~bzr-pqm/bzr/bzr.dev

# Copyright (C) 2005, 2006 Canonical Ltd
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA


import os
import errno
import warnings

from bzrlib import (
    osutils,
    registry,
    )
from bzrlib.branch import Branch
from bzrlib.conflicts import ConflictList, Conflict
from bzrlib.errors import (BzrCommandError,
                           BzrError,
                           NoCommonAncestor,
                           NoCommits,
                           NoSuchRevision,
                           NoSuchFile,
                           NotBranchError,
                           NotVersionedError,
                           UnrelatedBranches,
                           UnsupportedOperation,
                           WorkingTreeNotRevision,
                           BinaryFile,
                           )
from bzrlib.merge3 import Merge3
from bzrlib.osutils import rename, pathjoin
from progress import DummyProgress, ProgressPhase
from bzrlib.revision import (is_ancestor, NULL_REVISION, ensure_null)
from bzrlib.textfile import check_text_lines
from bzrlib.trace import mutter, warning, note
from bzrlib.transform import (TreeTransform, resolve_conflicts, cook_conflicts,
                              FinalPaths, create_by_entry, unique_add,
                              ROOT_PARENT)
from bzrlib.versionedfile import WeaveMerge
from bzrlib import ui

# TODO: Report back as changes are merged in

def _get_tree(treespec, local_branch=None, possible_transports=None):
    from bzrlib import workingtree
    location, revno = treespec
    if revno is None:
        tree = workingtree.WorkingTree.open_containing(location)[0]
        return tree.branch, tree
    branch = Branch.open_containing(location, possible_transports)[0]
    if revno == -1:
        revision_id = branch.last_revision()
    else:
        revision_id = branch.get_rev_id(revno)
    if revision_id is None:
        revision_id = NULL_REVISION
    return branch, _get_revid_tree(branch, revision_id, local_branch)


def _get_revid_tree(branch, revision_id, local_branch):
    if revision_id is None:
        base_tree = branch.bzrdir.open_workingtree()
    else:
        if local_branch is not None:
            if local_branch.base != branch.base:
                local_branch.fetch(branch, revision_id)
            base_tree = local_branch.repository.revision_tree(revision_id)
        else:
            base_tree = branch.repository.revision_tree(revision_id)
    return base_tree


def _get_revid_tree_from_tree(tree, revision_id, local_branch):
    if revision_id is None:
        return tree
    if local_branch is not None:
        if local_branch.base != tree.branch.base:
            local_branch.fetch(tree.branch, revision_id)
        return local_branch.repository.revision_tree(revision_id)
    return tree.branch.repository.revision_tree(revision_id)


def transform_tree(from_tree, to_tree, interesting_ids=None):
    merge_inner(from_tree.branch, to_tree, from_tree, ignore_zero=True,
                interesting_ids=interesting_ids, this_tree=from_tree)


class Merger(object):
    def __init__(self, this_branch, other_tree=None, base_tree=None,
                 this_tree=None, pb=DummyProgress(), change_reporter=None,
                 recurse='down'):
        object.__init__(self)
        assert this_tree is not None, "this_tree is required"
        self.this_branch = this_branch
        self.this_basis = this_branch.last_revision()
        self.this_rev_id = None
        self.this_tree = this_tree
        self.this_revision_tree = None
        self.this_basis_tree = None
        self.other_tree = other_tree
        self.other_branch = None
        self.base_tree = base_tree
        self.ignore_zero = False
        self.backup_files = False
        self.interesting_ids = None
        self.show_base = False
        self.reprocess = False
        self._pb = pb
        self.pp = None
        self.recurse = recurse
        self.change_reporter = change_reporter

    def revision_tree(self, revision_id):
        return self.this_branch.repository.revision_tree(revision_id)

    def ensure_revision_trees(self):
        if self.this_revision_tree is None:
            self.this_basis_tree = self.this_branch.repository.revision_tree(
                self.this_basis)
            if self.this_basis == self.this_rev_id:
                self.this_revision_tree = self.this_basis_tree

        if self.other_rev_id is None:
            other_basis_tree = self.revision_tree(self.other_basis)
            changes = other_basis_tree.changes_from(self.other_tree)
            if changes.has_changed():
                raise WorkingTreeNotRevision(self.this_tree)
            other_rev_id = self.other_basis
            self.other_tree = other_basis_tree

    def file_revisions(self, file_id):
        self.ensure_revision_trees()
        def get_id(tree, file_id):
            revision_id = tree.inventory[file_id].revision
            assert revision_id is not None
            return revision_id
        if self.this_rev_id is None:
            if self.this_basis_tree.get_file_sha1(file_id) != \
                self.this_tree.get_file_sha1(file_id):
                raise WorkingTreeNotRevision(self.this_tree)

        trees = (self.this_basis_tree, self.other_tree)
        return [get_id(tree, file_id) for tree in trees]

    def check_basis(self, check_clean, require_commits=True):
        if self.this_basis is None and require_commits is True:
            raise BzrCommandError("This branch has no commits."
                                  " (perhaps you would prefer 'bzr pull')")
        if check_clean:
            self.compare_basis()
            if self.this_basis != self.this_rev_id:
                raise BzrCommandError("Working tree has uncommitted changes.")

