~ubuntu-branches/ubuntu/precise/dulwich/precise-security

# test_diff_tree.py -- Tests for file and tree diff utilities.

# Copyright (C) 2010 Google, Inc.

#

# 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

# or (at your option) a later version of the License.

#

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

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

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

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

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

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,

# MA  02110-1301, USA.

"""Tests for file and tree diff utilities."""

from dulwich.diff_tree import (

    CHANGE_MODIFY,

    CHANGE_RENAME,

    CHANGE_COPY,

    CHANGE_UNCHANGED,

    TreeChange,

    _merge_entries,

    _merge_entries_py,

    tree_changes,

    tree_changes_for_merge,

    _count_blocks,

    _count_blocks_py,

    _similarity_score,

    _tree_change_key,

    RenameDetector,

    _is_tree,

    _is_tree_py

    )

from dulwich.index import (

    commit_tree,

    )

from dulwich._compat import (

    permutations,

    )

from dulwich.object_store import (

    MemoryObjectStore,

    )

from dulwich.objects import (

    ShaFile,

    Blob,

    TreeEntry,

    Tree,

    )

from dulwich.tests import (

    TestCase,

    )

from dulwich.tests.utils import (

    F,

    make_object,

    functest_builder,

    ext_functest_builder,

    )

class DiffTestCase(TestCase):

    def setUp(self):

        super(DiffTestCase, self).setUp()

        self.store = MemoryObjectStore()

        self.empty_tree = self.commit_tree([])

    def commit_tree(self, entries):

        commit_blobs = []

        for entry in entries:

            if len(entry) == 2:

                path, obj = entry

                mode = F

            else:

                path, obj, mode = entry

            if isinstance(obj, Blob):

                self.store.add_object(obj)

                sha = obj.id

            else:

                sha = obj

            commit_blobs.append((path, sha, mode))

        return self.store[commit_tree(self.store, commit_blobs)]

class TreeChangesTest(DiffTestCase):

    def setUp(self):

        super(TreeChangesTest, self).setUp()

        self.detector = RenameDetector(self.store)

    def assertMergeFails(self, merge_entries, name, mode, sha):

        t = Tree()

        t[name] = (mode, sha)

        self.assertRaises(TypeError, merge_entries, '', t, t)

    def _do_test_merge_entries(self, merge_entries):

        blob_a1 = make_object(Blob, data='a1')

        blob_a2 = make_object(Blob, data='a2')

        blob_b1 = make_object(Blob, data='b1')

        blob_c2 = make_object(Blob, data='c2')

        tree1 = self.commit_tree([('a', blob_a1, 0100644),

                                  ('b', blob_b1, 0100755)])

        tree2 = self.commit_tree([('a', blob_a2, 0100644),

                                  ('c', blob_c2, 0100755)])

        self.assertEqual([], merge_entries('', self.empty_tree,

                                           self.empty_tree))

        self.assertEqual([

          ((None, None, None), ('a', 0100644, blob_a1.id)),

          ((None, None, None), ('b', 0100755, blob_b1.id)),

          ], merge_entries('', self.empty_tree, tree1))

        self.assertEqual([

          ((None, None, None), ('x/a', 0100644, blob_a1.id)),

          ((None, None, None), ('x/b', 0100755, blob_b1.id)),

          ], merge_entries('x', self.empty_tree, tree1))

        self.assertEqual([

          (('a', 0100644, blob_a2.id), (None, None, None)),

          (('c', 0100755, blob_c2.id), (None, None, None)),

          ], merge_entries('', tree2, self.empty_tree))

        self.assertEqual([

          (('a', 0100644, blob_a1.id), ('a', 0100644, blob_a2.id)),

          (('b', 0100755, blob_b1.id), (None, None, None)),

          ((None, None, None), ('c', 0100755, blob_c2.id)),

          ], merge_entries('', tree1, tree2))

