tests/test-dirstate-race.t

checkheads: take future obsoleted heads into account

If we push some successors they will likely create a new head on
remote. However as the obsoleted head will disappear after the push we
are not really increasing the number of heads.

There is several case which will lead to extra being actually pushed. But this
first changeset aims to be simple. See the inline comment for details.

Without this change, you need to push --force every time you want to
push a newer version which is very error prone.

The remote side still display +n heads on unbundle because it does not have the
obsolete marker at unbundle time.

  $ hg init
  $ echo a > a
  $ hg add a
  $ hg commit -m test

Do we ever miss a sub-second change?:

  $ for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20; do
  >     hg co -qC 0
  >     echo b > a
  >     hg st
  > done
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a