split: make sure hg split preserve the phase of splitting cset (issue6048)
Before this patch, while splitting we were not taking the phase
of splitting cset into account. By default new commits would
have draft changes. As we know there can two possible phases
i.e draft and secret in rewriting csets thing, so this adds
the handling of secret phase (as default is draft)
Changes in test file reflect the added behaviour.
../../tests/test-topic-tutorial.t