~bzr-pqm/bzr/bzr.dev

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
# Copyright (C) 2005-2011 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

from bzrlib.lazy_import import lazy_import
lazy_import(globals(), """
import itertools
import time

from bzrlib import (
    bzrdir,
    config,
    controldir,
    debug,
    generate_ids,
    graph,
    lockable_files,
    lockdir,
    osutils,
    revision as _mod_revision,
    testament as _mod_testament,
    tsort,
    gpg,
    )
from bzrlib.bundle import serializer
""")

from bzrlib import (
    errors,
    registry,
    symbol_versioning,
    ui,
    )
from bzrlib.decorators import needs_read_lock, needs_write_lock, only_raises
from bzrlib.inter import InterObject
from bzrlib.lock import _RelockDebugMixin, LogicalLockResult
from bzrlib.trace import (
    log_exception_quietly, note, mutter, mutter_callsite, warning)


# Old formats display a warning, but only once
_deprecation_warning_done = False


class IsInWriteGroupError(errors.InternalBzrError):

    _fmt = "May not refresh_data of repo %(repo)s while in a write group."

    def __init__(self, repo):
        errors.InternalBzrError.__init__(self, repo=repo)


class CommitBuilder(object):
    """Provides an interface to build up a commit.

    This allows describing a tree to be committed without needing to
    know the internals of the format of the repository.
    """

    # all clients should supply tree roots.
    record_root_entry = True
    # whether this commit builder supports the record_entry_contents interface
    supports_record_entry_contents = False

    def __init__(self, repository, parents, config, timestamp=None,
                 timezone=None, committer=None, revprops=None,
                 revision_id=None, lossy=False):
        """Initiate a CommitBuilder.

        :param repository: Repository to commit to.
        :param parents: Revision ids of the parents of the new revision.
        :param timestamp: Optional timestamp recorded for commit.
        :param timezone: Optional timezone for timestamp.
        :param committer: Optional committer to set for commit.
        :param revprops: Optional dictionary of revision properties.
        :param revision_id: Optional revision id.
        :param lossy: Whether to discard data that can not be natively
            represented, when pushing to a foreign VCS 
        """
        self._config = config
        self._lossy = lossy

        if committer is None:
            self._committer = self._config.username()
        elif not isinstance(committer, unicode):
            self._committer = committer.decode() # throw if non-ascii
        else:
            self._committer = committer

        self._new_revision_id = revision_id
        self.parents = parents
        self.repository = repository

        self._revprops = {}
        if revprops is not None:
            self._validate_revprops(revprops)
            self._revprops.update(revprops)

        if timestamp is None:
            timestamp = time.time()
        # Restrict resolution to 1ms
        self._timestamp = round(timestamp, 3)

        if timezone is None:
            self._timezone = osutils.local_time_offset()
        else:
            self._timezone = int(timezone)

        self._generate_revision_if_needed()

    def any_changes(self):
        """Return True if any entries were changed.

        This includes merge-only changes. It is the core for the --unchanged
        detection in commit.

        :return: True if any changes have occured.
        """
        raise NotImplementedError(self.any_changes)

    def _validate_unicode_text(self, text, context):
        """Verify things like commit messages don't have bogus characters."""
        if '\r' in text:
            raise ValueError('Invalid value for %s: %r' % (context, text))

    def _validate_revprops(self, revprops):
        for key, value in revprops.iteritems():
            # We know that the XML serializers do not round trip '\r'
            # correctly, so refuse to accept them
            if not isinstance(value, basestring):
                raise ValueError('revision property (%s) is not a valid'
                                 ' (unicode) string: %r' % (key, value))
            self._validate_unicode_text(value,
                                        'revision property (%s)' % (key,))

    def commit(self, message):
        """Make the actual commit.

        :return: The revision id of the recorded revision.
        """
        raise NotImplementedError(self.commit)

    def abort(self):
        """Abort the commit that is being built.
        """
        raise NotImplementedError(self.abort)

    def revision_tree(self):
        """Return the tree that was just committed.

        After calling commit() this can be called to get a
        RevisionTree representing the newly committed tree. This is
        preferred to calling Repository.revision_tree() because that may
        require deserializing the inventory, while we already have a copy in
        memory.
        """
        raise NotImplementedError(self.revision_tree)

    def finish_inventory(self):
        """Tell the builder that the inventory is finished.

        :return: The inventory id in the repository, which can be used with
            repository.get_inventory.
        """
        raise NotImplementedError(self.finish_inventory)

    def _gen_revision_id(self):
        """Return new revision-id."""
        return generate_ids.gen_revision_id(self._committer, self._timestamp)

    def _generate_revision_if_needed(self):
        """Create a revision id if None was supplied.

        If the repository can not support user-specified revision ids
        they should override this function and raise CannotSetRevisionId
        if _new_revision_id is not None.

        :raises: CannotSetRevisionId
        """
        if self._new_revision_id is None:
            self._new_revision_id = self._gen_revision_id()
            self.random_revid = True
        else:
            self.random_revid = False

    def will_record_deletes(self):
        """Tell the commit builder that deletes are being notified.

        This enables the accumulation of an inventory delta; for the resulting
        commit to be valid, deletes against the basis MUST be recorded via
        builder.record_delete().
        """
        raise NotImplementedError(self.will_record_deletes)

    def record_iter_changes(self, tree, basis_revision_id, iter_changes):
        """Record a new tree via iter_changes.

