avoid failures when using a repo file in Dockerfiles

Should be cleaned up also for other cases and situations, but this
should help in most cases

build#590

obs-docker-support

@@ -51,7 +51,7 @@ zypper() {
 	exec /usr/bin/zypper -D $LOCAL_REPOS_D "${globalopts[@]}" "$cmd" "$@"
 	;;
     ar|addrepo)
-	exec /usr/bin/zypper "${globalopts[@]}" "$cmd" -C "$@"
+	exec /usr/bin/zypper "${globalopts[@]}" "$cmd" -C "${@%/*.repo}"
 	;;
     ref|refresh)
 	echo "skipping zypper refresh"