As pointed out in a review of the `--rebase-merges` patch series,
`rollback_lock_file()` clobbers errno. Therefore, we have to report the
error message that uses errno before calling said function.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>