Revert "Support unique labels for alembic branches"

A problem was found with the --expand (and --contract) options, see the bug report. I am reverting this patch so that I can redo it and have one single patch that can be back-ported.

Closes-Bug: #1599574

This reverts commit 88359e3fe9.

Change-Id: Iebca469c6fec32bac0480be6627ad5e9dedaad9d

doc/source/devref/alembic_migrations.rst

@@ -418,20 +418,6 @@ following directive should be added in the contraction script::
     depends_on = ('<expansion-revision>',)
 
 
-Expand and Contract Branch Labeling
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Before the Newton release, neutron and each sub-project had its own alembic
-environment and each repo could re-use the labels ``contract`` and ``expand``
-for their alembic branches. With the Newton release, all neutron sub-projects
-use neutron's alembic environment, and this requires globally unique branch
-labels.
-
-To be compatible with the Newton release of neutron, all projects must use
-unique alembic branch labels of the form ``<project>-contract`` and
-``<project>-expand``.
-
-
 HEAD files for conflict management
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

neutron/db/migration/alembic_migrations/versions/liberty/contract/30018084ec99_initial.py

@@ -25,7 +25,7 @@ from neutron.db.migration import cli
 # revision identifiers, used by Alembic.
 revision = '30018084ec99'
 down_revision = 'kilo'
-branch_labels = ('neutron-' + cli.CONTRACT_BRANCH,)
+branch_labels = (cli.CONTRACT_BRANCH,)
 
 
 def upgrade():

neutron/db/migration/alembic_migrations/versions/liberty/expand/354db87e3225_nsxv_vdr_metadata.py

@@ -30,7 +30,7 @@ from neutron.db.migration import cli
 # revision identifiers, used by Alembic.
 revision = '354db87e3225'
 down_revision = 'kilo'
-branch_labels = ('neutron-' + cli.EXPAND_BRANCH,)
+branch_labels = (cli.EXPAND_BRANCH,)
 
 
 def upgrade():

neutron/db/migration/autogen.py

@@ -54,8 +54,7 @@ def _migration_script_ops(context, directive, phase):
     version_path = cli._get_version_branch_path(
         context.config, release=cli.CURRENT_RELEASE, branch=phase)
     autogen_kwargs = {}
-    cli._check_bootstrap_new_branch(context.config, phase, version_path,
-                                    autogen_kwargs)
+    cli._check_bootstrap_new_branch(phase, version_path, autogen_kwargs)
 
     op = ops.MigrationScript(
         new_rev_id(),

neutron/db/migration/cli.py

@@ -93,14 +93,11 @@ CONF.register_cli_opts(_db_opts, 'database')
 
 
 def do_alembic_command(config, cmd, revision=None, desc=None, **kwargs):
-    project = config.get_main_option('neutron_project')
     args = []
     if revision:
-        # We use unique branch labels from Newton onwards.
-        if revision.split('@')[0] in MIGRATION_BRANCHES:
-            revision = '-'.join([project, revision])
         args.append(revision)
 
+    project = config.get_main_option('neutron_project')
     if desc:
         alembic_util.msg(_('Running %(cmd)s (%(desc)s) for %(project)s ...') %
                          {'cmd': cmd, 'desc': desc, 'project': project})
@@ -145,13 +142,13 @@ def add_branch_options(parser):
 def _find_milestone_revisions(config, milestone, branch=None):
     """Return the revision(s) for a given milestone."""
     script = alembic_script.ScriptDirectory.from_config(config)
-    milestone_revisions = []
-    for m in _get_revisions(script):
-        for branch_label in (m.branch_labels or [None]):
-            if milestone in getattr(m.module, 'neutron_milestone', []):
-                if branch is None or branch_label.endswith(branch):
-                    milestone_revisions.append((m.revision, branch))
-    return milestone_revisions
+    return [
+        (m.revision, label)
+        for m in _get_revisions(script)
+        for label in (m.branch_labels or [None])
+        if milestone in getattr(m.module, 'neutron_milestone', []) and
+        (branch is None or branch in m.branch_labels)
+    ]
 
 
 def do_upgrade(config, cmd):
@@ -164,11 +161,11 @@ def do_upgrade(config, cmd):
 
     if CONF.command.expand:
         branch = EXPAND_BRANCH
-        revision = _get_branch_head(config, EXPAND_BRANCH)
+        revision = _get_branch_head(EXPAND_BRANCH)
 
     elif CONF.command.contract:
         branch = CONTRACT_BRANCH
-        revision = _get_branch_head(config, CONTRACT_BRANCH)
+        revision = _get_branch_head(CONTRACT_BRANCH)
 
     elif not CONF.command.revision and not CONF.command.delta:
         raise SystemExit(_('You must provide a revision or relative delta'))
@@ -220,26 +217,14 @@ def do_stamp(config, cmd):
                        sql=CONF.command.sql)
 
