# Copyright (C) 2006-2011 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

"""BzrDir logic. The BzrDir is the basic control directory used by bzr.

At format 7 this was split out into Branch, Repository and Checkout control
directories.

Note: This module has a lot of ``open`` functions/methods that return
references to in-memory objects. As a rule, there are no matching ``close``
methods. To free any associated resources, simply stop referencing the
objects returned.
"""

from __future__ import absolute_import

import sys

from ..lazy_import import lazy_import
lazy_import(globals(), """
from breezy import (
    branch as _mod_branch,
    cleanup,
    lockable_files,
    lockdir,
    osutils,
    repository,
    revision as _mod_revision,
    transport as _mod_transport,
    ui,
    urlutils,
    win32utils,
    )
from breezy.bzr import (
    branch as _mod_bzrbranch,
    fetch,
    remote,
    vf_search,
    workingtree_3,
    workingtree_4,
    )
from breezy.bzr import fullhistory as fullhistorybranch
from breezy.bzr import knitpack_repo
from breezy.transport import (
    do_catching_redirections,
    local,
    )
from breezy.i18n import gettext
""")

from ..sixish import viewitems
from ..trace import (
    mutter,
    note,
    )

from .. import (
    config,
    controldir,
    errors,
    )


class MissingFeature(errors.BzrError):

    _fmt = ("Missing feature %(feature)s not provided by this "
            "version of Bazaar or any plugin.")

    def __init__(self, feature):
        self.feature = feature


class FeatureAlreadyRegistered(errors.BzrError):

    _fmt = 'The feature %(feature)s has already been registered.'

    def __init__(self, feature):
        self.feature = feature


class BzrDir(controldir.ControlDir):
    """A .bzr control diretory.

    BzrDir instances let you create or open any of the things that can be
    found within .bzr - checkouts, branches and repositories.

    :ivar transport:
        the transport which this bzr dir is rooted at (i.e. file:///.../.bzr/)
    :ivar root_transport:
        a transport connected to the directory this bzr was opened from
        (i.e. the parent directory holding the .bzr directory).

    Everything in the bzrdir should have the same file permissions.

    :cvar hooks: An instance of BzrDirHooks.
    """

    def break_lock(self):
        """Invoke break_lock on the first object in the bzrdir.

        If there is a tree, the tree is opened and break_lock() called.
        Otherwise, branch is tried, and finally repository.
        """
        # XXX: This seems more like a UI function than something that really
        # belongs in this class.
        try:
            thing_to_unlock = self.open_workingtree()
        except (errors.NotLocalUrl, errors.NoWorkingTree):
            try:
                thing_to_unlock = self.open_branch()
            except errors.NotBranchError:
                try:
                    thing_to_unlock = self.open_repository()
                except errors.NoRepositoryPresent:
                    return
        thing_to_unlock.break_lock()

    def check_conversion_target(self, target_format):
        """Check that a bzrdir as a whole can be converted to a new format."""
        # The only current restriction is that the repository content can be
        # fetched compatibly with the target.
        target_repo_format = target_format.repository_format
        try:
            self.open_repository()._format.check_conversion_target(
                target_repo_format)
        except errors.NoRepositoryPresent:
            # No repo, no problem.
            pass

    def clone_on_transport(self, transport, revision_id=None,
                           force_new_repo=False, preserve_stacking=False, stacked_on=None,
                           create_prefix=False, use_existing_dir=True, no_tree=False):
        """Clone this bzrdir and its contents to transport verbatim.

        :param transport: The transport for the location to produce the clone
            at.  If the target directory does not exist, it will be created.
        :param revision_id: The tip revision-id to use for any branch or
            working tree.  If not None, then the clone operation may tune
            itself to download less data.
        :param force_new_repo: Do not use a shared repository for the target,
                               even if one is available.
        :param preserve_stacking: When cloning a stacked branch, stack the
            new branch on top of the other branch's stacked-on branch.
        :param create_prefix: Create any missing directories leading up to
            to_transport.
        :param use_existing_dir: Use an existing directory if one exists.
        :param no_tree: If set to true prevents creation of a working tree.
        """
        # Overview: put together a broad description of what we want to end up
        # with; then make as few api calls as possible to do it.

        # We may want to create a repo/branch/tree, if we do so what format
        # would we want for each:
        require_stacking = (stacked_on is not None)
        format = self.cloning_metadir(require_stacking)

        # Figure out what objects we want:
        try:
            local_repo = self.find_repository()
        except errors.NoRepositoryPresent:
            local_repo = None
        try:
            local_branch = self.open_branch()
        except errors.NotBranchError:
            local_branch = None
        else:
            # enable fallbacks when branch is not a branch reference
            if local_branch.repository.has_same_location(local_repo):
                local_repo = local_branch.repository
            if preserve_stacking:
                try:
                    stacked_on = local_branch.get_stacked_on_url()
                except (_mod_branch.UnstackableBranchFormat,
                        errors.UnstackableRepositoryFormat,
                        errors.NotStacked):
                    pass
        # Bug: We create a metadir without knowing if it can support stacking,
        # we should look up the policy needs first, or just use it as a hint,
        # or something.
        if local_repo:
            make_working_trees = (local_repo.make_working_trees() and
                                  not no_tree)
            want_shared = local_repo.is_shared()
            repo_format_name = format.repository_format.network_name()
        else:
            make_working_trees = False
            want_shared = False
            repo_format_name = None

        result_repo, result, require_stacking, repository_policy = \
            format.initialize_on_transport_ex(
                transport, use_existing_dir=use_existing_dir,
                create_prefix=create_prefix, force_new_repo=force_new_repo,
                stacked_on=stacked_on, stack_on_pwd=self.root_transport.base,
                repo_format_name=repo_format_name,
                make_working_trees=make_working_trees, shared_repo=want_shared)
        if repo_format_name:
            try:
                # If the result repository is in the same place as the
                # resulting bzr dir, it will have no content, further if the
                # result is not stacked then we know all content should be
                # copied, and finally if we are copying up to a specific
                # revision_id then we can use the pending-ancestry-result which
                # does not require traversing all of history to describe it.
                if (result_repo.user_url == result.user_url
                    and not require_stacking
                        and revision_id is not None):
                    fetch_spec = vf_search.PendingAncestryResult(
                        [revision_id], local_repo)
                    result_repo.fetch(local_repo, fetch_spec=fetch_spec)
                else:
                    result_repo.fetch(local_repo, revision_id=revision_id)
            finally:
                result_repo.unlock()
        else:
            if result_repo is not None:
                raise AssertionError('result_repo not None(%r)' % result_repo)
        # 1 if there is a branch present
        #   make sure its content is available in the target repository
        #   clone it.
        if local_branch is not None:
            local_branch.clone(
                result, revision_id=revision_id,
                repository_policy=repository_policy)
        try:
            # Cheaper to check if the target is not local, than to try making
            # the tree and fail.
            result.root_transport.local_abspath('.')
            if result_repo is None or result_repo.make_working_trees():
                self.open_workingtree().clone(result, revision_id=revision_id)
        except (errors.NoWorkingTree, errors.NotLocalUrl):
            pass
        return result

    # TODO: This should be given a Transport, and should chdir up; otherwise
    # this will open a new connection.
    def _make_tail(self, url):
        t = _mod_transport.get_transport(url)
        t.ensure_base()

    def determine_repository_policy(self, force_new_repo=False, stack_on=None,
                                    stack_on_pwd=None, require_stacking=False):
        """Return an object representing a policy to use.

        This controls whether a new repository is created, and the format of
        that repository, or some existing shared repository used instead.

        If stack_on is supplied, will not seek a containing shared repo.