        :param tree: The tree to obtain text contents from for changed objects.
        :param basis_revision_id: The revision id of the tree the iter_changes
            has been generated against. Currently assumed to be the same
            as self.parents[0] - if it is not, errors may occur.
        :param iter_changes: An iter_changes iterator with the changes to apply
            to basis_revision_id. The iterator must not include any items with
            a current kind of None - missing items must be either filtered out
            or errored-on beefore record_iter_changes sees the item.
        :return: A generator of (file_id, relpath, fs_hash) tuples for use with
            tree._observed_sha1.
        """
        raise NotImplementedError(self.record_iter_changes)


class RepositoryWriteLockResult(LogicalLockResult):
    """The result of write locking a repository.

    :ivar repository_token: The token obtained from the underlying lock, or
        None.
    :ivar unlock: A callable which will unlock the lock.
    """

    def __init__(self, unlock, repository_token):
        LogicalLockResult.__init__(self, unlock)
        self.repository_token = repository_token

    def __repr__(self):
        return "RepositoryWriteLockResult(%s, %s)" % (self.repository_token,
            self.unlock)


######################################################################
# Repositories


class Repository(_RelockDebugMixin, controldir.ControlComponent):
    """Repository holding history for one or more branches.

    The repository holds and retrieves historical information including
    revisions and file history.  It's normally accessed only by the Branch,
    which views a particular line of development through that history.

    See VersionedFileRepository in bzrlib.vf_repository for the
    base class for most Bazaar repositories.
    """

    def abort_write_group(self, suppress_errors=False):
        """Commit the contents accrued within the current write group.

        :param suppress_errors: if true, abort_write_group will catch and log
            unexpected errors that happen during the abort, rather than
            allowing them to propagate.  Defaults to False.

        :seealso: start_write_group.
        """
        if self._write_group is not self.get_transaction():
            # has an unlock or relock occured ?
            if suppress_errors:
                mutter(
                '(suppressed) mismatched lock context and write group. %r, %r',
                self._write_group, self.get_transaction())
                return
            raise errors.BzrError(
                'mismatched lock context and write group. %r, %r' %
                (self._write_group, self.get_transaction()))
        try:
            self._abort_write_group()
        except Exception, exc:
            self._write_group = None
            if not suppress_errors:
                raise
            mutter('abort_write_group failed')
            log_exception_quietly()
            note('bzr: ERROR (ignored): %s', exc)
        self._write_group = None

    def _abort_write_group(self):
        """Template method for per-repository write group cleanup.

        This is called during abort before the write group is considered to be
        finished and should cleanup any internal state accrued during the write
        group. There is no requirement that data handed to the repository be
        *not* made available - this is not a rollback - but neither should any
        attempt be made to ensure that data added is fully commited. Abort is
        invoked when an error has occured so futher disk or network operations
        may not be possible or may error and if possible should not be
        attempted.
        """

    def add_fallback_repository(self, repository):
        """Add a repository to use for looking up data not held locally.

        :param repository: A repository.
        """
        raise NotImplementedError(self.add_fallback_repository)

    def _check_fallback_repository(self, repository):
        """Check that this repository can fallback to repository safely.

        Raise an error if not.

        :param repository: A repository to fallback to.
        """
        return InterRepository._assert_same_model(self, repository)

    def all_revision_ids(self):
        """Returns a list of all the revision ids in the repository.

        This is conceptually deprecated because code should generally work on
        the graph reachable from a particular revision, and ignore any other
        revisions that might be present.  There is no direct replacement
        method.
        """
        if 'evil' in debug.debug_flags:
            mutter_callsite(2, "all_revision_ids is linear with history.")
        return self._all_revision_ids()

    def _all_revision_ids(self):
        """Returns a list of all the revision ids in the repository.

        These are in as much topological order as the underlying store can
        present.
        """
        raise NotImplementedError(self._all_revision_ids)

    def break_lock(self):
        """Break a lock if one is present from another instance.

        Uses the ui factory to ask for confirmation if the lock may be from
        an active process.
        """
        self.control_files.break_lock()

    @needs_read_lock
    def _eliminate_revisions_not_present(self, revision_ids):
        """Check every revision id in revision_ids to see if we have it.

        Returns a set of the present revisions.
        """
        result = []
        graph = self.get_graph()
        parent_map = graph.get_parent_map(revision_ids)
        # The old API returned a list, should this actually be a set?
        return parent_map.keys()

    @staticmethod
    def create(a_bzrdir):
        """Construct the current default format repository in a_bzrdir."""
        return RepositoryFormat.get_default_format().initialize(a_bzrdir)

    def __init__(self, _format, a_bzrdir, control_files):
        """instantiate a Repository.

