~bzr-pqm/bzr/bzr.dev

# Copyright (C) 2005, 2006, 2007 Canonical Ltd

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

import os

from StringIO import StringIO

from bzrlib import (

    conflicts,

    errors,

    knit,

    merge as _mod_merge,

    option,

    progress,

    transform,

    versionedfile,

    )

from bzrlib.branch import Branch

from bzrlib.conflicts import ConflictList, TextConflict

from bzrlib.errors import UnrelatedBranches, NoCommits, BzrCommandError

from bzrlib.merge import transform_tree, merge_inner, _PlanMerge

from bzrlib.osutils import pathjoin, file_kind

from bzrlib.tests import TestCaseWithTransport, TestCaseWithMemoryTransport

from bzrlib.trace import (enable_test_log, disable_test_log)

from bzrlib.workingtree import WorkingTree

class TestMerge(TestCaseWithTransport):

    """Test appending more than one revision"""

    def test_pending(self):

        wt = self.make_branch_and_tree('.')

        rev_a = wt.commit("lala!")

        self.assertEqual([rev_a], wt.get_parent_ids())

        self.assertRaises(errors.PointlessMerge, wt.merge_from_branch,

                          wt.branch)

        self.assertEqual([rev_a], wt.get_parent_ids())

        return wt

    def test_undo(self):

        wt = self.make_branch_and_tree('.')

        wt.commit("lala!")

        wt.commit("haha!")

        wt.commit("blabla!")

        wt.merge_from_branch(wt.branch, wt.branch.get_rev_id(2),

                             wt.branch.get_rev_id(1))

    def test_nocommits(self):

        wt = self.test_pending()

        wt2 = self.make_branch_and_tree('branch2')

        self.assertRaises(NoCommits, wt.merge_from_branch, wt2.branch)

        return wt, wt2

    def test_unrelated(self):

        wt, wt2 = self.test_nocommits()

        wt2.commit("blah")

        self.assertRaises(UnrelatedBranches, wt.merge_from_branch, wt2.branch)

        return wt2

    def test_merge_one_file(self):

        """Do a partial merge of a tree which should not affect tree parents."""

        wt1 = self.make_branch_and_tree('branch1')

        tip = wt1.commit('empty commit')

        wt2 = self.make_branch_and_tree('branch2')

        wt2.pull(wt1.branch)

        file('branch1/foo', 'wb').write('foo')

        file('branch1/bar', 'wb').write('bar')

        wt1.add('foo')

        wt1.add('bar')

        wt1.commit('add foobar')

        os.chdir('branch2')

        self.run_bzr('merge ../branch1/baz', retcode=3)

        self.run_bzr('merge ../branch1/foo')

        self.failUnlessExists('foo')

        self.failIfExists('bar')

        wt2 = WorkingTree.open('.') # opens branch2

        self.assertEqual([tip], wt2.get_parent_ids())

    def test_pending_with_null(self):

        """When base is forced to revno 0, parent_ids are set"""

        wt2 = self.test_unrelated()

        wt1 = WorkingTree.open('.')

        br1 = wt1.branch

        br1.fetch(wt2.branch)

        # merge all of branch 2 into branch 1 even though they 

        # are not related.

        wt1.merge_from_branch(wt2.branch, wt2.last_revision(), 'null:')

        self.assertEqual([br1.last_revision(), wt2.branch.last_revision()],

            wt1.get_parent_ids())

        return (wt1, wt2.branch)

    def test_two_roots(self):

        """Merge base is sane when two unrelated branches are merged"""

        wt1, br2 = self.test_pending_with_null()

        wt1.commit("blah")

        wt1.lock_read()

        try:

            last = wt1.branch.last_revision()

            last2 = br2.last_revision()

            graph = wt1.branch.repository.get_graph()

            self.assertEqual(last2, graph.find_unique_lca(last, last2))

        finally:

            wt1.unlock()

    def test_create_rename(self):

        """Rename an inventory entry while creating the file"""

        tree =self.make_branch_and_tree('.')

        file('name1', 'wb').write('Hello')

        tree.add('name1')

        tree.commit(message="hello")

        tree.rename_one('name1', 'name2')

        os.unlink('name2')

        transform_tree(tree, tree.branch.basis_tree())

    def test_layered_rename(self):