        :param force_new_repo: If True, require a new repository to be created.
        :param stack_on: If supplied, the location to stack on.  If not
            supplied, a default_stack_on location may be used.
        :param stack_on_pwd: If stack_on is relative, the location it is
            relative to.
        """
        def repository_policy(found_bzrdir):
            stack_on = None
            stack_on_pwd = None
            config = found_bzrdir.get_config()
            stop = False
            stack_on = config.get_default_stack_on()
            if stack_on is not None:
                stack_on_pwd = found_bzrdir.user_url
                stop = True
            # does it have a repository ?
            try:
                repository = found_bzrdir.open_repository()
            except errors.NoRepositoryPresent:
                repository = None
            else:
                if (found_bzrdir.user_url != self.user_url and
                        not repository.is_shared()):
                    # Don't look higher, can't use a higher shared repo.
                    repository = None
                    stop = True
                else:
                    stop = True
            if not stop:
                return None, False
            if repository:
                return UseExistingRepository(
                    repository, stack_on, stack_on_pwd,
                    require_stacking=require_stacking), True
            else:
                return CreateRepository(
                    self, stack_on, stack_on_pwd,
                    require_stacking=require_stacking), True

        if not force_new_repo:
            if stack_on is None:
                policy = self._find_containing(repository_policy)
                if policy is not None:
                    return policy
            else:
                try:
                    return UseExistingRepository(
                        self.open_repository(), stack_on, stack_on_pwd,
                        require_stacking=require_stacking)
                except errors.NoRepositoryPresent:
                    pass
        return CreateRepository(self, stack_on, stack_on_pwd,
                                require_stacking=require_stacking)

    def _find_or_create_repository(self, force_new_repo):
        """Create a new repository if needed, returning the repository."""
        policy = self.determine_repository_policy(force_new_repo)
        return policy.acquire_repository()[0]

    def _find_source_repo(self, add_cleanup, source_branch):
        """Find the source branch and repo for a sprout operation.

        This is helper intended for use by _sprout.

        :returns: (source_branch, source_repository).  Either or both may be
            None.  If not None, they will be read-locked (and their unlock(s)
            scheduled via the add_cleanup param).
        """
        if source_branch is not None:
            add_cleanup(source_branch.lock_read().unlock)
            return source_branch, source_branch.repository
        try:
            source_branch = self.open_branch()
            source_repository = source_branch.repository
        except errors.NotBranchError:
            source_branch = None
            try:
                source_repository = self.open_repository()
            except errors.NoRepositoryPresent:
                source_repository = None
            else:
                add_cleanup(source_repository.lock_read().unlock)
        else:
            add_cleanup(source_branch.lock_read().unlock)
        return source_branch, source_repository

    def sprout(self, url, revision_id=None, force_new_repo=False,
               recurse='down', possible_transports=None,
               accelerator_tree=None, hardlink=False, stacked=False,
               source_branch=None, create_tree_if_local=True,
               lossy=False):
        """Create a copy of this controldir prepared for use as a new line of
        development.

        If url's last component does not exist, it will be created.

        Attributes related to the identity of the source branch like
        branch nickname will be cleaned, a working tree is created
        whether one existed before or not; and a local branch is always
        created.

        if revision_id is not None, then the clone operation may tune
            itself to download less data.

        :param accelerator_tree: A tree which can be used for retrieving file
            contents more quickly than the revision tree, i.e. a workingtree.
            The revision tree will be used for cases where accelerator_tree's
            content is different.
        :param hardlink: If true, hard-link files from accelerator_tree,
            where possible.
        :param stacked: If true, create a stacked branch referring to the
            location of this control directory.
        :param create_tree_if_local: If true, a working-tree will be created
            when working locally.
        :return: The created control directory
        """
        operation = cleanup.OperationWithCleanups(self._sprout)
        return operation.run(
            url, revision_id=revision_id, force_new_repo=force_new_repo,
            recurse=recurse, possible_transports=possible_transports,
            accelerator_tree=accelerator_tree, hardlink=hardlink,
            stacked=stacked, source_branch=source_branch,
            create_tree_if_local=create_tree_if_local)

    def _sprout(self, op, url, revision_id=None, force_new_repo=False,
                recurse='down', possible_transports=None,
                accelerator_tree=None, hardlink=False, stacked=False,
                source_branch=None, create_tree_if_local=True, lossy=False):
        add_cleanup = op.add_cleanup
        fetch_spec_factory = fetch.FetchSpecFactory()
        if revision_id is not None:
            fetch_spec_factory.add_revision_ids([revision_id])
            fetch_spec_factory.source_branch_stop_revision_id = revision_id
        if possible_transports is None:
            possible_transports = []
        else:
            possible_transports = list(possible_transports) + [
                self.root_transport]
        target_transport = _mod_transport.get_transport(url,
                                                        possible_transports)
        target_transport.ensure_base()
        cloning_format = self.cloning_metadir(stacked)
        # Create/update the result branch
        try:
            result = controldir.ControlDir.open_from_transport(
                target_transport)
        except errors.NotBranchError:
            result = cloning_format.initialize_on_transport(target_transport)
        source_branch, source_repository = self._find_source_repo(
            add_cleanup, source_branch)
        fetch_spec_factory.source_branch = source_branch
        # if a stacked branch wasn't requested, we don't create one
        # even if the origin was stacked
        if stacked and source_branch is not None:
            stacked_branch_url = self.root_transport.base
        else:
            stacked_branch_url = None
        repository_policy = result.determine_repository_policy(
            force_new_repo, stacked_branch_url, require_stacking=stacked)
        result_repo, is_new_repo = repository_policy.acquire_repository(
            possible_transports=possible_transports)
        add_cleanup(result_repo.lock_write().unlock)
        fetch_spec_factory.source_repo = source_repository
        fetch_spec_factory.target_repo = result_repo
        if stacked or (len(result_repo._fallback_repositories) != 0):
            target_repo_kind = fetch.TargetRepoKinds.STACKED
        elif is_new_repo:
            target_repo_kind = fetch.TargetRepoKinds.EMPTY
        else:
            target_repo_kind = fetch.TargetRepoKinds.PREEXISTING
        fetch_spec_factory.target_repo_kind = target_repo_kind
        if source_repository is not None:
            fetch_spec = fetch_spec_factory.make_fetch_spec()
            result_repo.fetch(source_repository, fetch_spec=fetch_spec)

        if source_branch is None:
            # this is for sprouting a controldir without a branch; is that
            # actually useful?
            # Not especially, but it's part of the contract.
            result_branch = result.create_branch()
        else:
            result_branch = source_branch.sprout(
                result, revision_id=revision_id,
                repository_policy=repository_policy, repository=result_repo)
        mutter("created new branch %r" % (result_branch,))

        # Create/update the result working tree
        if (create_tree_if_local and not result.has_workingtree()
                and isinstance(target_transport, local.LocalTransport)
                and (result_repo is None or result_repo.make_working_trees())
                and result.open_branch(
                    name="",
                    possible_transports=possible_transports).name == result_branch.name):
            wt = result.create_workingtree(
                accelerator_tree=accelerator_tree, hardlink=hardlink,
                from_branch=result_branch)
            with wt.lock_write():
                if not wt.is_versioned(''):
                    try:
                        wt.set_root_id(self.open_workingtree.get_root_id())
                    except errors.NoWorkingTree:
                        pass
        else:
            wt = None
        if recurse == 'down':
            basis = None
            if wt is not None:
                basis = wt.basis_tree()
            elif result_branch is not None:
                basis = result_branch.basis_tree()
            elif source_branch is not None:
                basis = source_branch.basis_tree()
            if basis is not None:
                add_cleanup(basis.lock_read().unlock)
                subtrees = basis.iter_references()
            else:
                subtrees = []
            for path, file_id in subtrees:
                target = urlutils.join(url, urlutils.escape(path))
                sublocation = source_branch.reference_parent(path, file_id)
                sublocation.controldir.sprout(
                    target, basis.get_reference_revision(path),
                    force_new_repo=force_new_repo, recurse=recurse,
                    stacked=stacked)
        return result

    def _available_backup_name(self, base):
        """Find a non-existing backup file name based on base.

