dulwich/dulwich/tests/test_diff_tree.py

# 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,
    _count_blocks,
    _count_blocks_py,
    _similarity_score,
    _tree_change_key,
    RenameDetector,
    _is_tree,
    _is_tree_py
    )
from dulwich.index import (
    commit_tree,
    )
from dulwich.misc 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 (
    make_object,
    functest_builder,
    ext_functest_builder,
    )

# Shorthand mode for Files.
F = 0100644


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 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)


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, **kwargs):
        detector = RenameDetector(self.store, tree1.id, tree2.id, **kwargs)
        return detector.changes_with_renames()

    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)])
        tree2 = self.commit_tree([('c', blob1), ('d', blob2)])
        self.assertEqual(
          [TreeChange(CHANGE_RENAME, ('a', F, blob1.id), ('c', F, blob1.id)),
           TreeChange(CHANGE_RENAME, ('b', F, blob2.id), ('d', F, blob2.id))],
          self.detect_renames(tree1, tree2))

    def test_exact_rename_split_different_type(self):
        blob = make_object(Blob, data='/foo')
        tree1 = self.commit_tree([('a', blob, 0100644)])
        tree2 = self.commit_tree([('a', blob, 0120000)])
        self.assertEqual(
          [TreeChange.add(('a', 0120000, blob.id)),
           TreeChange.delete(('a', 0100644, blob.id))],
          self.detect_renames(tree1, tree2))

    def test_exact_rename_and_different_type(self):
        blob1 = make_object(Blob, data='1')
        blob2 = make_object(Blob, data='2')
        tree1 = self.commit_tree([('a', blob1)])
        tree2 = self.commit_tree([('a', blob2, 0120000), ('b', blob1)])
        self.assertEqual(
          [TreeChange.add(('a', 0120000, blob2.id)),
           TreeChange(CHANGE_RENAME, ('a', F, blob1.id), ('b', F, blob1.id))],
          self.detect_renames(tree1, tree2))

    def test_exact_rename_one_to_many(self):
        blob = make_object(Blob, data='1')
        tree1 = self.commit_tree([('a', blob)])
        tree2 = self.commit_tree([('b', blob), ('c', blob)])
        self.assertEqual(
          [TreeChange(CHANGE_RENAME, ('a', F, blob.id), ('b', F, blob.id)),
           TreeChange(CHANGE_COPY, ('a', F, blob.id), ('c', F, blob.id))],
          self.detect_renames(tree1, tree2))

    def test_exact_rename_many_to_one(self):
        blob = make_object(Blob, data='1')
        tree1 = self.commit_tree([('a', blob), ('b', blob)])
        tree2 = self.commit_tree([('c', blob)])
        self.assertEqual(
          [TreeChange(CHANGE_RENAME, ('a', F, blob.id), ('c', F, blob.id)),
           TreeChange.delete(('b', F, blob.id))],
          self.detect_renames(tree1, tree2))

    def test_exact_rename_many_to_many(self):
        blob = make_object(Blob, data='1')
        tree1 = self.commit_tree([('a', blob), ('b', blob)])
        tree2 = self.commit_tree([('c', blob), ('d', blob), ('e', blob)])
        self.assertEqual(
          [TreeChange(CHANGE_RENAME, ('a', F, blob.id), ('c', F, blob.id)),
           TreeChange(CHANGE_COPY, ('a', F, blob.id), ('e', F, blob.id)),
           TreeChange(CHANGE_RENAME, ('b', F, blob.id), ('d', F, blob.id))],
          self.detect_renames(tree1, tree2))

    def test_rename_threshold(self):
        blob1 = make_object(Blob, data='a\nb\nc\n')
        blob2 = make_object(Blob, data='a\nb\nd\n')
        tree1 = self.commit_tree([('a', blob1)])
        tree2 = self.commit_tree([('b', blob2)])
        self.assertEqual(
          [TreeChange(CHANGE_RENAME, ('a', F, blob1.id), ('b', F, blob2.id))],
          self.detect_renames(tree1, tree2, rename_threshold=50))
        self.assertEqual(
          [TreeChange.delete(('a', F, blob1.id)),
           TreeChange.add(('b', F, blob2.id))],
          self.detect_renames(tree1, tree2, rename_threshold=75))

