hgext/narrow/narrowbundle2.py

git: skeleton of a new extension to _directly_ operate on git repos

This is based in part of work I did years ago in hgit, but it's mostly
new code since I'm using pygit2 instead of dulwich and the hg storage
interfaces have improved. Some cleanup of old hgit code by Pulkit,
which I greatly appreciate.

test-git-interop.t does not cover a whole lot of cases, but it
passes. It includes status, diff, making a new commit, and `hg annotate`
working on the git repository.

This is _not_ (yet) production quality code: this is an
experiment. Known technical debt lurking in this implementation:

 * Writing bookmarks just totally ignores transactions.
 * The way progress is threaded down into the gitstore is awful.
 * Ideally we'd find a way to incrementally reindex DAGs. I'm not sure
   how to do that efficiently, so we might need a "known only fast-forwards"
   mode on the DAG indexer for use on `hg commit` and friends.
 * We don't even _try_ to do anything reasonable for `hg pull` or `hg push`.
 * Mercurial need an interface for the changelog type.

Tests currently require git 2.24 as far as I'm aware: `git status` has
some changed output that I didn't try and handle in a compatible way.

This patch has produced some interesting cleanups, most recently on
the manifest type. I expect continuing down this road will produce
other meritorious cleanups throughout our code.

Differential Revision: https://phab.mercurial-scm.org/D6734

# narrowbundle2.py - bundle2 extensions for narrow repository support
#
# 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.

from __future__ import absolute_import

import errno
import struct

from mercurial.i18n import _
from mercurial.node import nullid
from mercurial import (
    bundle2,
    changegroup,
    error,
    exchange,
    localrepo,
    narrowspec,
    repair,
    util,
    wireprototypes,
)
from mercurial.interfaces import repository
from mercurial.utils import stringutil

_NARROWACL_SECTION = b'narrowacl'
_CHANGESPECPART = b'narrow:changespec'
_RESSPECS = b'narrow:responsespec'
_SPECPART = b'narrow:spec'
_SPECPART_INCLUDE = b'include'
_SPECPART_EXCLUDE = b'exclude'
_KILLNODESIGNAL = b'KILL'
_DONESIGNAL = b'DONE'
_ELIDEDCSHEADER = b'>20s20s20sl'  # cset id, p1, p2, len(text)
_ELIDEDMFHEADER = b'>20s20s20s20sl'  # manifest id, p1, p2, link id, len(text)
_CSHEADERSIZE = struct.calcsize(_ELIDEDCSHEADER)
_MFHEADERSIZE = struct.calcsize(_ELIDEDMFHEADER)

# Serve a changegroup for a client with a narrow clone.
def getbundlechangegrouppart_narrow(
    bundler,
    repo,
    source,
    bundlecaps=None,
    b2caps=None,
    heads=None,
    common=None,
    **kwargs
):
    assert repo.ui.configbool(b'experimental', b'narrowservebrokenellipses')

    cgversions = b2caps.get(b'changegroup')
    cgversions = [
        v
        for v in cgversions
        if v in changegroup.supportedoutgoingversions(repo)
    ]
    if not cgversions:
        raise ValueError(_(b'no common changegroup version'))
    version = max(cgversions)

    include = sorted(filter(bool, kwargs.get('includepats', [])))
    exclude = sorted(filter(bool, kwargs.get('excludepats', [])))
    generateellipsesbundle2(
        bundler,
        repo,
        include,
        exclude,
        version,
        common,
        heads,
        kwargs.get('depth', None),
    )


def generateellipsesbundle2(
    bundler, repo, include, exclude, version, common, heads, depth,
):
    match = narrowspec.match(repo.root, include=include, exclude=exclude)
    if depth is not None:
        depth = int(depth)
        if depth < 1:
            raise error.Abort(_(b'depth must be positive, got %d') % depth)

    heads = set(heads or repo.heads())
    common = set(common or [nullid])

    visitnodes, relevant_nodes, ellipsisroots = exchange._computeellipsis(
        repo, common, heads, set(), match, depth=depth
    )

    repo.ui.debug(b'Found %d relevant revs\n' % len(relevant_nodes))
    if visitnodes:
        packer = changegroup.getbundler(
            version,
            repo,
            matcher=match,
            ellipses=True,
            shallow=depth is not None,
            ellipsisroots=ellipsisroots,
            fullnodes=relevant_nodes,
        )
        cgdata = packer.generate(common, visitnodes, False, b'narrow_widen')