        See breezy.osutils.available_backup_name about race conditions.
        """
        return osutils.available_backup_name(base, self.root_transport.has)

    def backup_bzrdir(self):
        """Backup this bzr control directory.

        :return: Tuple with old path name and new path name
        """

        with ui.ui_factory.nested_progress_bar():
            old_path = self.root_transport.abspath('.bzr')
            backup_dir = self._available_backup_name('backup.bzr')
            new_path = self.root_transport.abspath(backup_dir)
            ui.ui_factory.note(
                gettext('making backup of {0}\n  to {1}').format(
                    urlutils.unescape_for_display(old_path, 'utf-8'),
                    urlutils.unescape_for_display(new_path, 'utf-8')))
            self.root_transport.copy_tree('.bzr', backup_dir)
            return (old_path, new_path)

    def retire_bzrdir(self, limit=10000):
        """Permanently disable the bzrdir.

        This is done by renaming it to give the user some ability to recover
        if there was a problem.

        This will have horrible consequences if anyone has anything locked or
        in use.
        :param limit: number of times to retry
        """
        i = 0
        while True:
            try:
                to_path = '.bzr.retired.%d' % i
                self.root_transport.rename('.bzr', to_path)
                note(gettext("renamed {0} to {1}").format(
                    self.root_transport.abspath('.bzr'), to_path))
                return
            except (errors.TransportError, IOError, errors.PathError):
                i += 1
                if i > limit:
                    raise
                else:
                    pass

    def _find_containing(self, evaluate):
        """Find something in a containing control directory.

        This method will scan containing control dirs, until it finds what
        it is looking for, decides that it will never find it, or runs out
        of containing control directories to check.

        It is used to implement find_repository and
        determine_repository_policy.

        :param evaluate: A function returning (value, stop).  If stop is True,
            the value will be returned.
        """
        found_bzrdir = self
        while True:
            result, stop = evaluate(found_bzrdir)
            if stop:
                return result
            next_transport = found_bzrdir.root_transport.clone('..')
            if (found_bzrdir.user_url == next_transport.base):
                # top of the file system
                return None
            # find the next containing bzrdir
            try:
                found_bzrdir = self.open_containing_from_transport(
                    next_transport)[0]
            except errors.NotBranchError:
                return None

    def find_repository(self):
        """Find the repository that should be used.

        This does not require a branch as we use it to find the repo for
        new branches as well as to hook existing branches up to their
        repository.
        """
        def usable_repository(found_bzrdir):
            # does it have a repository ?
            try:
                repository = found_bzrdir.open_repository()
            except errors.NoRepositoryPresent:
                return None, False
            if found_bzrdir.user_url == self.user_url:
                return repository, True
            elif repository.is_shared():
                return repository, True
            else:
                return None, True

        found_repo = self._find_containing(usable_repository)
        if found_repo is None:
            raise errors.NoRepositoryPresent(self)
        return found_repo

    def _find_creation_modes(self):
        """Determine the appropriate modes for files and directories.

        They're always set to be consistent with the base directory,
        assuming that this transport allows setting modes.
        """
        # TODO: Do we need or want an option (maybe a config setting) to turn
        # this off or override it for particular locations? -- mbp 20080512
        if self._mode_check_done:
            return
        self._mode_check_done = True
        try:
            st = self.transport.stat('.')
        except errors.TransportNotPossible:
            self._dir_mode = None
            self._file_mode = None
        else:
            # Check the directory mode, but also make sure the created
            # directories and files are read-write for this user. This is
            # mostly a workaround for filesystems which lie about being able to
            # write to a directory (cygwin & win32)
            if (st.st_mode & 0o7777 == 00000):
                # FTP allows stat but does not return dir/file modes
                self._dir_mode = None
                self._file_mode = None
            else:
                self._dir_mode = (st.st_mode & 0o7777) | 0o0700
                # Remove the sticky and execute bits for files
                self._file_mode = self._dir_mode & ~0o7111

    def _get_file_mode(self):
        """Return Unix mode for newly created files, or None.
        """
        if not self._mode_check_done:
            self._find_creation_modes()
        return self._file_mode

    def _get_dir_mode(self):
        """Return Unix mode for newly created directories, or None.
        """
        if not self._mode_check_done:
            self._find_creation_modes()
        return self._dir_mode

    def get_config(self):
        """Get configuration for this BzrDir."""
        return config.BzrDirConfig(self)

    def _get_config(self):
        """By default, no configuration is available."""
        return None

    def __init__(self, _transport, _format):
        """Initialize a Bzr control dir object.

        Only really common logic should reside here, concrete classes should be
        made with varying behaviours.

        :param _format: the format that is creating this BzrDir instance.
        :param _transport: the transport this dir is based at.
        """
        self._format = _format
        # these are also under the more standard names of
        # control_transport and user_transport
        self.transport = _transport.clone('.bzr')
        self.root_transport = _transport
        self._mode_check_done = False

    @property
    def user_transport(self):
        return self.root_transport

    @property
    def control_transport(self):
        return self.transport

    def is_control_filename(self, filename):
        """True if filename is the name of a path which is reserved for bzrdir's.

        :param filename: A filename within the root transport of this bzrdir.

        This is true IF and ONLY IF the filename is part of the namespace
        reserved for bzr control dirs. Currently this is the '.bzr' directory
        in the root of the root_transport.
        """
        # this might be better on the BzrDirFormat class because it refers to
        # all the possible bzrdir disk formats.
        # This method is tested via the workingtree is_control_filename tests-
        # it was extracted from WorkingTree.is_control_filename. If the
        # method's contract is extended beyond the current trivial
        # implementation, please add new tests for it to the appropriate place.
        return filename == '.bzr' or filename.startswith('.bzr/')

    def _cloning_metadir(self):
        """Produce a metadir suitable for cloning with.

        :returns: (destination_bzrdir_format, source_repository)
        """
        result_format = self._format.__class__()
        try:
            try:
                branch = self.open_branch(ignore_fallbacks=True)
                source_repository = branch.repository
                result_format._branch_format = branch._format
            except errors.NotBranchError:
                source_repository = self.open_repository()
        except errors.NoRepositoryPresent:
            source_repository = None
        else:
            # XXX TODO: This isinstance is here because we have not implemented
            # the fix recommended in bug # 103195 - to delegate this choice the
            # repository itself.
            repo_format = source_repository._format
            if isinstance(repo_format, remote.RemoteRepositoryFormat):
                source_repository._ensure_real()
                repo_format = source_repository._real_repository._format
            result_format.repository_format = repo_format
        try:
            # TODO: Couldn't we just probe for the format in these cases,
            # rather than opening the whole tree?  It would be a little
            # faster. mbp 20070401
            tree = self.open_workingtree(recommend_upgrade=False)
        except (errors.NoWorkingTree, errors.NotLocalUrl):
            result_format.workingtree_format = None
        else:
            result_format.workingtree_format = tree._format.__class__()
        return result_format, source_repository

    def cloning_metadir(self, require_stacking=False):
        """Produce a metadir suitable for cloning or sprouting with.

        These operations may produce workingtrees (yes, even though they're
        "cloning" something that doesn't have a tree), so a viable workingtree
        format must be selected.

        :require_stacking: If True, non-stackable formats will be upgraded
            to similar stackable formats.
        :returns: a ControlDirFormat with all component formats either set
            appropriately or set to None if that component should not be
            created.
        """
        format, repository = self._cloning_metadir()
        if format._workingtree_format is None:
            # No tree in self.
            if repository is None:
                # No repository either
                return format
            # We have a repository, so set a working tree? (Why? This seems to
            # contradict the stated return value in the docstring).
            tree_format = (
                repository._format._matchingcontroldir.workingtree_format)
            format.workingtree_format = tree_format.__class__()
        if require_stacking:
            format.require_stacking()
        return format

    def get_branch_transport(self, branch_format, name=None):
        """Get the transport for use by branch format in this BzrDir.

