tests/test-rebuildstate.t

reachableroots: default to the C implementation

This patch is part of a series of patches to speed up the computation of
revset.reachableroots by introducing a C implementation. The main motivation is to
speed up smartlog on big repositories. At the end of the series, on our big
repositories the computation of reachableroots is 10-50x faster and smartlog on is
2x-5x faster.

Before this patch, reachableroots was computed in pure Python by default. This
patch makes the C implementation the default and provides a speedup for
reachableroots.

basic test for hg debugrebuildstate

  $ hg init repo
  $ cd repo

  $ touch foo bar
  $ hg ci -Am 'add foo bar'
  adding bar
  adding foo

  $ touch baz
  $ hg add baz
  $ hg rm bar

  $ hg debugrebuildstate

state dump after

  $ hg debugstate --nodates | sort
  n 644         -1 set                 bar
  n 644         -1 set                 foo

status

  $ hg st -A
  ! bar
  ? baz
  C foo

  $ cd ..