    def compare_basis(self):
        changes = self.this_tree.changes_from(self.this_tree.basis_tree())
        if not changes.has_changed():
            self.this_rev_id = self.this_basis

    def set_interesting_files(self, file_list):
        try:
            self._set_interesting_files(file_list)
        except NotVersionedError, e:
            raise BzrCommandError("%s is not a source file in any"
                                      " tree." % e.path)

    def _set_interesting_files(self, file_list):
        """Set the list of interesting ids from a list of files."""
        if file_list is None:
            self.interesting_ids = None
            return

        interesting_ids = set()
        for path in file_list:
            found_id = False
            # TODO: jam 20070226 The trees are not locked at this time,
            #       wouldn't it make merge faster if it locks everything in the
            #       beginning? It locks at do_merge time, but this happens
            #       before that.
            for tree in (self.this_tree, self.base_tree, self.other_tree):
                file_id = tree.path2id(path)
                if file_id is not None:
                    interesting_ids.add(file_id)
                    found_id = True
            if not found_id:
                raise NotVersionedError(path=path)
        self.interesting_ids = interesting_ids

    def set_pending(self):
        if not self.base_is_ancestor:
            return
        if self.other_rev_id is None:
            return
        ancestry = self.this_branch.repository.get_ancestry(self.this_basis)
        if self.other_rev_id in ancestry:
            return
        self.this_tree.add_parent_tree((self.other_rev_id, self.other_tree))

    def set_other(self, other_revision, possible_transports=None):
        """Set the revision and tree to merge from.

        This sets the other_tree, other_rev_id, other_basis attributes.

        :param other_revision: The [path, revision] list to merge from.
        """
        self.other_branch, self.other_tree = _get_tree(other_revision,
                                                       self.this_branch,
                                                       possible_transports)
        if other_revision[1] == -1:
            self.other_rev_id = self.other_branch.last_revision()
            if self.other_rev_id is None:
                raise NoCommits(self.other_branch)
            self.other_basis = self.other_rev_id
        elif other_revision[1] is not None:
            self.other_rev_id = self.other_branch.get_rev_id(other_revision[1])
            self.other_basis = self.other_rev_id
        else:
            self.other_rev_id = None
            self.other_basis = self.other_branch.last_revision()
            if self.other_basis is None:
                raise NoCommits(self.other_branch)
        if self.other_branch.base != self.this_branch.base:
            self.this_branch.fetch(self.other_branch,
                                   last_revision=self.other_basis)

    def set_other_revision(self, revision_id, other_branch):
        """Set 'other' based on a branch and revision id

        :param revision_id: The revision to use for a tree
        :param other_branch: The branch containing this tree
        """
        self.other_rev_id = revision_id
        self.other_branch = other_branch
        self.this_branch.fetch(other_branch, self.other_rev_id)
        self.other_tree = self.revision_tree(revision_id)
        self.other_basis = revision_id

    def find_base(self):
        self.set_base([None, None])

    def set_base(self, base_revision):
        """Set the base revision to use for the merge.

        :param base_revision: A 2-list containing a path and revision number.
        """
        mutter("doing merge() with no base_revision specified")
        if base_revision == [None, None]:
            try:
                pb = ui.ui_factory.nested_progress_bar()
                try:
                    this_repo = self.this_branch.repository
                    graph = this_repo.get_graph()
                    revisions = [ensure_null(self.this_basis),
                                 ensure_null(self.other_basis)]
                    if NULL_REVISION in revisions:
                        self.base_rev_id = NULL_REVISION
                    else:
                        self.base_rev_id = graph.find_unique_lca(*revisions)
                        if self.base_rev_id == NULL_REVISION:
                            raise UnrelatedBranches()
                finally:
                    pb.finished()
            except NoCommonAncestor:
                raise UnrelatedBranches()
            self.base_tree = _get_revid_tree_from_tree(self.this_tree,
                                                       self.base_rev_id,
                                                       None)
            self.base_is_ancestor = True
        else:
            base_branch, self.base_tree = _get_tree(base_revision)
            if base_revision[1] == -1:
                self.base_rev_id = base_branch.last_revision()
            elif base_revision[1] is None:
                self.base_rev_id = None
            else:
                self.base_rev_id = base_branch.get_rev_id(base_revision[1])
            if self.this_branch.base != base_branch.base:
                self.this_branch.fetch(base_branch)
            self.base_is_ancestor = is_ancestor(self.this_basis, 
                                                self.base_rev_id,
                                                self.this_branch)