        Note that bzr dirs that do not support format strings will raise
        IncompatibleFormat if the branch format they are given has
        a format string, and vice versa.

        If branch_format is None, the transport is returned with no
        checking. If it is not None, then the returned transport is
        guaranteed to point to an existing directory ready for use.
        """
        raise NotImplementedError(self.get_branch_transport)

    def get_repository_transport(self, repository_format):
        """Get the transport for use by repository format in this BzrDir.

        Note that bzr dirs that do not support format strings will raise
        IncompatibleFormat if the repository format they are given has
        a format string, and vice versa.

        If repository_format is None, the transport is returned with no
        checking. If it is not None, then the returned transport is
        guaranteed to point to an existing directory ready for use.
        """
        raise NotImplementedError(self.get_repository_transport)

    def get_workingtree_transport(self, tree_format):
        """Get the transport for use by workingtree format in this BzrDir.

        Note that bzr dirs that do not support format strings will raise
        IncompatibleFormat if the workingtree format they are given has a
        format string, and vice versa.

        If workingtree_format is None, the transport is returned with no
        checking. If it is not None, then the returned transport is
        guaranteed to point to an existing directory ready for use.
        """
        raise NotImplementedError(self.get_workingtree_transport)

    @classmethod
    def create(cls, base, format=None, possible_transports=None):
        """Create a new BzrDir at the url 'base'.

        :param format: If supplied, the format of branch to create.  If not
            supplied, the default is used.
        :param possible_transports: If supplied, a list of transports that
            can be reused to share a remote connection.
        """
        if cls is not BzrDir:
            raise AssertionError("BzrDir.create always creates the "
                                 "default format, not one of %r" % cls)
        return controldir.ControlDir.create(
            base, format=format, possible_transports=possible_transports)

    def __repr__(self):
        return "<%s at %r>" % (self.__class__.__name__, self.user_url)

    def update_feature_flags(self, updated_flags):
        """Update the features required by this bzrdir.

        :param updated_flags: Dictionary mapping feature names to necessities
            A necessity can be None to indicate the feature should be removed
        """
        self.control_files.lock_write()
        try:
            self._format._update_feature_flags(updated_flags)
            self.transport.put_bytes('branch-format', self._format.as_string())
        finally:
            self.control_files.unlock()


class BzrDirMeta1(BzrDir):
    """A .bzr meta version 1 control object.

    This is the first control object where the
    individual aspects are really split out: there are separate repository,
    workingtree and branch subdirectories and any subset of the three can be
    present within a BzrDir.
    """

    def _get_branch_path(self, name):
        """Obtain the branch path to use.

        This uses the API specified branch name first, and then falls back to
        the branch name specified in the URL. If neither of those is specified,
        it uses the default branch.

        :param name: Optional branch name to use
        :return: Relative path to branch
        """
        if name == "":
            return 'branch'
        return urlutils.join('branches', urlutils.escape(name))

    def _read_branch_list(self):
        """Read the branch list.

        :return: List of branch names.
        """
        try:
            f = self.control_transport.get('branch-list')
        except errors.NoSuchFile:
            return []

        ret = []
        try:
            for name in f:
                ret.append(name.rstrip(b"\n").decode('utf-8'))
        finally:
            f.close()
        return ret

    def _write_branch_list(self, branches):
        """Write out the branch list.

        :param branches: List of utf-8 branch names to write
        """
        self.transport.put_bytes(
            'branch-list',
            b"".join([name.encode('utf-8') + b"\n" for name in branches]))

    def __init__(self, _transport, _format):
        super(BzrDirMeta1, self).__init__(_transport, _format)
        self.control_files = lockable_files.LockableFiles(
            self.control_transport, self._format._lock_file_name,
            self._format._lock_class)

    def can_convert_format(self):
        """See BzrDir.can_convert_format()."""
        return True

    def create_branch(self, name=None, repository=None,
                      append_revisions_only=None):
        """See ControlDir.create_branch."""
        if name is None:
            name = self._get_selected_branch()
        return self._format.get_branch_format().initialize(
            self, name=name, repository=repository,
            append_revisions_only=append_revisions_only)

    def destroy_branch(self, name=None):
        """See ControlDir.destroy_branch."""
        if name is None:
            name = self._get_selected_branch()
        path = self._get_branch_path(name)
        if name != u"":
            self.control_files.lock_write()
            try:
                branches = self._read_branch_list()
                try:
                    branches.remove(name)
                except ValueError:
                    raise errors.NotBranchError(name)
                self._write_branch_list(branches)
            finally:
                self.control_files.unlock()
        try:
            self.transport.delete_tree(path)
        except errors.NoSuchFile:
            raise errors.NotBranchError(
                path=urlutils.join(self.transport.base, path), controldir=self)

    def create_repository(self, shared=False):
        """See BzrDir.create_repository."""
        return self._format.repository_format.initialize(self, shared)

    def destroy_repository(self):
        """See BzrDir.destroy_repository."""
        try:
            self.transport.delete_tree('repository')
        except errors.NoSuchFile:
            raise errors.NoRepositoryPresent(self)

    def create_workingtree(self, revision_id=None, from_branch=None,
                           accelerator_tree=None, hardlink=False):
        """See BzrDir.create_workingtree."""
        return self._format.workingtree_format.initialize(
            self, revision_id, from_branch=from_branch,
            accelerator_tree=accelerator_tree, hardlink=hardlink)

    def destroy_workingtree(self):
        """See BzrDir.destroy_workingtree."""
        wt = self.open_workingtree(recommend_upgrade=False)
        repository = wt.branch.repository
        empty = repository.revision_tree(_mod_revision.NULL_REVISION)
        # We ignore the conflicts returned by wt.revert since we're about to
        # delete the wt metadata anyway, all that should be left here are
        # detritus. But see bug #634470 about subtree .bzr dirs.
        wt.revert(old_tree=empty)
        self.destroy_workingtree_metadata()

    def destroy_workingtree_metadata(self):
        self.transport.delete_tree('checkout')

    def find_branch_format(self, name=None):
        """Find the branch 'format' for this bzrdir.

        This might be a synthetic object for e.g. RemoteBranch and SVN.
        """
        from .branch import BranchFormatMetadir
        return BranchFormatMetadir.find_format(self, name=name)

    def _get_mkdir_mode(self):
        """Figure out the mode to use when creating a bzrdir subdir."""
        temp_control = lockable_files.LockableFiles(
            self.transport, '', lockable_files.TransportLock)
        return temp_control._dir_mode

    def get_branch_reference(self, name=None):
        """See BzrDir.get_branch_reference()."""
        from .branch import BranchFormatMetadir
        format = BranchFormatMetadir.find_format(self, name=name)
        return format.get_reference(self, name=name)

    def set_branch_reference(self, target_branch, name=None):
        format = _mod_bzrbranch.BranchReferenceFormat()
        if (self.control_url == target_branch.controldir.control_url
                and name == target_branch.name):
            raise controldir.BranchReferenceLoop(target_branch)
        return format.initialize(self, target_branch=target_branch, name=name)