        part = bundler.newpart(b'changegroup', data=cgdata)
        part.addparam(b'version', version)
        if b'treemanifest' in repo.requirements:
            part.addparam(b'treemanifest', b'1')


def generate_ellipses_bundle2_for_widening(
    bundler, repo, oldmatch, newmatch, version, common, known,
):
    common = set(common or [nullid])
    # Steps:
    # 1. Send kill for "$known & ::common"
    #
    # 2. Send changegroup for ::common
    #
    # 3. Proceed.
    #
    # In the future, we can send kills for only the specific
    # nodes we know should go away or change shape, and then
    # send a data stream that tells the client something like this:
    #
    # a) apply this changegroup
    # b) apply nodes XXX, YYY, ZZZ that you already have
    # c) goto a
    #
    # until they've built up the full new state.
    knownrevs = {repo.changelog.rev(n) for n in known}
    # TODO: we could send only roots() of this set, and the
    # list of nodes in common, and the client could work out
    # what to strip, instead of us explicitly sending every
    # single node.
    deadrevs = knownrevs

    def genkills():
        for r in deadrevs:
            yield _KILLNODESIGNAL
            yield repo.changelog.node(r)
        yield _DONESIGNAL

    bundler.newpart(_CHANGESPECPART, data=genkills())
    newvisit, newfull, newellipsis = exchange._computeellipsis(
        repo, set(), common, knownrevs, newmatch
    )
    if newvisit:
        packer = changegroup.getbundler(
            version,
            repo,
            matcher=newmatch,
            ellipses=True,
            shallow=False,
            ellipsisroots=newellipsis,
            fullnodes=newfull,
        )
        cgdata = packer.generate(common, newvisit, False, b'narrow_widen')

        part = bundler.newpart(b'changegroup', data=cgdata)
        part.addparam(b'version', version)
        if b'treemanifest' in repo.requirements:
            part.addparam(b'treemanifest', b'1')


@bundle2.parthandler(_SPECPART, (_SPECPART_INCLUDE, _SPECPART_EXCLUDE))
def _handlechangespec_2(op, inpart):
    # XXX: This bundle2 handling is buggy and should be removed after hg5.2 is
    # released. New servers will send a mandatory bundle2 part named
    # 'Narrowspec' and will send specs as data instead of params.
    # Refer to issue5952 and 6019
    includepats = set(inpart.params.get(_SPECPART_INCLUDE, b'').splitlines())
    excludepats = set(inpart.params.get(_SPECPART_EXCLUDE, b'').splitlines())
    narrowspec.validatepatterns(includepats)
    narrowspec.validatepatterns(excludepats)

    if not repository.NARROW_REQUIREMENT in op.repo.requirements:
        op.repo.requirements.add(repository.NARROW_REQUIREMENT)
        op.repo._writerequirements()
    op.repo.setnarrowpats(includepats, excludepats)
    narrowspec.copytoworkingcopy(op.repo)


@bundle2.parthandler(_RESSPECS)
def _handlenarrowspecs(op, inpart):
    data = inpart.read()
    inc, exc = data.split(b'\0')
    includepats = set(inc.splitlines())
    excludepats = set(exc.splitlines())
    narrowspec.validatepatterns(includepats)
    narrowspec.validatepatterns(excludepats)

    if repository.NARROW_REQUIREMENT not in op.repo.requirements:
        op.repo.requirements.add(repository.NARROW_REQUIREMENT)
        op.repo._writerequirements()
    op.repo.setnarrowpats(includepats, excludepats)
    narrowspec.copytoworkingcopy(op.repo)


@bundle2.parthandler(_CHANGESPECPART)
def _handlechangespec(op, inpart):
    repo = op.repo
    cl = repo.changelog

    # changesets which need to be stripped entirely. either they're no longer
    # needed in the new narrow spec, or the server is sending a replacement
    # in the changegroup part.
    clkills = set()