    def do_merge(self):
        kwargs = {'working_tree':self.this_tree, 'this_tree': self.this_tree,
                  'other_tree': self.other_tree,
                  'interesting_ids': self.interesting_ids,
                  'pp': self.pp}
        if self.merge_type.requires_base:
            kwargs['base_tree'] = self.base_tree
        if self.merge_type.supports_reprocess:
            kwargs['reprocess'] = self.reprocess
        elif self.reprocess:
            raise BzrError("Conflict reduction is not supported for merge"
                                  " type %s." % self.merge_type)
        if self.merge_type.supports_show_base:
            kwargs['show_base'] = self.show_base
        elif self.show_base:
            raise BzrError("Showing base is not supported for this"
                                  " merge type. %s" % self.merge_type)
        self.this_tree.lock_tree_write()
        if self.base_tree is not None:
            self.base_tree.lock_read()
        if self.other_tree is not None:
            self.other_tree.lock_read()
        try:
            merge = self.merge_type(pb=self._pb,
                                    change_reporter=self.change_reporter,
                                    **kwargs)
            if self.recurse == 'down':
                for path, file_id in self.this_tree.iter_references():
                    sub_tree = self.this_tree.get_nested_tree(file_id, path)
                    other_revision = self.other_tree.get_reference_revision(
                        file_id, path)
                    if  other_revision == sub_tree.last_revision():
                        continue
                    sub_merge = Merger(sub_tree.branch, this_tree=sub_tree)
                    sub_merge.merge_type = self.merge_type
                    relpath = self.this_tree.relpath(path)
                    other_branch = self.other_branch.reference_parent(file_id, relpath)
                    sub_merge.set_other_revision(other_revision, other_branch)
                    base_revision = self.base_tree.get_reference_revision(file_id)
                    sub_merge.base_tree = \
                        sub_tree.branch.repository.revision_tree(base_revision)
                    sub_merge.do_merge()

        finally:
            if self.other_tree is not None:
                self.other_tree.unlock()
            if self.base_tree is not None:
                self.base_tree.unlock()
            self.this_tree.unlock()
        if len(merge.cooked_conflicts) == 0:
            if not self.ignore_zero:
                note("All changes applied successfully.")
        else:
            note("%d conflicts encountered." % len(merge.cooked_conflicts))

        return len(merge.cooked_conflicts)

    def regen_inventory(self, new_entries):
        old_entries = self.this_tree.read_working_inventory()
        new_inventory = {}
        by_path = {}
        new_entries_map = {} 
        for path, file_id in new_entries:
            if path is None:
                continue
            new_entries_map[file_id] = path

        def id2path(file_id):
            path = new_entries_map.get(file_id)
            if path is not None:
                return path
            entry = old_entries[file_id]
            if entry.parent_id is None:
                return entry.name
            return pathjoin(id2path(entry.parent_id), entry.name)
            
        for file_id in old_entries:
            entry = old_entries[file_id]
            path = id2path(file_id)
            if file_id in self.base_tree.inventory:
                executable = getattr(self.base_tree.inventory[file_id], 'executable', False)
            else:
                executable = getattr(entry, 'executable', False)
            new_inventory[file_id] = (path, file_id, entry.parent_id, 
                                      entry.kind, executable)
                                      
            by_path[path] = file_id
        
        deletions = 0
        insertions = 0
        new_path_list = []
        for path, file_id in new_entries:
            if path is None:
                del new_inventory[file_id]
                deletions += 1
            else:
                new_path_list.append((path, file_id))
                if file_id not in old_entries:
                    insertions += 1
        # Ensure no file is added before its parent
        new_path_list.sort()
        for path, file_id in new_path_list:
            if path == '':
                parent = None
            else:
                parent = by_path[os.path.dirname(path)]
            abspath = pathjoin(self.this_tree.basedir, path)
            kind = osutils.file_kind(abspath)
            if file_id in self.base_tree.inventory:
                executable = getattr(self.base_tree.inventory[file_id], 'executable', False)
            else:
                executable = False
            new_inventory[file_id] = (path, file_id, parent, kind, executable)
            by_path[path] = file_id 