    def get_branch_transport(self, branch_format, name=None):
        """See BzrDir.get_branch_transport()."""
        if name is None:
            name = self._get_selected_branch()
        path = self._get_branch_path(name)
        # XXX: this shouldn't implicitly create the directory if it's just
        # promising to get a transport -- mbp 20090727
        if branch_format is None:
            return self.transport.clone(path)
        try:
            branch_format.get_format_string()
        except NotImplementedError:
            raise errors.IncompatibleFormat(branch_format, self._format)
        if name != "":
            branches = self._read_branch_list()
            if name not in branches:
                self.control_files.lock_write()
                try:
                    branches = self._read_branch_list()
                    dirname = urlutils.dirname(name)
                    if dirname != u"" and dirname in branches:
                        raise errors.ParentBranchExists(name)
                    child_branches = [
                        b.startswith(name + u"/") for b in branches]
                    if any(child_branches):
                        raise errors.AlreadyBranchError(name)
                    branches.append(name)
                    self._write_branch_list(branches)
                finally:
                    self.control_files.unlock()
        branch_transport = self.transport.clone(path)
        mode = self._get_mkdir_mode()
        branch_transport.create_prefix(mode=mode)
        try:
            self.transport.mkdir(path, mode=mode)
        except errors.FileExists:
            pass
        return self.transport.clone(path)

    def get_repository_transport(self, repository_format):
        """See BzrDir.get_repository_transport()."""
        if repository_format is None:
            return self.transport.clone('repository')
        try:
            repository_format.get_format_string()
        except NotImplementedError:
            raise errors.IncompatibleFormat(repository_format, self._format)
        try:
            self.transport.mkdir('repository', mode=self._get_mkdir_mode())
        except errors.FileExists:
            pass
        return self.transport.clone('repository')

    def get_workingtree_transport(self, workingtree_format):
        """See BzrDir.get_workingtree_transport()."""
        if workingtree_format is None:
            return self.transport.clone('checkout')
        try:
            workingtree_format.get_format_string()
        except NotImplementedError:
            raise errors.IncompatibleFormat(workingtree_format, self._format)
        try:
            self.transport.mkdir('checkout', mode=self._get_mkdir_mode())
        except errors.FileExists:
            pass
        return self.transport.clone('checkout')

    def get_branches(self):
        """See ControlDir.get_branches."""
        ret = {}
        try:
            ret[""] = self.open_branch(name="")
        except (errors.NotBranchError, errors.NoRepositoryPresent):
            pass

        for name in self._read_branch_list():
            ret[name] = self.open_branch(name=name)

        return ret

    def has_workingtree(self):
        """Tell if this bzrdir contains a working tree.

        Note: if you're going to open the working tree, you should just go
        ahead and try, and not ask permission first.
        """
        from .workingtree import WorkingTreeFormatMetaDir
        try:
            WorkingTreeFormatMetaDir.find_format_string(self)
        except errors.NoWorkingTree:
            return False
        return True

    def needs_format_conversion(self, format):
        """See BzrDir.needs_format_conversion()."""
        if (not isinstance(self._format, format.__class__)
                or self._format.get_format_string() != format.get_format_string()):
            # it is not a meta dir format, conversion is needed.
            return True
        # we might want to push this down to the repository?
        try:
            if not isinstance(self.open_repository()._format,
                              format.repository_format.__class__):
                # the repository needs an upgrade.
                return True
        except errors.NoRepositoryPresent:
            pass
        for branch in self.list_branches():
            if not isinstance(branch._format,
                              format.get_branch_format().__class__):
                # the branch needs an upgrade.
                return True
        try:
            my_wt = self.open_workingtree(recommend_upgrade=False)
            if not isinstance(my_wt._format,
                              format.workingtree_format.__class__):
                # the workingtree needs an upgrade.
                return True
        except (errors.NoWorkingTree, errors.NotLocalUrl):
            pass
        return False

    def open_branch(self, name=None, unsupported=False,
                    ignore_fallbacks=False, possible_transports=None):
        """See ControlDir.open_branch."""
        if name is None:
            name = self._get_selected_branch()
        format = self.find_branch_format(name=name)
        format.check_support_status(unsupported)
        if possible_transports is None:
            possible_transports = []
        else:
            possible_transports = list(possible_transports)
        possible_transports.append(self.root_transport)
        return format.open(self, name=name,
                           _found=True, ignore_fallbacks=ignore_fallbacks,
                           possible_transports=possible_transports)

    def open_repository(self, unsupported=False):
        """See BzrDir.open_repository."""
        from .repository import RepositoryFormatMetaDir
        format = RepositoryFormatMetaDir.find_format(self)
        format.check_support_status(unsupported)
        return format.open(self, _found=True)

    def open_workingtree(self, unsupported=False,
                         recommend_upgrade=True):
        """See BzrDir.open_workingtree."""
        from .workingtree import WorkingTreeFormatMetaDir
        format = WorkingTreeFormatMetaDir.find_format(self)
        format.check_support_status(unsupported, recommend_upgrade,
                                    basedir=self.root_transport.base)
        return format.open(self, _found=True)

    def _get_config(self):
        return config.TransportConfig(self.transport, 'control.conf')


class BzrFormat(object):
    """Base class for all formats of things living in metadirs.

    This class manages the format string that is stored in the 'format'
    or 'branch-format' file.

    All classes for (branch-, repository-, workingtree-) formats that
    live in meta directories and have their own 'format' file
    (i.e. different from .bzr/branch-format) derive from this class,
    as well as the relevant base class for their kind
    (BranchFormat, WorkingTreeFormat, RepositoryFormat).

    Each format is identified by a "format" or "branch-format" file with a
    single line containing the base format name and then an optional list of
    feature flags.

    Feature flags are supported as of bzr 2.5. Setting feature flags on formats
    will render them inaccessible to older versions of bzr.

    :ivar features: Dictionary mapping feature names to their necessity
    """

    _present_features = set()

    def __init__(self):
        self.features = {}

    @classmethod
    def register_feature(cls, name):
        """Register a feature as being present.

        :param name: Name of the feature
        """
        if b" " in name:
            raise ValueError("spaces are not allowed in feature names")
        if name in cls._present_features:
            raise FeatureAlreadyRegistered(name)
        cls._present_features.add(name)

    @classmethod
    def unregister_feature(cls, name):
        """Unregister a feature."""
        cls._present_features.remove(name)

    def check_support_status(self, allow_unsupported, recommend_upgrade=True,
                             basedir=None):
        for name, necessity in viewitems(self.features):
            if name in self._present_features:
                continue
            if necessity == b"optional":
                mutter("ignoring optional missing feature %s", name)
                continue
            elif necessity == b"required":
                raise MissingFeature(name)
            else:
                mutter("treating unknown necessity as require for %s",
                       name)
                raise MissingFeature(name)

    @classmethod
    def get_format_string(cls):
        """Return the ASCII format string that identifies this format."""
        raise NotImplementedError(cls.get_format_string)

    @classmethod
    def from_string(cls, text):
        format_string = cls.get_format_string()
        if not text.startswith(format_string):
            raise AssertionError(
                "Invalid format header %r for %r" % (text, cls))
        lines = text[len(format_string):].splitlines()
        ret = cls()
        for lineno, line in enumerate(lines):
            try:
                (necessity, feature) = line.split(b" ", 1)
            except ValueError:
                raise errors.ParseFormatError(format=cls, lineno=lineno + 2,
                                              line=line, text=text)
            ret.features[feature] = necessity
        return ret

    def as_string(self):
        """Return the string representation of this format.
        """
        lines = [self.get_format_string()]
        lines.extend([(item[1] + b" " + item[0] + b"\n")
                      for item in sorted(viewitems(self.features))])
        return b"".join(lines)

    @classmethod
    def _find_format(klass, registry, kind, format_string):
        try:
            first_line = format_string[:format_string.index(b"\n") + 1]
        except ValueError:
            first_line = format_string
        try:
            cls = registry.get(first_line)
        except KeyError:
            raise errors.UnknownFormatError(format=first_line, kind=kind)
        return cls.from_string(format_string)

    def network_name(self):
        """A simple byte string uniquely identifying this format for RPC calls.

        Metadir branch formats use their format string.
        """
        return self.as_string()

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

    def _update_feature_flags(self, updated_flags):
        """Update the feature flags in this format.