    # A changespec part contains all the updates to ellipsis nodes
    # that will happen as a result of widening or narrowing a
    # repo. All the changes that this block encounters are ellipsis
    # nodes or flags to kill an existing ellipsis.
    chunksignal = changegroup.readexactly(inpart, 4)
    while chunksignal != _DONESIGNAL:
        if chunksignal == _KILLNODESIGNAL:
            # a node used to be an ellipsis but isn't anymore
            ck = changegroup.readexactly(inpart, 20)
            if cl.hasnode(ck):
                clkills.add(ck)
        else:
            raise error.Abort(
                _(b'unexpected changespec node chunk type: %s') % chunksignal
            )
        chunksignal = changegroup.readexactly(inpart, 4)

    if clkills:
        # preserve bookmarks that repair.strip() would otherwise strip
        op._bookmarksbackup = repo._bookmarks

        class dummybmstore(dict):
            def applychanges(self, repo, tr, changes):
                pass

        localrepo.localrepository._bookmarks.set(repo, dummybmstore())
        chgrpfile = repair.strip(
            op.ui, repo, list(clkills), backup=True, topic=b'widen'
        )
        if chgrpfile:
            op._widen_uninterr = repo.ui.uninterruptible()
            op._widen_uninterr.__enter__()
            # presence of _widen_bundle attribute activates widen handler later
            op._widen_bundle = chgrpfile
    # Set the new narrowspec if we're widening. The setnewnarrowpats() method
    # will currently always be there when using the core+narrowhg server, but
    # other servers may include a changespec part even when not widening (e.g.
    # because we're deepening a shallow repo).
    if util.safehasattr(repo, 'setnewnarrowpats'):
        repo.setnewnarrowpats()


def handlechangegroup_widen(op, inpart):
    """Changegroup exchange handler which restores temporarily-stripped nodes"""
    # We saved a bundle with stripped node data we must now restore.
    # This approach is based on mercurial/repair.py@6ee26a53c111.
    repo = op.repo
    ui = op.ui

    chgrpfile = op._widen_bundle
    del op._widen_bundle
    vfs = repo.vfs

    ui.note(_(b"adding branch\n"))
    f = vfs.open(chgrpfile, b"rb")
    try:
        gen = exchange.readbundle(ui, f, chgrpfile, vfs)
        # silence internal shuffling chatter
        override = {(b'ui', b'quiet'): True}
        if ui.verbose:
            override = {}
        with ui.configoverride(override):
            if isinstance(gen, bundle2.unbundle20):
                with repo.transaction(b'strip') as tr:
                    bundle2.processbundle(repo, gen, lambda: tr)
            else:
                gen.apply(
                    repo, b'strip', b'bundle:' + vfs.join(chgrpfile), True
                )
    finally:
        f.close()

    # remove undo files
    for undovfs, undofile in repo.undofiles():
        try:
            undovfs.unlink(undofile)
        except OSError as e:
            if e.errno != errno.ENOENT:
                ui.warn(
                    _(b'error removing %s: %s\n')
                    % (undovfs.join(undofile), stringutil.forcebytestr(e))
                )

    # Remove partial backup only if there were no exceptions
    op._widen_uninterr.__exit__(None, None, None)
    vfs.unlink(chgrpfile)


def setup():
    """Enable narrow repo support in bundle2-related extension points."""
    getbundleargs = wireprototypes.GETBUNDLE_ARGUMENTS

    getbundleargs[b'narrow'] = b'boolean'
    getbundleargs[b'depth'] = b'plain'
    getbundleargs[b'oldincludepats'] = b'csv'
    getbundleargs[b'oldexcludepats'] = b'csv'
    getbundleargs[b'known'] = b'csv'

    # Extend changegroup serving to handle requests from narrow clients.
    origcgfn = exchange.getbundle2partsmapping[b'changegroup']

    def wrappedcgfn(*args, **kwargs):
        repo = args[1]
        if repo.ui.has_section(_NARROWACL_SECTION):
            kwargs = exchange.applynarrowacl(repo, kwargs)

        if kwargs.get('narrow', False) and repo.ui.configbool(
            b'experimental', b'narrowservebrokenellipses'
        ):
            getbundlechangegrouppart_narrow(*args, **kwargs)
        else:
            origcgfn(*args, **kwargs)

    exchange.getbundle2partsmapping[b'changegroup'] = wrappedcgfn

    # Extend changegroup receiver so client can fixup after widen requests.
    origcghandler = bundle2.parthandlermapping[b'changegroup']

    def wrappedcghandler(op, inpart):
        origcghandler(op, inpart)
        if util.safehasattr(op, '_widen_bundle'):
            handlechangegroup_widen(op, inpart)
        if util.safehasattr(op, '_bookmarksbackup'):
            localrepo.localrepository._bookmarks.set(
                op.repo, op._bookmarksbackup
            )
            del op._bookmarksbackup

    wrappedcghandler.params = origcghandler.params
    bundle2.parthandlermapping[b'changegroup'] = wrappedcghandler