        # Get a list in insertion order
        new_inventory_list = new_inventory.values()
        mutter ("""Inventory regeneration:
    old length: %i insertions: %i deletions: %i new_length: %i"""\
            % (len(old_entries), insertions, deletions, 
               len(new_inventory_list)))
        assert len(new_inventory_list) == len(old_entries) + insertions\
            - deletions
        new_inventory_list.sort()
        return new_inventory_list


class Merge3Merger(object):
    """Three-way merger that uses the merge3 text merger"""
    requires_base = True
    supports_reprocess = True
    supports_show_base = True
    history_based = False

    def __init__(self, working_tree, this_tree, base_tree, other_tree, 
                 interesting_ids=None, reprocess=False, show_base=False,
                 pb=DummyProgress(), pp=None, change_reporter=None):
        """Initialize the merger object and perform the merge."""
        object.__init__(self)
        self.this_tree = working_tree
        self.this_tree.lock_tree_write()
        self.base_tree = base_tree
        self.base_tree.lock_read()
        self.other_tree = other_tree
        self.other_tree.lock_read()
        self._raw_conflicts = []
        self.cooked_conflicts = []
        self.reprocess = reprocess
        self.show_base = show_base
        self.pb = pb
        self.pp = pp
        self.change_reporter = change_reporter
        if self.pp is None:
            self.pp = ProgressPhase("Merge phase", 3, self.pb)

        if interesting_ids is not None:
            all_ids = interesting_ids
        else:
            all_ids = set(base_tree)
            all_ids.update(other_tree)
        self.tt = TreeTransform(working_tree, self.pb)
        try:
            self.pp.next_phase()
            child_pb = ui.ui_factory.nested_progress_bar()
            try:
                for num, file_id in enumerate(all_ids):
                    child_pb.update('Preparing file merge', num, len(all_ids))
                    self.merge_names(file_id)
                    file_status = self.merge_contents(file_id)
                    self.merge_executable(file_id, file_status)
            finally:
                child_pb.finished()
            self.fix_root()
            self.pp.next_phase()
            child_pb = ui.ui_factory.nested_progress_bar()
            try:
                fs_conflicts = resolve_conflicts(self.tt, child_pb)
            finally:
                child_pb.finished()
            if change_reporter is not None:
                from bzrlib import delta
                delta.report_changes(self.tt._iter_changes(), change_reporter)
            self.cook_conflicts(fs_conflicts)
            for conflict in self.cooked_conflicts:
                warning(conflict)
            self.pp.next_phase()
            results = self.tt.apply()
            self.write_modified(results)
            try:
                working_tree.add_conflicts(self.cooked_conflicts)
            except UnsupportedOperation:
                pass
        finally:
            self.tt.finalize()
            self.other_tree.unlock()
            self.base_tree.unlock()
            self.this_tree.unlock()
            self.pb.clear()

    def fix_root(self):
        try:
            self.tt.final_kind(self.tt.root)
        except NoSuchFile:
            self.tt.cancel_deletion(self.tt.root)
        if self.tt.final_file_id(self.tt.root) is None:
            self.tt.version_file(self.tt.tree_file_id(self.tt.root), 
                                 self.tt.root)
        if self.other_tree.inventory.root is None:
            return
        other_root_file_id = self.other_tree.inventory.root.file_id
        other_root = self.tt.trans_id_file_id(other_root_file_id)
        if other_root == self.tt.root:
            return
        try:
            self.tt.final_kind(other_root)
        except NoSuchFile:
            return
        self.reparent_children(self.other_tree.inventory.root, self.tt.root)
        self.tt.cancel_creation(other_root)
        self.tt.cancel_versioning(other_root)

    def reparent_children(self, ie, target):
        for thing, child in ie.children.iteritems():
            trans_id = self.tt.trans_id_file_id(child.file_id)
            self.tt.adjust_path(self.tt.final_name(trans_id), target, trans_id)

    def write_modified(self, results):
        modified_hashes = {}
        for path in results.modified_paths:
            file_id = self.this_tree.path2id(self.this_tree.relpath(path))
            if file_id is None:
                continue
            hash = self.this_tree.get_file_sha1(file_id)
            if hash is None:
                continue
            modified_hashes[file_id] = hash
        self.this_tree.set_merge_modified(modified_hashes)

    @staticmethod
    def parent(entry, file_id):
        """Determine the parent for a file_id (used as a key method)"""
        if entry is None:
            return None
        return entry.parent_id

    @staticmethod
    def name(entry, file_id):
        """Determine the name for a file_id (used as a key method)"""
        if entry is None:
            return None
        return entry.name
    
    @staticmethod
    def contents_sha1(tree, file_id):
        """Determine the sha1 of the file contents (used as a key method)."""
        if file_id not in tree:
            return None
        return tree.get_file_sha1(file_id)

    @staticmethod
    def executable(tree, file_id):
        """Determine the executability of a file-id (used as a key method)."""
        if file_id not in tree:
            return None
        if tree.kind(file_id) != "file":
            return False
        return tree.is_executable(file_id)