    def test_content_rename_max_files(self):
        blob1 = make_object(Blob, data='a\nb\nc\nd')
        blob4 = make_object(Blob, data='a\nb\nc\ne\n')
        blob2 = make_object(Blob, data='e\nf\ng\nh\n')
        blob3 = make_object(Blob, data='e\nf\ng\ni\n')
        tree1 = self.commit_tree([('a', blob1), ('b', blob2)])
        tree2 = self.commit_tree([('c', blob3), ('d', blob4)])
        self.assertEqual(
          [TreeChange(CHANGE_RENAME, ('a', F, blob1.id), ('d', F, blob4.id)),
           TreeChange(CHANGE_RENAME, ('b', F, blob2.id), ('c', F, blob3.id))],
          self.detect_renames(tree1, tree2))
        self.assertEqual(
          [TreeChange.delete(('a', F, blob1.id)),
           TreeChange.delete(('b', F, blob2.id)),
           TreeChange.add(('c', F, blob3.id)),
           TreeChange.add(('d', F, blob4.id))],
          self.detect_renames(tree1, tree2, max_files=1))

    def test_content_rename_one_to_one(self):
        b11 = make_object(Blob, data='a\nb\nc\nd\n')
        b12 = make_object(Blob, data='a\nb\nc\ne\n')
        b21 = make_object(Blob, data='e\nf\ng\n\h')
        b22 = make_object(Blob, data='e\nf\ng\n\i')
        tree1 = self.commit_tree([('a', b11), ('b', b21)])
        tree2 = self.commit_tree([('c', b12), ('d', b22)])
        self.assertEqual(
          [TreeChange(CHANGE_RENAME, ('a', F, b11.id), ('c', F, b12.id)),
           TreeChange(CHANGE_RENAME, ('b', F, b21.id), ('d', F, b22.id))],
          self.detect_renames(tree1, tree2))

    def test_content_rename_one_to_one_ordering(self):
        blob1 = make_object(Blob, data='a\nb\nc\nd\ne\nf\n')
        blob2 = make_object(Blob, data='a\nb\nc\nd\ng\nh\n')
        # 6/10 match to blob1, 8/10 match to blob2
        blob3 = make_object(Blob, data='a\nb\nc\nd\ng\ni\n')
        tree1 = self.commit_tree([('a', blob1), ('b', blob2)])
        tree2 = self.commit_tree([('c', blob3)])
        self.assertEqual(
          [TreeChange.delete(('a', F, blob1.id)),
           TreeChange(CHANGE_RENAME, ('b', F, blob2.id), ('c', F, blob3.id))],
          self.detect_renames(tree1, tree2))

        tree3 = self.commit_tree([('a', blob2), ('b', blob1)])
        tree4 = self.commit_tree([('c', blob3)])
        self.assertEqual(
          [TreeChange(CHANGE_RENAME, ('a', F, blob2.id), ('c', F, blob3.id)),
           TreeChange.delete(('b', F, blob1.id))],
          self.detect_renames(tree3, tree4))

    def test_content_rename_one_to_many(self):
        blob1 = make_object(Blob, data='aa\nb\nc\nd\ne\n')
        blob2 = make_object(Blob, data='ab\nb\nc\nd\ne\n')  # 8/11 match
        blob3 = make_object(Blob, data='aa\nb\nc\nd\nf\n')  # 9/11 match
        tree1 = self.commit_tree([('a', blob1)])
        tree2 = self.commit_tree([('b', blob2), ('c', blob3)])
        self.assertEqual(
          [TreeChange(CHANGE_COPY, ('a', F, blob1.id), ('b', F, blob2.id)),
           TreeChange(CHANGE_RENAME, ('a', F, blob1.id), ('c', F, blob3.id))],
          self.detect_renames(tree1, tree2))