 
-def _get_branch_head(config, branch):
+def _get_branch_head(branch):
     '''Get the latest @head specification for a branch.'''
-    script_dir = alembic_script.ScriptDirectory.from_config(config)
-    revs = script_dir.revision_map.get_revisions('heads')
-    for rev in revs:
-        for branch_label in rev.branch_labels:
-            # For forwards and backwards compatibility we handle branch
-            # names of either
-            #    'contract/expand'
-            # or
-            #    'subproject-contract/subproject-expand'.
-            if branch_label.endswith(branch):
-                branch = branch_label
-                break
     return '%s@head' % branch
 
 
-def _check_bootstrap_new_branch(config, branch, version_path, addn_kwargs):
+def _check_bootstrap_new_branch(branch, version_path, addn_kwargs):
     addn_kwargs['version_path'] = version_path
-    addn_kwargs['head'] = _get_branch_head(config, branch)
+    addn_kwargs['head'] = _get_branch_head(branch)
     if not os.path.exists(version_path):
         # Bootstrap initial directory structure
         utils.ensure_dir(version_path)
@@ -266,7 +251,7 @@ def do_revision(config, cmd):
             args = copy.copy(kwargs)
             version_path = _get_version_branch_path(
                 config, release=CURRENT_RELEASE, branch=branch)
-            _check_bootstrap_new_branch(config, branch, version_path, args)
+            _check_bootstrap_new_branch(branch, version_path, args)
             do_alembic_command(config, cmd, **args)
     else:
         # autogeneration code will take care of enforcing proper directories
@@ -275,15 +260,32 @@ def do_revision(config, cmd):
     update_head_files(config)
 
 
+def _get_release_labels(labels):
+    result = set()
+    for label in labels:
+        # release labels were introduced Liberty for a short time and dropped
+        # in that same release cycle
+        result.add('%s_%s' % (migration.LIBERTY, label))
+    return result
+
+
 def _compare_labels(revision, expected_labels):
     # validate that the script has expected labels only
-    expected_branch_labels = set()
-    for label in revision.branch_labels:
-        for expected_label in expected_labels:
-            if label.endswith(expected_label):
-                expected_branch_labels.add(label)
-    bad_labels = revision.branch_labels - expected_branch_labels
+    bad_labels = revision.branch_labels - expected_labels
     if bad_labels:
+        # NOTE(ihrachyshka): this hack is temporary to accommodate those
+        # projects that already initialized their branches with liberty_*
+        # labels. Let's notify them about the deprecation for now and drop it
+        # later.
+        bad_labels_with_release = (revision.branch_labels -
+                                   _get_release_labels(expected_labels))
+        if not bad_labels_with_release:
+            alembic_util.warn(
+                _('Release aware branch labels (%s) are deprecated. '
+                  'Please switch to expand@ and contract@ '
+                  'labels.') % bad_labels)
+            return
+
         script_name = os.path.basename(revision.path)
         alembic_util.err(
             _('Unexpected label for script %(script_name)s: %(labels)s') %
@@ -337,14 +339,6 @@ def _get_revisions(script):
     return list(script.walk_revisions(base='base', head='heads'))
 
 
-def _get_branch_type(revision):
-    for branch_label in revision.branch_labels:
-        if branch_label.endswith(CONTRACT_BRANCH):
-            return CONTRACT_BRANCH
-        if branch_label.endswith(EXPAND_BRANCH):
-            return EXPAND_BRANCH
-
-
 def _get_branch_points(script):
     branchpoints = []
     for revision in _get_revisions(script):
@@ -358,7 +352,10 @@ def _get_heads_map(config):
     heads = script.get_heads()
     head_map = {}
     for head in heads:
-        head_map[_get_branch_type(script.get_revision(head))] = head
+        if CONTRACT_BRANCH in script.get_revision(head).branch_labels:
+            head_map[CONTRACT_BRANCH] = head
+        else:
+            head_map[EXPAND_BRANCH] = head
     return head_map
 