        :param _format: The format of the repository on disk.
        :param a_bzrdir: The BzrDir of the repository.
        :param control_files: Control files to use for locking, etc.
        """
        # In the future we will have a single api for all stores for
        # getting file texts, inventories and revisions, then
        # this construct will accept instances of those things.
        super(Repository, self).__init__()
        self._format = _format
        # the following are part of the public API for Repository:
        self.bzrdir = a_bzrdir
        self.control_files = control_files
        self._transport = control_files._transport
        self.base = self._transport.base
        # for tests
        self._write_group = None
        # Additional places to query for data.
        self._fallback_repositories = []

    @property
    def user_transport(self):
        return self.bzrdir.user_transport

    @property
    def control_transport(self):
        return self._transport

    def __repr__(self):
        if self._fallback_repositories:
            return '%s(%r, fallback_repositories=%r)' % (
                self.__class__.__name__,
                self.base,
                self._fallback_repositories)
        else:
            return '%s(%r)' % (self.__class__.__name__,
                               self.base)

    def _has_same_fallbacks(self, other_repo):
        """Returns true if the repositories have the same fallbacks."""
        my_fb = self._fallback_repositories
        other_fb = other_repo._fallback_repositories
        if len(my_fb) != len(other_fb):
            return False
        for f, g in zip(my_fb, other_fb):
            if not f.has_same_location(g):
                return False
        return True

    def has_same_location(self, other):
        """Returns a boolean indicating if this repository is at the same
        location as another repository.

        This might return False even when two repository objects are accessing
        the same physical repository via different URLs.
        """
        if self.__class__ is not other.__class__:
            return False
        return (self._transport.base == other._transport.base)

    def is_in_write_group(self):
        """Return True if there is an open write group.

        :seealso: start_write_group.
        """
        return self._write_group is not None

    def is_locked(self):
        return self.control_files.is_locked()

    def is_write_locked(self):
        """Return True if this object is write locked."""
        return self.is_locked() and self.control_files._lock_mode == 'w'

    def lock_write(self, token=None):
        """Lock this repository for writing.

        This causes caching within the repository obejct to start accumlating
        data during reads, and allows a 'write_group' to be obtained. Write
        groups must be used for actual data insertion.

        A token should be passed in if you know that you have locked the object
        some other way, and need to synchronise this object's state with that
        fact.

        XXX: this docstring is duplicated in many places, e.g. lockable_files.py

        :param token: if this is already locked, then lock_write will fail
            unless the token matches the existing lock.
        :returns: a token if this instance supports tokens, otherwise None.
        :raises TokenLockingNotSupported: when a token is given but this
            instance doesn't support using token locks.
        :raises MismatchedToken: if the specified token doesn't match the token
            of the existing lock.
        :seealso: start_write_group.
        :return: A RepositoryWriteLockResult.
        """
        locked = self.is_locked()
        token = self.control_files.lock_write(token=token)
        if not locked:
            self._warn_if_deprecated()
            self._note_lock('w')
            for repo in self._fallback_repositories:
                # Writes don't affect fallback repos
                repo.lock_read()
            self._refresh_data()
        return RepositoryWriteLockResult(self.unlock, token)

    def lock_read(self):
        """Lock the repository for read operations.

        :return: An object with an unlock method which will release the lock
            obtained.
        """
        locked = self.is_locked()
        self.control_files.lock_read()
        if not locked:
            self._warn_if_deprecated()
            self._note_lock('r')
            for repo in self._fallback_repositories:
                repo.lock_read()
            self._refresh_data()
        return LogicalLockResult(self.unlock)

    def get_physical_lock_status(self):
        return self.control_files.get_physical_lock_status()

    def leave_lock_in_place(self):
        """Tell this repository not to release the physical lock when this
        object is unlocked.

        If lock_write doesn't return a token, then this method is not supported.
        """
        self.control_files.leave_in_place()

    def dont_leave_lock_in_place(self):
        """Tell this repository to release the physical lock when this
        object is unlocked, even if it didn't originally acquire it.

        If lock_write doesn't return a token, then this method is not supported.
        """
        self.control_files.dont_leave_in_place()

    @needs_read_lock
    def gather_stats(self, revid=None, committers=None):
        """Gather statistics from a revision id.

        :param revid: The revision id to gather statistics from, if None, then
            no revision specific statistics are gathered.
        :param committers: Optional parameter controlling whether to grab
            a count of committers from the revision specific statistics.
        :return: A dictionary of statistics. Currently this contains:
            committers: The number of committers if requested.
            firstrev: A tuple with timestamp, timezone for the penultimate left
                most ancestor of revid, if revid is not the NULL_REVISION.
            latestrev: A tuple with timestamp, timezone for revid, if revid is
                not the NULL_REVISION.
            revisions: The total revision count in the repository.
            size: An estimate disk size of the repository in bytes.
        """
        result = {}
        if revid and committers:
            result['committers'] = 0
        if revid and revid != _mod_revision.NULL_REVISION:
            graph = self.get_graph()
            if committers:
                all_committers = set()
            revisions = [r for (r, p) in graph.iter_ancestry([revid])
                        if r != _mod_revision.NULL_REVISION]
            last_revision = None
            if not committers:
                # ignore the revisions in the middle - just grab first and last
                revisions = revisions[0], revisions[-1]
            for revision in self.get_revisions(revisions):
                if not last_revision:
                    last_revision = revision
                if committers:
                    all_committers.add(revision.committer)
            first_revision = revision
            if committers:
                result['committers'] = len(all_committers)
            result['firstrev'] = (first_revision.timestamp,
                first_revision.timezone)
            result['latestrev'] = (last_revision.timestamp,
                last_revision.timezone)
        return result

    def find_branches(self, using=False):
        """Find branches underneath this repository.

        This will include branches inside other branches.