    def test_content_rename_many_to_one(self):
        blob1 = make_object(Blob, data='a\nb\nc\nd\n')
        blob2 = make_object(Blob, data='a\nb\nc\ne\n')
        blob3 = make_object(Blob, data='a\nb\nc\nf\n')
        tree1 = self.commit_tree([('a', blob1), ('b', blob2)])
        tree2 = self.commit_tree([('c', blob3)])
        self.assertEqual(
          [TreeChange(CHANGE_RENAME, ('a', F, blob1.id), ('c', F, blob3.id)),
           TreeChange.delete(('b', F, blob2.id))],
          self.detect_renames(tree1, tree2))

    def test_content_rename_many_to_many(self):
        blob1 = make_object(Blob, data='a\nb\nc\nd\n')
        blob2 = make_object(Blob, data='a\nb\nc\ne\n')
        blob3 = make_object(Blob, data='a\nb\nc\nf\n')
        blob4 = make_object(Blob, data='a\nb\nc\ng\n')
        tree1 = self.commit_tree([('a', blob1), ('b', blob2)])
        tree2 = self.commit_tree([('c', blob3), ('d', blob4)])
        # TODO(dborowitz): Distribute renames rather than greedily choosing
        # copies.
        self.assertEqual(
          [TreeChange(CHANGE_RENAME, ('a', F, blob1.id), ('c', F, blob3.id)),
           TreeChange(CHANGE_COPY, ('a', F, blob1.id), ('d', F, blob4.id)),
           TreeChange.delete(('b', F, blob2.id))],
          self.detect_renames(tree1, tree2))

    def test_content_rename_gitlink(self):
        blob1 = make_object(Blob, data='blob1')
        blob2 = make_object(Blob, data='blob2')
        link1 = '1' * 40
        link2 = '2' * 40
        tree1 = self.commit_tree([('a', blob1), ('b', link1, 0160000)])
        tree2 = self.commit_tree([('c', blob2), ('d', link2, 0160000)])
        self.assertEqual(
          [TreeChange.delete(('a', 0100644, blob1.id)),
           TreeChange.delete(('b', 0160000, link1)),
           TreeChange.add(('c', 0100644, blob2.id)),
           TreeChange.add(('d', 0160000, link2))],
          self.detect_renames(tree1, tree2))

    def test_exact_rename_swap(self):
        blob1 = make_object(Blob, data='1')
        blob2 = make_object(Blob, data='2')
        tree1 = self.commit_tree([('a', blob1), ('b', blob2)])
        tree2 = self.commit_tree([('a', blob2), ('b', blob1)])
        self.assertEqual(
          [TreeChange(CHANGE_MODIFY, ('a', F, blob1.id), ('a', F, blob2.id)),
           TreeChange(CHANGE_MODIFY, ('b', F, blob2.id), ('b', F, blob1.id))],
          self.detect_renames(tree1, tree2))
        self.assertEqual(
          [TreeChange(CHANGE_RENAME, ('a', F, blob1.id), ('b', F, blob1.id)),
           TreeChange(CHANGE_RENAME, ('b', F, blob2.id), ('a', F, blob2.id))],
          self.detect_renames(tree1, tree2, rewrite_threshold=50))

    def test_content_rename_swap(self):
        blob1 = make_object(Blob, data='a\nb\nc\nd\n')
        blob2 = make_object(Blob, data='e\nf\ng\nh\n')
        blob3 = make_object(Blob, data='a\nb\nc\ne\n')
        blob4 = make_object(Blob, data='e\nf\ng\ni\n')
        tree1 = self.commit_tree([('a', blob1), ('b', blob2)])
        tree2 = self.commit_tree([('a', blob4), ('b', blob3)])
        self.assertEqual(
          [TreeChange(CHANGE_RENAME, ('a', F, blob1.id), ('b', F, blob3.id)),
           TreeChange(CHANGE_RENAME, ('b', F, blob2.id), ('a', F, blob4.id))],
          self.detect_renames(tree1, tree2, rewrite_threshold=60))

    def test_rewrite_threshold(self):
        blob1 = make_object(Blob, data='a\nb\nc\nd\n')
        blob2 = make_object(Blob, data='a\nb\nc\ne\n')
        blob3 = make_object(Blob, data='a\nb\nf\ng\n')

