hgext/narrow/__init__.py

narrow: the first version of narrow_widen wireprotocol command

This patch introduces a wireprotocol command narrow_widen() which will be used
to widen a narrow copy using `hg tracked` command provided by narrow extension.

The wireprotocol command takes the old and new includes and excludes, common
heads, changegroup version, known revs, and a boolean ellipses and generates a
bundle2 of the required data and send it. The clients receives the bundle2
and applies that.

A bundle2 instead of changegroup because in future we might want to add more
things to send while widening. Thanks for martinvonz for the suggestion.

I am not sure whether we need changegroup version as an argument to the command
as I *think* narrow needs changegroup3 already.

The tests shows that we don't exchange phase data now while widening which is
nice. Also we don't check for pushkeys, rbc-cache, bookmarks etc.

This does not support ellipses cases for now but will be supported in future
patches. Since we send bundle2, it won't be hard to plug the ellipses logic in
here.

The existing code for widening a non-ellipses case is also dropped in this
patch.

Differential Revision: https://phab.mercurial-scm.org/D4813

# __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

    if repository.NARROW_REQUIREMENT in repo.requirements:
        narrowrepo.wraprepo(repo)
        narrowwirepeer.reposetup(repo)

templatekeyword = narrowtemplates.templatekeyword
revsetpredicate = narrowtemplates.revsetpredicate