~bzr-pqm/bzr/bzr.dev : contents of bzrlib/changeset.py at revision 1440

~bzr-pqm/bzr/bzr.dev : (revision 1440)
# Copyright (C) 2004 Aaron Bentley <aaron.bentley@utoronto.ca>
#
#    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
import os.path
import errno
import patch
import stat
from bzrlib.trace import mutter
from bzrlib.osutils import rename
import bzrlib

# XXX: mbp: I'm not totally convinced that we should handle conflicts
# as part of changeset application, rather than only in the merge
# operation.

"""Represent and apply a changeset

Conflicts in applying a changeset are represented as exceptions.
"""

__docformat__ = "restructuredtext"

NULL_ID = "!NULL"

class OldFailedTreeOp(Exception):
    def __init__(self):
        Exception.__init__(self, "bzr-tree-change contains files from a"
                           " previous failed merge operation.")
def invert_dict(dict):
    newdict = {}
    for (key,value) in dict.iteritems():
        newdict[value] = key
    return newdict

       
class ChangeExecFlag(object):
    """This is two-way change, suitable for file modification, creation,
    deletion"""
    def __init__(self, old_exec_flag, new_exec_flag):
        self.old_exec_flag = old_exec_flag
        self.new_exec_flag = new_exec_flag

    def apply(self, filename, conflict_handler, reverse=False):
        if not reverse:
            from_exec_flag = self.old_exec_flag
            to_exec_flag = self.new_exec_flag
        else:
            from_exec_flag = self.new_exec_flag
            to_exec_flag = self.old_exec_flag
        try:
            current_exec_flag = bool(os.stat(filename).st_mode & 0111)
        except OSError, e:
            if e.errno == errno.ENOENT:
                if conflict_handler.missing_for_exec_flag(filename) == "skip":
                    return
                else:
                    current_exec_flag = from_exec_flag

        if from_exec_flag is not None and current_exec_flag != from_exec_flag:
            if conflict_handler.wrong_old_exec_flag(filename,
                        from_exec_flag, current_exec_flag) != "continue":
                return

        if to_exec_flag is not None:
            current_mode = os.stat(filename).st_mode
            if to_exec_flag:
                umask = os.umask(0)
                os.umask(umask)
                to_mode = current_mode | (0100 & ~umask)
                # Enable x-bit for others only if they can read it.
                if current_mode & 0004:
                    to_mode |= 0001 & ~umask
                if current_mode & 0040:
                    to_mode |= 0010 & ~umask
            else:
                to_mode = current_mode & ~0111
            try:
                os.chmod(filename, to_mode)
            except IOError, e:
                if e.errno == errno.ENOENT:
                    conflict_handler.missing_for_exec_flag(filename)

    def __eq__(self, other):
        return (isinstance(other, ChangeExecFlag) and
                self.old_exec_flag == other.old_exec_flag and
                self.new_exec_flag == other.new_exec_flag)

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


def dir_create(filename, conflict_handler, reverse):
    """Creates the directory, or deletes it if reverse is true.  Intended to be
    used with ReplaceContents.

    :param filename: The name of the directory to create
    :type filename: str
    :param reverse: If true, delete the directory, instead
    :type reverse: bool
    """
    if not reverse:
        try:
            os.mkdir(filename)
        except OSError, e:
            if e.errno != errno.EEXIST:
                raise
            if conflict_handler.dir_exists(filename) == "continue":
                os.mkdir(filename)
        except IOError, e:
            if e.errno == errno.ENOENT:
                if conflict_handler.missing_parent(filename)=="continue":
                    file(filename, "wb").write(self.contents)
    else:
        try:
            os.rmdir(filename)
        except OSError, e:
            if e.errno != errno.ENOTEMPTY:
                raise
            if conflict_handler.rmdir_non_empty(filename) == "skip":
                return
            os.rmdir(filename)


class SymlinkCreate(object):
    """Creates or deletes a symlink (for use with ReplaceContents)"""
    def __init__(self, contents):
        """Constructor.

        :param contents: The filename of the target the symlink should point to
        :type contents: str
        """
        self.target = contents

    def __call__(self, filename, conflict_handler, reverse):
        """Creates or destroys the symlink.

        :param filename: The name of the symlink to create
        :type filename: str
        """
        if reverse:
            assert(os.readlink(filename) == self.target)
            os.unlink(filename)
        else:
            try:
                os.symlink(self.target, filename)
            except OSError, e:
                if e.errno != errno.EEXIST:
                    raise
                if conflict_handler.link_name_exists(filename) == "continue":
                    os.symlink(self.target, filename)

    def __eq__(self, other):
        if not isinstance(other, SymlinkCreate):
            return False
        elif self.target != other.target:
            return False
        else:
            return True

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

class FileCreate(object):
    """Create or delete a file (for use with ReplaceContents)"""
    def __init__(self, contents):
        """Constructor

        :param contents: The contents of the file to write
        :type contents: str
        """
        self.contents = contents

    def __repr__(self):
        return "FileCreate(%i b)" % len(self.contents)

    def __eq__(self, other):
        if not isinstance(other, FileCreate):
            return False
        elif self.contents != other.contents:
            return False
        else:
            return True

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

    def __call__(self, filename, conflict_handler, reverse):
        """Create or delete a file

        :param filename: The name of the file to create
        :type filename: str
        :param reverse: Delete the file instead of creating it
        :type reverse: bool
        """
        if not reverse:
            try:
                file(filename, "wb").write(self.contents)
            except IOError, e:
                if e.errno == errno.ENOENT:
                    if conflict_handler.missing_parent(filename)=="continue":
                        file(filename, "wb").write(self.contents)
                else:
                    raise

        else:
            try:
                if (file(filename, "rb").read() != self.contents):
                    direction = conflict_handler.wrong_old_contents(filename,
                                                                    self.contents)
                    if  direction != "continue":
                        return
                os.unlink(filename)
            except IOError, e:
                if e.errno != errno.ENOENT:
                    raise
                if conflict_handler.missing_for_rm(filename, undo) == "skip":
                    return

                    

def reversed(sequence):
    max = len(sequence) - 1
    for i in range(len(sequence)):
        yield sequence[max - i]

class ReplaceContents(object):
    """A contents-replacement framework.  It allows a file/directory/symlink to
    be created, deleted, or replaced with another file/directory/symlink.
    Arguments must be callable with (filename, reverse).
    """
    def __init__(self, old_contents, new_contents):
        """Constructor.

