tests/lockdelay.py

help: add internals.extensions topic

I think it's better to include the API overview in core as we now have the
internals section in our help system.

Retrieved from the wiki, and formatted as reST. Several wiki links are
removed since they are invalid in the help. The sections about example
extension are removed at all as they seemed too verbose.

https://www.mercurial-scm.org/wiki/WritingExtensions

# 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

def reposetup(ui, repo):

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