        self.assertEqual([

          (('a', 0100644, blob_a2.id), ('a', 0100644, blob_a1.id)),

          ((None, None, None), ('b', 0100755, blob_b1.id)),

          (('c', 0100755, blob_c2.id), (None, None, None)),

          ], merge_entries('', tree2, tree1))

        self.assertMergeFails(merge_entries, 0xdeadbeef, 0100644, '1' * 40)

        self.assertMergeFails(merge_entries, 'a', 'deadbeef', '1' * 40)

        self.assertMergeFails(merge_entries, 'a', 0100644, 0xdeadbeef)

    test_merge_entries = functest_builder(_do_test_merge_entries,

                                          _merge_entries_py)

    test_merge_entries_extension = ext_functest_builder(_do_test_merge_entries,

                                                        _merge_entries)

    def _do_test_is_tree(self, is_tree):

        self.assertFalse(is_tree(TreeEntry(None, None, None)))

        self.assertFalse(is_tree(TreeEntry('a', 0100644, 'a' * 40)))

        self.assertFalse(is_tree(TreeEntry('a', 0100755, 'a' * 40)))

        self.assertFalse(is_tree(TreeEntry('a', 0120000, 'a' * 40)))

        self.assertTrue(is_tree(TreeEntry('a', 0040000, 'a' * 40)))

        self.assertRaises(TypeError, is_tree, TreeEntry('a', 'x', 'a' * 40))

        self.assertRaises(AttributeError, is_tree, 1234)

    test_is_tree = functest_builder(_do_test_is_tree, _is_tree_py)

    test_is_tree_extension = ext_functest_builder(_do_test_is_tree, _is_tree)

    def assertChangesEqual(self, expected, tree1, tree2, **kwargs):

        actual = list(tree_changes(self.store, tree1.id, tree2.id, **kwargs))

        self.assertEqual(expected, actual)

    # For brevity, the following tests use tuples instead of TreeEntry objects.

    def test_tree_changes_empty(self):

        self.assertChangesEqual([], self.empty_tree, self.empty_tree)

    def test_tree_changes_no_changes(self):

        blob = make_object(Blob, data='blob')

        tree = self.commit_tree([('a', blob), ('b/c', blob)])

        self.assertChangesEqual([], self.empty_tree, self.empty_tree)

        self.assertChangesEqual([], tree, tree)

        self.assertChangesEqual(

          [TreeChange(CHANGE_UNCHANGED, ('a', F, blob.id), ('a', F, blob.id)),

           TreeChange(CHANGE_UNCHANGED, ('b/c', F, blob.id),

                      ('b/c', F, blob.id))],

          tree, tree, want_unchanged=True)

    def test_tree_changes_add_delete(self):

        blob_a = make_object(Blob, data='a')

        blob_b = make_object(Blob, data='b')

        tree = self.commit_tree([('a', blob_a, 0100644),

                                 ('x/b', blob_b, 0100755)])

        self.assertChangesEqual(

          [TreeChange.add(('a', 0100644, blob_a.id)),

           TreeChange.add(('x/b', 0100755, blob_b.id))],

          self.empty_tree, tree)

        self.assertChangesEqual(

          [TreeChange.delete(('a', 0100644, blob_a.id)),

           TreeChange.delete(('x/b', 0100755, blob_b.id))],

          tree, self.empty_tree)

    def test_tree_changes_modify_contents(self):

        blob_a1 = make_object(Blob, data='a1')

        blob_a2 = make_object(Blob, data='a2')

        tree1 = self.commit_tree([('a', blob_a1)])

        tree2 = self.commit_tree([('a', blob_a2)])

        self.assertChangesEqual(

          [TreeChange(CHANGE_MODIFY, ('a', F, blob_a1.id),

                      ('a', F, blob_a2.id))], tree1, tree2)

    def test_tree_changes_modify_mode(self):

        blob_a = make_object(Blob, data='a')