        """Rename both child and parent at same time"""

        tree =self.make_branch_and_tree('.')

        os.mkdir('dirname1')

        tree.add('dirname1')

        filename = pathjoin('dirname1', 'name1')

        file(filename, 'wb').write('Hello')

        tree.add(filename)

        tree.commit(message="hello")

        filename2 = pathjoin('dirname1', 'name2')

        tree.rename_one(filename, filename2)

        tree.rename_one('dirname1', 'dirname2')

        transform_tree(tree, tree.branch.basis_tree())

    def test_ignore_zero_merge_inner(self):

        # Test that merge_inner's ignore zero parameter is effective

        tree_a =self.make_branch_and_tree('a')

        tree_a.commit(message="hello")

        dir_b = tree_a.bzrdir.sprout('b')

        tree_b = dir_b.open_workingtree()

        tree_b.lock_write()

        self.addCleanup(tree_b.unlock)

        tree_a.commit(message="hello again")

        log = StringIO()

        merge_inner(tree_b.branch, tree_a, tree_b.basis_tree(), 

                    this_tree=tree_b, ignore_zero=True)

        log = self._get_log(keep_log_file=True)

        self.failUnless('All changes applied successfully.\n' not in log)

        tree_b.revert()

        merge_inner(tree_b.branch, tree_a, tree_b.basis_tree(), 

                    this_tree=tree_b, ignore_zero=False)

        log = self._get_log(keep_log_file=True)

        self.failUnless('All changes applied successfully.\n' in log)

    def test_merge_inner_conflicts(self):

        tree_a = self.make_branch_and_tree('a')

        tree_a.set_conflicts(ConflictList([TextConflict('patha')]))

        merge_inner(tree_a.branch, tree_a, tree_a, this_tree=tree_a)

        self.assertEqual(1, len(tree_a.conflicts()))

    def test_rmdir_conflict(self):

        tree_a = self.make_branch_and_tree('a')

        self.build_tree(['a/b/'])

        tree_a.add('b', 'b-id')

        tree_a.commit('added b')

        # basis_tree() is only guaranteed to be valid as long as it is actually

        # the basis tree. This mutates the tree after grabbing basis, so go to

        # the repository.

        base_tree = tree_a.branch.repository.revision_tree(tree_a.last_revision())

        tree_z = tree_a.bzrdir.sprout('z').open_workingtree()

        self.build_tree(['a/b/c'])

        tree_a.add('b/c')

        tree_a.commit('added c')

        os.rmdir('z/b')

        tree_z.commit('removed b')

        merge_inner(tree_z.branch, tree_a, base_tree, this_tree=tree_z)

        self.assertEqual([

            conflicts.MissingParent('Created directory', 'b', 'b-id'),

            conflicts.UnversionedParent('Versioned directory', 'b', 'b-id')],

            tree_z.conflicts())

        merge_inner(tree_a.branch, tree_z.basis_tree(), base_tree,

                    this_tree=tree_a)

        self.assertEqual([

            conflicts.DeletingParent('Not deleting', 'b', 'b-id'),

            conflicts.UnversionedParent('Versioned directory', 'b', 'b-id')],

            tree_a.conflicts())

    def test_nested_merge(self):

        tree = self.make_branch_and_tree('tree',

            format='dirstate-with-subtree')

        sub_tree = self.make_branch_and_tree('tree/sub-tree',

            format='dirstate-with-subtree')

        sub_tree.set_root_id('sub-tree-root')

        self.build_tree_contents([('tree/sub-tree/file', 'text1')])

        sub_tree.add('file')

        sub_tree.commit('foo')

        tree.add_reference(sub_tree)

        tree.commit('set text to 1')

        tree2 = tree.bzrdir.sprout('tree2').open_workingtree()

        # modify the file in the subtree

        self.build_tree_contents([('tree2/sub-tree/file', 'text2')])

        # and merge the changes from the diverged subtree into the containing

        # tree

        tree2.commit('changed file text')

        tree.merge_from_branch(tree2.branch)

        self.assertFileEqual('text2', 'tree/sub-tree/file')

    def test_merge_with_missing(self):

        tree_a = self.make_branch_and_tree('tree_a')

        self.build_tree_contents([('tree_a/file', 'content_1')])

        tree_a.add('file')

        tree_a.commit('commit base')

