
+          [[ "${{ github.ref }}" == "refs/tags/"* ]] && VERSION=$(echo $VERSION | sed -e 's/^v//')
 
           # Use Docker `latest` tag convention
           [ "$VERSION" == "master" ] && VERSION=latest