        :param updated_flags: Updated feature flags
        """
        for name, necessity in updated_flags.items():
            if necessity is None:
                try:
                    del self.features[name]
                except KeyError:
                    pass
            else:
                self.features[name] = necessity


class BzrDirFormat(BzrFormat, controldir.ControlDirFormat):
    """ControlDirFormat base class for .bzr/ directories.

    Formats are placed in a dict by their format string for reference
    during bzrdir opening. These should be subclasses of BzrDirFormat
    for consistency.

    Once a format is deprecated, just deprecate the initialize and open
    methods on the format class. Do not deprecate the object, as the
    object will be created every system load.
    """

    _lock_file_name = 'branch-lock'

    # _lock_class must be set in subclasses to the lock type, typ.
    # TransportLock or LockDir

    def initialize_on_transport(self, transport):
        """Initialize a new bzrdir in the base directory of a Transport."""
        try:
            # can we hand off the request to the smart server rather than using
            # vfs calls?
            client_medium = transport.get_smart_medium()
        except errors.NoSmartMedium:
            return self._initialize_on_transport_vfs(transport)
        else:
            # Current RPC's only know how to create bzr metadir1 instances, so
            # we still delegate to vfs methods if the requested format is not a
            # metadir1
            if not isinstance(self, BzrDirMetaFormat1):
                return self._initialize_on_transport_vfs(transport)
            from .remote import RemoteBzrDirFormat
            remote_format = RemoteBzrDirFormat()
            self._supply_sub_formats_to(remote_format)
            return remote_format.initialize_on_transport(transport)

    def initialize_on_transport_ex(self, transport, use_existing_dir=False,
                                   create_prefix=False, force_new_repo=False, stacked_on=None,
                                   stack_on_pwd=None, repo_format_name=None, make_working_trees=None,
                                   shared_repo=False, vfs_only=False):
        """Create this format on transport.

        The directory to initialize will be created.

        :param force_new_repo: Do not use a shared repository for the target,
                               even if one is available.
        :param create_prefix: Create any missing directories leading up to
            to_transport.
        :param use_existing_dir: Use an existing directory if one exists.
        :param stacked_on: A url to stack any created branch on, None to follow
            any target stacking policy.
        :param stack_on_pwd: If stack_on is relative, the location it is
            relative to.
        :param repo_format_name: If non-None, a repository will be
            made-or-found. Should none be found, or if force_new_repo is True
            the repo_format_name is used to select the format of repository to
            create.
        :param make_working_trees: Control the setting of make_working_trees
            for a new shared repository when one is made. None to use whatever
            default the format has.
        :param shared_repo: Control whether made repositories are shared or
            not.
        :param vfs_only: If True do not attempt to use a smart server
        :return: repo, controldir, require_stacking, repository_policy. repo is
            None if none was created or found, bzrdir is always valid.
            require_stacking is the result of examining the stacked_on
            parameter and any stacking policy found for the target.
        """
        if not vfs_only:
            # Try to hand off to a smart server
            try:
                client_medium = transport.get_smart_medium()
            except errors.NoSmartMedium:
                pass
            else:
                from .remote import RemoteBzrDirFormat
                # TODO: lookup the local format from a server hint.
                remote_dir_format = RemoteBzrDirFormat()
                remote_dir_format._network_name = self.network_name()
                self._supply_sub_formats_to(remote_dir_format)
                return remote_dir_format.initialize_on_transport_ex(transport,
                                                                    use_existing_dir=use_existing_dir, create_prefix=create_prefix,
                                                                    force_new_repo=force_new_repo, stacked_on=stacked_on,
                                                                    stack_on_pwd=stack_on_pwd, repo_format_name=repo_format_name,
                                                                    make_working_trees=make_working_trees, shared_repo=shared_repo)
        # XXX: Refactor the create_prefix/no_create_prefix code into a
        #      common helper function
        # The destination may not exist - if so make it according to policy.

        def make_directory(transport):
            transport.mkdir('.')
            return transport

        def redirected(transport, e, redirection_notice):
            note(redirection_notice)
            return transport._redirected_to(e.source, e.target)
        try:
            transport = do_catching_redirections(make_directory, transport,
                                                 redirected)
        except errors.FileExists:
            if not use_existing_dir:
                raise
        except errors.NoSuchFile:
            if not create_prefix:
                raise
            transport.create_prefix()

        require_stacking = (stacked_on is not None)
        # Now the target directory exists, but doesn't have a .bzr
        # directory. So we need to create it, along with any work to create
        # all of the dependent branches, etc.

        result = self.initialize_on_transport(transport)
        if repo_format_name:
            try:
                # use a custom format
                result._format.repository_format = \
                    repository.network_format_registry.get(repo_format_name)
            except AttributeError:
                # The format didn't permit it to be set.
                pass
            # A repository is desired, either in-place or shared.
            repository_policy = result.determine_repository_policy(
                force_new_repo, stacked_on, stack_on_pwd,
                require_stacking=require_stacking)
            result_repo, is_new_repo = repository_policy.acquire_repository(
                make_working_trees, shared_repo)
            if not require_stacking and repository_policy._require_stacking:
                require_stacking = True
                result._format.require_stacking()
            result_repo.lock_write()
        else:
            result_repo = None
            repository_policy = None
        return result_repo, result, require_stacking, repository_policy

    def _initialize_on_transport_vfs(self, transport):
        """Initialize a new bzrdir using VFS calls.

        :param transport: The transport to create the .bzr directory in.
        :return: A
        """
        # Since we are creating a .bzr directory, inherit the
        # mode from the root directory
        temp_control = lockable_files.LockableFiles(transport,
                                                    '', lockable_files.TransportLock)
        try:
            temp_control._transport.mkdir('.bzr',
                                          # FIXME: RBC 20060121 don't peek under
                                          # the covers
                                          mode=temp_control._dir_mode)
        except errors.FileExists:
            raise errors.AlreadyControlDirError(transport.base)
        if sys.platform == 'win32' and isinstance(transport, local.LocalTransport):
            win32utils.set_file_attr_hidden(transport._abspath('.bzr'))
        file_mode = temp_control._file_mode
        del temp_control
        bzrdir_transport = transport.clone('.bzr')
        utf8_files = [('README',
                       b"This is a Bazaar control directory.\n"
                       b"Do not change any files in this directory.\n"
                       b"See http://bazaar.canonical.com/ for more information about Bazaar.\n"),
                      ('branch-format', self.as_string()),
                      ]
        # NB: no need to escape relative paths that are url safe.
        control_files = lockable_files.LockableFiles(bzrdir_transport,
                                                     self._lock_file_name, self._lock_class)
        control_files.create_lock()
        control_files.lock_write()
        try:
            for (filename, content) in utf8_files:
                bzrdir_transport.put_bytes(filename, content,
                                           mode=file_mode)
        finally:
            control_files.unlock()
        return self.open(transport, _found=True)

    def open(self, transport, _found=False):
        """Return an instance of this format for the dir transport points at.

        _found is a private parameter, do not use it.
        """
        if not _found:
            found_format = controldir.ControlDirFormat.find_format(transport)
            if not isinstance(found_format, self.__class__):
                raise AssertionError("%s was asked to open %s, but it seems to need "
                                     "format %s"
                                     % (self, transport, found_format))
            # Allow subclasses - use the found format.
            self._supply_sub_formats_to(found_format)
            return found_format._open(transport)
        return self._open(transport)

    def _open(self, transport):
        """Template method helper for opening BzrDirectories.

        This performs the actual open and any additional logic or parameter
        passing.
        """
        raise NotImplementedError(self._open)

    def _supply_sub_formats_to(self, other_format):
        """Give other_format the same values for sub formats as this has.

        This method is expected to be used when parameterising a
        RemoteBzrDirFormat instance with the parameters from a
        BzrDirMetaFormat1 instance.

