Use Alpine-related commit for detecting version in generate-stackbrew-library.sh

Author: jnoordsij

generate-stackbrew-library.sh

@@ -107,6 +107,7 @@ for version in "${versions[@]}"; do
 	done
 
 
+	commit="$(dirCommit "$version/alpine-slim")"
 	alpineVersion="$(git show "$commit":"$version/alpine-slim/Dockerfile" | awk -F: '$1 == "FROM alpine" { print $2; exit }')"
 
 	for variant in alpine alpine-perl alpine-slim; do