        :param old_contents: The change to reverse apply (e.g. a deletion), \
        when going forwards.
        :type old_contents: `dir_create`, `SymlinkCreate`, `FileCreate`, \
        NoneType, etc.
        :param new_contents: The second change to apply (e.g. a creation), \
        when going forwards.
        :type new_contents: `dir_create`, `SymlinkCreate`, `FileCreate`, \
        NoneType, etc.
        """
        self.old_contents=old_contents
        self.new_contents=new_contents

    def __repr__(self):
        return "ReplaceContents(%r -> %r)" % (self.old_contents,
                                              self.new_contents)

    def __eq__(self, other):
        if not isinstance(other, ReplaceContents):
            return False
        elif self.old_contents != other.old_contents:
            return False
        elif self.new_contents != other.new_contents:
            return False
        else:
            return True
    def __ne__(self, other):
        return not (self == other)

    def apply(self, filename, conflict_handler, reverse=False):
        """Applies the FileReplacement to the specified filename

        :param filename: The name of the file to apply changes to
        :type filename: str
        :param reverse: If true, apply the change in reverse
        :type reverse: bool
        """
        if not reverse:
            undo = self.old_contents
            perform = self.new_contents
        else:
            undo = self.new_contents
            perform = self.old_contents
        mode = None
        if undo is not None:
            try:
                mode = os.lstat(filename).st_mode
                if stat.S_ISLNK(mode):
                    mode = None
            except OSError, e:
                if e.errno != errno.ENOENT:
                    raise
                if conflict_handler.missing_for_rm(filename, undo) == "skip":
                    return
            undo(filename, conflict_handler, reverse=True)
        if perform is not None:
            perform(filename, conflict_handler, reverse=False)
            if mode is not None:
                os.chmod(filename, mode)

class ApplySequence(object):
    def __init__(self, changes=None):
        self.changes = []
        if changes is not None:
            self.changes.extend(changes)

    def __eq__(self, other):
        if not isinstance(other, ApplySequence):
            return False
        elif len(other.changes) != len(self.changes):
            return False
        else:
            for i in range(len(self.changes)):
                if self.changes[i] != other.changes[i]:
                    return False
            return True

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

    
    def apply(self, filename, conflict_handler, reverse=False):
        if not reverse:
            iter = self.changes
        else:
            iter = reversed(self.changes)
        for change in iter:
            change.apply(filename, conflict_handler, reverse)


class Diff3Merge(object):
    def __init__(self, file_id, base, other):
        self.file_id = file_id
        self.base = base
        self.other = other

    def __eq__(self, other):
        if not isinstance(other, Diff3Merge):
            return False
        return (self.base == other.base and 
                self.other == other.other and self.file_id == other.file_id)

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

    def apply(self, filename, conflict_handler, reverse=False):
        new_file = filename+".new"
        base_file = self.base.readonly_path(self.file_id)
        other_file = self.other.readonly_path(self.file_id)
        if not reverse:
            base = base_file
            other = other_file
        else:
            base = other_file
            other = base_file
        status = patch.diff3(new_file, filename, base, other)
        if status == 0:
            os.chmod(new_file, os.stat(filename).st_mode)
            rename(new_file, filename)
            return
        else:
            assert(status == 1)
            def get_lines(filename):
                my_file = file(filename, "rb")
                lines = my_file.readlines()
                my_file.close()
                return lines
            base_lines = get_lines(base)
            other_lines = get_lines(other)
            conflict_handler.merge_conflict(new_file, filename, base_lines, 
                                            other_lines)


def CreateDir():
    """Convenience function to create a directory.

    :return: A ReplaceContents that will create a directory
    :rtype: `ReplaceContents`
    """
    return ReplaceContents(None, dir_create)

def DeleteDir():
    """Convenience function to delete a directory.

    :return: A ReplaceContents that will delete a directory
    :rtype: `ReplaceContents`
    """
    return ReplaceContents(dir_create, None)

def CreateFile(contents):
    """Convenience fucntion to create a file.
    
    :param contents: The contents of the file to create 
    :type contents: str
    :return: A ReplaceContents that will create a file 
    :rtype: `ReplaceContents`
    """
    return ReplaceContents(None, FileCreate(contents))

def DeleteFile(contents):
    """Convenience fucntion to delete a file.
    
    :param contents: The contents of the file to delete
    :type contents: str
    :return: A ReplaceContents that will delete a file 
    :rtype: `ReplaceContents`
    """
    return ReplaceContents(FileCreate(contents), None)

def ReplaceFileContents(old_contents, new_contents):
    """Convenience fucntion to replace the contents of a file.
    
    :param old_contents: The contents of the file to replace 
    :type old_contents: str
    :param new_contents: The contents to replace the file with
    :type new_contents: str
    :return: A ReplaceContents that will replace the contents of a file a file 
    :rtype: `ReplaceContents`
    """
    return ReplaceContents(FileCreate(old_contents), FileCreate(new_contents))

def CreateSymlink(target):
    """Convenience fucntion to create a symlink.
    