        :param other_format: other_format is a format which should be
            compatible with whatever sub formats are supported by self.
        :return: None.
        """
        other_format.features = dict(self.features)

    def supports_transport(self, transport):
        # bzr formats can be opened over all known transports
        return True

    def check_support_status(self, allow_unsupported, recommend_upgrade=True,
                             basedir=None):
        controldir.ControlDirFormat.check_support_status(self,
                                                         allow_unsupported=allow_unsupported, recommend_upgrade=recommend_upgrade,
                                                         basedir=basedir)
        BzrFormat.check_support_status(self, allow_unsupported=allow_unsupported,
                                       recommend_upgrade=recommend_upgrade, basedir=basedir)


class BzrDirMetaFormat1(BzrDirFormat):
    """Bzr meta control format 1

    This is the first format with split out working tree, branch and repository
    disk storage.

    It has:

    - Format 3 working trees [optional]
    - Format 5 branches [optional]
    - Format 7 repositories [optional]
    """

    _lock_class = lockdir.LockDir

    fixed_components = False

    colocated_branches = True

    def __init__(self):
        BzrDirFormat.__init__(self)
        self._workingtree_format = None
        self._branch_format = None
        self._repository_format = None

    def __eq__(self, other):
        if other.__class__ is not self.__class__:
            return False
        if other.repository_format != self.repository_format:
            return False
        if other.workingtree_format != self.workingtree_format:
            return False
        if other.features != self.features:
            return False
        return True

    def __ne__(self, other):
        return not self == other

    def get_branch_format(self):
        if self._branch_format is None:
            from .branch import format_registry as branch_format_registry
            self._branch_format = branch_format_registry.get_default()
        return self._branch_format

    def set_branch_format(self, format):
        self._branch_format = format

    def require_stacking(self, stack_on=None, possible_transports=None,
                         _skip_repo=False):
        """We have a request to stack, try to ensure the formats support it.

        :param stack_on: If supplied, it is the URL to a branch that we want to
            stack on. Check to see if that format supports stacking before
            forcing an upgrade.
        """
        # Stacking is desired. requested by the target, but does the place it
        # points at support stacking? If it doesn't then we should
        # not implicitly upgrade. We check this here.
        new_repo_format = None
        new_branch_format = None

        # a bit of state for get_target_branch so that we don't try to open it
        # 2 times, for both repo *and* branch
        target = [None, False, None]  # target_branch, checked, upgrade anyway

        def get_target_branch():
            if target[1]:
                # We've checked, don't check again
                return target
            if stack_on is None:
                # No target format, that means we want to force upgrading
                target[:] = [None, True, True]
                return target
            try:
                target_dir = BzrDir.open(stack_on,
                                         possible_transports=possible_transports)
            except errors.NotBranchError:
                # Nothing there, don't change formats
                target[:] = [None, True, False]
                return target
            except errors.JailBreak:
                # JailBreak, JFDI and upgrade anyway
                target[:] = [None, True, True]
                return target
            try:
                target_branch = target_dir.open_branch()
            except errors.NotBranchError:
                # No branch, don't upgrade formats
                target[:] = [None, True, False]
                return target
            target[:] = [target_branch, True, False]
            return target

        if (not _skip_repo
                and not self.repository_format.supports_external_lookups):
            # We need to upgrade the Repository.
            target_branch, _, do_upgrade = get_target_branch()
            if target_branch is None:
                # We don't have a target branch, should we upgrade anyway?
                if do_upgrade:
                    # stack_on is inaccessible, JFDI.
                    # TODO: bad monkey, hard-coded formats...
                    if self.repository_format.rich_root_data:
                        new_repo_format = knitpack_repo.RepositoryFormatKnitPack5RichRoot()
                    else:
                        new_repo_format = knitpack_repo.RepositoryFormatKnitPack5()
            else:
                # If the target already supports stacking, then we know the
                # project is already able to use stacking, so auto-upgrade
                # for them
                new_repo_format = target_branch.repository._format
                if not new_repo_format.supports_external_lookups:
                    # target doesn't, source doesn't, so don't auto upgrade
                    # repo
                    new_repo_format = None
            if new_repo_format is not None:
                self.repository_format = new_repo_format
                note(gettext('Source repository format does not support stacking,'
                             ' using format:\n  %s'),
                     new_repo_format.get_format_description())

        if not self.get_branch_format().supports_stacking():
            # We just checked the repo, now lets check if we need to
            # upgrade the branch format
            target_branch, _, do_upgrade = get_target_branch()
            if target_branch is None:
                if do_upgrade:
                    # TODO: bad monkey, hard-coded formats...
                    from .branch import BzrBranchFormat7
                    new_branch_format = BzrBranchFormat7()
            else:
                new_branch_format = target_branch._format
                if not new_branch_format.supports_stacking():
                    new_branch_format = None
            if new_branch_format is not None:
                # Does support stacking, use its format.
                self.set_branch_format(new_branch_format)
                note(gettext('Source branch format does not support stacking,'
                             ' using format:\n  %s'),
                     new_branch_format.get_format_description())

    def get_converter(self, format=None):
        """See BzrDirFormat.get_converter()."""
        if format is None:
            format = BzrDirFormat.get_default_format()
        if (isinstance(self, BzrDirMetaFormat1)
                and isinstance(format, BzrDirMetaFormat1Colo)):
            return ConvertMetaToColo(format)
        if (isinstance(self, BzrDirMetaFormat1Colo)
                and isinstance(format, BzrDirMetaFormat1)):
            return ConvertMetaToColo(format)
        if not isinstance(self, format.__class__):
            # converting away from metadir is not implemented
            raise NotImplementedError(self.get_converter)
        return ConvertMetaToMeta(format)

    @classmethod
    def get_format_string(cls):
        """See BzrDirFormat.get_format_string()."""
        return b"Bazaar-NG meta directory, format 1\n"

    def get_format_description(self):
        """See BzrDirFormat.get_format_description()."""
        return "Meta directory format 1"

    def _open(self, transport):
        """See BzrDirFormat._open."""
        # Create a new format instance because otherwise initialisation of new
        # metadirs share the global default format object leading to alias
        # problems.
        format = BzrDirMetaFormat1()
        self._supply_sub_formats_to(format)
        return BzrDirMeta1(transport, format)

    def __return_repository_format(self):
        """Circular import protection."""
        if self._repository_format:
            return self._repository_format
        from .repository import format_registry
        return format_registry.get_default()

    def _set_repository_format(self, value):
        """Allow changing the repository format for metadir formats."""
        self._repository_format = value

    repository_format = property(__return_repository_format,
                                 _set_repository_format)

    def _supply_sub_formats_to(self, other_format):
        """Give other_format the same values for sub formats as this has.

        This method is expected to be used when parameterising a
        RemoteBzrDirFormat instance with the parameters from a
        BzrDirMetaFormat1 instance.

        :param other_format: other_format is a format which should be
            compatible with whatever sub formats are supported by self.
        :return: None.
        """
        super(BzrDirMetaFormat1, self)._supply_sub_formats_to(other_format)
        if getattr(self, '_repository_format', None) is not None:
            other_format.repository_format = self.repository_format
        if self._branch_format is not None:
            other_format._branch_format = self._branch_format
        if self._workingtree_format is not None:
            other_format.workingtree_format = self.workingtree_format

    def __get_workingtree_format(self):
        if self._workingtree_format is None:
            from .workingtree import (
                format_registry as wt_format_registry,
                )
            self._workingtree_format = wt_format_registry.get_default()
        return self._workingtree_format

    def __set_workingtree_format(self, wt_format):
        self._workingtree_format = wt_format

    def __repr__(self):
        return "<%r>" % (self.__class__.__name__,)

    workingtree_format = property(__get_workingtree_format,
                                  __set_workingtree_format)


class BzrDirMetaFormat1Colo(BzrDirMetaFormat1):
    """BzrDirMeta1 format with support for colocated branches."""

    colocated_branches = True

    @classmethod
    def get_format_string(cls):
        """See BzrDirFormat.get_format_string()."""
        return b"Bazaar meta directory, format 1 (with colocated branches)\n"

    def get_format_description(self):
        """See BzrDirFormat.get_format_description()."""
        return "Meta directory format 1 with support for colocated branches"

    def _open(self, transport):
        """See BzrDirFormat._open."""
        # Create a new format instance because otherwise initialisation of new
        # metadirs share the global default format object leading to alias
        # problems.
        format = BzrDirMetaFormat1Colo()
        self._supply_sub_formats_to(format)
        return BzrDirMeta1(transport, format)


class ConvertMetaToMeta(controldir.Converter):
    """Converts the components of metadirs."""

    def __init__(self, target_format):
        """Create a metadir to metadir converter.