    @staticmethod
    def kind(tree, file_id):
        """Determine the kind of a file-id (used as a key method)."""
        if file_id not in tree:
            return None
        return tree.kind(file_id)

    @staticmethod
    def scalar_three_way(this_tree, base_tree, other_tree, file_id, key):
        """Do a three-way test on a scalar.
        Return "this", "other" or "conflict", depending whether a value wins.
        """
        key_base = key(base_tree, file_id)
        key_other = key(other_tree, file_id)
        #if base == other, either they all agree, or only THIS has changed.
        if key_base == key_other:
            return "this"
        key_this = key(this_tree, file_id)
        if key_this not in (key_base, key_other):
            return "conflict"
        # "Ambiguous clean merge"
        elif key_this == key_other:
            return "this"
        else:
            assert key_this == key_base
            return "other"

    def merge_names(self, file_id):
        """Perform a merge on file_id names and parents"""
        def get_entry(tree):
            if file_id in tree.inventory:
                return tree.inventory[file_id]
            else:
                return None
        this_entry = get_entry(self.this_tree)
        other_entry = get_entry(self.other_tree)
        base_entry = get_entry(self.base_tree)
        name_winner = self.scalar_three_way(this_entry, base_entry, 
                                            other_entry, file_id, self.name)
        parent_id_winner = self.scalar_three_way(this_entry, base_entry, 
                                                 other_entry, file_id, 
                                                 self.parent)
        if this_entry is None:
            if name_winner == "this":
                name_winner = "other"
            if parent_id_winner == "this":
                parent_id_winner = "other"
        if name_winner == "this" and parent_id_winner == "this":
            return
        if name_winner == "conflict":
            trans_id = self.tt.trans_id_file_id(file_id)
            self._raw_conflicts.append(('name conflict', trans_id, 
                                        self.name(this_entry, file_id), 
                                        self.name(other_entry, file_id)))
        if parent_id_winner == "conflict":
            trans_id = self.tt.trans_id_file_id(file_id)
            self._raw_conflicts.append(('parent conflict', trans_id, 
                                        self.parent(this_entry, file_id), 
                                        self.parent(other_entry, file_id)))
        if other_entry is None:
            # it doesn't matter whether the result was 'other' or 
            # 'conflict'-- if there's no 'other', we leave it alone.
            return
        # if we get here, name_winner and parent_winner are set to safe values.
        winner_entry = {"this": this_entry, "other": other_entry, 
                        "conflict": other_entry}
        trans_id = self.tt.trans_id_file_id(file_id)
        parent_id = winner_entry[parent_id_winner].parent_id
        if parent_id is not None:
            parent_trans_id = self.tt.trans_id_file_id(parent_id)
            self.tt.adjust_path(winner_entry[name_winner].name, 
                                parent_trans_id, trans_id)

    def merge_contents(self, file_id):
        """Performa a merge on file_id contents."""
        def contents_pair(tree):
            if file_id not in tree:
                return (None, None)
            kind = tree.kind(file_id)
            if kind == "file":
                contents = tree.get_file_sha1(file_id)
            elif kind == "symlink":
                contents = tree.get_symlink_target(file_id)
            else:
                contents = None
            return kind, contents

        def contents_conflict():
            trans_id = self.tt.trans_id_file_id(file_id)
            name = self.tt.final_name(trans_id)
            parent_id = self.tt.final_parent(trans_id)
            if file_id in self.this_tree.inventory:
                self.tt.unversion_file(trans_id)
                if file_id in self.this_tree:
                    self.tt.delete_contents(trans_id)
            file_group = self._dump_conflicts(name, parent_id, file_id, 
                                              set_version=True)
            self._raw_conflicts.append(('contents conflict', file_group))