        :param using: If True, list only branches using this repository.
        """
        if using and not self.is_shared():
            return self.bzrdir.list_branches()
        class Evaluator(object):

            def __init__(self):
                self.first_call = True

            def __call__(self, bzrdir):
                # On the first call, the parameter is always the bzrdir
                # containing the current repo.
                if not self.first_call:
                    try:
                        repository = bzrdir.open_repository()
                    except errors.NoRepositoryPresent:
                        pass
                    else:
                        return False, ([], repository)
                self.first_call = False
                value = (bzrdir.list_branches(), None)
                return True, value

        ret = []
        for branches, repository in bzrdir.BzrDir.find_bzrdirs(
                self.user_transport, evaluate=Evaluator()):
            if branches is not None:
                ret.extend(branches)
            if not using and repository is not None:
                ret.extend(repository.find_branches())
        return ret

    @needs_read_lock
    def search_missing_revision_ids(self, other,
            revision_id=symbol_versioning.DEPRECATED_PARAMETER,
            find_ghosts=True, revision_ids=None, if_present_ids=None,
            limit=None):
        """Return the revision ids that other has that this does not.

        These are returned in topological order.

        revision_id: only return revision ids included by revision_id.
        """
        if symbol_versioning.deprecated_passed(revision_id):
            symbol_versioning.warn(
                'search_missing_revision_ids(revision_id=...) was '
                'deprecated in 2.4.  Use revision_ids=[...] instead.',
                DeprecationWarning, stacklevel=3)
            if revision_ids is not None:
                raise AssertionError(
                    'revision_ids is mutually exclusive with revision_id')
            if revision_id is not None:
                revision_ids = [revision_id]
        return InterRepository.get(other, self).search_missing_revision_ids(
            find_ghosts=find_ghosts, revision_ids=revision_ids,
            if_present_ids=if_present_ids, limit=limit)

    @staticmethod
    def open(base):
        """Open the repository rooted at base.

        For instance, if the repository is at URL/.bzr/repository,
        Repository.open(URL) -> a Repository instance.
        """
        control = bzrdir.BzrDir.open(base)
        return control.open_repository()

    def copy_content_into(self, destination, revision_id=None):
        """Make a complete copy of the content in self into destination.

        This is a destructive operation! Do not use it on existing
        repositories.
        """
        return InterRepository.get(self, destination).copy_content(revision_id)

    def commit_write_group(self):
        """Commit the contents accrued within the current write group.

        :seealso: start_write_group.
        
        :return: it may return an opaque hint that can be passed to 'pack'.
        """
        if self._write_group is not self.get_transaction():
            # has an unlock or relock occured ?
            raise errors.BzrError('mismatched lock context %r and '
                'write group %r.' %
                (self.get_transaction(), self._write_group))
        result = self._commit_write_group()
        self._write_group = None
        return result

    def _commit_write_group(self):
        """Template method for per-repository write group cleanup.

        This is called before the write group is considered to be
        finished and should ensure that all data handed to the repository
        for writing during the write group is safely committed (to the
        extent possible considering file system caching etc).
        """

    def suspend_write_group(self):
        raise errors.UnsuspendableWriteGroup(self)

    def refresh_data(self):
        """Re-read any data needed to synchronise with disk.

        This method is intended to be called after another repository instance
        (such as one used by a smart server) has inserted data into the
        repository. On all repositories this will work outside of write groups.
        Some repository formats (pack and newer for bzrlib native formats)
        support refresh_data inside write groups. If called inside a write
        group on a repository that does not support refreshing in a write group
        IsInWriteGroupError will be raised.
        """
        self._refresh_data()

    def resume_write_group(self, tokens):
        if not self.is_write_locked():
            raise errors.NotWriteLocked(self)
        if self._write_group:
            raise errors.BzrError('already in a write group')
        self._resume_write_group(tokens)
        # so we can detect unlock/relock - the write group is now entered.
        self._write_group = self.get_transaction()

    def _resume_write_group(self, tokens):
        raise errors.UnsuspendableWriteGroup(self)

    def fetch(self, source, revision_id=None, find_ghosts=False,
            fetch_spec=None):
        """Fetch the content required to construct revision_id from source.

        If revision_id is None and fetch_spec is None, then all content is
        copied.

        fetch() may not be used when the repository is in a write group -
        either finish the current write group before using fetch, or use
        fetch before starting the write group.

        :param find_ghosts: Find and copy revisions in the source that are
            ghosts in the target (and not reachable directly by walking out to
            the first-present revision in target from revision_id).
        :param revision_id: If specified, all the content needed for this
            revision ID will be copied to the target.  Fetch will determine for
            itself which content needs to be copied.
        :param fetch_spec: If specified, a SearchResult or
            PendingAncestryResult that describes which revisions to copy.  This
            allows copying multiple heads at once.  Mutually exclusive with
            revision_id.
        """
        if fetch_spec is not None and revision_id is not None:
            raise AssertionError(
                "fetch_spec and revision_id are mutually exclusive.")
        if self.is_in_write_group():
            raise errors.InternalBzrError(
                "May not fetch while in a write group.")
        # fast path same-url fetch operations
        # TODO: lift out to somewhere common with RemoteRepository
        # <https://bugs.launchpad.net/bzr/+bug/401646>
        if (self.has_same_location(source)
            and fetch_spec is None
            and self._has_same_fallbacks(source)):
            # check that last_revision is in 'from' and then return a
            # no-operation.
            if (revision_id is not None and
                not _mod_revision.is_null(revision_id)):
                self.get_revision(revision_id)
            return 0, []
        inter = InterRepository.get(source, self)
        return inter.fetch(revision_id=revision_id,
            find_ghosts=find_ghosts, fetch_spec=fetch_spec)

    def create_bundle(self, target, base, fileobj, format=None):
        return serializer.write_bundle(self, target, base, fileobj, format)

    def get_commit_builder(self, branch, parents, config, timestamp=None,
                           timezone=None, committer=None, revprops=None,
                           revision_id=None, lossy=False):
        """Obtain a CommitBuilder for this repository.