        :param target_format: The final metadir format that is desired.
        """
        self.target_format = target_format

    def convert(self, to_convert, pb):
        """See Converter.convert()."""
        self.controldir = to_convert
        self.pb = ui.ui_factory.nested_progress_bar()
        self.count = 0
        self.total = 1
        self.step('checking repository format')
        try:
            repo = self.controldir.open_repository()
        except errors.NoRepositoryPresent:
            pass
        else:
            repo_fmt = self.target_format.repository_format
            if not isinstance(repo._format, repo_fmt.__class__):
                from ..repository import CopyConverter
                ui.ui_factory.note(gettext('starting repository conversion'))
                if not repo_fmt.supports_overriding_transport:
                    raise AssertionError(
                        "Repository in metadir does not support "
                        "overriding transport")
                converter = CopyConverter(self.target_format.repository_format)
                converter.convert(repo, pb)
        for branch in self.controldir.list_branches():
            # TODO: conversions of Branch and Tree should be done by
            # InterXFormat lookups/some sort of registry.
            # Avoid circular imports
            old = branch._format.__class__
            new = self.target_format.get_branch_format().__class__
            while old != new:
                if (old == fullhistorybranch.BzrBranchFormat5
                    and new in (_mod_bzrbranch.BzrBranchFormat6,
                                _mod_bzrbranch.BzrBranchFormat7,
                                _mod_bzrbranch.BzrBranchFormat8)):
                    branch_converter = _mod_bzrbranch.Converter5to6()
                elif (old == _mod_bzrbranch.BzrBranchFormat6
                      and new in (_mod_bzrbranch.BzrBranchFormat7,
                                  _mod_bzrbranch.BzrBranchFormat8)):
                    branch_converter = _mod_bzrbranch.Converter6to7()
                elif (old == _mod_bzrbranch.BzrBranchFormat7
                      and new is _mod_bzrbranch.BzrBranchFormat8):
                    branch_converter = _mod_bzrbranch.Converter7to8()
                else:
                    raise errors.BadConversionTarget("No converter", new,
                                                     branch._format)
                branch_converter.convert(branch)
                branch = self.controldir.open_branch()
                old = branch._format.__class__
        try:
            tree = self.controldir.open_workingtree(recommend_upgrade=False)
        except (errors.NoWorkingTree, errors.NotLocalUrl):
            pass
        else:
            # TODO: conversions of Branch and Tree should be done by
            # InterXFormat lookups
            if (isinstance(tree, workingtree_3.WorkingTree3)
                and not isinstance(tree, workingtree_4.DirStateWorkingTree)
                and isinstance(self.target_format.workingtree_format,
                               workingtree_4.DirStateWorkingTreeFormat)):
                workingtree_4.Converter3to4().convert(tree)
            if (isinstance(tree, workingtree_4.DirStateWorkingTree)
                and not isinstance(tree, workingtree_4.WorkingTree5)
                and isinstance(self.target_format.workingtree_format,
                               workingtree_4.WorkingTreeFormat5)):
                workingtree_4.Converter4to5().convert(tree)
            if (isinstance(tree, workingtree_4.DirStateWorkingTree)
                and not isinstance(tree, workingtree_4.WorkingTree6)
                and isinstance(self.target_format.workingtree_format,
                               workingtree_4.WorkingTreeFormat6)):
                workingtree_4.Converter4or5to6().convert(tree)
        self.pb.finished()
        return to_convert


class ConvertMetaToColo(controldir.Converter):
    """Add colocated branch support."""

    def __init__(self, target_format):
        """Create a converter.that upgrades a metadir to the colo format.

        :param target_format: The final metadir format that is desired.
        """
        self.target_format = target_format

    def convert(self, to_convert, pb):
        """See Converter.convert()."""
        to_convert.transport.put_bytes('branch-format',
                                       self.target_format.as_string())
        return BzrDir.open_from_transport(to_convert.root_transport)


class ConvertMetaToColo(controldir.Converter):
    """Convert a 'development-colo' bzrdir to a '2a' bzrdir."""

    def __init__(self, target_format):
        """Create a converter that converts a 'development-colo' metadir
        to a '2a' metadir.

        :param target_format: The final metadir format that is desired.
        """
        self.target_format = target_format

    def convert(self, to_convert, pb):
        """See Converter.convert()."""
        to_convert.transport.put_bytes('branch-format',
                                       self.target_format.as_string())
        return BzrDir.open_from_transport(to_convert.root_transport)


class CreateRepository(controldir.RepositoryAcquisitionPolicy):
    """A policy of creating a new repository"""

    def __init__(self, controldir, stack_on=None, stack_on_pwd=None,
                 require_stacking=False):
        """Constructor.

        :param controldir: The controldir to create the repository on.
        :param stack_on: A location to stack on
        :param stack_on_pwd: If stack_on is relative, the location it is
            relative to.
        """
        super(CreateRepository, self).__init__(
            stack_on, stack_on_pwd, require_stacking)
        self._controldir = controldir

    def acquire_repository(self, make_working_trees=None, shared=False,
                           possible_transports=None):
        """Implementation of RepositoryAcquisitionPolicy.acquire_repository

        Creates the desired repository in the controldir we already have.
        """
        if possible_transports is None:
            possible_transports = []
        else:
            possible_transports = list(possible_transports)
        possible_transports.append(self._controldir.root_transport)
        stack_on = self._get_full_stack_on()
        if stack_on:
            format = self._controldir._format
            format.require_stacking(stack_on=stack_on,
                                    possible_transports=possible_transports)
            if not self._require_stacking:
                # We have picked up automatic stacking somewhere.
                note(gettext('Using default stacking branch {0} at {1}').format(
                    self._stack_on, self._stack_on_pwd))
        repository = self._controldir.create_repository(shared=shared)
        self._add_fallback(repository,
                           possible_transports=possible_transports)
        if make_working_trees is not None:
            repository.set_make_working_trees(make_working_trees)
        return repository, True


class UseExistingRepository(controldir.RepositoryAcquisitionPolicy):
    """A policy of reusing an existing repository"""

    def __init__(self, repository, stack_on=None, stack_on_pwd=None,
                 require_stacking=False):
        """Constructor.

        :param repository: The repository to use.
        :param stack_on: A location to stack on
        :param stack_on_pwd: If stack_on is relative, the location it is
            relative to.
        """
        super(UseExistingRepository, self).__init__(
            stack_on, stack_on_pwd, require_stacking)
        self._repository = repository

    def acquire_repository(self, make_working_trees=None, shared=False,
                           possible_transports=None):
        """Implementation of RepositoryAcquisitionPolicy.acquire_repository

        Returns an existing repository to use.
        """
        if possible_transports is None:
            possible_transports = []
        else:
            possible_transports = list(possible_transports)
        possible_transports.append(self._repository.controldir.transport)
        self._add_fallback(self._repository,
                           possible_transports=possible_transports)
        return self._repository, False


controldir.ControlDirFormat._default_format = BzrDirMetaFormat1()