        # basis_tree() is only guaranteed to be valid as long as it is actually

        # the basis tree. This mutates the tree after grabbing basis, so go to

        # the repository.

        base_tree = tree_a.branch.repository.revision_tree(tree_a.last_revision())

        tree_b = tree_a.bzrdir.sprout('tree_b').open_workingtree()

        self.build_tree_contents([('tree_a/file', 'content_2')])

        tree_a.commit('commit other')

        other_tree = tree_a.basis_tree()

        os.unlink('tree_b/file')

        merge_inner(tree_b.branch, other_tree, base_tree, this_tree=tree_b)

    def test_merge_kind_change(self):

        tree_a = self.make_branch_and_tree('tree_a')

        self.build_tree_contents([('tree_a/file', 'content_1')])

        tree_a.add('file', 'file-id')

        tree_a.commit('added file')

        tree_b = tree_a.bzrdir.sprout('tree_b').open_workingtree()

        os.unlink('tree_a/file')

        self.build_tree(['tree_a/file/'])

        tree_a.commit('changed file to directory')

        tree_b.merge_from_branch(tree_a.branch)

        self.assertEqual('directory', file_kind('tree_b/file'))

        tree_b.revert()

        self.assertEqual('file', file_kind('tree_b/file'))

        self.build_tree_contents([('tree_b/file', 'content_2')])

        tree_b.commit('content change')

        tree_b.merge_from_branch(tree_a.branch)

        self.assertEqual(tree_b.conflicts(),

                         [conflicts.ContentsConflict('file',

                          file_id='file-id')])

    def test_merge_type_registry(self):

        merge_type_option = option.Option.OPTIONS['merge-type']

        self.assertFalse('merge4' in [x[0] for x in 

                        merge_type_option.iter_switches()])

        registry = _mod_merge.get_merge_type_registry()

        registry.register_lazy('merge4', 'bzrlib.merge', 'Merge4Merger',

                               'time-travelling merge')

        self.assertTrue('merge4' in [x[0] for x in 

                        merge_type_option.iter_switches()])

        registry.remove('merge4')

        self.assertFalse('merge4' in [x[0] for x in 

                        merge_type_option.iter_switches()])

    def test_merge_other_moves_we_deleted(self):

        tree_a = self.make_branch_and_tree('A')

        tree_a.lock_write()

        self.addCleanup(tree_a.unlock)

        self.build_tree(['A/a'])

        tree_a.add('a')

        tree_a.commit('1', rev_id='rev-1')

        tree_a.flush()

        tree_a.rename_one('a', 'b')

        tree_a.commit('2')

        bzrdir_b = tree_a.bzrdir.sprout('B', revision_id='rev-1')

        tree_b = bzrdir_b.open_workingtree()

        tree_b.lock_write()

        self.addCleanup(tree_b.unlock)

        os.unlink('B/a')

        tree_b.commit('3')

        try:

            tree_b.merge_from_branch(tree_a.branch)

        except AttributeError:

            self.fail('tried to join a path when name was None')

    def test_merge_uncommitted_otherbasis_ancestor_of_thisbasis(self):

        tree_a = self.make_branch_and_tree('a')

        self.build_tree(['a/file_1', 'a/file_2'])

        tree_a.add(['file_1'])

        tree_a.commit('commit 1')

        tree_a.add(['file_2'])

        tree_a.commit('commit 2')

        tree_b = tree_a.bzrdir.sprout('b').open_workingtree()

        tree_b.rename_one('file_1', 'renamed')

        merger = _mod_merge.Merger.from_uncommitted(tree_a, tree_b,

                                                    progress.DummyProgress())

        merger.merge_type = _mod_merge.Merge3Merger

        merger.do_merge()

        self.assertEqual(tree_a.get_parent_ids(), [tree_b.last_revision()])

    def test_merge_uncommitted_otherbasis_ancestor_of_thisbasis_weave(self):

        tree_a = self.make_branch_and_tree('a')

        self.build_tree(['a/file_1', 'a/file_2'])

        tree_a.add(['file_1'])

        tree_a.commit('commit 1')

        tree_a.add(['file_2'])

        tree_a.commit('commit 2')

        tree_b = tree_a.bzrdir.sprout('b').open_workingtree()

        tree_b.rename_one('file_1', 'renamed')

        merger = _mod_merge.Merger.from_uncommitted(tree_a, tree_b,

                                                    progress.DummyProgress())

        merger.merge_type = _mod_merge.WeaveMerger

        merger.do_merge()

        self.assertEqual(tree_a.get_parent_ids(), [tree_b.last_revision()])

    def prepare_cherrypick(self):

        """Prepare a pair of trees for cherrypicking tests.

