Similar to the `preserve` mode simply passing the `--preserve-merges` option to the `rebase` command, the `merges` mode simply passes the `--rebase-merges` option. This will allow users to conveniently rebase non-trivial commit topologies when pulling new commits, without flattening them. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>