        tree1 = self.commit_tree([('a', blob_a, 0100644)])

        tree2 = self.commit_tree([('a', blob_a, 0100755)])

        self.assertChangesEqual(

          [TreeChange(CHANGE_MODIFY, ('a', 0100644, blob_a.id),

                      ('a', 0100755, blob_a.id))], tree1, tree2)

    def test_tree_changes_change_type(self):

        blob_a1 = make_object(Blob, data='a')

        blob_a2 = make_object(Blob, data='/foo/bar')

        tree1 = self.commit_tree([('a', blob_a1, 0100644)])

        tree2 = self.commit_tree([('a', blob_a2, 0120000)])

        self.assertChangesEqual(

          [TreeChange.delete(('a', 0100644, blob_a1.id)),

           TreeChange.add(('a', 0120000, blob_a2.id))],

          tree1, tree2)

    def test_tree_changes_to_tree(self):

        blob_a = make_object(Blob, data='a')

        blob_x = make_object(Blob, data='x')

        tree1 = self.commit_tree([('a', blob_a)])

        tree2 = self.commit_tree([('a/x', blob_x)])

        self.assertChangesEqual(

          [TreeChange.delete(('a', F, blob_a.id)),

           TreeChange.add(('a/x', F, blob_x.id))],

          tree1, tree2)

    def test_tree_changes_complex(self):

        blob_a_1 = make_object(Blob, data='a1_1')

        blob_bx1_1 = make_object(Blob, data='bx1_1')

        blob_bx2_1 = make_object(Blob, data='bx2_1')

        blob_by1_1 = make_object(Blob, data='by1_1')

        blob_by2_1 = make_object(Blob, data='by2_1')

        tree1 = self.commit_tree([

          ('a', blob_a_1),

          ('b/x/1', blob_bx1_1),

          ('b/x/2', blob_bx2_1),

          ('b/y/1', blob_by1_1),

          ('b/y/2', blob_by2_1),

          ])

        blob_a_2 = make_object(Blob, data='a1_2')

        blob_bx1_2 = blob_bx1_1

        blob_by_2 = make_object(Blob, data='by_2')

        blob_c_2 = make_object(Blob, data='c_2')

        tree2 = self.commit_tree([

          ('a', blob_a_2),

          ('b/x/1', blob_bx1_2),

          ('b/y', blob_by_2),

          ('c', blob_c_2),

          ])

        self.assertChangesEqual(

          [TreeChange(CHANGE_MODIFY, ('a', F, blob_a_1.id),

                      ('a', F, blob_a_2.id)),

           TreeChange.delete(('b/x/2', F, blob_bx2_1.id)),

           TreeChange.add(('b/y', F, blob_by_2.id)),

           TreeChange.delete(('b/y/1', F, blob_by1_1.id)),

           TreeChange.delete(('b/y/2', F, blob_by2_1.id)),

           TreeChange.add(('c', F, blob_c_2.id))],

          tree1, tree2)

    def test_tree_changes_name_order(self):

        blob = make_object(Blob, data='a')

        tree1 = self.commit_tree([('a', blob), ('a.', blob), ('a..', blob)])

        # Tree order is the reverse of this, so if we used tree order, 'a..'

        # would not be merged.

        tree2 = self.commit_tree([('a/x', blob), ('a./x', blob), ('a..', blob)])

        self.assertChangesEqual(

          [TreeChange.delete(('a', F, blob.id)),

           TreeChange.add(('a/x', F, blob.id)),

           TreeChange.delete(('a.', F, blob.id)),

           TreeChange.add(('a./x', F, blob.id))],

          tree1, tree2)

    def test_tree_changes_prune(self):

        blob_a1 = make_object(Blob, data='a1')

        blob_a2 = make_object(Blob, data='a2')

        blob_x = make_object(Blob, data='x')

        tree1 = self.commit_tree([('a', blob_a1), ('b/x', blob_x)])

        tree2 = self.commit_tree([('a', blob_a2), ('b/x', blob_x)])

