/brz/remove-bazaar : contents of bzrlib/remote.py at revision 2481.2.1

: (revision 2481.2.1)

To get this branch, use:

bzr branch
http://gegoxaren.bato24.eu/bzr/brz/remove-bazaar

# Copyright (C) 2006, 2007 Canonical Ltd
#
# 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, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

# TODO: At some point, handle upgrades by just passing the whole request
# across to run on the server.

from cStringIO import StringIO

from bzrlib import branch, errors, lockdir, repository
from bzrlib.branch import BranchReferenceFormat
from bzrlib.bzrdir import BzrDir, RemoteBzrDirFormat
from bzrlib.config import BranchConfig, TreeConfig
from bzrlib.decorators import needs_read_lock, needs_write_lock
from bzrlib.errors import NoSuchRevision
from bzrlib.lockable_files import LockableFiles
from bzrlib.revision import NULL_REVISION
from bzrlib.smart import client, vfs
from bzrlib.trace import note

# Note: RemoteBzrDirFormat is in bzrdir.py

class RemoteBzrDir(BzrDir):
    """Control directory on a remote server, accessed via bzr:// or similar."""

    def __init__(self, transport, _client=None):
        """Construct a RemoteBzrDir.

        :param _client: Private parameter for testing. Disables probing and the
            use of a real bzrdir.
        """
        BzrDir.__init__(self, transport, RemoteBzrDirFormat())
        # this object holds a delegated bzrdir that uses file-level operations
        # to talk to the other side
        self._real_bzrdir = None

        if _client is None:
            self._medium = transport.get_smart_client()
            self._client = client._SmartClient(self._medium)
        else:
            self._client = _client
            self._medium = None
            return

        path = self._path_for_remote_call(self._client)
        response = self._client.call('BzrDir.open', path)
        if response not in [('yes',), ('no',)]:
            raise errors.UnexpectedSmartServerResponse(response)
        if response == ('no',):
            raise errors.NotBranchError(path=transport.base)

    def _ensure_real(self):
        """Ensure that there is a _real_bzrdir set.

        Used before calls to self._real_bzrdir.
        """
        if not self._real_bzrdir:
            self._real_bzrdir = BzrDir.open_from_transport(
                self.root_transport, _server_formats=False)

    def create_repository(self, shared=False):
        self._ensure_real()
        self._real_bzrdir.create_repository(shared=shared)
        return self.open_repository()

    def create_branch(self):
        self._ensure_real()
        real_branch = self._real_bzrdir.create_branch()
        return RemoteBranch(self, self.find_repository(), real_branch)

    def create_workingtree(self, revision_id=None):
        raise errors.NotLocalUrl(self.transport.base)

    def find_branch_format(self):
        """Find the branch 'format' for this bzrdir.

        This might be a synthetic object for e.g. RemoteBranch and SVN.
        """
        b = self.open_branch()
        return b._format

    def get_branch_reference(self):
        """See BzrDir.get_branch_reference()."""
        path = self._path_for_remote_call(self._client)
        response = self._client.call('BzrDir.open_branch', path)
        if response[0] == 'ok':
            if response[1] == '':
                # branch at this location.
                return None
            else:
                # a branch reference, use the existing BranchReference logic.
                return response[1]
        elif response == ('nobranch',):
            raise errors.NotBranchError(path=self.root_transport.base)
        else:
            assert False, 'unexpected response code %r' % (response,)

    def open_branch(self, _unsupported=False):
        assert _unsupported == False, 'unsupported flag support not implemented yet.'
        reference_url = self.get_branch_reference()
        if reference_url is None:
            # branch at this location.
            return RemoteBranch(self, self.find_repository())
        else:
            # a branch reference, use the existing BranchReference logic.
            format = BranchReferenceFormat()
            return format.open(self, _found=True, location=reference_url)
                
    def open_repository(self):
        path = self._path_for_remote_call(self._client)
        response = self._client.call('BzrDir.find_repository', path)
        assert response[0] in ('ok', 'norepository'), \
            'unexpected response code %s' % (response,)
        if response[0] == 'norepository':
            raise errors.NoRepositoryPresent(self)
        assert len(response) == 4, 'incorrect response length %s' % (response,)
        if response[1] == '':
            format = RemoteRepositoryFormat()
            format.rich_root_data = (response[2] == 'yes')
            format.supports_tree_reference = (response[3] == 'yes')
            return RemoteRepository(self, format)
        else:
            raise errors.NoRepositoryPresent(self)