        # See SPOT run.  run, SPOT, run.
        # So we're not QUITE repeating ourselves; we do tricky things with
        # file kind...
        base_pair = contents_pair(self.base_tree)
        other_pair = contents_pair(self.other_tree)
        if base_pair == other_pair:
            # OTHER introduced no changes
            return "unmodified"
        this_pair = contents_pair(self.this_tree)
        if this_pair == other_pair:
            # THIS and OTHER introduced the same changes
            return "unmodified"
        else:
            trans_id = self.tt.trans_id_file_id(file_id)
            if this_pair == base_pair:
                # only OTHER introduced changes
                if file_id in self.this_tree:
                    # Remove any existing contents
                    self.tt.delete_contents(trans_id)
                if file_id in self.other_tree:
                    # OTHER changed the file
                    create_by_entry(self.tt, 
                                    self.other_tree.inventory[file_id], 
                                    self.other_tree, trans_id)
                    if file_id not in self.this_tree.inventory:
                        self.tt.version_file(file_id, trans_id)
                    return "modified"
                elif file_id in self.this_tree.inventory:
                    # OTHER deleted the file
                    self.tt.unversion_file(trans_id)
                    return "deleted"
            #BOTH THIS and OTHER introduced changes; scalar conflict
            elif this_pair[0] == "file" and other_pair[0] == "file":
                # THIS and OTHER are both files, so text merge.  Either
                # BASE is a file, or both converted to files, so at least we
                # have agreement that output should be a file.
                try:
                    self.text_merge(file_id, trans_id)
                except BinaryFile:
                    return contents_conflict()
                if file_id not in self.this_tree.inventory:
                    self.tt.version_file(file_id, trans_id)
                try:
                    self.tt.tree_kind(trans_id)
                    self.tt.delete_contents(trans_id)
                except NoSuchFile:
                    pass
                return "modified"
            else:
                # Scalar conflict, can't text merge.  Dump conflicts
                return contents_conflict()

    def get_lines(self, tree, file_id):
        """Return the lines in a file, or an empty list."""
        if file_id in tree:
            return tree.get_file(file_id).readlines()
        else:
            return []

    def text_merge(self, file_id, trans_id):
        """Perform a three-way text merge on a file_id"""
        # it's possible that we got here with base as a different type.
        # if so, we just want two-way text conflicts.
        if file_id in self.base_tree and \
            self.base_tree.kind(file_id) == "file":
            base_lines = self.get_lines(self.base_tree, file_id)
        else:
            base_lines = []
        other_lines = self.get_lines(self.other_tree, file_id)
        this_lines = self.get_lines(self.this_tree, file_id)
        m3 = Merge3(base_lines, this_lines, other_lines)
        start_marker = "!START OF MERGE CONFLICT!" + "I HOPE THIS IS UNIQUE"
        if self.show_base is True:
            base_marker = '|' * 7
        else:
            base_marker = None

        def iter_merge3(retval):
            retval["text_conflicts"] = False
            for line in m3.merge_lines(name_a = "TREE", 
                                       name_b = "MERGE-SOURCE", 
                                       name_base = "BASE-REVISION",
                                       start_marker=start_marker, 
                                       base_marker=base_marker,
                                       reprocess=self.reprocess):
                if line.startswith(start_marker):
                    retval["text_conflicts"] = True
                    yield line.replace(start_marker, '<' * 7)
                else:
                    yield line
        retval = {}
        merge3_iterator = iter_merge3(retval)
        self.tt.create_file(merge3_iterator, trans_id)
        if retval["text_conflicts"] is True:
            self._raw_conflicts.append(('text conflict', trans_id))
            name = self.tt.final_name(trans_id)
            parent_id = self.tt.final_parent(trans_id)
            file_group = self._dump_conflicts(name, parent_id, file_id, 
                                              this_lines, base_lines,
                                              other_lines)
            file_group.append(trans_id)

    def _dump_conflicts(self, name, parent_id, file_id, this_lines=None, 
                        base_lines=None, other_lines=None, set_version=False,
                        no_base=False):
        """Emit conflict files.
        If this_lines, base_lines, or other_lines are omitted, they will be
        determined automatically.  If set_version is true, the .OTHER, .THIS
        or .BASE (in that order) will be created as versioned files.
        """
        data = [('OTHER', self.other_tree, other_lines), 
                ('THIS', self.this_tree, this_lines)]
        if not no_base:
            data.append(('BASE', self.base_tree, base_lines))
        versioned = False
        file_group = []
        for suffix, tree, lines in data:
            if file_id in tree:
                trans_id = self._conflict_file(name, parent_id, tree, file_id,
                                               suffix, lines)
                file_group.append(trans_id)
                if set_version and not versioned:
                    self.tt.version_file(file_id, trans_id)
                    versioned = True
        return file_group
           
    def _conflict_file(self, name, parent_id, tree, file_id, suffix, 
                       lines=None):
        """Emit a single conflict file."""
        name = name + '.' + suffix
        trans_id = self.tt.create_path(name, parent_id)
        entry = tree.inventory[file_id]
        create_by_entry(self.tt, entry, tree, trans_id, lines)
        return trans_id