        Both trees have a file, 'file'.

        rev1 sets content to 'a'.

        rev2b adds 'b'.

        rev3b adds 'c'.

        A full merge of rev2b and rev3b into this_tree would add both 'b' and

        'c'.  A successful cherrypick of rev2b-rev3b into this_tree will add

        'c', but not 'b'.

        """

        this_tree = self.make_branch_and_tree('this')

        self.build_tree_contents([('this/file', "a\n")])

        this_tree.add('file')

        this_tree.commit('rev1')

        other_tree = this_tree.bzrdir.sprout('other').open_workingtree()

        self.build_tree_contents([('other/file', "a\nb\n")])

        other_tree.commit('rev2b', rev_id='rev2b')

        self.build_tree_contents([('other/file', "c\na\nb\n")])

        other_tree.commit('rev3b', rev_id='rev3b')

        this_tree.lock_write()

        self.addCleanup(this_tree.unlock)

        return this_tree, other_tree

    def test_weave_cherrypick(self):

        this_tree, other_tree = self.prepare_cherrypick()

        merger = _mod_merge.Merger.from_revision_ids(progress.DummyProgress(),

            this_tree, 'rev3b', 'rev2b', other_tree.branch)

        merger.merge_type = _mod_merge.WeaveMerger

        merger.do_merge()

        self.assertFileEqual('c\na\n', 'this/file')

    def test_weave_cannot_reverse_cherrypick(self):

        this_tree, other_tree = self.prepare_cherrypick()

        merger = _mod_merge.Merger.from_revision_ids(progress.DummyProgress(),

            this_tree, 'rev2b', 'rev3b', other_tree.branch)

        merger.merge_type = _mod_merge.WeaveMerger

        self.assertRaises(errors.CannotReverseCherrypick, merger.do_merge)

    def test_merge3_can_reverse_cherrypick(self):

        this_tree, other_tree = self.prepare_cherrypick()

        merger = _mod_merge.Merger.from_revision_ids(progress.DummyProgress(),

            this_tree, 'rev2b', 'rev3b', other_tree.branch)

        merger.merge_type = _mod_merge.Merge3Merger

        merger.do_merge()

    def test_merge3_will_detect_cherrypick(self):

        this_tree = self.make_branch_and_tree('this')

        self.build_tree_contents([('this/file', "a\n")])

        this_tree.add('file')

        this_tree.commit('rev1')

        other_tree = this_tree.bzrdir.sprout('other').open_workingtree()

        self.build_tree_contents([('other/file', "a\nb\n")])

        other_tree.commit('rev2b', rev_id='rev2b')

        self.build_tree_contents([('other/file', "a\nb\nc\n")])

        other_tree.commit('rev3b', rev_id='rev3b')

        this_tree.lock_write()

        self.addCleanup(this_tree.unlock)

        merger = _mod_merge.Merger.from_revision_ids(progress.DummyProgress(),

            this_tree, 'rev3b', 'rev2b', other_tree.branch)

        merger.merge_type = _mod_merge.Merge3Merger

        merger.do_merge()

        self.assertFileEqual('a\n'

                             '<<<<<<< TREE\n'

                             '=======\n'

                             'c\n'