    :param target: The path the link should point to
    :type target: str
    :return: A ReplaceContents that will delete a file 
    :rtype: `ReplaceContents`
    """
    return ReplaceContents(None, SymlinkCreate(target))

def DeleteSymlink(target):
    """Convenience fucntion to delete a symlink.
    
    :param target: The path the link should point to
    :type target: str
    :return: A ReplaceContents that will delete a file 
    :rtype: `ReplaceContents`
    """
    return ReplaceContents(SymlinkCreate(target), None)

def ChangeTarget(old_target, new_target):
    """Convenience fucntion to change the target of a symlink.
    
    :param old_target: The current link target
    :type old_target: str
    :param new_target: The new link target to use
    :type new_target: str
    :return: A ReplaceContents that will delete a file 
    :rtype: `ReplaceContents`
    """
    return ReplaceContents(SymlinkCreate(old_target), SymlinkCreate(new_target))


class InvalidEntry(Exception):
    """Raise when a ChangesetEntry is invalid in some way"""
    def __init__(self, entry, problem):
        """Constructor.

        :param entry: The invalid ChangesetEntry
        :type entry: `ChangesetEntry`
        :param problem: The problem with the entry
        :type problem: str
        """
        msg = "Changeset entry for %s (%s) is invalid.\n%s" % (entry.id, 
                                                               entry.path, 
                                                               problem)
        Exception.__init__(self, msg)
        self.entry = entry


class SourceRootHasName(InvalidEntry):
    """This changeset entry has a name other than "", but its parent is !NULL"""
    def __init__(self, entry, name):
        """Constructor.

        :param entry: The invalid ChangesetEntry
        :type entry: `ChangesetEntry`
        :param name: The name of the entry
        :type name: str
        """
        msg = 'Child of !NULL is named "%s", not "./.".' % name
        InvalidEntry.__init__(self, entry, msg)

class NullIDAssigned(InvalidEntry):
    """The id !NULL was assigned to a real entry"""
    def __init__(self, entry):
        """Constructor.

        :param entry: The invalid ChangesetEntry
        :type entry: `ChangesetEntry`
        """
        msg = '"!NULL" id assigned to a file "%s".' % entry.path
        InvalidEntry.__init__(self, entry, msg)

class ParentIDIsSelf(InvalidEntry):
    """An entry is marked as its own parent"""
    def __init__(self, entry):
        """Constructor.

        :param entry: The invalid ChangesetEntry
        :type entry: `ChangesetEntry`
        """
        msg = 'file %s has "%s" id for both self id and parent id.' % \
            (entry.path, entry.id)
        InvalidEntry.__init__(self, entry, msg)

class ChangesetEntry(object):
    """An entry the changeset"""
    def __init__(self, id, parent, path):
        """Constructor. Sets parent and name assuming it was not
        renamed/created/deleted.
        :param id: The id associated with the entry
        :param parent: The id of the parent of this entry (or !NULL if no
        parent)
        :param path: The file path relative to the tree root of this entry
        """
        self.id = id
        self.path = path 
        self.new_path = path
        self.parent = parent
        self.new_parent = parent
        self.contents_change = None
        self.metadata_change = None
        if parent == NULL_ID and path !='./.':
            raise SourceRootHasName(self, path)
        if self.id == NULL_ID:
            raise NullIDAssigned(self)
        if self.id  == self.parent:
            raise ParentIDIsSelf(self)

    def __str__(self):
        return "ChangesetEntry(%s)" % self.id

    def __get_dir(self):
        if self.path is None:
            return None
        return os.path.dirname(self.path)

    def __set_dir(self, dir):
        self.path = os.path.join(dir, os.path.basename(self.path))

    dir = property(__get_dir, __set_dir)
    
    def __get_name(self):
        if self.path is None:
            return None
        return os.path.basename(self.path)

    def __set_name(self, name):
        self.path = os.path.join(os.path.dirname(self.path), name)

    name = property(__get_name, __set_name)

    def __get_new_dir(self):
        if self.new_path is None:
            return None
        return os.path.dirname(self.new_path)

    def __set_new_dir(self, dir):
        self.new_path = os.path.join(dir, os.path.basename(self.new_path))

    new_dir = property(__get_new_dir, __set_new_dir)

    def __get_new_name(self):
        if self.new_path is None:
            return None
        return os.path.basename(self.new_path)

    def __set_new_name(self, name):
        self.new_path = os.path.join(os.path.dirname(self.new_path), name)

    new_name = property(__get_new_name, __set_new_name)

    def needs_rename(self):
        """Determines whether the entry requires renaming.

        :rtype: bool
        """

        return (self.parent != self.new_parent or self.name != self.new_name)

    def is_deletion(self, reverse):
        """Return true if applying the entry would delete a file/directory.

        :param reverse: if true, the changeset is being applied in reverse
        :rtype: bool
        """
        return ((self.new_parent is None and not reverse) or 
                (self.parent is None and reverse))

    def is_creation(self, reverse):
        """Return true if applying the entry would create a file/directory.

        :param reverse: if true, the changeset is being applied in reverse
        :rtype: bool
        """
        return ((self.parent is None and not reverse) or 
                (self.new_parent is None and reverse))

    def is_creation_or_deletion(self):
        """Return true if applying the entry would create or delete a 
        file/directory.

        :rtype: bool
        """
        return self.parent is None or self.new_parent is None

    def get_cset_path(self, mod=False):
        """Determine the path of the entry according to the changeset.