        # Remove identical items so lookups will fail unless we prune.

        subtree = self.store[tree1['b'][1]]

        for entry in subtree.iteritems():

            del self.store[entry.sha]

        del self.store[subtree.id]

        self.assertChangesEqual(

          [TreeChange(CHANGE_MODIFY, ('a', F, blob_a1.id),

                      ('a', F, blob_a2.id))],

          tree1, tree2)

    def test_tree_changes_rename_detector(self):

        blob_a1 = make_object(Blob, data='a\nb\nc\nd\n')

        blob_a2 = make_object(Blob, data='a\nb\nc\ne\n')

        blob_b = make_object(Blob, data='b')

        tree1 = self.commit_tree([('a', blob_a1), ('b', blob_b)])

        tree2 = self.commit_tree([('c', blob_a2), ('b', blob_b)])

        detector = RenameDetector(self.store)

        self.assertChangesEqual(

          [TreeChange.delete(('a', F, blob_a1.id)),

           TreeChange.add(('c', F, blob_a2.id))],

          tree1, tree2)

        self.assertChangesEqual(

          [TreeChange.delete(('a', F, blob_a1.id)),

           TreeChange(CHANGE_UNCHANGED, ('b', F, blob_b.id),

                      ('b', F, blob_b.id)),

           TreeChange.add(('c', F, blob_a2.id))],

          tree1, tree2, want_unchanged=True)

        self.assertChangesEqual(

          [TreeChange(CHANGE_RENAME, ('a', F, blob_a1.id),

                      ('c', F, blob_a2.id))],

          tree1, tree2, rename_detector=detector)

        self.assertChangesEqual(

          [TreeChange(CHANGE_RENAME, ('a', F, blob_a1.id),

                      ('c', F, blob_a2.id)),

           TreeChange(CHANGE_UNCHANGED, ('b', F, blob_b.id),

                      ('b', F, blob_b.id))],

          tree1, tree2, rename_detector=detector, want_unchanged=True)

    def assertChangesForMergeEqual(self, expected, parent_trees, merge_tree,

                                   **kwargs):

        parent_tree_ids = [t.id for t in parent_trees]

        actual = list(tree_changes_for_merge(

          self.store, parent_tree_ids, merge_tree.id, **kwargs))

        self.assertEqual(expected, actual)

        parent_tree_ids.reverse()

        expected = [list(reversed(cs)) for cs in expected]

        actual = list(tree_changes_for_merge(

          self.store, parent_tree_ids, merge_tree.id, **kwargs))

        self.assertEqual(expected, actual)

    def test_tree_changes_for_merge_add_no_conflict(self):

        blob = make_object(Blob, data='blob')

        parent1 = self.commit_tree([])

        parent2 = merge = self.commit_tree([('a', blob)])

        self.assertChangesForMergeEqual([], [parent1, parent2], merge)

        self.assertChangesForMergeEqual([], [parent2, parent2], merge)

    def test_tree_changes_for_merge_add_modify_conflict(self):

        blob1 = make_object(Blob, data='1')

        blob2 = make_object(Blob, data='2')

        parent1 = self.commit_tree([])

        parent2 = self.commit_tree([('a', blob1)])

        merge = self.commit_tree([('a', blob2)])

        self.assertChangesForMergeEqual(

          [[TreeChange.add(('a', F, blob2.id)),

            TreeChange(CHANGE_MODIFY, ('a', F, blob1.id), ('a', F, blob2.id))]],

          [parent1, parent2], merge)

    def test_tree_changes_for_merge_modify_modify_conflict(self):

        blob1 = make_object(Blob, data='1')

        blob2 = make_object(Blob, data='2')

        blob3 = make_object(Blob, data='3')

        parent1 = self.commit_tree([('a', blob1)])

