hgext/narrow/__init__.py

narrow: introduce a config option to check if narrow is enabled or not

This patch introduces a new config option experimental.narrow which is set to
False by default and set to True by the narrow extension.

While moving narrow related logic into core, we need to know at places whether
narrow extension is enabled or not. Checking the list of extension enabled is
one solution but once narrow is inbuilt, we will definitely want a config option
to check whether narrow is turned on or not.

So this patch introduces a config option, which will evolve to the main point to
turn narrow capability on and off once all the narrow is in core.

Differential Revision: https://phab.mercurial-scm.org/D4889

# __init__.py - narrowhg extension
#
# Copyright 2017 Google, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
'''create clones which fetch history data for subset of files (EXPERIMENTAL)'''

from __future__ import absolute_import

# Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
# be specifying the version(s) of Mercurial they are tested with, or
# leave the attribute unspecified.
testedwith = 'ships-with-hg-core'

from mercurial import (
    localrepo,
    registrar,
    repository,
)

from . import (
    narrowbundle2,
    narrowcommands,
    narrowrepo,
    narrowtemplates,
    narrowwirepeer,
)

configtable = {}
configitem = registrar.configitem(configtable)
# Narrowhg *has* support for serving ellipsis nodes (which are used at
# least by Google's internal server), but that support is pretty
# fragile and has a lot of problems on real-world repositories that
# have complex graph topologies. This could probably be corrected, but
# absent someone needing the full support for ellipsis nodes in
# repositories with merges, it's unlikely this work will get done. As
# of this writining in late 2017, all repositories large enough for
# ellipsis nodes to be a hard requirement also enforce strictly linear
# history for other scaling reasons.
configitem('experimental', 'narrowservebrokenellipses',
           default=False,
           alias=[('narrow', 'serveellipses')],
)

# Export the commands table for Mercurial to see.
cmdtable = narrowcommands.table

def featuresetup(ui, features):
    features.add(repository.NARROW_REQUIREMENT)

def uisetup(ui):
    """Wraps user-facing mercurial commands with narrow-aware versions."""
    localrepo.featuresetupfuncs.add(featuresetup)
    narrowbundle2.setup()
    narrowcommands.setup()
    narrowwirepeer.uisetup()

def reposetup(ui, repo):
    """Wraps local repositories with narrow repo support."""
    if not repo.local():
        return

    repo.ui.setconfig('experimental', 'narrow', True, 'narrow-ext')
    if repository.NARROW_REQUIREMENT in repo.requirements:
        narrowrepo.wraprepo(repo)
        narrowwirepeer.reposetup(repo)

templatekeyword = narrowtemplates.templatekeyword
revsetpredicate = narrowtemplates.revsetpredicate