    def open_workingtree(self, recommend_upgrade=True):
        self._ensure_real()
        if self._real_bzrdir.has_workingtree():
            raise errors.NotLocalUrl(self.root_transport)
        else:
            raise errors.NoWorkingTree(self.root_transport.base)

    def _path_for_remote_call(self, client):
        """Return the path to be used for this bzrdir in a remote call."""
        return client.remote_path_from_transport(self.root_transport)

    def get_branch_transport(self, branch_format):
        self._ensure_real()
        return self._real_bzrdir.get_branch_transport(branch_format)

    def get_repository_transport(self, repository_format):
        self._ensure_real()
        return self._real_bzrdir.get_repository_transport(repository_format)

    def get_workingtree_transport(self, workingtree_format):
        self._ensure_real()
        return self._real_bzrdir.get_workingtree_transport(workingtree_format)

    def can_convert_format(self):
        """Upgrading of remote bzrdirs is not supported yet."""
        return False

    def needs_format_conversion(self, format=None):
        """Upgrading of remote bzrdirs is not supported yet."""
        return False

    def clone(self, url, revision_id=None, force_new_repo=False):
        self._ensure_real()
        return self._real_bzrdir.clone(url, revision_id=revision_id,
            force_new_repo=force_new_repo)


class RemoteRepositoryFormat(repository.RepositoryFormat):
    """Format for repositories accessed over a _SmartClient.

    Instances of this repository are represented by RemoteRepository
    instances.

    The RemoteRepositoryFormat is parameterised during construction
    to reflect the capabilities of the real, remote format. Specifically
    the attributes rich_root_data and supports_tree_reference are set
    on a per instance basis, and are not set (and should not be) at
    the class level.
    """

    _matchingbzrdir = RemoteBzrDirFormat

    def initialize(self, a_bzrdir, shared=False):
        assert isinstance(a_bzrdir, RemoteBzrDir), \
            '%r is not a RemoteBzrDir' % (a_bzrdir,)
        return a_bzrdir.create_repository(shared=shared)
    
    def open(self, a_bzrdir):
        assert isinstance(a_bzrdir, RemoteBzrDir)
        return a_bzrdir.open_repository()

    def get_format_description(self):
        return 'bzr remote repository'

    def __eq__(self, other):
        return self.__class__ == other.__class__

    def check_conversion_target(self, target_format):
        if self.rich_root_data and not target_format.rich_root_data:
            raise errors.BadConversionTarget(
                'Does not support rich root data.', target_format)
        if (self.supports_tree_reference and
            not getattr(target_format, 'supports_tree_reference', False)):
            raise errors.BadConversionTarget(
                'Does not support nested trees', target_format)


class RemoteRepository(object):
    """Repository accessed over rpc.

    For the moment most operations are performed using local transport-backed
    Repository objects.
    """

    def __init__(self, remote_bzrdir, format, real_repository=None, _client=None):
        """Create a RemoteRepository instance.
        
        :param remote_bzrdir: The bzrdir hosting this repository.
        :param format: The RemoteFormat object to use.
        :param real_repository: If not None, a local implementation of the
            repository logic for the repository, usually accessing the data
            via the VFS.
        :param _client: Private testing parameter - override the smart client
            to be used by the repository.
        """
        if real_repository:
            self._real_repository = real_repository
        else:
            self._real_repository = None
        self.bzrdir = remote_bzrdir
        if _client is None:
            self._client = client._SmartClient(self.bzrdir._medium)
        else:
            self._client = _client
        self._format = format
        self._lock_mode = None
        self._lock_token = None
        self._lock_count = 0
        self._leave_lock = False

    def _ensure_real(self):
        """Ensure that there is a _real_repository set.

