tests/test-dirstate-race.t

bookmarks: allow pushing active bookmark on new remote head (issue5236)

Before 'hg push -B .' on new remote head complained with:
abort: push creates new remote head ...

It was because _nowarnheads was not expanding active bookmark
name, so it didn't add active bookmark "proper" name to no
warn heads list.

  $ 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