        :param branch: Branch to commit to.
        :param parents: Revision ids of the parents of the new revision.
        :param config: Configuration to use.
        :param timestamp: Optional timestamp recorded for commit.
        :param timezone: Optional timezone for timestamp.
        :param committer: Optional committer to set for commit.
        :param revprops: Optional dictionary of revision properties.
        :param revision_id: Optional revision id.
        :param lossy: Whether to discard data that can not be natively
            represented, when pushing to a foreign VCS
        """
        raise NotImplementedError(self.get_commit_builder)

    @only_raises(errors.LockNotHeld, errors.LockBroken)
    def unlock(self):
        if (self.control_files._lock_count == 1 and
            self.control_files._lock_mode == 'w'):
            if self._write_group is not None:
                self.abort_write_group()
                self.control_files.unlock()
                raise errors.BzrError(
                    'Must end write groups before releasing write locks.')
        self.control_files.unlock()
        if self.control_files._lock_count == 0:
            for repo in self._fallback_repositories:
                repo.unlock()

    @needs_read_lock
    def clone(self, a_bzrdir, revision_id=None):
        """Clone this repository into a_bzrdir using the current format.

        Currently no check is made that the format of this repository and
        the bzrdir format are compatible. FIXME RBC 20060201.

        :return: The newly created destination repository.
        """
        # TODO: deprecate after 0.16; cloning this with all its settings is
        # probably not very useful -- mbp 20070423
        dest_repo = self._create_sprouting_repo(a_bzrdir, shared=self.is_shared())
        self.copy_content_into(dest_repo, revision_id)
        return dest_repo

    def start_write_group(self):
        """Start a write group in the repository.

        Write groups are used by repositories which do not have a 1:1 mapping
        between file ids and backend store to manage the insertion of data from
        both fetch and commit operations.

        A write lock is required around the start_write_group/commit_write_group
        for the support of lock-requiring repository formats.

        One can only insert data into a repository inside a write group.

        :return: None.
        """
        if not self.is_write_locked():
            raise errors.NotWriteLocked(self)
        if self._write_group:
            raise errors.BzrError('already in a write group')
        self._start_write_group()
        # so we can detect unlock/relock - the write group is now entered.
        self._write_group = self.get_transaction()

    def _start_write_group(self):
        """Template method for per-repository write group startup.

        This is called before the write group is considered to be
        entered.
        """

    @needs_read_lock
    def sprout(self, to_bzrdir, revision_id=None):
        """Create a descendent repository for new development.

        Unlike clone, this does not copy the settings of the repository.
        """
        dest_repo = self._create_sprouting_repo(to_bzrdir, shared=False)
        dest_repo.fetch(self, revision_id=revision_id)
        return dest_repo

    def _create_sprouting_repo(self, a_bzrdir, shared):
        if not isinstance(a_bzrdir._format, self.bzrdir._format.__class__):
            # use target default format.
            dest_repo = a_bzrdir.create_repository()
        else:
            # Most control formats need the repository to be specifically
            # created, but on some old all-in-one formats it's not needed
            try:
                dest_repo = self._format.initialize(a_bzrdir, shared=shared)
            except errors.UninitializableFormat:
                dest_repo = a_bzrdir.open_repository()
        return dest_repo

    @needs_read_lock
    def has_revision(self, revision_id):
        """True if this repository has a copy of the revision."""
        return revision_id in self.has_revisions((revision_id,))

    @needs_read_lock
    def has_revisions(self, revision_ids):
        """Probe to find out the presence of multiple revisions.

        :param revision_ids: An iterable of revision_ids.
        :return: A set of the revision_ids that were present.
        """
        raise NotImplementedError(self.has_revisions)

    @needs_read_lock
    def get_revision(self, revision_id):
        """Return the Revision object for a named revision."""
        return self.get_revisions([revision_id])[0]

    def get_revision_reconcile(self, revision_id):
        """'reconcile' helper routine that allows access to a revision always.

        This variant of get_revision does not cross check the weave graph
        against the revision one as get_revision does: but it should only
        be used by reconcile, or reconcile-alike commands that are correcting
        or testing the revision graph.
        """
        raise NotImplementedError(self.get_revision_reconcile)

    def get_revisions(self, revision_ids):
        """Get many revisions at once.
        
        Repositories that need to check data on every revision read should 
        subclass this method.
        """
        raise NotImplementedError(self.get_revisions)

    def get_deltas_for_revisions(self, revisions, specific_fileids=None):
        """Produce a generator of revision deltas.

        Note that the input is a sequence of REVISIONS, not revision_ids.
        Trees will be held in memory until the generator exits.
        Each delta is relative to the revision's lefthand predecessor.