 

neutron/tests/functional/db/test_migrations.py

@@ -237,12 +237,7 @@ class TestModelsMigrationsMysql(_TestModelsMigrations,
             script = alembic_script.ScriptDirectory.from_config(
                 self.alembic_config)
             for m in list(script.walk_revisions(base='base', head='heads')):
-                branches = set()
-                for bl in m.branch_labels:
-                    if bl.endswith(migration.CONTRACT_BRANCH):
-                        branches.add(migration.CONTRACT_BRANCH)
-                    elif bl.endswith(migration.EXPAND_BRANCH):
-                        branches.add(migration.EXPAND_BRANCH)
+                branches = m.branch_labels or []
                 if migration.CONTRACT_BRANCH in branches:
                     method_name = 'contract_creation_exceptions'
                     exceptions_dict = creation_exceptions

neutron/tests/unit/db/test_migration.py

@@ -148,28 +148,7 @@ class TestCli(base.BaseTestCase):
                                                   attrs=attrs)
             cli.migration_entrypoints[project] = entrypoint
 
-        self.old_labels_revs = {
-            'a': FakeRevision(labels={cli.CONTRACT_BRANCH}),
-            'b': FakeRevision(labels={cli.EXPAND_BRANCH})
-        }
-        self.new_labels_revs = {
-            'x': FakeRevision(labels={'foo-' + cli.CONTRACT_BRANCH}),
-            'y': FakeRevision(labels={'foo-' + cli.EXPAND_BRANCH})
-        }
-
-    @staticmethod
-    def _old_and_new_label_combination_helper(test_method):
-        old_cb = cli.CONTRACT_BRANCH
-        new_cb = 'foo-' + cli.CONTRACT_BRANCH
-        old_eb = cli.EXPAND_BRANCH
-        new_eb = 'foo-' + cli.EXPAND_BRANCH
-        # Test all combinations of old and new branch labels.
-        test_method(old_cb, old_eb)
-        test_method(old_cb, new_eb)
-        test_method(new_cb, old_eb)
-        test_method(new_cb, new_eb)
-
-    def _main_test_helper(self, argv, func_name, exp_kwargs=None):
+    def _main_test_helper(self, argv, func_name, exp_kwargs=[{}]):
         with mock.patch.object(sys, 'argv', argv),\
                 mock.patch.object(cli, 'run_sanity_checks'),\
                 mock.patch.object(cli, 'validate_revisions'):
@@ -184,7 +163,7 @@ class TestCli(base.BaseTestCase):
 
             self.do_alembic_cmd.assert_has_calls(
                 [mock.call(mock.ANY, func_name, **_append_version_path(kwargs))
-                 for kwargs in (exp_kwargs or [{}])]
+                 for kwargs in exp_kwargs]
             )
 
     def test_stamp(self):
@@ -228,11 +207,10 @@ class TestCli(base.BaseTestCase):
             self._main_test_helper(['prog', 'check_migration'], 'branches')
             self.assertEqual(len(self.projects), validate.call_count)
 
-    def _test_database_sync_revision(self, revs):
-        with mock.patch.object(cli, 'update_head_files') as update,\
-                mock.patch('alembic.script.ScriptDirectory.from_config') as fc:
-            fc.return_value.get_revisions.side_effect = revs
-            mock.patch('os.path.exists').start()
+    def _test_database_sync_revision(self, separate_branches=True):
+        with mock.patch.object(cli, 'update_head_files') as update:
+            if separate_branches:
+                mock.patch('os.path.exists').start()
             expected_kwargs = [{
                 'message': 'message', 'sql': False, 'autogenerate': True,
             }]
@@ -248,7 +226,7 @@ class TestCli(base.BaseTestCase):
                 'message': 'message',
                 'sql': True,
                 'autogenerate': False,
-                'head': cli._get_branch_head(self.configs[0], branch)
+                'head': cli._get_branch_head(branch)
             } for branch in cli.MIGRATION_BRANCHES]
             for kwarg in expected_kwargs:
                 kwarg['autogenerate'] = False
@@ -286,11 +264,12 @@ class TestCli(base.BaseTestCase):
             )
             self.assertEqual(len(self.projects), update.call_count)
 
