Set aggressive flag in git_merge_trees() when rename detection is turned off.
This allows read_tree() to auto resolve more cases that would have otherwise
been handled by the rename detection.
Reviewed-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Ben Peart <benpeart@microsoft.com> Reviewed-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>