                             '>>>>>>> MERGE-SOURCE\n',

                             'this/file')

    def test_make_merger(self):

        this_tree = self.make_branch_and_tree('this')

        this_tree.commit('rev1', rev_id='rev1')

        other_tree = this_tree.bzrdir.sprout('other').open_workingtree()

        this_tree.commit('rev2', rev_id='rev2a')

        other_tree.commit('rev2', rev_id='rev2b')

        this_tree.lock_write()

        self.addCleanup(this_tree.unlock)

        merger = _mod_merge.Merger.from_revision_ids(progress.DummyProgress,

            this_tree, 'rev2b', other_branch=other_tree.branch)

        merger.merge_type = _mod_merge.Merge3Merger

        tree_merger = merger.make_merger()

        self.assertIs(_mod_merge.Merge3Merger, tree_merger.__class__)

        self.assertEqual('rev2b', tree_merger.other_tree.get_revision_id())

        self.assertEqual('rev1', tree_merger.base_tree.get_revision_id())

    def test_make_preview_transform(self):

        this_tree = self.make_branch_and_tree('this')

        self.build_tree_contents([('this/file', '1\n')])

        this_tree.add('file', 'file-id')

        this_tree.commit('rev1', rev_id='rev1')

        other_tree = this_tree.bzrdir.sprout('other').open_workingtree()

        self.build_tree_contents([('this/file', '1\n2a\n')])

        this_tree.commit('rev2', rev_id='rev2a')

        self.build_tree_contents([('other/file', '2b\n1\n')])

        other_tree.commit('rev2', rev_id='rev2b')

        this_tree.lock_write()

        self.addCleanup(this_tree.unlock)

        merger = _mod_merge.Merger.from_revision_ids(progress.DummyProgress(),

            this_tree, 'rev2b', other_branch=other_tree.branch)

        merger.merge_type = _mod_merge.Merge3Merger

        tree_merger = merger.make_merger()

        tt = tree_merger.make_preview_transform()

        self.addCleanup(tt.finalize)

        preview_tree = tt.get_preview_tree()

        tree_file = this_tree.get_file('file-id')

        try:

            self.assertEqual('1\n2a\n', tree_file.read())

        finally:

            tree_file.close()

        preview_file = preview_tree.get_file('file-id')

        try:

            self.assertEqual('2b\n1\n2a\n', preview_file.read())

        finally:

            preview_file.close()

    def test_do_merge(self):

        this_tree = self.make_branch_and_tree('this')

        self.build_tree_contents([('this/file', '1\n')])

        this_tree.add('file', 'file-id')

        this_tree.commit('rev1', rev_id='rev1')

        other_tree = this_tree.bzrdir.sprout('other').open_workingtree()

        self.build_tree_contents([('this/file', '1\n2a\n')])

        this_tree.commit('rev2', rev_id='rev2a')

        self.build_tree_contents([('other/file', '2b\n1\n')])

        other_tree.commit('rev2', rev_id='rev2b')

        this_tree.lock_write()

        self.addCleanup(this_tree.unlock)

        merger = _mod_merge.Merger.from_revision_ids(progress.DummyProgress(),

            this_tree, 'rev2b', other_branch=other_tree.branch)

        merger.merge_type = _mod_merge.Merge3Merger

        tree_merger = merger.make_merger()

        tt = tree_merger.do_merge()

        tree_file = this_tree.get_file('file-id')

        try:

            self.assertEqual('2b\n1\n2a\n', tree_file.read())

        finally:

            tree_file.close()

    def test_merge_add_into_deleted_root(self):

        # Yes, people actually do this.  And report bugs if it breaks.

        source = self.make_branch_and_tree('source', format='rich-root-pack')

        self.build_tree(['source/foo/'])

        source.add('foo', 'foo-id')

        source.commit('Add foo')

        target = source.bzrdir.sprout('target').open_workingtree()

        subtree = target.extract('foo-id')

        subtree.commit('Delete root')

        self.build_tree(['source/bar'])

        source.add('bar', 'bar-id')

        source.commit('Add bar')

        subtree.merge_from_branch(source.branch)

class TestPlanMerge(TestCaseWithMemoryTransport):

    def setUp(self):