        tree1 = self.commit_tree([('a', blob1)])
        tree2 = self.commit_tree([('a', blob3), ('b', blob2)])

        no_renames = [
          TreeChange(CHANGE_MODIFY, ('a', F, blob1.id), ('a', F, blob3.id)),
          TreeChange.add(('b', F, blob2.id))]
        self.assertEqual(
          no_renames, self.detect_renames(tree1, tree2))
        self.assertEqual(
          no_renames, self.detect_renames(tree1, tree2, rewrite_threshold=40))
        self.assertEqual(
          [TreeChange.add(('a', F, blob3.id)),
           TreeChange(CHANGE_RENAME, ('a', F, blob1.id), ('b', F, blob2.id))],
          self.detect_renames(tree1, tree2, rewrite_threshold=80))

    def test_find_copies_harder_exact(self):
        blob = make_object(Blob, data='blob')
        tree1 = self.commit_tree([('a', blob)])
        tree2 = self.commit_tree([('a', blob), ('b', blob)])
        self.assertEqual([TreeChange.add(('b', F, blob.id))],
                         self.detect_renames(tree1, tree2))
        self.assertEqual(
          [TreeChange(CHANGE_COPY, ('a', F, blob.id), ('b', F, blob.id))],
          self.detect_renames(tree1, tree2, find_copies_harder=True))

    def test_find_copies_harder_content(self):
        blob1 = make_object(Blob, data='a\nb\nc\nd\n')
        blob2 = make_object(Blob, data='a\nb\nc\ne\n')
        tree1 = self.commit_tree([('a', blob1)])
        tree2 = self.commit_tree([('a', blob1), ('b', blob2)])
        self.assertEqual([TreeChange.add(('b', F, blob2.id))],
                         self.detect_renames(tree1, tree2))
        self.assertEqual(
          [TreeChange(CHANGE_COPY, ('a', F, blob1.id), ('b', F, blob2.id))],
          self.detect_renames(tree1, tree2, find_copies_harder=True))

    def test_find_copies_harder_modify(self):
        blob1 = make_object(Blob, data='a\nb\nc\nd\n')
        blob2 = make_object(Blob, data='a\nb\nc\ne\n')
        tree1 = self.commit_tree([('a', blob1)])
        tree2 = self.commit_tree([('a', blob2), ('b', blob2)])
        self.assertEqual(
          [TreeChange(CHANGE_MODIFY, ('a', F, blob1.id), ('a', F, blob2.id)),
           TreeChange.add(('b', F, blob2.id))],
          self.detect_renames(tree1, tree2))
        self.assertEqual(
          [TreeChange(CHANGE_MODIFY, ('a', F, blob1.id), ('a', F, blob2.id)),
           TreeChange(CHANGE_COPY, ('a', F, blob1.id), ('b', F, blob2.id))],
          self.detect_renames(tree1, tree2, find_copies_harder=True))

    def test_find_copies_harder_with_rewrites(self):
        blob_a1 = make_object(Blob, data='a\nb\nc\nd\n')
        blob_a2 = make_object(Blob, data='f\ng\nh\ni\n')
        blob_b2 = make_object(Blob, data='a\nb\nc\ne\n')
        tree1 = self.commit_tree([('a', blob_a1)])
        tree2 = self.commit_tree([('a', blob_a2), ('b', blob_b2)])
        self.assertEqual(
          [TreeChange(CHANGE_MODIFY, ('a', F, blob_a1.id),
                      ('a', F, blob_a2.id)),
           TreeChange(CHANGE_COPY, ('a', F, blob_a1.id), ('b', F, blob_b2.id))],
          self.detect_renames(tree1, tree2, find_copies_harder=True))
        self.assertEqual(
          [TreeChange.add(('a', F, blob_a2.id)),
           TreeChange(CHANGE_RENAME, ('a', F, blob_a1.id),
                      ('b', F, blob_b2.id))],
          self.detect_renames(tree1, tree2, rewrite_threshold=50,
                              find_copies_harder=True))