        :param changeset: The changeset to derive the path from
        :type changeset: `Changeset`
        :param mod: If true, generate the MOD path.  Otherwise, generate the \
        ORIG path.
        :return: the path of the entry, or None if it did not exist in the \
        requested tree.
        :rtype: str or NoneType
        """
        if mod:
            if self.new_parent == NULL_ID:
                return "./."
            elif self.new_parent is None:
                return None
            return self.new_path
        else:
            if self.parent == NULL_ID:
                return "./."
            elif self.parent is None:
                return None
            return self.path

    def summarize_name(self, reverse=False):
        """Produce a one-line summary of the filename.  Indicates renames as
        old => new, indicates creation as None => new, indicates deletion as
        old => None.

        :param changeset: The changeset to get paths from
        :type changeset: `Changeset`
        :param reverse: If true, reverse the names in the output
        :type reverse: bool
        :rtype: str
        """
        orig_path = self.get_cset_path(False)
        mod_path = self.get_cset_path(True)
        if orig_path is not None:
            orig_path = orig_path[2:]
        if mod_path is not None:
            mod_path = mod_path[2:]
        if orig_path == mod_path:
            return orig_path
        else:
            if not reverse:
                return "%s => %s" % (orig_path, mod_path)
            else:
                return "%s => %s" % (mod_path, orig_path)


    def get_new_path(self, id_map, changeset, reverse=False):
        """Determine the full pathname to rename to

        :param id_map: The map of ids to filenames for the tree
        :type id_map: Dictionary
        :param changeset: The changeset to get data from
        :type changeset: `Changeset`
        :param reverse: If true, we're applying the changeset in reverse
        :type reverse: bool
        :rtype: str
        """
        mutter("Finding new path for %s" % self.summarize_name())
        if reverse:
            parent = self.parent
            to_dir = self.dir
            from_dir = self.new_dir
            to_name = self.name
            from_name = self.new_name
        else:
            parent = self.new_parent
            to_dir = self.new_dir
            from_dir = self.dir
            to_name = self.new_name
            from_name = self.name

        if to_name is None:
            return None

        if parent == NULL_ID or parent is None:
            if to_name != '.':
                raise SourceRootHasName(self, to_name)
            else:
                return '.'
        if from_dir == to_dir:
            dir = os.path.dirname(id_map[self.id])
        else:
            mutter("path, new_path: %r %r" % (self.path, self.new_path))
            parent_entry = changeset.entries[parent]
            dir = parent_entry.get_new_path(id_map, changeset, reverse)
        if from_name == to_name:
            name = os.path.basename(id_map[self.id])
        else:
            name = to_name
            assert(from_name is None or from_name == os.path.basename(id_map[self.id]))
        return os.path.join(dir, name)

    def is_boring(self):
        """Determines whether the entry does nothing
        
        :return: True if the entry does no renames or content changes
        :rtype: bool
        """
        if self.contents_change is not None:
            return False
        elif self.metadata_change is not None:
            return False
        elif self.parent != self.new_parent:
            return False
        elif self.name != self.new_name:
            return False
        else:
            return True

    def apply(self, filename, conflict_handler, reverse=False):
        """Applies the file content and/or metadata changes.

        :param filename: the filename of the entry
        :type filename: str
        :param reverse: If true, apply the changes in reverse
        :type reverse: bool
        """
        if self.is_deletion(reverse) and self.metadata_change is not None:
            self.metadata_change.apply(filename, conflict_handler, reverse)
        if self.contents_change is not None:
            self.contents_change.apply(filename, conflict_handler, reverse)
        if not self.is_deletion(reverse) and self.metadata_change is not None:
            self.metadata_change.apply(filename, conflict_handler, reverse)

class IDPresent(Exception):
    def __init__(self, id):
        msg = "Cannot add entry because that id has already been used:\n%s" %\
            id
        Exception.__init__(self, msg)
        self.id = id

class Changeset(object):
    """A set of changes to apply"""
    def __init__(self):
        self.entries = {}

    def add_entry(self, entry):
        """Add an entry to the list of entries"""
        if self.entries.has_key(entry.id):
            raise IDPresent(entry.id)
        self.entries[entry.id] = entry

def my_sort(sequence, key, reverse=False):
    """A sort function that supports supplying a key for comparison
    
    :param sequence: The sequence to sort
    :param key: A callable object that returns the values to be compared
    :param reverse: If true, sort in reverse order
    :type reverse: bool
    """
    def cmp_by_key(entry_a, entry_b):
        if reverse:
            tmp=entry_a
            entry_a = entry_b
            entry_b = tmp
        return cmp(key(entry_a), key(entry_b))
    sequence.sort(cmp_by_key)

def get_rename_entries(changeset, inventory, reverse):
    """Return a list of entries that will be renamed.  Entries are sorted from
    longest to shortest source path and from shortest to longest target path.

    :param changeset: The changeset to look in
    :type changeset: `Changeset`
    :param inventory: The source of current tree paths for the given ids
    :type inventory: Dictionary
    :param reverse: If true, the changeset is being applied in reverse
    :type reverse: bool
    :return: source entries and target entries as a tuple
    :rtype: (List, List)
    """
    source_entries = [x for x in changeset.entries.itervalues() 
                      if x.needs_rename()]
    # these are done from longest path to shortest, to avoid deleting a
    # parent before its children are deleted/renamed 
    def longest_to_shortest(entry):
        path = inventory.get(entry.id)
        if path is None:
            return 0
        else:
            return len(path)
    my_sort(source_entries, longest_to_shortest, reverse=True)

    target_entries = source_entries[:]
    # These are done from shortest to longest path, to avoid creating a
    # child before its parent has been created/renamed
    def shortest_to_longest(entry):
        path = entry.get_new_path(inventory, changeset, reverse)
        if path is None:
            return 0
        else:
            return len(path)
    my_sort(target_entries, shortest_to_longest)
    return (source_entries, target_entries)

def rename_to_temp_delete(source_entries, inventory, dir, temp_dir, 
                          conflict_handler, reverse):
    """Delete and rename entries as appropriate.  Entries are renamed to temp
    names.  A map of id -> temp name (or None, for deletions) is returned.