        Used before calls to self._real_repository.
        """
        if not self._real_repository:
            self.bzrdir._ensure_real()
            #self._real_repository = self.bzrdir._real_bzrdir.open_repository()
            self._set_real_repository(self.bzrdir._real_bzrdir.open_repository())

    def get_revision_graph(self, revision_id=None):
        """See Repository.get_revision_graph()."""
        if revision_id is None:
            revision_id = ''
        elif revision_id == NULL_REVISION:
            return {}

        path = self.bzrdir._path_for_remote_call(self._client)
        assert type(revision_id) is str
        response = self._client.call_expecting_body(
            'Repository.get_revision_graph', path, revision_id)
        if response[0][0] not in ['ok', 'nosuchrevision']:
            raise errors.UnexpectedSmartServerResponse(response[0])
        if response[0][0] == 'ok':
            coded = response[1].read_body_bytes()
            if coded == '':
                # no revisions in this repository!
                return {}
            lines = coded.split('\n')
            revision_graph = {}
            for line in lines:
                d = list(line.split())
                revision_graph[d[0]] = d[1:]
                
            return revision_graph
        else:
            response_body = response[1].read_body_bytes()
            assert response_body == ''
            raise NoSuchRevision(self, revision_id)

    def has_revision(self, revision_id):
        """See Repository.has_revision()."""
        if revision_id is None:
            # The null revision is always present.
            return True
        path = self.bzrdir._path_for_remote_call(self._client)
        response = self._client.call('Repository.has_revision', path, revision_id)
        assert response[0] in ('yes', 'no'), 'unexpected response code %s' % (response,)
        return response[0] == 'yes'

    def gather_stats(self, revid=None, committers=None):
        """See Repository.gather_stats()."""
        path = self.bzrdir._path_for_remote_call(self._client)
        if revid in (None, NULL_REVISION):
            fmt_revid = ''
        else:
            fmt_revid = revid
        if committers is None or not committers:
            fmt_committers = 'no'
        else:
            fmt_committers = 'yes'
        response = self._client.call_expecting_body(
            'Repository.gather_stats', path, fmt_revid, fmt_committers)
        assert response[0][0] == 'ok', \
            'unexpected response code %s' % (response[0],)

        body = response[1].read_body_bytes()
        result = {}
        for line in body.split('\n'):
            if not line:
                continue
            key, val_text = line.split(':')
            if key in ('revisions', 'size', 'committers'):
                result[key] = int(val_text)
            elif key in ('firstrev', 'latestrev'):
                values = val_text.split(' ')[1:]
                result[key] = (float(values[0]), long(values[1]))

        return result

    def get_physical_lock_status(self):
        """See Repository.get_physical_lock_status()."""
        return False

    def is_shared(self):
        """See Repository.is_shared()."""
        path = self.bzrdir._path_for_remote_call(self._client)
        response = self._client.call('Repository.is_shared', path)
        assert response[0] in ('yes', 'no'), 'unexpected response code %s' % (response,)
        return response[0] == 'yes'

    def lock_read(self):
        # wrong eventually - want a local lock cache context
        if not self._lock_mode:
            self._lock_mode = 'r'
            self._lock_count = 1
            if self._real_repository is not None:
                self._real_repository.lock_read()
        else:
            self._lock_count += 1

    def _remote_lock_write(self, token):
        path = self.bzrdir._path_for_remote_call(self._client)
        if token is None:
            token = ''
        response = self._client.call('Repository.lock_write', path, token)
        if response[0] == 'ok':
            ok, token = response
            return token
        elif response[0] == 'LockContention':
            raise errors.LockContention('(remote lock)')
        elif response[0] == 'UnlockableTransport':
            raise errors.UnlockableTransport(self.bzrdir.root_transport)
        else:
            assert False, 'unexpected response code %s' % (response,)

    def lock_write(self, token=None):
        if not self._lock_mode:
            self._lock_token = self._remote_lock_write(token)
            assert self._lock_token, 'Remote server did not return a token!'
            if self._real_repository is not None:
                self._real_repository.lock_write(token=self._lock_token)
            if token is not None:
                self._leave_lock = True
            else:
                self._leave_lock = False
            self._lock_mode = 'w'
            self._lock_count = 1
        elif self._lock_mode == 'r':
            raise errors.ReadOnlyError(self)
        else:
            self._lock_count += 1
        return self._lock_token

    def leave_lock_in_place(self):
        self._leave_lock = True

    def dont_leave_lock_in_place(self):
        self._leave_lock = False

    def _set_real_repository(self, repository):
        """Set the _real_repository for this repository.

