tests/test-dirstate-race.t

perf: replace ui.configint() by getint() for Mercurial earlier than 1.9

Before this patch, using ui.configint() prevents perf.py from
measuring performance with Mercurial earlier than 1.9 (or
fa2b596db182), because ui.configint() isn't available in such
Mercurial, even though there are some code paths for Mercurial earlier
than 1.9 in perf.py.

For example, setting "_prereadsize" attribute in perfindex() and
perfnodelookup() is effective only with hg earlier than 1.8 (or
61c9bc3da402).

This patch replaces ui.configint() invocations by newly introduced
getint().

This patch also adds check-perf-code.py an extra check entry to detect
direct usage of ui.configint() in perf.py.

BTW, this patch doesn't choose adding configint() method at runtime by
replacing ui.__class__ like below, even though this is the recommended
way to modern Mercurial extensions.

    def uisetup(ui):
        if not util.safehasattr(ui, 'configint'):
            class uiwrap(ui.__class__):
                def configint(self, section, name, ....):
                    ....
            ui.__class__ = uiwrap

Because changes to ui.__class__ by uisetup() of loaded extension have
been propagated since 1.6.1 (or d8d0fc3988ca), the recommended way
above doesn't work as expected with Mercurial earlier than it.

  $ 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