        parent2 = self.commit_tree([('a', blob2)])

        merge = self.commit_tree([('a', blob3)])

        self.assertChangesForMergeEqual(

          [[TreeChange(CHANGE_MODIFY, ('a', F, blob1.id), ('a', F, blob3.id)),

            TreeChange(CHANGE_MODIFY, ('a', F, blob2.id), ('a', F, blob3.id))]],

          [parent1, parent2], merge)

    def test_tree_changes_for_merge_modify_no_conflict(self):

        blob1 = make_object(Blob, data='1')

        blob2 = make_object(Blob, data='2')

        parent1 = self.commit_tree([('a', blob1)])

        parent2 = merge = self.commit_tree([('a', blob2)])

        self.assertChangesForMergeEqual([], [parent1, parent2], merge)

    def test_tree_changes_for_merge_delete_delete_conflict(self):

        blob1 = make_object(Blob, data='1')

        blob2 = make_object(Blob, data='2')

        parent1 = self.commit_tree([('a', blob1)])

        parent2 = self.commit_tree([('a', blob2)])

        merge = self.commit_tree([])

        self.assertChangesForMergeEqual(

          [[TreeChange.delete(('a', F, blob1.id)),

            TreeChange.delete(('a', F, blob2.id))]],

          [parent1, parent2], merge)

    def test_tree_changes_for_merge_delete_no_conflict(self):

        blob = make_object(Blob, data='blob')

        has = self.commit_tree([('a', blob)])

        doesnt_have = self.commit_tree([])

        self.assertChangesForMergeEqual([], [has, has], doesnt_have)

        self.assertChangesForMergeEqual([], [has, doesnt_have], doesnt_have)

    def test_tree_changes_for_merge_octopus_no_conflict(self):

        r = range(5)

        blobs = [make_object(Blob, data=str(i)) for i in r]

        parents = [self.commit_tree([('a', blobs[i])]) for i in r]

        for i in r:

            # Take the SHA from each of the parents.

            self.assertChangesForMergeEqual([], parents, parents[i])

    def test_tree_changes_for_merge_octopus_modify_conflict(self):

        # Because the octopus merge strategy is limited, I doubt it's possible

        # to create this with the git command line. But the output is well-

        # defined, so test it anyway.

        r = range(5)

        parent_blobs = [make_object(Blob, data=str(i)) for i in r]

        merge_blob = make_object(Blob, data='merge')

        parents = [self.commit_tree([('a', parent_blobs[i])]) for i in r]

        merge = self.commit_tree([('a', merge_blob)])

        expected = [[TreeChange(CHANGE_MODIFY, ('a', F, parent_blobs[i].id),

                                ('a', F, merge_blob.id)) for i in r]]

        self.assertChangesForMergeEqual(expected, parents, merge)

    def test_tree_changes_for_merge_octopus_delete(self):

        blob1 = make_object(Blob, data='1')

        blob2 = make_object(Blob, data='3')

        parent1 = self.commit_tree([('a', blob1)])

        parent2 = self.commit_tree([('a', blob2)])

        parent3 = merge = self.commit_tree([])

        self.assertChangesForMergeEqual([], [parent1, parent1, parent1], merge)

        self.assertChangesForMergeEqual([], [parent1, parent1, parent3], merge)

        self.assertChangesForMergeEqual([], [parent1, parent3, parent3], merge)

        self.assertChangesForMergeEqual(

          [[TreeChange.delete(('a', F, blob1.id)),

            TreeChange.delete(('a', F, blob2.id)),

            None]],

          [parent1, parent2, parent3], merge)

    def test_tree_changes_for_merge_add_add_same_conflict(self):

        blob = make_object(Blob, data='a\nb\nc\nd\n')

        parent1 = self.commit_tree([('a', blob)])

        parent2 = self.commit_tree([])

        merge = self.commit_tree([('b', blob)])