        :param repository: The repository to fallback to for non-hpss
            implemented operations.
        """
        assert not isinstance(repository, RemoteRepository)
        self._real_repository = repository
        if self._lock_mode == 'w':
            # if we are already locked, the real repository must be able to
            # acquire the lock with our token.
            self._real_repository.lock_write(self._lock_token)
        elif self._lock_mode == 'r':
            self._real_repository.lock_read()

    def _unlock(self, token):
        path = self.bzrdir._path_for_remote_call(self._client)
        response = self._client.call('Repository.unlock', path, token)
        if response == ('ok',):
            return
        elif response[0] == 'TokenMismatch':
            raise errors.TokenMismatch(token, '(remote token)')
        else:
            assert False, 'unexpected response code %s' % (response,)

    def unlock(self):
        self._lock_count -= 1
        if not self._lock_count:
            mode = self._lock_mode
            self._lock_mode = None
            if self._real_repository is not None:
                self._real_repository.unlock()
            if mode != 'w':
                # Only write-locked repositories need to make a remote method
                # call to perfom the unlock.
                return
            assert self._lock_token, 'Locked, but no token!'
            token = self._lock_token
            self._lock_token = None
            if not self._leave_lock:
                self._unlock(token)

    def break_lock(self):
        # should hand off to the network
        self._ensure_real()
        return self._real_repository.break_lock()

    def _get_tarball(self, compression):
        """Return a TemporaryFile containing a repository tarball"""
        import tempfile
        path = self.bzrdir._path_for_remote_call(self._client)
        response, protocol = self._client.call_expecting_body(
            'Repository.tarball', path, compression)
        assert response[0] in ('ok', 'failure'), \
            'unexpected response code %s' % (response,)
        if response[0] == 'ok':
            # Extract the tarball and return it
            t = tempfile.NamedTemporaryFile()
            # TODO: rpc layer should read directly into it...
            t.write(protocol.read_body_bytes())
            t.seek(0)
            return t
        else:
            raise errors.SmartServerError(error_code=response)

    def sprout(self, to_bzrdir, revision_id=None):
        # TODO: Option to control what format is created?
        to_repo = to_bzrdir.create_repository()
        self._copy_repository_tarball(to_repo, revision_id)
        return to_repo

    ### These methods are just thin shims to the VFS object for now.

    def revision_tree(self, revision_id):
        self._ensure_real()
        return self._real_repository.revision_tree(revision_id)

    def get_commit_builder(self, branch, parents, config, timestamp=None,
                           timezone=None, committer=None, revprops=None,
                           revision_id=None):
        # FIXME: It ought to be possible to call this without immediately
        # triggering _ensure_real.  For now it's the easiest thing to do.
        self._ensure_real()
        builder = self._real_repository.get_commit_builder(branch, parents,
                config, timestamp=timestamp, timezone=timezone,
                committer=committer, revprops=revprops, revision_id=revision_id)
        # Make the builder use this RemoteRepository rather than the real one.
        builder.repository = self
        return builder

    @needs_write_lock
    def add_inventory(self, revid, inv, parents):
        self._ensure_real()
        return self._real_repository.add_inventory(revid, inv, parents)

    @needs_write_lock
    def add_revision(self, rev_id, rev, inv=None, config=None):
        self._ensure_real()
        return self._real_repository.add_revision(
            rev_id, rev, inv=inv, config=config)

    @needs_read_lock
    def get_inventory(self, revision_id):
        self._ensure_real()
        return self._real_repository.get_inventory(revision_id)

    @needs_read_lock
    def get_revision(self, revision_id):
        self._ensure_real()
        return self._real_repository.get_revision(revision_id)

    @property
    def weave_store(self):
        self._ensure_real()
        return self._real_repository.weave_store

    def get_transaction(self):
        self._ensure_real()
        return self._real_repository.get_transaction()

    @needs_read_lock
    def clone(self, a_bzrdir, revision_id=None):
        self._ensure_real()
        return self._real_repository.clone(a_bzrdir, revision_id=revision_id)

    def make_working_trees(self):
        """RemoteRepositories never create working trees by default."""
        return False

    def fetch(self, source, revision_id=None, pb=None):
        self._ensure_real()
        return self._real_repository.fetch(
            source, revision_id=revision_id, pb=pb)

    @property
    def control_weaves(self):
        self._ensure_real()
        return self._real_repository.control_weaves

    @needs_read_lock
    def get_ancestry(self, revision_id):
        self._ensure_real()
        return self._real_repository.get_ancestry(revision_id)

    @needs_read_lock
    def get_inventory_weave(self):
        self._ensure_real()
        return self._real_repository.get_inventory_weave()

    def fileids_altered_by_revision_ids(self, revision_ids):
        self._ensure_real()
        return self._real_repository.fileids_altered_by_revision_ids(revision_ids)