    def merge_executable(self, file_id, file_status):
        """Perform a merge on the execute bit."""
        if file_status == "deleted":
            return
        trans_id = self.tt.trans_id_file_id(file_id)
        try:
            if self.tt.final_kind(trans_id) != "file":
                return
        except NoSuchFile:
            return
        winner = self.scalar_three_way(self.this_tree, self.base_tree, 
                                       self.other_tree, file_id, 
                                       self.executable)
        if winner == "conflict":
        # There must be a None in here, if we have a conflict, but we
        # need executability since file status was not deleted.
            if self.executable(self.other_tree, file_id) is None:
                winner = "this"
            else:
                winner = "other"
        if winner == "this":
            if file_status == "modified":
                executability = self.this_tree.is_executable(file_id)
                if executability is not None:
                    trans_id = self.tt.trans_id_file_id(file_id)
                    self.tt.set_executability(executability, trans_id)
        else:
            assert winner == "other"
            if file_id in self.other_tree:
                executability = self.other_tree.is_executable(file_id)
            elif file_id in self.this_tree:
                executability = self.this_tree.is_executable(file_id)
            elif file_id in self.base_tree:
                executability = self.base_tree.is_executable(file_id)
            if executability is not None:
                trans_id = self.tt.trans_id_file_id(file_id)
                self.tt.set_executability(executability, trans_id)

    def cook_conflicts(self, fs_conflicts):
        """Convert all conflicts into a form that doesn't depend on trans_id"""
        from conflicts import Conflict
        name_conflicts = {}
        self.cooked_conflicts.extend(cook_conflicts(fs_conflicts, self.tt))
        fp = FinalPaths(self.tt)
        for conflict in self._raw_conflicts:
            conflict_type = conflict[0]
            if conflict_type in ('name conflict', 'parent conflict'):
                trans_id = conflict[1]
                conflict_args = conflict[2:]
                if trans_id not in name_conflicts:
                    name_conflicts[trans_id] = {}
                unique_add(name_conflicts[trans_id], conflict_type, 
                           conflict_args)
            if conflict_type == 'contents conflict':
                for trans_id in conflict[1]:
                    file_id = self.tt.final_file_id(trans_id)
                    if file_id is not None:
                        break
                path = fp.get_path(trans_id)
                for suffix in ('.BASE', '.THIS', '.OTHER'):
                    if path.endswith(suffix):
                        path = path[:-len(suffix)]
                        break
                c = Conflict.factory(conflict_type, path=path, file_id=file_id)
                self.cooked_conflicts.append(c)
            if conflict_type == 'text conflict':
                trans_id = conflict[1]
                path = fp.get_path(trans_id)
                file_id = self.tt.final_file_id(trans_id)
                c = Conflict.factory(conflict_type, path=path, file_id=file_id)
                self.cooked_conflicts.append(c)

        for trans_id, conflicts in name_conflicts.iteritems():
            try:
                this_parent, other_parent = conflicts['parent conflict']
                assert this_parent != other_parent
            except KeyError:
                this_parent = other_parent = \
                    self.tt.final_file_id(self.tt.final_parent(trans_id))
            try:
                this_name, other_name = conflicts['name conflict']
                assert this_name != other_name
            except KeyError:
                this_name = other_name = self.tt.final_name(trans_id)
            other_path = fp.get_path(trans_id)
            if this_parent is not None and this_name is not None:
                this_parent_path = \
                    fp.get_path(self.tt.trans_id_file_id(this_parent))
                this_path = pathjoin(this_parent_path, this_name)
            else:
                this_path = "<deleted>"
            file_id = self.tt.final_file_id(trans_id)
            c = Conflict.factory('path conflict', path=this_path,
                                 conflict_path=other_path, file_id=file_id)
            self.cooked_conflicts.append(c)
        self.cooked_conflicts.sort(key=Conflict.sort_key)


class WeaveMerger(Merge3Merger):
    """Three-way tree merger, text weave merger."""
    supports_reprocess = True
    supports_show_base = False

    def __init__(self, working_tree, this_tree, base_tree, other_tree, 
                 interesting_ids=None, pb=DummyProgress(), pp=None,
                 reprocess=False, change_reporter=None):
        self.this_revision_tree = self._get_revision_tree(this_tree)
        self.other_revision_tree = self._get_revision_tree(other_tree)
        super(WeaveMerger, self).__init__(working_tree, this_tree, 
                                          base_tree, other_tree, 
                                          interesting_ids=interesting_ids, 
                                          pb=pb, pp=pp, reprocess=reprocess,
                                          change_reporter=change_reporter)

    def _get_revision_tree(self, tree):
        """Return a revision tree related to this tree.
        If the tree is a WorkingTree, the basis will be returned.
        """
        if getattr(tree, 'get_weave', False) is False:
            # If we have a WorkingTree, try using the basis
            return tree.branch.basis_tree()
        else:
            return tree

    def _check_file(self, file_id):
        """Check that the revision tree's version of the file matches."""
        for tree, rt in ((self.this_tree, self.this_revision_tree), 
                         (self.other_tree, self.other_revision_tree)):
            if rt is tree:
                continue
            if tree.get_file_sha1(file_id) != rt.get_file_sha1(file_id):
                raise WorkingTreeNotRevision(self.this_tree)