    :param source_entries: The entries to rename and delete
    :type source_entries: List of `ChangesetEntry`
    :param inventory: The map of id -> filename in the current tree
    :type inventory: Dictionary
    :param dir: The directory to apply changes to
    :type dir: str
    :param reverse: Apply changes in reverse
    :type reverse: bool
    :return: a mapping of id to temporary name
    :rtype: Dictionary
    """
    temp_name = {}
    for i in range(len(source_entries)):
        entry = source_entries[i]
        if entry.is_deletion(reverse):
            path = os.path.join(dir, inventory[entry.id])
            entry.apply(path, conflict_handler, reverse)
            temp_name[entry.id] = None

        else:
            to_name = os.path.join(temp_dir, str(i))
            src_path = inventory.get(entry.id)
            if src_path is not None:
                src_path = os.path.join(dir, src_path)
                try:
                    rename(src_path, to_name)
                    temp_name[entry.id] = to_name
                except OSError, e:
                    if e.errno != errno.ENOENT:
                        raise
                    if conflict_handler.missing_for_rename(src_path) == "skip":
                        continue

    return temp_name


def rename_to_new_create(changed_inventory, target_entries, inventory, 
                         changeset, dir, conflict_handler, reverse):
    """Rename entries with temp names to their final names, create new files.

    :param changed_inventory: A mapping of id to temporary name
    :type changed_inventory: Dictionary
    :param target_entries: The entries to apply changes to
    :type target_entries: List of `ChangesetEntry`
    :param changeset: The changeset to apply
    :type changeset: `Changeset`
    :param dir: The directory to apply changes to
    :type dir: str
    :param reverse: If true, apply changes in reverse
    :type reverse: bool
    """
    for entry in target_entries:
        new_tree_path = entry.get_new_path(inventory, changeset, reverse)
        if new_tree_path is None:
            continue
        new_path = os.path.join(dir, new_tree_path)
        old_path = changed_inventory.get(entry.id)
        if bzrlib.osutils.lexists(new_path):
            if conflict_handler.target_exists(entry, new_path, old_path) == \
                "skip":
                continue
        if entry.is_creation(reverse):
            entry.apply(new_path, conflict_handler, reverse)
            changed_inventory[entry.id] = new_tree_path
        else:
            if old_path is None:
                continue
            try:
                rename(old_path, new_path)
                changed_inventory[entry.id] = new_tree_path
            except OSError, e:
                raise Exception ("%s is missing" % new_path)

class TargetExists(Exception):
    def __init__(self, entry, target):
        msg = "The path %s already exists" % target
        Exception.__init__(self, msg)
        self.entry = entry
        self.target = target

class RenameConflict(Exception):
    def __init__(self, id, this_name, base_name, other_name):
        msg = """Trees all have different names for a file
 this: %s
 base: %s
other: %s
   id: %s""" % (this_name, base_name, other_name, id)
        Exception.__init__(self, msg)
        self.this_name = this_name
        self.base_name = base_name
        self_other_name = other_name

class MoveConflict(Exception):
    def __init__(self, id, this_parent, base_parent, other_parent):
        msg = """The file is in different directories in every tree
 this: %s
 base: %s
other: %s
   id: %s""" % (this_parent, base_parent, other_parent, id)
        Exception.__init__(self, msg)
        self.this_parent = this_parent
        self.base_parent = base_parent
        self_other_parent = other_parent

class MergeConflict(Exception):
    def __init__(self, this_path):
        Exception.__init__(self, "Conflict applying changes to %s" % this_path)
        self.this_path = this_path

class WrongOldContents(Exception):
    def __init__(self, filename):
        msg = "Contents mismatch deleting %s" % filename
        self.filename = filename
        Exception.__init__(self, msg)

class WrongOldExecFlag(Exception):
    def __init__(self, filename, old_exec_flag, new_exec_flag):
        msg = "Executable flag missmatch on %s:\n" \
        "Expected %s, got %s." % (filename, old_exec_flag, new_exec_flag)
        self.filename = filename
        Exception.__init__(self, msg)

class RemoveContentsConflict(Exception):
    def __init__(self, filename):
        msg = "Conflict deleting %s, which has different contents in BASE"\
            " and THIS" % filename
        self.filename = filename
        Exception.__init__(self, msg)

class DeletingNonEmptyDirectory(Exception):
    def __init__(self, filename):
        msg = "Trying to remove dir %s while it still had files" % filename
        self.filename = filename
        Exception.__init__(self, msg)


class PatchTargetMissing(Exception):
    def __init__(self, filename):
        msg = "Attempt to patch %s, which does not exist" % filename
        Exception.__init__(self, msg)
        self.filename = filename

class MissingForSetExec(Exception):
    def __init__(self, filename):
        msg = "Attempt to change permissions on  %s, which does not exist" %\
            filename
        Exception.__init__(self, msg)
        self.filename = filename

class MissingForRm(Exception):
    def __init__(self, filename):
        msg = "Attempt to remove missing path %s" % filename
        Exception.__init__(self, msg)
        self.filename = filename


class MissingForRename(Exception):
    def __init__(self, filename):
        msg = "Attempt to move missing path %s" % (filename)
        Exception.__init__(self, msg)
        self.filename = filename

class NewContentsConflict(Exception):
    def __init__(self, filename):
        msg = "Conflicting contents for new file %s" % (filename)
        Exception.__init__(self, msg)


class MissingForMerge(Exception):
    def __init__(self, filename):
        msg = "The file %s was modified, but does not exist in this tree"\
            % (filename)
        Exception.__init__(self, msg)


class ExceptionConflictHandler(object):
    """Default handler for merge exceptions.