-    def test_database_sync_revision_old_branch_labels(self):
-        self._test_database_sync_revision(self.old_labels_revs)
+    def test_database_sync_revision(self):
+        self._test_database_sync_revision()
 
-    def test_database_sync_revision_new_branch_labels(self):
-        self._test_database_sync_revision(self.new_labels_revs)
+    def test_database_sync_revision_no_branches(self):
+        # Test that old branchless approach is still supported
+        self._test_database_sync_revision(separate_branches=False)
 
     def test_upgrade_revision(self):
         self._main_test_helper(
@@ -313,22 +292,14 @@ class TestCli(base.BaseTestCase):
             [{'desc': None, 'revision': 'kilo+3', 'sql': False}]
         )
 
-    def _test_upgrade_expand(self, revs):
-        with mock.patch('alembic.script.ScriptDirectory.from_config') as fc:
-            fc.return_value.get_revisions.side_effect = revs
-            self._main_test_helper(
-                ['prog', 'upgrade', '--expand'],
-                'upgrade',
-                [{'desc': cli.EXPAND_BRANCH,
-                  'revision': 'expand@head',
-                  'sql': False}]
-            )
-
-    def test_upgrade_expand_old_labels(self):
-        self._test_upgrade_expand(self.old_labels_revs)
-
-    def test_upgrade_expand_new_labels(self):
-        self._test_upgrade_expand(self.new_labels_revs)
+    def test_upgrade_expand(self):
+        self._main_test_helper(
+            ['prog', 'upgrade', '--expand'],
+            'upgrade',
+            [{'desc': cli.EXPAND_BRANCH,
+              'revision': 'expand@head',
+              'sql': False}]
+        )
 
     def test_upgrade_expand_contract_are_mutually_exclusive(self):
         with testlib_api.ExpectedException(SystemExit):
@@ -371,31 +342,20 @@ class TestCli(base.BaseTestCase):
     def test_upgrade_contract_conflicts_with_delta(self):
         self._test_upgrade_conflicts_with_delta('contract')
 
-    def _test_upgrade_contract(self, revs):
-        with mock.patch('alembic.script.ScriptDirectory.from_config') as fc:
-            fc.return_value.get_revisions.side_effect = revs
-            self._main_test_helper(
-                ['prog', 'upgrade', '--contract'],
-                'upgrade',
-                [{'desc': cli.CONTRACT_BRANCH,
-                  'revision': 'contract@head',
-                  'sql': False}]
-            )
-
-    def test_upgrade_contract_old_labels(self):
-        self._test_upgrade_contract(self.old_labels_revs)
-
-    def test_upgrade_contract_new_labels(self):
-        self._test_upgrade_contract(self.new_labels_revs)
+    def test_upgrade_contract(self):
+        self._main_test_helper(
+            ['prog', 'upgrade', '--contract'],
+            'upgrade',
+            [{'desc': cli.CONTRACT_BRANCH,
+              'revision': 'contract@head',
+              'sql': False}]
+        )
 
     @mock.patch('alembic.script.ScriptDirectory.walk_revisions')
-    def _test_upgrade_milestone_expand_before_contract(self,
-                                                       contract_label,
-                                                       expand_label,
-                                                       walk_mock):
-        c_revs = [FakeRevision(labels={contract_label}) for r in range(5)]
+    def test_upgrade_milestone_expand_before_contract(self, walk_mock):
+        c_revs = [FakeRevision(labels={cli.CONTRACT_BRANCH}) for r in range(5)]
         c_revs[1].module.neutron_milestone = [migration.LIBERTY]
-        e_revs = [FakeRevision(labels={expand_label}) for r in range(5)]
+        e_revs = [FakeRevision(labels={cli.EXPAND_BRANCH}) for r in range(5)]
         e_revs[3].module.neutron_milestone = [migration.LIBERTY]
         walk_mock.return_value = c_revs + e_revs
         self._main_test_helper(
@@ -409,10 +369,6 @@ class TestCli(base.BaseTestCase):
               'sql': False}]
         )
 