        add = TreeChange.add(('b', F, blob.id))

        self.assertChangesForMergeEqual([[add, add]], [parent1, parent2], merge)

    def test_tree_changes_for_merge_add_exact_rename_conflict(self):

        blob = make_object(Blob, data='a\nb\nc\nd\n')

        parent1 = self.commit_tree([('a', blob)])

        parent2 = self.commit_tree([])

        merge = self.commit_tree([('b', blob)])

        self.assertChangesForMergeEqual(

          [[TreeChange(CHANGE_RENAME, ('a', F, blob.id), ('b', F, blob.id)),

            TreeChange.add(('b', F, blob.id))]],

          [parent1, parent2], merge, rename_detector=self.detector)

    def test_tree_changes_for_merge_add_content_rename_conflict(self):

        blob1 = make_object(Blob, data='a\nb\nc\nd\n')

        blob2 = make_object(Blob, data='a\nb\nc\ne\n')

        parent1 = self.commit_tree([('a', blob1)])

        parent2 = self.commit_tree([])

        merge = self.commit_tree([('b', blob2)])

        self.assertChangesForMergeEqual(

          [[TreeChange(CHANGE_RENAME, ('a', F, blob1.id), ('b', F, blob2.id)),

            TreeChange.add(('b', F, blob2.id))]],

          [parent1, parent2], merge, rename_detector=self.detector)

    def test_tree_changes_for_merge_modify_rename_conflict(self):

        blob1 = make_object(Blob, data='a\nb\nc\nd\n')

        blob2 = make_object(Blob, data='a\nb\nc\ne\n')

        parent1 = self.commit_tree([('a', blob1)])

        parent2 = self.commit_tree([('b', blob1)])

        merge = self.commit_tree([('b', blob2)])

        self.assertChangesForMergeEqual(

          [[TreeChange(CHANGE_RENAME, ('a', F, blob1.id), ('b', F, blob2.id)),

            TreeChange(CHANGE_MODIFY, ('b', F, blob1.id), ('b', F, blob2.id))]],

          [parent1, parent2], merge, rename_detector=self.detector)

class RenameDetectionTest(DiffTestCase):

    def _do_test_count_blocks(self, count_blocks):

        blob = make_object(Blob, data='a\nb\na\n')

        self.assertEqual({hash('a\n'): 4, hash('b\n'): 2}, count_blocks(blob))

    test_count_blocks = functest_builder(_do_test_count_blocks,

                                         _count_blocks_py)

    test_count_blocks_extension = ext_functest_builder(_do_test_count_blocks,

                                                       _count_blocks)

    def _do_test_count_blocks_no_newline(self, count_blocks):

        blob = make_object(Blob, data='a\na')

        self.assertEqual({hash('a\n'): 2, hash('a'): 1}, _count_blocks(blob))

    test_count_blocks_no_newline = functest_builder(

      _do_test_count_blocks_no_newline, _count_blocks_py)

    test_count_blocks_no_newline_extension = ext_functest_builder(

       _do_test_count_blocks_no_newline, _count_blocks)

    def _do_test_count_blocks_chunks(self, count_blocks):

        blob = ShaFile.from_raw_chunks(Blob.type_num, ['a\nb', '\na\n'])

        self.assertEqual({hash('a\n'): 4, hash('b\n'): 2}, _count_blocks(blob))

    test_count_blocks_chunks = functest_builder(_do_test_count_blocks_chunks,

                                                _count_blocks_py)

    test_count_blocks_chunks_extension = ext_functest_builder(

      _do_test_count_blocks_chunks, _count_blocks)

    def _do_test_count_blocks_long_lines(self, count_blocks):

        a = 'a' * 64

        data = a + 'xxx\ny\n' + a + 'zzz\n'

        blob = make_object(Blob, data=data)