    @needs_read_lock
    def get_signature_text(self, revision_id):
        self._ensure_real()
        return self._real_repository.get_signature_text(revision_id)

    @needs_read_lock
    def get_revision_graph_with_ghosts(self, revision_ids=None):
        self._ensure_real()
        return self._real_repository.get_revision_graph_with_ghosts(
            revision_ids=revision_ids)

    @needs_read_lock
    def get_inventory_xml(self, revision_id):
        self._ensure_real()
        return self._real_repository.get_inventory_xml(revision_id)

    def deserialise_inventory(self, revision_id, xml):
        self._ensure_real()
        return self._real_repository.deserialise_inventory(revision_id, xml)

    def reconcile(self, other=None, thorough=False):
        self._ensure_real()
        return self._real_repository.reconcile(other=other, thorough=thorough)
        
    def all_revision_ids(self):
        self._ensure_real()
        return self._real_repository.all_revision_ids()
    
    @needs_read_lock
    def get_deltas_for_revisions(self, revisions):
        self._ensure_real()
        return self._real_repository.get_deltas_for_revisions(revisions)

    @needs_read_lock
    def get_revision_delta(self, revision_id):
        self._ensure_real()
        return self._real_repository.get_revision_delta(revision_id)

    @needs_read_lock
    def revision_trees(self, revision_ids):
        self._ensure_real()
        return self._real_repository.revision_trees(revision_ids)

    @needs_read_lock
    def get_revision_reconcile(self, revision_id):
        self._ensure_real()
        return self._real_repository.get_revision_reconcile(revision_id)

    @needs_read_lock
    def check(self, revision_ids):
        self._ensure_real()
        return self._real_repository.check(revision_ids)

    def copy_content_into(self, destination, revision_id=None):
        self._ensure_real()
        return self._real_repository.copy_content_into(
            destination, revision_id=revision_id)

    def _copy_repository_tarball(self, destination, revision_id=None):
        # get a tarball of the remote repository, and copy from that into the
        # destination
        from bzrlib import osutils
        import tarfile
        import tempfile
        from StringIO import StringIO
        # TODO: Maybe a progress bar while streaming the tarball?
        note("Copying repository content as tarball...")
        tar_file = self._get_tarball('bz2')
        try:
            tar = tarfile.open('repository', fileobj=tar_file,
                mode='r|bz2')
            tmpdir = tempfile.mkdtemp()
            try:
                _extract_tar(tar, tmpdir)
                tmp_bzrdir = BzrDir.open(tmpdir)
                tmp_repo = tmp_bzrdir.open_repository()
                tmp_repo.copy_content_into(destination, revision_id)
            finally:
                osutils.rmtree(tmpdir)
        finally:
            tar_file.close()
        # TODO: if the server doesn't support this operation, maybe do it the
        # slow way using the _real_repository?
        #
        # TODO: Suggestion from john: using external tar is much faster than
        # python's tarfile library, but it may not work on windows.

    def set_make_working_trees(self, new_value):
        raise NotImplementedError(self.set_make_working_trees)

    @needs_write_lock
    def sign_revision(self, revision_id, gpg_strategy):
        self._ensure_real()
        return self._real_repository.sign_revision(revision_id, gpg_strategy)

    @needs_read_lock
    def get_revisions(self, revision_ids):
        self._ensure_real()
        return self._real_repository.get_revisions(revision_ids)

    def supports_rich_root(self):
        self._ensure_real()
        return self._real_repository.supports_rich_root()

    def iter_reverse_revision_history(self, revision_id):
        self._ensure_real()
        return self._real_repository.iter_reverse_revision_history(revision_id)

    @property
    def _serializer(self):
        self._ensure_real()
        return self._real_repository._serializer

    def store_revision_signature(self, gpg_strategy, plaintext, revision_id):
        self._ensure_real()
        return self._real_repository.store_revision_signature(
            gpg_strategy, plaintext, revision_id)

    def has_signature_for_revision_id(self, revision_id):
        self._ensure_real()
        return self._real_repository.has_signature_for_revision_id(revision_id)


class RemoteBranchLockableFiles(LockableFiles):
    """A 'LockableFiles' implementation that talks to a smart server.
    