        :param specific_fileids: if not None, the result is filtered
          so that only those file-ids, their parents and their
          children are included.
        """
        # Get the revision-ids of interest
        required_trees = set()
        for revision in revisions:
            required_trees.add(revision.revision_id)
            required_trees.update(revision.parent_ids[:1])

        # Get the matching filtered trees. Note that it's more
        # efficient to pass filtered trees to changes_from() rather
        # than doing the filtering afterwards. changes_from() could
        # arguably do the filtering itself but it's path-based, not
        # file-id based, so filtering before or afterwards is
        # currently easier.
        if specific_fileids is None:
            trees = dict((t.get_revision_id(), t) for
                t in self.revision_trees(required_trees))
        else:
            trees = dict((t.get_revision_id(), t) for
                t in self._filtered_revision_trees(required_trees,
                specific_fileids))

        # Calculate the deltas
        for revision in revisions:
            if not revision.parent_ids:
                old_tree = self.revision_tree(_mod_revision.NULL_REVISION)
            else:
                old_tree = trees[revision.parent_ids[0]]
            yield trees[revision.revision_id].changes_from(old_tree)

    @needs_read_lock
    def get_revision_delta(self, revision_id, specific_fileids=None):
        """Return the delta for one revision.

        The delta is relative to the left-hand predecessor of the
        revision.

        :param specific_fileids: if not None, the result is filtered
          so that only those file-ids, their parents and their
          children are included.
        """
        r = self.get_revision(revision_id)
        return list(self.get_deltas_for_revisions([r],
            specific_fileids=specific_fileids))[0]

    @needs_write_lock
    def store_revision_signature(self, gpg_strategy, plaintext, revision_id):
        signature = gpg_strategy.sign(plaintext)
        self.add_signature_text(revision_id, signature)

    def add_signature_text(self, revision_id, signature):
        """Store a signature text for a revision.

        :param revision_id: Revision id of the revision
        :param signature: Signature text.
        """
        raise NotImplementedError(self.add_signature_text)

    def _find_parent_ids_of_revisions(self, revision_ids):
        """Find all parent ids that are mentioned in the revision graph.

        :return: set of revisions that are parents of revision_ids which are
            not part of revision_ids themselves
        """
        parent_map = self.get_parent_map(revision_ids)
        parent_ids = set()
        map(parent_ids.update, parent_map.itervalues())
        parent_ids.difference_update(revision_ids)
        parent_ids.discard(_mod_revision.NULL_REVISION)
        return parent_ids

    def fileids_altered_by_revision_ids(self, revision_ids):
        """Find the file ids and versions affected by revisions.

        :param revisions: an iterable containing revision ids.
        :return: a dictionary mapping altered file-ids to an iterable of
            revision_ids. Each altered file-ids has the exact revision_ids
            that altered it listed explicitly.
        """
        raise NotImplementedError(self.fileids_altered_by_revision_ids)

    def iter_files_bytes(self, desired_files):
        """Iterate through file versions.

        Files will not necessarily be returned in the order they occur in
        desired_files.  No specific order is guaranteed.

        Yields pairs of identifier, bytes_iterator.  identifier is an opaque
        value supplied by the caller as part of desired_files.  It should
        uniquely identify the file version in the caller's context.  (Examples:
        an index number or a TreeTransform trans_id.)

        :param desired_files: a list of (file_id, revision_id, identifier)
            triples
        """
        raise NotImplementedError(self.iter_files_bytes)

    def get_rev_id_for_revno(self, revno, known_pair):
        """Return the revision id of a revno, given a later (revno, revid)
        pair in the same history.

        :return: if found (True, revid).  If the available history ran out
            before reaching the revno, then this returns
            (False, (closest_revno, closest_revid)).
        """
        known_revno, known_revid = known_pair
        partial_history = [known_revid]
        distance_from_known = known_revno - revno
        if distance_from_known < 0:
            raise ValueError(
                'requested revno (%d) is later than given known revno (%d)'
                % (revno, known_revno))
        try:
            _iter_for_revno(
                self, partial_history, stop_index=distance_from_known)
        except errors.RevisionNotPresent, err:
            if err.revision_id == known_revid:
                # The start revision (known_revid) wasn't found.
                raise
            # This is a stacked repository with no fallbacks, or a there's a
            # left-hand ghost.  Either way, even though the revision named in
            # the error isn't in this repo, we know it's the next step in this
            # left-hand history.
            partial_history.append(err.revision_id)
        if len(partial_history) <= distance_from_known:
            # Didn't find enough history to get a revid for the revno.
            earliest_revno = known_revno - len(partial_history) + 1
            return (False, (earliest_revno, partial_history[-1]))
        if len(partial_history) - 1 > distance_from_known:
            raise AssertionError('_iter_for_revno returned too much history')
        return (True, partial_history[-1])

    @symbol_versioning.deprecated_method(symbol_versioning.deprecated_in((2, 4, 0)))
    def iter_reverse_revision_history(self, revision_id):
        """Iterate backwards through revision ids in the lefthand history

        :param revision_id: The revision id to start with.  All its lefthand
            ancestors will be traversed.
        """
        graph = self.get_graph()
        stop_revisions = (None, _mod_revision.NULL_REVISION)
        return graph.iter_lefthand_ancestry(revision_id, stop_revisions)

    def is_shared(self):
        """Return True if this repository is flagged as a shared repository."""
        raise NotImplementedError(self.is_shared)

    @needs_write_lock
    def reconcile(self, other=None, thorough=False):
        """Reconcile this repository."""
        from bzrlib.reconcile import RepoReconciler
        reconciler = RepoReconciler(self, thorough=thorough)
        reconciler.reconcile()
        return reconciler

    def _refresh_data(self):
        """Helper called from lock_* to ensure coherency with disk.

