main/setup-apkrepos: use edge repo for *_alpha* releases

setup-apkrepos.in

@@ -95,7 +95,7 @@ add_from_list() {
 get_alpine_release() {
 	local version=$(cat /etc/alpine-release 2>/dev/null)
 	case "$version" in
-		*_git*) release="edge";;
+		*_git*|*_alpha*) release="edge";;
 		[0-9]*.[0-9]*.[0-9]*)
 			# release in x.y.z format, cut last digit
 			release=v${version%.[0-9]*};;