        self.assertEqual({hash('a' * 64): 128, hash('xxx\n'): 4, hash('y\n'): 2,

                          hash('zzz\n'): 4},

                         _count_blocks(blob))

    test_count_blocks_long_lines = functest_builder(

      _do_test_count_blocks_long_lines, _count_blocks_py)

    test_count_blocks_long_lines_extension = ext_functest_builder(

      _do_test_count_blocks_long_lines, _count_blocks)

    def assertSimilar(self, expected_score, blob1, blob2):

        self.assertEqual(expected_score, _similarity_score(blob1, blob2))

        self.assertEqual(expected_score, _similarity_score(blob2, blob1))

    def test_similarity_score(self):

        blob0 = make_object(Blob, data='')

        blob1 = make_object(Blob, data='ab\ncd\ncd\n')

        blob2 = make_object(Blob, data='ab\n')

        blob3 = make_object(Blob, data='cd\n')

        blob4 = make_object(Blob, data='cd\ncd\n')

        self.assertSimilar(100, blob0, blob0)

        self.assertSimilar(0, blob0, blob1)

        self.assertSimilar(33, blob1, blob2)

        self.assertSimilar(33, blob1, blob3)

        self.assertSimilar(66, blob1, blob4)

        self.assertSimilar(0, blob2, blob3)

        self.assertSimilar(50, blob3, blob4)

    def test_similarity_score_cache(self):

        blob1 = make_object(Blob, data='ab\ncd\n')

        blob2 = make_object(Blob, data='ab\n')

        block_cache = {}

        self.assertEqual(

          50, _similarity_score(blob1, blob2, block_cache=block_cache))

        self.assertEqual(set([blob1.id, blob2.id]), set(block_cache))

        def fail_chunks():

            self.fail('Unexpected call to as_raw_chunks()')

        blob1.as_raw_chunks = blob2.as_raw_chunks = fail_chunks

        blob1.raw_length = lambda: 6

        blob2.raw_length = lambda: 3

        self.assertEqual(

          50, _similarity_score(blob1, blob2, block_cache=block_cache))

    def test_tree_entry_sort(self):

        sha = 'abcd' * 10

        expected_entries = [

          TreeChange.add(TreeEntry('aaa', F, sha)),

          TreeChange(CHANGE_COPY, TreeEntry('bbb', F, sha),

                     TreeEntry('aab', F, sha)),

          TreeChange(CHANGE_MODIFY, TreeEntry('bbb', F, sha),

                     TreeEntry('bbb', F, 'dabc' * 10)),

          TreeChange(CHANGE_RENAME, TreeEntry('bbc', F, sha),

                     TreeEntry('ddd', F, sha)),

          TreeChange.delete(TreeEntry('ccc', F, sha)),

          ]

        for perm in permutations(expected_entries):

            self.assertEqual(expected_entries,

                             sorted(perm, key=_tree_change_key))

    def detect_renames(self, tree1, tree2, want_unchanged=False, **kwargs):

        detector = RenameDetector(self.store, **kwargs)

        return detector.changes_with_renames(tree1.id, tree2.id,

                                             want_unchanged=want_unchanged)

    def test_no_renames(self):

        blob1 = make_object(Blob, data='a\nb\nc\nd\n')

        blob2 = make_object(Blob, data='a\nb\ne\nf\n')

        blob3 = make_object(Blob, data='a\nb\ng\nh\n')

        tree1 = self.commit_tree([('a', blob1), ('b', blob2)])

        tree2 = self.commit_tree([('a', blob1), ('b', blob3)])

        self.assertEqual(

          [TreeChange(CHANGE_MODIFY, ('b', F, blob2.id), ('b', F, blob3.id))],

          self.detect_renames(tree1, tree2))

    def test_exact_rename_one_to_one(self):

        blob1 = make_object(Blob, data='1')

        blob2 = make_object(Blob, data='2')

        tree1 = self.commit_tree([('a', blob1), ('b', blob2)])