Use rev-list --simplify-merges everywhere. This changes the behaviour
of --subdirectory-filter in cases such as
O -- A -\
\ \
\- B -- M
where A and B bring the same changes to the subdirectory: It now keeps
both sides of the merge. Previously, the history would have been
simplified to 'O -- A'. Merges of unrelated side histories that never
touch the subdirectory are still removed.
Signed-off-by: Thomas Rast <trast@student.ethz.ch> Signed-off-by: Junio C Hamano <gitster@pobox.com>