-    def test_upgrade_milestone_expand_before_contract(self):
-        self._old_and_new_label_combination_helper(
-            self._test_upgrade_milestone_expand_before_contract)
-
     def assert_command_fails(self, command):
         # Avoid cluttering stdout with argparse error messages
         mock.patch('argparse.ArgumentParser._print_message').start()
@@ -432,8 +388,8 @@ class TestCli(base.BaseTestCase):
     def test_upgrade_rejects_delta_with_relative_revision(self):
         self.assert_command_fails(['prog', 'upgrade', '+2', '--delta', '3'])
 
-    def _test_validate_head_files_common(self, heads, revs,
-                                         contract_head='', expand_head=''):
+    def _test_validate_head_files_helper(self, heads, contract_head='',
+                                         expand_head=''):
         fake_config = self.configs[0]
         head_files_not_exist = (contract_head == expand_head == '')
         with mock.patch('alembic.script.ScriptDirectory.from_config') as fc,\
@@ -444,6 +400,9 @@ class TestCli(base.BaseTestCase):
                 os_mock.return_value = True
 
             fc.return_value.get_heads.return_value = heads
+
+            revs = {heads[0]: FakeRevision(labels=cli.CONTRACT_BRANCH),
+                    heads[1]: FakeRevision(labels=cli.EXPAND_BRANCH)}
             fc.return_value.get_revision.side_effect = revs.__getitem__
             mock_open_con = self.useFixture(
                 tools.OpenFixture(cli._get_contract_head_file_path(
@@ -474,23 +433,6 @@ class TestCli(base.BaseTestCase):
             if not head_files_not_exist:
                 fc.assert_called_once_with(fake_config)
 
-    def _test_validate_head_files_helper(self, heads,
-                                         contract_head='', expand_head=''):
-        old_labels_revs = {
-            heads[0]: FakeRevision(labels={cli.CONTRACT_BRANCH}),
-            heads[1]: FakeRevision(labels={cli.EXPAND_BRANCH})
-        }
-        new_labels_revs = {
-            heads[0]: FakeRevision(labels={'foo-' + cli.CONTRACT_BRANCH}),
-            heads[1]: FakeRevision(labels={'foo-' + cli.EXPAND_BRANCH})
-        }
-        self._test_validate_head_files_common(heads, old_labels_revs,
-                                              contract_head=contract_head,
-                                              expand_head=expand_head)
-        self._test_validate_head_files_common(heads, new_labels_revs,
-                                              contract_head=contract_head,
-                                              expand_head=expand_head)
-
     def test_validate_head_files_success(self):
         self._test_validate_head_files_helper(['a', 'b'], contract_head='a',
                                               expand_head='b')
@@ -503,14 +445,8 @@ class TestCli(base.BaseTestCase):
                                               expand_head='d')
 
     @mock.patch.object(fileutils, 'delete_if_exists')
-    def _test_update_head_files_success(self, revs, *mocks):
-        contract_head = expand_head = None
-        for rev, revision in revs.items():
-            for branch_label in revision.branch_labels:
-                if branch_label.endswith(cli.CONTRACT_BRANCH):
-                    contract_head = rev
-                if branch_label.endswith(cli.EXPAND_BRANCH):
-                    expand_head = rev
+    def test_update_head_files_success(self, *mocks):
+        heads = ['a', 'b']
         mock_open_con = self.useFixture(
                     tools.OpenFixture(cli._get_contract_head_file_path(
                         self.configs[0]))).mock_open
@@ -518,13 +454,14 @@ class TestCli(base.BaseTestCase):
             tools.OpenFixture(cli._get_expand_head_file_path(
                 self.configs[0]))).mock_open
         with mock.patch('alembic.script.ScriptDirectory.from_config') as fc:
-            fc.return_value.get_heads.return_value = list(revs)
+            fc.return_value.get_heads.return_value = heads
+            revs = {heads[0]: FakeRevision(labels=cli.CONTRACT_BRANCH),
+                    heads[1]: FakeRevision(labels=cli.EXPAND_BRANCH)}
             fc.return_value.get_revision.side_effect = revs.__getitem__
             cli.update_head_files(self.configs[0])
             mock_open_con.return_value.write.assert_called_with(
-                contract_head + '\n')
-            mock_open_ex.return_value.write.assert_called_with(
-                expand_head + '\n')
+                heads[0] + '\n')
+            mock_open_ex.return_value.write.assert_called_with(heads[1] + '\n')
 
             old_head_file = cli._get_head_file_path(
                 self.configs[0])
@@ -536,12 +473,6 @@ class TestCli(base.BaseTestCase):
             self.assertIn(mock.call(old_heads_file),
                           delete_if_exists.call_args_list)
 