        The default implementation does nothing; it is however possible
        for repositories to maintain loaded indices across multiple locks
        by checking inside their implementation of this method to see
        whether their indices are still valid. This depends of course on
        the disk format being validatable in this manner. This method is
        also called by the refresh_data() public interface to cause a refresh
        to occur while in a write lock so that data inserted by a smart server
        push operation is visible on the client's instance of the physical
        repository.
        """

    @needs_read_lock
    def revision_tree(self, revision_id):
        """Return Tree for a revision on this branch.

        `revision_id` may be NULL_REVISION for the empty tree revision.
        """
        raise NotImplementedError(self.revision_tree)

    def revision_trees(self, revision_ids):
        """Return Trees for revisions in this repository.

        :param revision_ids: a sequence of revision-ids;
          a revision-id may not be None or 'null:'
        """
        raise NotImplementedError(self.revision_trees)

    @needs_read_lock
    @symbol_versioning.deprecated_method(
        symbol_versioning.deprecated_in((2, 4, 0)))
    def get_ancestry(self, revision_id, topo_sorted=True):
        """Return a list of revision-ids integrated by a revision.

        The first element of the list is always None, indicating the origin
        revision.  This might change when we have history horizons, or
        perhaps we should have a new API.

        This is topologically sorted.
        """
        if 'evil' in debug.debug_flags:
            mutter_callsite(2, "get_ancestry is linear with history.")
        if _mod_revision.is_null(revision_id):
            return [None]
        if not self.has_revision(revision_id):
            raise errors.NoSuchRevision(self, revision_id)
        graph = self.get_graph()
        keys = set()
        search = graph._make_breadth_first_searcher([revision_id])
        while True:
            try:
                found, ghosts = search.next_with_ghosts()
            except StopIteration:
                break
            keys.update(found)
        if _mod_revision.NULL_REVISION in keys:
            keys.remove(_mod_revision.NULL_REVISION)
        if topo_sorted:
            parent_map = graph.get_parent_map(keys)
            keys = tsort.topo_sort(parent_map)
        return [None] + list(keys)

    def pack(self, hint=None, clean_obsolete_packs=False):
        """Compress the data within the repository.

        This operation only makes sense for some repository types. For other
        types it should be a no-op that just returns.

        This stub method does not require a lock, but subclasses should use
        @needs_write_lock as this is a long running call it's reasonable to
        implicitly lock for the user.

        :param hint: If not supplied, the whole repository is packed.
            If supplied, the repository may use the hint parameter as a
            hint for the parts of the repository to pack. A hint can be
            obtained from the result of commit_write_group(). Out of
            date hints are simply ignored, because concurrent operations
            can obsolete them rapidly.

        :param clean_obsolete_packs: Clean obsolete packs immediately after
            the pack operation.
        """

    def get_transaction(self):
        return self.control_files.get_transaction()

    def get_parent_map(self, revision_ids):
        """See graph.StackedParentsProvider.get_parent_map"""
        raise NotImplementedError(self.get_parent_map)

    def _get_parent_map_no_fallbacks(self, revision_ids):
        """Same as Repository.get_parent_map except doesn't query fallbacks."""
        # revisions index works in keys; this just works in revisions
        # therefore wrap and unwrap
        query_keys = []
        result = {}
        for revision_id in revision_ids:
            if revision_id == _mod_revision.NULL_REVISION:
                result[revision_id] = ()
            elif revision_id is None:
                raise ValueError('get_parent_map(None) is not valid')
            else:
                query_keys.append((revision_id ,))
        vf = self.revisions.without_fallbacks()
        for ((revision_id,), parent_keys) in \
                vf.get_parent_map(query_keys).iteritems():
            if parent_keys:
                result[revision_id] = tuple([parent_revid
                    for (parent_revid,) in parent_keys])
            else:
                result[revision_id] = (_mod_revision.NULL_REVISION,)
        return result

    def _make_parents_provider(self):
        if not self._format.supports_external_lookups:
            return self
        return graph.StackedParentsProvider(_LazyListJoin(
            [self._make_parents_provider_unstacked()],
            self._fallback_repositories))

    def _make_parents_provider_unstacked(self):
        return graph.CallableToParentsProviderAdapter(
            self._get_parent_map_no_fallbacks)

    @needs_read_lock
    def get_known_graph_ancestry(self, revision_ids):
        """Return the known graph for a set of revision ids and their ancestors.
        """
        raise NotImplementedError(self.get_known_graph_ancestry)

    def get_file_graph(self):
        """Return the graph walker for files."""
        raise NotImplementedError(self.get_file_graph)

    def get_graph(self, other_repository=None):
        """Return the graph walker for this repository format"""
        parents_provider = self._make_parents_provider()
        if (other_repository is not None and
            not self.has_same_location(other_repository)):
            parents_provider = graph.StackedParentsProvider(
                [parents_provider, other_repository._make_parents_provider()])
        return graph.Graph(parents_provider)

    def revision_ids_to_search_result(self, result_set):
        """Convert a set of revision ids to a graph SearchResult."""
        result_parents = set()
        for parents in self.get_graph().get_parent_map(
            result_set).itervalues():
            result_parents.update(parents)
        included_keys = result_set.intersection(result_parents)
        start_keys = result_set.difference(included_keys)
        exclude_keys = result_parents.difference(result_set)
        result = graph.SearchResult(start_keys, exclude_keys,
            len(result_set), result_set)
        return result

    @needs_write_lock
    def set_make_working_trees(self, new_value):
        """Set the policy flag for making working trees when creating branches.

