Document that rev-list --graph triggers parent rewriting.
Document that rev-list --graph triggers parent rewriting.

This may help to understand why --graph causes more comments to
be selected.

Signed-off-by: Yann Dirson <69228ceb6f6706d8bbf6135fa4ad3d70b54c46ed@altern.org>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git