    This is not a public interface class.
    """

    def __init__(self, bzrdir, _client):
        self.bzrdir = bzrdir
        self._client = _client
        self._need_find_modes = True
        LockableFiles.__init__(
            self, bzrdir.get_branch_transport(None),
            'lock', lockdir.LockDir)

    def _find_modes(self):
        # RemoteBranches don't let the client set the mode of control files.
        self._dir_mode = None
        self._file_mode = None

    def get(self, path):
        """'get' a remote path as per the LockableFiles interface.

        :param path: the file to 'get'. If this is 'branch.conf', we do not
             just retrieve a file, instead we ask the smart server to generate
             a configuration for us - which is retrieved as an INI file.
        """
        if path == 'branch.conf':
            path = self.bzrdir._path_for_remote_call(self._client)
            response = self._client.call_expecting_body(
                'Branch.get_config_file', path)
            assert response[0][0] == 'ok', \
                'unexpected response code %s' % (response[0],)
            return StringIO(response[1].read_body_bytes())
        else:
            # VFS fallback.
            return LockableFiles.get(self, path)


class RemoteBranchFormat(branch.BranchFormat):

    def __eq__(self, other):
        return (isinstance(other, RemoteBranchFormat) and 
            self.__dict__ == other.__dict__)

    def get_format_description(self):
        return 'Remote BZR Branch'

    def get_format_string(self):
        return 'Remote BZR Branch'

    def open(self, a_bzrdir):
        assert isinstance(a_bzrdir, RemoteBzrDir)
        return a_bzrdir.open_branch()

    def initialize(self, a_bzrdir):
        assert isinstance(a_bzrdir, RemoteBzrDir)
        return a_bzrdir.create_branch()


class RemoteBranch(branch.Branch):
    """Branch stored on a server accessed by HPSS RPC.

    At the moment most operations are mapped down to simple file operations.
    """

    def __init__(self, remote_bzrdir, remote_repository, real_branch=None,
        _client=None):
        """Create a RemoteBranch instance.

        :param real_branch: An optional local implementation of the branch
            format, usually accessing the data via the VFS.
        :param _client: Private parameter for testing.
        """
        # We intentionally don't call the parent class's __init__, because it
        # will try to assign to self.tags, which is a property in this subclass.
        # And the parent's __init__ doesn't do much anyway.
        self._revision_history_cache = None
        self.bzrdir = remote_bzrdir
        if _client is not None:
            self._client = _client
        else:
            self._client = client._SmartClient(self.bzrdir._medium)
        self.repository = remote_repository
        if real_branch is not None:
            self._real_branch = real_branch
            # Give the remote repository the matching real repo.
            real_repo = self._real_branch.repository
            if isinstance(real_repo, RemoteRepository):
                real_repo._ensure_real()
                real_repo = real_repo._real_repository
            self.repository._set_real_repository(real_repo)
            # Give the branch the remote repository to let fast-pathing happen.
            self._real_branch.repository = self.repository
        else:
            self._real_branch = None
        # Fill out expected attributes of branch for bzrlib api users.
        self._format = RemoteBranchFormat()
        self.base = self.bzrdir.root_transport.base
        self._control_files = None
        self._lock_mode = None
        self._lock_token = None
        self._lock_count = 0
        self._leave_lock = False

    def _ensure_real(self):
        """Ensure that there is a _real_branch set.

        Used before calls to self._real_branch.
        """
        if not self._real_branch:
            assert vfs.vfs_enabled()
            self.bzrdir._ensure_real()
            self._real_branch = self.bzrdir._real_bzrdir.open_branch()
            # Give the remote repository the matching real repo.
            real_repo = self._real_branch.repository
            if isinstance(real_repo, RemoteRepository):
                real_repo._ensure_real()
                real_repo = real_repo._real_repository
            self.repository._set_real_repository(real_repo)
            # Give the branch the remote repository to let fast-pathing happen.
            self._real_branch.repository = self.repository
            # XXX: deal with _lock_mode == 'w'
            if self._lock_mode == 'r':
                self._real_branch.lock_read()