-    def test_update_head_files_success_old_labels(self):
-        self._test_update_head_files_success(self.old_labels_revs)
-
-    def test_update_head_files_success_new_labels(self):
-        self._test_update_head_files_success(self.new_labels_revs)
-
     def test_get_project_base(self):
         config = alembic_config.Config()
         config.set_main_option('script_location', 'a.b.c:d')
@@ -658,7 +589,7 @@ class TestCli(base.BaseTestCase):
 
     @mock.patch('alembic.script.ScriptDirectory.walk_revisions')
     def test__get_branch_points(self, walk_mock):
-        revisions = [FakeRevision(is_branch_point=tools.get_random_boolean())
+        revisions = [FakeRevision(is_branch_point=tools.get_random_boolean)
                      for i in range(50)]
         walk_mock.return_value = revisions
         script_dir = alembic_script.ScriptDirectory.from_config(
@@ -732,10 +663,8 @@ class TestCli(base.BaseTestCase):
         )
 
         directives = [migration_script]
-        context = mock.Mock()
-        context.config = self.configs[0]
         autogen.process_revision_directives(
-            context, mock.Mock(), directives
+            mock.Mock(), mock.Mock(), directives
         )
 
         expand = directives[0]
@@ -770,33 +699,23 @@ class TestCli(base.BaseTestCase):
         )
 
     @mock.patch('alembic.script.ScriptDirectory.walk_revisions')
-    def _test__find_milestone_revisions_one_branch(self,
-                                                   contract_label,
-                                                   expand_label,
-                                                   walk_mock):
-        c_revs = [FakeRevision(labels={contract_label}) for r in range(5)]
+    def test__find_milestone_revisions_one_branch(self, walk_mock):
+        c_revs = [FakeRevision(labels={cli.CONTRACT_BRANCH}) for r in range(5)]
         c_revs[1].module.neutron_milestone = [migration.LIBERTY]
 
         walk_mock.return_value = c_revs
         m = cli._find_milestone_revisions(self.configs[0], 'liberty',
-                                          contract_label)
+                                          cli.CONTRACT_BRANCH)
         self.assertEqual(1, len(m))
         m = cli._find_milestone_revisions(self.configs[0], 'liberty',
-                                          expand_label)
+                                          cli.EXPAND_BRANCH)
         self.assertEqual(0, len(m))
 
-    def test__find_milestone_revisions_one_branch(self):
-        self._old_and_new_label_combination_helper(
-            self._test__find_milestone_revisions_one_branch)
-
     @mock.patch('alembic.script.ScriptDirectory.walk_revisions')
-    def _test__find_milestone_revisions_two_branches(self,
-                                                     contract_label,
-                                                     expand_label,
-                                                     walk_mock):
-        c_revs = [FakeRevision(labels={contract_label}) for r in range(5)]
+    def test__find_milestone_revisions_two_branches(self, walk_mock):
+        c_revs = [FakeRevision(labels={cli.CONTRACT_BRANCH}) for r in range(5)]
         c_revs[1].module.neutron_milestone = [migration.LIBERTY]
-        e_revs = [FakeRevision(labels={expand_label}) for r in range(5)]
+        e_revs = [FakeRevision(labels={cli.EXPAND_BRANCH}) for r in range(5)]
         e_revs[3].module.neutron_milestone = [migration.LIBERTY]
 
         walk_mock.return_value = c_revs + e_revs
@@ -806,10 +725,6 @@ class TestCli(base.BaseTestCase):
         m = cli._find_milestone_revisions(self.configs[0], 'mitaka')
         self.assertEqual(0, len(m))
 
-    def test__find_milestone_revisions_two_branches(self):
-        self._old_and_new_label_combination_helper(
-            self._test__find_milestone_revisions_two_branches)
-
     @mock.patch('alembic.script.ScriptDirectory.walk_revisions')
     def test__find_milestone_revisions_branchless(self, walk_mock):
         revisions = [FakeRevision() for r in range(5)]