    This throws an error on any kind of conflict.  Conflict handlers can
    descend from this class if they have a better way to handle some or
    all types of conflict.
    """
    def missing_parent(self, pathname):
        parent = os.path.dirname(pathname)
        raise Exception("Parent directory missing for %s" % pathname)

    def dir_exists(self, pathname):
        raise Exception("Directory already exists for %s" % pathname)

    def failed_hunks(self, pathname):
        raise Exception("Failed to apply some hunks for %s" % pathname)

    def target_exists(self, entry, target, old_path):
        raise TargetExists(entry, target)

    def rename_conflict(self, id, this_name, base_name, other_name):
        raise RenameConflict(id, this_name, base_name, other_name)

    def move_conflict(self, id, this_dir, base_dir, other_dir):
        raise MoveConflict(id, this_dir, base_dir, other_dir)

    def merge_conflict(self, new_file, this_path, base_lines, other_lines):
        os.unlink(new_file)
        raise MergeConflict(this_path)

    def wrong_old_contents(self, filename, expected_contents):
        raise WrongOldContents(filename)

    def rem_contents_conflict(self, filename, this_contents, base_contents):
        raise RemoveContentsConflict(filename)

    def wrong_old_exec_flag(self, filename, old_exec_flag, new_exec_flag):
        raise WrongOldExecFlag(filename, old_exec_flag, new_exec_flag)

    def rmdir_non_empty(self, filename):
        raise DeletingNonEmptyDirectory(filename)

    def link_name_exists(self, filename):
        raise TargetExists(filename)

    def patch_target_missing(self, filename, contents):
        raise PatchTargetMissing(filename)

    def missing_for_exec_flag(self, filename):
        raise MissingForExecFlag(filename)

    def missing_for_rm(self, filename, change):
        raise MissingForRm(filename)

    def missing_for_rename(self, filename):
        raise MissingForRename(filename)

    def missing_for_merge(self, file_id, other_path):
        raise MissingForMerge(other_path)

    def new_contents_conflict(self, filename, other_contents):
        raise NewContentsConflict(filename)

    def finalize(self):
        pass

def apply_changeset(changeset, inventory, dir, conflict_handler=None, 
                    reverse=False):
    """Apply a changeset to a directory.

    :param changeset: The changes to perform
    :type changeset: `Changeset`
    :param inventory: The mapping of id to filename for the directory
    :type inventory: Dictionary
    :param dir: The path of the directory to apply the changes to
    :type dir: str
    :param reverse: If true, apply the changes in reverse
    :type reverse: bool
    :return: The mapping of the changed entries
    :rtype: Dictionary
    """
    if conflict_handler is None:
        conflict_handler = ExceptionConflictHandler()
    temp_dir = os.path.join(dir, "bzr-tree-change")
    try:
        os.mkdir(temp_dir)
    except OSError, e:
        if e.errno == errno.EEXIST:
            try:
                os.rmdir(temp_dir)
            except OSError, e:
                if e.errno == errno.ENOTEMPTY:
                    raise OldFailedTreeOp()
            os.mkdir(temp_dir)
        else:
            raise
    
    #apply changes that don't affect filenames
    for entry in changeset.entries.itervalues():
        if not entry.is_creation_or_deletion():
            path = os.path.join(dir, inventory[entry.id])
            entry.apply(path, conflict_handler, reverse)

    # Apply renames in stages, to minimize conflicts:
    # Only files whose name or parent change are interesting, because their
    # target name may exist in the source tree.  If a directory's name changes,
    # that doesn't make its children interesting.
    (source_entries, target_entries) = get_rename_entries(changeset, inventory,
                                                          reverse)

    changed_inventory = rename_to_temp_delete(source_entries, inventory, dir,
                                              temp_dir, conflict_handler,
                                              reverse)

    rename_to_new_create(changed_inventory, target_entries, inventory,
                         changeset, dir, conflict_handler, reverse)
    os.rmdir(temp_dir)
    return changed_inventory


def apply_changeset_tree(cset, tree, reverse=False):
    r_inventory = {}
    for entry in tree.source_inventory().itervalues():
        inventory[entry.id] = entry.path
    new_inventory = apply_changeset(cset, r_inventory, tree.root,
                                    reverse=reverse)
    new_entries, remove_entries = \
        get_inventory_change(inventory, new_inventory, cset, reverse)
    tree.update_source_inventory(new_entries, remove_entries)


def get_inventory_change(inventory, new_inventory, cset, reverse=False):
    new_entries = {}
    remove_entries = []
    for entry in cset.entries.itervalues():
        if entry.needs_rename():
            new_path = entry.get_new_path(inventory, cset)
            if new_path is None:
                remove_entries.append(entry.id)
            else:
                new_entries[new_path] = entry.id
    return new_entries, remove_entries


def print_changeset(cset):
    """Print all non-boring changeset entries
    
    :param cset: The changeset to print
    :type cset: `Changeset`
    """
    for entry in cset.entries.itervalues():
        if entry.is_boring():
            continue
        print entry.id
        print entry.summarize_name(cset)

class CompositionFailure(Exception):
    def __init__(self, old_entry, new_entry, problem):
        msg = "Unable to conpose entries.\n %s" % problem
        Exception.__init__(self, msg)

class IDMismatch(CompositionFailure):
    def __init__(self, old_entry, new_entry):
        problem = "Attempt to compose entries with different ids: %s and %s" %\
            (old_entry.id, new_entry.id)
        CompositionFailure.__init__(self, old_entry, new_entry, problem)

def compose_changesets(old_cset, new_cset):
    """Combine two changesets into one.  This works well for exact patching.
    Otherwise, not so well.