    def _merged_lines(self, file_id):
        """Generate the merged lines.
        There is no distinction between lines that are meant to contain <<<<<<<
        and conflicts.
        """
        weave = self.this_revision_tree.get_weave(file_id)
        this_revision_id = self.this_revision_tree.inventory[file_id].revision
        other_revision_id = \
            self.other_revision_tree.inventory[file_id].revision
        wm = WeaveMerge(weave, this_revision_id, other_revision_id, 
                        '<<<<<<< TREE\n', '>>>>>>> MERGE-SOURCE\n')
        return wm.merge_lines(self.reprocess)

    def text_merge(self, file_id, trans_id):
        """Perform a (weave) text merge for a given file and file-id.
        If conflicts are encountered, .THIS and .OTHER files will be emitted,
        and a conflict will be noted.
        """
        self._check_file(file_id)
        lines, conflicts = self._merged_lines(file_id)
        lines = list(lines)
        # Note we're checking whether the OUTPUT is binary in this case, 
        # because we don't want to get into weave merge guts.
        check_text_lines(lines)
        self.tt.create_file(lines, trans_id)
        if conflicts:
            self._raw_conflicts.append(('text conflict', trans_id))
            name = self.tt.final_name(trans_id)
            parent_id = self.tt.final_parent(trans_id)
            file_group = self._dump_conflicts(name, parent_id, file_id, 
                                              no_base=True)
            file_group.append(trans_id)


class Diff3Merger(Merge3Merger):
    """Three-way merger using external diff3 for text merging"""

    def dump_file(self, temp_dir, name, tree, file_id):
        out_path = pathjoin(temp_dir, name)
        out_file = open(out_path, "wb")
        try:
            in_file = tree.get_file(file_id)
            for line in in_file:
                out_file.write(line)
        finally:
            out_file.close()
        return out_path

    def text_merge(self, file_id, trans_id):
        """Perform a diff3 merge using a specified file-id and trans-id.
        If conflicts are encountered, .BASE, .THIS. and .OTHER conflict files
        will be dumped, and a will be conflict noted.
        """
        import bzrlib.patch
        temp_dir = osutils.mkdtemp(prefix="bzr-")
        try:
            new_file = pathjoin(temp_dir, "new")
            this = self.dump_file(temp_dir, "this", self.this_tree, file_id)
            base = self.dump_file(temp_dir, "base", self.base_tree, file_id)
            other = self.dump_file(temp_dir, "other", self.other_tree, file_id)
            status = bzrlib.patch.diff3(new_file, this, base, other)
            if status not in (0, 1):
                raise BzrError("Unhandled diff3 exit code")
            f = open(new_file, 'rb')
            try:
                self.tt.create_file(f, trans_id)
            finally:
                f.close()
            if status == 1:
                name = self.tt.final_name(trans_id)
                parent_id = self.tt.final_parent(trans_id)
                self._dump_conflicts(name, parent_id, file_id)
                self._raw_conflicts.append(('text conflict', trans_id))
        finally:
            osutils.rmtree(temp_dir)


def merge_inner(this_branch, other_tree, base_tree, ignore_zero=False,
                backup_files=False,
                merge_type=Merge3Merger,
                interesting_ids=None,
                show_base=False,
                reprocess=False,
                other_rev_id=None,
                interesting_files=None,
                this_tree=None,
                pb=DummyProgress(),
                change_reporter=None):
    """Primary interface for merging. 

        typical use is probably 
        'merge_inner(branch, branch.get_revision_tree(other_revision),
                     branch.get_revision_tree(base_revision))'
        """
    if this_tree is None:
        raise BzrError("bzrlib.merge.merge_inner requires a this_tree "
            "parameter as of bzrlib version 0.8.")
    merger = Merger(this_branch, other_tree, base_tree, this_tree=this_tree,
                    pb=pb, change_reporter=change_reporter)
    merger.backup_files = backup_files
    merger.merge_type = merge_type
    merger.interesting_ids = interesting_ids
    merger.ignore_zero = ignore_zero
    if interesting_files:
        assert not interesting_ids, ('Only supply interesting_ids'
                                     ' or interesting_files')
        merger._set_interesting_files(interesting_files)
    merger.show_base = show_base
    merger.reprocess = reprocess
    merger.other_rev_id = other_rev_id
    merger.other_basis = other_rev_id
    return merger.do_merge()

def get_merge_type_registry():
    """Merge type registry is in bzrlib.option to avoid circular imports.

    This method provides a sanctioned way to retrieve it.
    """
    from bzrlib import option
    return option._merge_type_registry