tests/lockdelay.py

localrepo: use dirstate savebackup instead of handling dirstate file manually

This is one step towards having dirstate manage its own storage. It will
be useful for the implementation of sql dirstate [1].

This introduced a small test change: now we always write the dirstate before
saving backup so in some cases where dirstate file didn't exist yet
savebackup can create it.

[1] https://www.mercurial-scm.org/wiki/SQLDirstatePlan

# Dummy extension that adds a delay after acquiring a lock.
#
# This extension can be used to test race conditions between lock acquisition.

from __future__ import absolute_import

import os
import time

from mercurial import (
    lock as lockmod,
)

class delaylock(lockmod.lock):
    def lock(self):
        delay = float(os.environ.get('HGPRELOCKDELAY', '0.0'))
        if delay:
            time.sleep(delay)
        res = super(delaylock, self).lock()
        delay = float(os.environ.get('HGPOSTLOCKDELAY', '0.0'))
        if delay:
            time.sleep(delay)
        return res

def extsetup(ui):
    lockmod.lock = delaylock