    :param old_cset: The first changeset that would be applied
    :type old_cset: `Changeset`
    :param new_cset: The second changeset that would be applied
    :type new_cset: `Changeset`
    :return: A changeset that combines the changes in both changesets
    :rtype: `Changeset`
    """
    composed = Changeset()
    for old_entry in old_cset.entries.itervalues():
        new_entry = new_cset.entries.get(old_entry.id)
        if new_entry is None:
            composed.add_entry(old_entry)
        else:
            composed_entry = compose_entries(old_entry, new_entry)
            if composed_entry.parent is not None or\
                composed_entry.new_parent is not None:
                composed.add_entry(composed_entry)
    for new_entry in new_cset.entries.itervalues():
        if not old_cset.entries.has_key(new_entry.id):
            composed.add_entry(new_entry)
    return composed

def compose_entries(old_entry, new_entry):
    """Combine two entries into one.

    :param old_entry: The first entry that would be applied
    :type old_entry: ChangesetEntry
    :param old_entry: The second entry that would be applied
    :type old_entry: ChangesetEntry
    :return: A changeset entry combining both entries
    :rtype: `ChangesetEntry`
    """
    if old_entry.id != new_entry.id:
        raise IDMismatch(old_entry, new_entry)
    output = ChangesetEntry(old_entry.id, old_entry.parent, old_entry.path)

    if (old_entry.parent != old_entry.new_parent or 
        new_entry.parent != new_entry.new_parent):
        output.new_parent = new_entry.new_parent

    if (old_entry.path != old_entry.new_path or 
        new_entry.path != new_entry.new_path):
        output.new_path = new_entry.new_path

    output.contents_change = compose_contents(old_entry, new_entry)
    output.metadata_change = compose_metadata(old_entry, new_entry)
    return output

def compose_contents(old_entry, new_entry):
    """Combine the contents of two changeset entries.  Entries are combined
    intelligently where possible, but the fallback behavior returns an 
    ApplySequence.

    :param old_entry: The first entry that would be applied
    :type old_entry: `ChangesetEntry`
    :param new_entry: The second entry that would be applied
    :type new_entry: `ChangesetEntry`
    :return: A combined contents change
    :rtype: anything supporting the apply(reverse=False) method
    """
    old_contents = old_entry.contents_change
    new_contents = new_entry.contents_change
    if old_entry.contents_change is None:
        return new_entry.contents_change
    elif new_entry.contents_change is None:
        return old_entry.contents_change
    elif isinstance(old_contents, ReplaceContents) and \
        isinstance(new_contents, ReplaceContents):
        if old_contents.old_contents == new_contents.new_contents:
            return None
        else:
            return ReplaceContents(old_contents.old_contents,
                                   new_contents.new_contents)
    elif isinstance(old_contents, ApplySequence):
        output = ApplySequence(old_contents.changes)
        if isinstance(new_contents, ApplySequence):
            output.changes.extend(new_contents.changes)
        else:
            output.changes.append(new_contents)
        return output
    elif isinstance(new_contents, ApplySequence):
        output = ApplySequence((old_contents.changes,))
        output.extend(new_contents.changes)
        return output
    else:
        return ApplySequence((old_contents, new_contents))

def compose_metadata(old_entry, new_entry):
    old_meta = old_entry.metadata_change
    new_meta = new_entry.metadata_change
    if old_meta is None:
        return new_meta
    elif new_meta is None:
        return old_meta
    elif (isinstance(old_meta, ChangeExecFlag) and
          isinstance(new_meta, ChangeExecFlag)):
        return ChangeExecFlag(old_meta.old_exec_flag, new_meta.new_exec_flag)
    else:
        return ApplySequence(old_meta, new_meta)


def changeset_is_null(changeset):
    for entry in changeset.entries.itervalues():
        if not entry.is_boring():
            return False
    return True

class UnsuppportedFiletype(Exception):
    def __init__(self, full_path, stat_result):
        msg = "The file \"%s\" is not a supported filetype." % full_path
        Exception.__init__(self, msg)
        self.full_path = full_path
        self.stat_result = stat_result

def generate_changeset(tree_a, tree_b, interesting_ids=None):
    return ChangesetGenerator(tree_a, tree_b, interesting_ids)()

class ChangesetGenerator(object):
    def __init__(self, tree_a, tree_b, interesting_ids=None):
        object.__init__(self)
        self.tree_a = tree_a
        self.tree_b = tree_b
        self._interesting_ids = interesting_ids

    def iter_both_tree_ids(self):
        for file_id in self.tree_a:
            yield file_id
        for file_id in self.tree_b:
            if file_id not in self.tree_a:
                yield file_id

    def __call__(self):
        cset = Changeset()
        for file_id in self.iter_both_tree_ids():
            cs_entry = self.make_entry(file_id)
            if cs_entry is not None and not cs_entry.is_boring():
                cset.add_entry(cs_entry)

        for entry in list(cset.entries.itervalues()):
            if entry.parent != entry.new_parent:
                if not cset.entries.has_key(entry.parent) and\
                    entry.parent != NULL_ID and entry.parent is not None:
                    parent_entry = self.make_boring_entry(entry.parent)
                    cset.add_entry(parent_entry)
                if not cset.entries.has_key(entry.new_parent) and\
                    entry.new_parent != NULL_ID and \
                    entry.new_parent is not None:
                    parent_entry = self.make_boring_entry(entry.new_parent)
                    cset.add_entry(parent_entry)
        return cset

    def iter_inventory(self, tree):
        for file_id in tree:
            yield self.get_entry(file_id, tree)

    def get_entry(self, file_id, tree):
        if not tree.has_or_had_id(file_id):
            return None
        return tree.tree.inventory[file_id]

    def get_entry_parent(self, entry):
        if entry is None:
            return None
        return entry.parent_id

