hgext/convert/transport.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

# -*- coding: utf-8 -*-

# Copyright (C) 2007 Daniel Holth <[e-mail]>
# This is a stripped-down version of the original bzr-svn transport.py,
# Copyright (C) 2006 Jelmer Vernooij <[e-mail]>

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program; if not, see <http://www.gnu.org/licenses/>.
from __future__ import absolute_import

import svn.client
import svn.core
import svn.ra

Pool = svn.core.Pool
SubversionException = svn.core.SubversionException

from mercurial.pycompat import getattr
from mercurial import util

# Some older versions of the Python bindings need to be
# explicitly initialized. But what we want to do probably
# won't work worth a darn against those libraries anyway!
svn.ra.initialize()

svn_config = None


def _create_auth_baton(pool):
    """Create a Subversion authentication baton. """
    import svn.client

    # Give the client context baton a suite of authentication
    # providers.h
    providers = [
        svn.client.get_simple_provider(pool),
        svn.client.get_username_provider(pool),
        svn.client.get_ssl_client_cert_file_provider(pool),
        svn.client.get_ssl_client_cert_pw_file_provider(pool),
        svn.client.get_ssl_server_trust_file_provider(pool),
    ]
    # Platform-dependent authentication methods
    getprovider = getattr(
        svn.core, 'svn_auth_get_platform_specific_provider', None
    )
    if getprovider:
        # Available in svn >= 1.6
        for name in (b'gnome_keyring', b'keychain', b'kwallet', b'windows'):
            for type in (b'simple', b'ssl_client_cert_pw', b'ssl_server_trust'):
                p = getprovider(name, type, pool)
                if p:
                    providers.append(p)
    else:
        if util.safehasattr(svn.client, b'get_windows_simple_provider'):
            providers.append(svn.client.get_windows_simple_provider(pool))

    return svn.core.svn_auth_open(providers, pool)


class NotBranchError(SubversionException):
    pass


class SvnRaTransport(object):
    """
    Open an ra connection to a Subversion repository.
    """

    def __init__(self, url=b"", ra=None):
        self.pool = Pool()
        self.svn_url = url
        self.username = b''
        self.password = b''

        # Only Subversion 1.4 has reparent()
        if ra is None or not util.safehasattr(svn.ra, b'reparent'):
            self.client = svn.client.create_context(self.pool)
            ab = _create_auth_baton(self.pool)
            self.client.auth_baton = ab
            global svn_config
            if svn_config is None:
                svn_config = svn.core.svn_config_get_config(None)
            self.client.config = svn_config
            try:
                self.ra = svn.client.open_ra_session(
                    self.svn_url, self.client, self.pool
                )
            except SubversionException as xxx_todo_changeme:
                (inst, num) = xxx_todo_changeme.args
                if num in (
                    svn.core.SVN_ERR_RA_ILLEGAL_URL,
                    svn.core.SVN_ERR_RA_LOCAL_REPOS_OPEN_FAILED,
                    svn.core.SVN_ERR_BAD_URL,
                ):
                    raise NotBranchError(url)
                raise
        else:
            self.ra = ra
            svn.ra.reparent(self.ra, self.svn_url.encode('utf8'))

    class Reporter(object):
        def __init__(self, reporter_data):
            self._reporter, self._baton = reporter_data

        def set_path(self, path, revnum, start_empty, lock_token, pool=None):
            svn.ra.reporter2_invoke_set_path(
                self._reporter,
                self._baton,
                path,
                revnum,
                start_empty,
                lock_token,
                pool,
            )

        def delete_path(self, path, pool=None):
            svn.ra.reporter2_invoke_delete_path(
                self._reporter, self._baton, path, pool
            )

        def link_path(
            self, path, url, revision, start_empty, lock_token, pool=None
        ):
            svn.ra.reporter2_invoke_link_path(
                self._reporter,
                self._baton,
                path,
                url,
                revision,
                start_empty,
                lock_token,
                pool,
            )

        def finish_report(self, pool=None):
            svn.ra.reporter2_invoke_finish_report(
                self._reporter, self._baton, pool
            )

        def abort_report(self, pool=None):
            svn.ra.reporter2_invoke_abort_report(
                self._reporter, self._baton, pool
            )

    def do_update(self, revnum, path, *args, **kwargs):
        return self.Reporter(
            svn.ra.do_update(self.ra, revnum, path, *args, **kwargs)
        )