    @property
    def control_files(self):
        # Defer actually creating RemoteBranchLockableFiles until its needed,
        # because it triggers an _ensure_real that we otherwise might not need.
        if self._control_files is None:
            self._control_files = RemoteBranchLockableFiles(
                self.bzrdir, self._client)
        return self._control_files

    def _get_checkout_format(self):
        self._ensure_real()
        return self._real_branch._get_checkout_format()

    def get_physical_lock_status(self):
        """See Branch.get_physical_lock_status()."""
        # should be an API call to the server, as branches must be lockable.
        self._ensure_real()
        return self._real_branch.get_physical_lock_status()

    def lock_read(self):
        if not self._lock_mode:
            self._lock_mode = 'r'
            self._lock_count = 1
            if self._real_branch is not None:
                self._real_branch.lock_read()
        else:
            self._lock_count += 1

    def _remote_lock_write(self, token):
        if token is None:
            branch_token = repo_token = ''
        else:
            branch_token = token
            repo_token = self.repository.lock_write()
            self.repository.unlock()
        path = self.bzrdir._path_for_remote_call(self._client)
        response = self._client.call('Branch.lock_write', path, branch_token,
                                     repo_token)
        if response[0] == 'ok':
            ok, branch_token, repo_token = response
            return branch_token, repo_token
        elif response[0] == 'LockContention':
            raise errors.LockContention('(remote lock)')
        elif response[0] == 'TokenMismatch':
            raise errors.TokenMismatch(token, '(remote token)')
        elif response[0] == 'UnlockableTransport':
            raise errors.UnlockableTransport(self.bzrdir.root_transport)
        elif response[0] == 'ReadOnlyError':
            raise errors.ReadOnlyError(self)
        else:
            assert False, 'unexpected response code %r' % (response,)
            
    def lock_write(self, token=None):
        if not self._lock_mode:
            remote_tokens = self._remote_lock_write(token)
            self._lock_token, self._repo_lock_token = remote_tokens
            assert self._lock_token, 'Remote server did not return a token!'
            # TODO: We really, really, really don't want to call _ensure_real
            # here, but it's the easiest way to ensure coherency between the
            # state of the RemoteBranch and RemoteRepository objects and the
            # physical locks.  If we don't materialise the real objects here,
            # then getting everything in the right state later is complex, so
            # for now we just do it the lazy way.
            #   -- Andrew Bennetts, 2007-02-22.
            self._ensure_real()
            if self._real_branch is not None:
                self._real_branch.repository.lock_write(
                    token=self._repo_lock_token)
                try:
                    self._real_branch.lock_write(token=self._lock_token)
                finally:
                    self._real_branch.repository.unlock()
            if token is not None:
                self._leave_lock = True
            else:
                # XXX: this case seems to be unreachable; token cannot be None.
                self._leave_lock = False
            self._lock_mode = 'w'
            self._lock_count = 1
        elif self._lock_mode == 'r':
            raise errors.ReadOnlyTransaction
        else:
            if token is not None:
                # A token was given to lock_write, and we're relocking, so check
                # that the given token actually matches the one we already have.
                if token != self._lock_token:
                    raise errors.TokenMismatch(token, self._lock_token)
            self._lock_count += 1
        return self._lock_token

    def _unlock(self, branch_token, repo_token):
        path = self.bzrdir._path_for_remote_call(self._client)
        response = self._client.call('Branch.unlock', path, branch_token,
                                     repo_token)
        if response == ('ok',):
            return
        elif response[0] == 'TokenMismatch':
            raise errors.TokenMismatch(
                str((branch_token, repo_token)), '(remote tokens)')
        else:
            assert False, 'unexpected response code %s' % (response,)

    def unlock(self):
        self._lock_count -= 1
        if not self._lock_count:
            self._clear_cached_state()
            mode = self._lock_mode
            self._lock_mode = None
            if self._real_branch is not None:
                if not self._leave_lock:
                    # If this RemoteBranch will remove the physical lock for the
                    # repository, make sure the _real_branch doesn't do it
                    # first.  (Because the _real_branch's repository is set to
                    # be the RemoteRepository.)
                    self._real_branch.repository.leave_lock_in_place()
                self._real_branch.unlock()
            if mode != 'w':
                # Only write-locked branched need to make a remote method call
                # to perfom the unlock.
                return
            assert self._lock_token, 'Locked, but no token!'
            branch_token = self._lock_token
            repo_token = self._repo_lock_token
            self._lock_token = None
            self._repo_lock_token = None
            if not self._leave_lock:
                self._unlock(branch_token, repo_token)

    def break_lock(self):
        self._ensure_real()
        return self._real_branch.break_lock()