    def get_path(self, file_id, tree):
        if not tree.has_or_had_id(file_id):
            return None
        path = tree.id2path(file_id)
        if path == '':
            return './.'
        else:
            return path

    def make_basic_entry(self, file_id, only_interesting):
        entry_a = self.get_entry(file_id, self.tree_a)
        entry_b = self.get_entry(file_id, self.tree_b)
        if only_interesting and not self.is_interesting(entry_a, entry_b):
            return None
        parent = self.get_entry_parent(entry_a)
        path = self.get_path(file_id, self.tree_a)
        cs_entry = ChangesetEntry(file_id, parent, path)
        new_parent = self.get_entry_parent(entry_b)

        new_path = self.get_path(file_id, self.tree_b)

        cs_entry.new_path = new_path
        cs_entry.new_parent = new_parent
        return cs_entry

    def is_interesting(self, entry_a, entry_b):
        if self._interesting_ids is None:
            return True
        if entry_a is not None:
            file_id = entry_a.file_id
        elif entry_b is not None:
            file_id = entry_b.file_id
        else:
            return False
        return file_id in self._interesting_ids

    def make_boring_entry(self, id):
        cs_entry = self.make_basic_entry(id, only_interesting=False)
        if cs_entry.is_creation_or_deletion():
            return self.make_entry(id, only_interesting=False)
        else:
            return cs_entry
        

    def make_entry(self, id, only_interesting=True):
        cs_entry = self.make_basic_entry(id, only_interesting)

        if cs_entry is None:
            return None

        full_path_a = self.tree_a.readonly_path(id)
        full_path_b = self.tree_b.readonly_path(id)
        stat_a = self.lstat(full_path_a)
        stat_b = self.lstat(full_path_b)

        cs_entry.metadata_change = self.make_exec_flag_change(stat_a, stat_b)

        if id in self.tree_a and id in self.tree_b:
            a_sha1 = self.tree_a.get_file_sha1(id)
            b_sha1 = self.tree_b.get_file_sha1(id)
            if None not in (a_sha1, b_sha1) and a_sha1 == b_sha1:
                return cs_entry

        cs_entry.contents_change = self.make_contents_change(full_path_a,
                                                             stat_a, 
                                                             full_path_b, 
                                                             stat_b)
        return cs_entry

    def make_exec_flag_change(self, stat_a, stat_b):
        exec_flag_a = exec_flag_b = None
        if stat_a is not None and not stat.S_ISLNK(stat_a.st_mode):
            exec_flag_a = bool(stat_a.st_mode & 0111)
        if stat_b is not None and not stat.S_ISLNK(stat_b.st_mode):
            exec_flag_b = bool(stat_b.st_mode & 0111)
        if exec_flag_a == exec_flag_b:
            return None
        return ChangeExecFlag(exec_flag_a, exec_flag_b)

    def make_contents_change(self, full_path_a, stat_a, full_path_b, stat_b):
        if stat_a is None and stat_b is None:
            return None
        if None not in (stat_a, stat_b) and stat.S_ISDIR(stat_a.st_mode) and\
            stat.S_ISDIR(stat_b.st_mode):
            return None
        if None not in (stat_a, stat_b) and stat.S_ISREG(stat_a.st_mode) and\
            stat.S_ISREG(stat_b.st_mode):
            if stat_a.st_ino == stat_b.st_ino and \
                stat_a.st_dev == stat_b.st_dev:
                return None

        a_contents = self.get_contents(stat_a, full_path_a)
        b_contents = self.get_contents(stat_b, full_path_b)
        if a_contents == b_contents:
            return None
        return ReplaceContents(a_contents, b_contents)

    def get_contents(self, stat_result, full_path):
        if stat_result is None:
            return None
        elif stat.S_ISREG(stat_result.st_mode):
            return FileCreate(file(full_path, "rb").read())
        elif stat.S_ISDIR(stat_result.st_mode):
            return dir_create
        elif stat.S_ISLNK(stat_result.st_mode):
            return SymlinkCreate(os.readlink(full_path))
        else:
            raise UnsupportedFiletype(full_path, stat_result)

    def lstat(self, full_path):
        stat_result = None
        if full_path is not None:
            try:
                stat_result = os.lstat(full_path)
            except OSError, e:
                if e.errno != errno.ENOENT:
                    raise
        return stat_result


def full_path(entry, tree):
    return os.path.join(tree.root, entry.path)

def new_delete_entry(entry, tree, inventory, delete):
    if entry.path == "":
        parent = NULL_ID
    else:
        parent = inventory[dirname(entry.path)].id
    cs_entry = ChangesetEntry(parent, entry.path)
    if delete:
        cs_entry.new_path = None
        cs_entry.new_parent = None
    else:
        cs_entry.path = None
        cs_entry.parent = None
    full_path = full_path(entry, tree)
    status = os.lstat(full_path)
    if stat.S_ISDIR(file_stat.st_mode):
        action = dir_create
    


        
# XXX: Can't we unify this with the regular inventory object
class Inventory(object):
    def __init__(self, inventory):
        self.inventory = inventory
        self.rinventory = None

    def get_rinventory(self):
        if self.rinventory is None:
            self.rinventory  = invert_dict(self.inventory)
        return self.rinventory

    def get_path(self, id):
        return self.inventory.get(id)

    def get_name(self, id):
        path = self.get_path(id)
        if path is None:
            return None
        else:
            return os.path.basename(path)

    def get_dir(self, id):
        path = self.get_path(id)
        if path == "":
            return None
        if path is None:
            return None
        return os.path.dirname(path)

    def get_parent(self, id):
        if self.get_path(id) is None:
            return None
        directory = self.get_dir(id)
        if directory == '.':
            directory = './.'
        if directory is None:
            return NULL_ID
        return self.get_rinventory().get(directory)