        TestCaseWithMemoryTransport.setUp(self)

        mapper = versionedfile.PrefixMapper()

        factory = knit.make_file_factory(True, mapper)

        self.vf = factory(self.get_transport())

        self.plan_merge_vf = versionedfile._PlanMergeVersionedFile('root')

        self.plan_merge_vf.fallback_versionedfiles.append(self.vf)

    def add_version(self, key, parents, text):

        self.vf.add_lines(key, parents, [c+'\n' for c in text])

    def add_rev(self, prefix, revision_id, parents, text):

        self.add_version((prefix, revision_id), [(prefix, p) for p in parents],

                         text)

    def add_uncommitted_version(self, key, parents, text):

        self.plan_merge_vf.add_lines(key, parents,

                                     [c+'\n' for c in text])

    def setup_plan_merge(self):

        self.add_rev('root', 'A', [], 'abc')

        self.add_rev('root', 'B', ['A'], 'acehg')

        self.add_rev('root', 'C', ['A'], 'fabg')

        return _PlanMerge('B', 'C', self.plan_merge_vf, ('root',))

    def setup_plan_merge_uncommitted(self):

        self.add_version(('root', 'A'), [], 'abc')

        self.add_uncommitted_version(('root', 'B:'), [('root', 'A')], 'acehg')

        self.add_uncommitted_version(('root', 'C:'), [('root', 'A')], 'fabg')

        return _PlanMerge('B:', 'C:', self.plan_merge_vf, ('root',))

    def test_unique_lines(self):

        plan = self.setup_plan_merge()

        self.assertEqual(plan._unique_lines(

            plan._get_matching_blocks('B', 'C')),

            ([1, 2, 3], [0, 2]))

    def test_plan_merge(self):

        self.setup_plan_merge()

        plan = self.plan_merge_vf.plan_merge('B', 'C')

        self.assertEqual([

                          ('new-b', 'f\n'),

                          ('unchanged', 'a\n'),

                          ('killed-a', 'b\n'),

                          ('killed-b', 'c\n'),

                          ('new-a', 'e\n'),

                          ('new-a', 'h\n'),

                          ('new-a', 'g\n'),

                          ('new-b', 'g\n')],

                         list(plan))

    def test_plan_merge_cherrypick(self):

        self.add_rev('root', 'A', [], 'abc')

        self.add_rev('root', 'B', ['A'], 'abcde')

        self.add_rev('root', 'C', ['A'], 'abcefg')

        self.add_rev('root', 'D', ['A', 'B', 'C'], 'abcdegh')

        my_plan = _PlanMerge('B', 'D', self.plan_merge_vf, ('root',))

        # We shortcut when one text supersedes the other in the per-file graph.

        # We don't actually need to compare the texts at this point.

        self.assertEqual([

                          ('new-b', 'a\n'),

                          ('new-b', 'b\n'),

                          ('new-b', 'c\n'),

                          ('new-b', 'd\n'),

                          ('new-b', 'e\n'),

                          ('new-b', 'g\n'),

                          ('new-b', 'h\n')],

                          list(my_plan.plan_merge()))

    def test_plan_merge_no_common_ancestor(self):

        self.add_rev('root', 'A', [], 'abc')

        self.add_rev('root', 'B', [], 'xyz')

        my_plan = _PlanMerge('A', 'B', self.plan_merge_vf, ('root',))

        self.assertEqual([

                          ('new-a', 'a\n'),

                          ('new-a', 'b\n'),

                          ('new-a', 'c\n'),

                          ('new-b', 'x\n'),

                          ('new-b', 'y\n'),

                          ('new-b', 'z\n')],

                          list(my_plan.plan_merge()))

    def test_plan_merge_tail_ancestors(self):

        # The graph looks like this:

        #       A       # Common to all ancestors

        #      / \

        #     B   C     # Ancestors of E, only common to one side

        #     |\ /|

        #     D E F     # D, F are unique to G, H respectively

        #     |/ \|     # E is the LCA for G & H, and the unique LCA for

        #     G   H     # I, J

        #     |\ /|

        #     | X |

        #     |/ \|

        #     I   J     # criss-cross merge of G, H

        #

        # In this situation, a simple pruning of ancestors of E will leave D &

        # F "dangling", which looks like they introduce lines different from

        # the ones in E, but in actuality C&B introduced the lines, and they

        # are already present in E

        # Introduce the base text

        self.add_rev('root', 'A', [], 'abc')

        # Introduces a new line B

        self.add_rev('root', 'B', ['A'], 'aBbc')

        # Introduces a new line C

        self.add_rev('root', 'C', ['A'], 'abCc')

        # Introduce new line D