    def leave_lock_in_place(self):
        self._leave_lock = True

    def dont_leave_lock_in_place(self):
        self._leave_lock = False

    def last_revision_info(self):
        """See Branch.last_revision_info()."""
        path = self.bzrdir._path_for_remote_call(self._client)
        response = self._client.call('Branch.last_revision_info', path)
        assert response[0] == 'ok', 'unexpected response code %s' % (response,)
        revno = int(response[1])
        last_revision = response[2]
        return (revno, last_revision)

    def _gen_revision_history(self):
        """See Branch._gen_revision_history()."""
        path = self.bzrdir._path_for_remote_call(self._client)
        response = self._client.call_expecting_body(
            'Branch.revision_history', path)
        assert response[0][0] == 'ok', ('unexpected response code %s'
                                        % (response[0],))
        result = response[1].read_body_bytes().split('\x00')
        if result == ['']:
            return []
        return result

    @needs_write_lock
    def set_revision_history(self, rev_history):
        # Send just the tip revision of the history; the server will generate
        # the full history from that.  If the revision doesn't exist in this
        # branch, NoSuchRevision will be raised.
        path = self.bzrdir._path_for_remote_call(self._client)
        if rev_history == []:
            rev_id = 'null:'
        else:
            rev_id = rev_history[-1]
        self._clear_cached_state()
        response = self._client.call('Branch.set_last_revision',
            path, self._lock_token, self._repo_lock_token, rev_id)
        if response[0] == 'NoSuchRevision':
            raise NoSuchRevision(self, rev_id)
        else:
            assert response == ('ok',), (
                'unexpected response code %r' % (response,))
        self._cache_revision_history(rev_history)

    def get_parent(self):
        self._ensure_real()
        return self._real_branch.get_parent()
        
    def set_parent(self, url):
        self._ensure_real()
        return self._real_branch.set_parent(url)
        
    def get_config(self):
        return RemoteBranchConfig(self)

    def sprout(self, to_bzrdir, revision_id=None):
        # Like Branch.sprout, except that it sprouts a branch in the default
        # format, because RemoteBranches can't be created at arbitrary URLs.
        # XXX: if to_bzrdir is a RemoteBranch, this should perhaps do
        # to_bzrdir.create_branch...
        result = branch.BranchFormat.get_default_format().initialize(to_bzrdir)
        self.copy_content_into(result, revision_id=revision_id)
        result.set_parent(self.bzrdir.root_transport.base)
        return result

    @needs_write_lock
    def append_revision(self, *revision_ids):
        self._ensure_real()
        return self._real_branch.append_revision(*revision_ids)

    @needs_write_lock
    def pull(self, source, overwrite=False, stop_revision=None):
        self._ensure_real()
        self._real_branch.pull(
            source, overwrite=overwrite, stop_revision=stop_revision)

    @needs_read_lock
    def push(self, target, overwrite=False, stop_revision=None):
        self._ensure_real()
        return self._real_branch.push(
            target, overwrite=overwrite, stop_revision=stop_revision)

    def is_locked(self):
        return self._lock_count >= 1

    def set_last_revision_info(self, revno, revision_id):
        self._ensure_real()
        self._clear_cached_state()
        return self._real_branch.set_last_revision_info(revno, revision_id)

    def generate_revision_history(self, revision_id, last_rev=None,
                                  other_branch=None):
        self._ensure_real()
        return self._real_branch.generate_revision_history(
            revision_id, last_rev=last_rev, other_branch=other_branch)

    @property
    def tags(self):
        self._ensure_real()
        return self._real_branch.tags

    def set_push_location(self, location):
        self._ensure_real()
        return self._real_branch.set_push_location(location)

    def update_revisions(self, other, stop_revision=None):
        self._ensure_real()
        return self._real_branch.update_revisions(
            other, stop_revision=stop_revision)


class RemoteBranchConfig(BranchConfig):

    def username(self):
        self.branch._ensure_real()
        return self.branch._real_branch.get_config().username()

    def _get_branch_data_config(self):
        self.branch._ensure_real()
        if self._branch_data_config is None:
            self._branch_data_config = TreeConfig(self.branch._real_branch)
        return self._branch_data_config


def _extract_tar(tar, to_dir):
    """Extract all the contents of a tarfile object.

    A replacement for extractall, which is not present in python2.4
    """
    for tarinfo in tar:
        tar.extract(tarinfo, to_dir)