        This only applies to branches that use this repository.

        The default is 'True'.
        :param new_value: True to restore the default, False to disable making
                          working trees.
        """
        raise NotImplementedError(self.set_make_working_trees)

    def make_working_trees(self):
        """Returns the policy for making working trees on new branches."""
        raise NotImplementedError(self.make_working_trees)

    @needs_write_lock
    def sign_revision(self, revision_id, gpg_strategy):
        testament = _mod_testament.Testament.from_revision(self, revision_id)
        plaintext = testament.as_short_text()
        self.store_revision_signature(gpg_strategy, plaintext, revision_id)

    @needs_read_lock
    def verify_revision(self, revision_id, gpg_strategy):
        """Verify the signature on a revision.
        
        :param revision_id: the revision to verify
        :gpg_strategy: the GPGStrategy object to used
        
        :return: gpg.SIGNATURE_VALID or a failed SIGNATURE_ value
        """
        if not self.has_signature_for_revision_id(revision_id):
            return gpg.SIGNATURE_NOT_SIGNED, None
        signature = self.get_signature_text(revision_id)

        testament = _mod_testament.Testament.from_revision(self, revision_id)
        plaintext = testament.as_short_text()

        return gpg_strategy.verify(signature, plaintext)

    def has_signature_for_revision_id(self, revision_id):
        """Query for a revision signature for revision_id in the repository."""
        raise NotImplementedError(self.has_signature_for_revision_id)

    def get_signature_text(self, revision_id):
        """Return the text for a signature."""
        raise NotImplementedError(self.get_signature_text)

    def check(self, revision_ids=None, callback_refs=None, check_repo=True):
        """Check consistency of all history of given revision_ids.

        Different repository implementations should override _check().

        :param revision_ids: A non-empty list of revision_ids whose ancestry
             will be checked.  Typically the last revision_id of a branch.
        :param callback_refs: A dict of check-refs to resolve and callback
            the check/_check method on the items listed as wanting the ref.
            see bzrlib.check.
        :param check_repo: If False do not check the repository contents, just 
            calculate the data callback_refs requires and call them back.
        """
        return self._check(revision_ids=revision_ids, callback_refs=callback_refs,
            check_repo=check_repo)

    def _check(self, revision_ids=None, callback_refs=None, check_repo=True):
        raise NotImplementedError(self.check)

    def _warn_if_deprecated(self, branch=None):
        if not self._format.is_deprecated():
            return
        global _deprecation_warning_done
        if _deprecation_warning_done:
            return
        try:
            if branch is None:
                conf = config.GlobalConfig()
            else:
                conf = branch.get_config()
            if conf.suppress_warning('format_deprecation'):
                return
            warning("Format %s for %s is deprecated -"
                    " please use 'bzr upgrade' to get better performance"
                    % (self._format, self.bzrdir.transport.base))
        finally:
            _deprecation_warning_done = True

    def supports_rich_root(self):
        return self._format.rich_root_data

    def _check_ascii_revisionid(self, revision_id, method):
        """Private helper for ascii-only repositories."""
        # weave repositories refuse to store revisionids that are non-ascii.
        if revision_id is not None:
            # weaves require ascii revision ids.
            if isinstance(revision_id, unicode):
                try:
                    revision_id.encode('ascii')
                except UnicodeEncodeError:
                    raise errors.NonAsciiRevisionId(method, self)
            else:
                try:
                    revision_id.decode('ascii')
                except UnicodeDecodeError:
                    raise errors.NonAsciiRevisionId(method, self)


class MetaDirRepository(Repository):
    """Repositories in the new meta-dir layout.

    :ivar _transport: Transport for access to repository control files,
        typically pointing to .bzr/repository.
    """

    def __init__(self, _format, a_bzrdir, control_files):
        super(MetaDirRepository, self).__init__(_format, a_bzrdir, control_files)
        self._transport = control_files._transport

    def is_shared(self):
        """Return True if this repository is flagged as a shared repository."""
        return self._transport.has('shared-storage')

    @needs_write_lock
    def set_make_working_trees(self, new_value):
        """Set the policy flag for making working trees when creating branches.

        This only applies to branches that use this repository.

        The default is 'True'.
        :param new_value: True to restore the default, False to disable making
                          working trees.
        """
        if new_value:
            try:
                self._transport.delete('no-working-trees')
            except errors.NoSuchFile:
                pass
        else:
            self._transport.put_bytes('no-working-trees', '',
                mode=self.bzrdir._get_file_mode())

    def make_working_trees(self):
        """Returns the policy for making working trees on new branches."""
        return not self._transport.has('no-working-trees')


class RepositoryFormatRegistry(controldir.ControlComponentFormatRegistry):
    """Repository format registry."""

    def get_default(self):
        """Return the current default format."""
        from bzrlib import bzrdir
        return bzrdir.format_registry.make_bzrdir('default').repository_format


network_format_registry = registry.FormatRegistry()
"""Registry of formats indexed by their network name.

The network name for a repository format is an identifier that can be used when
referring to formats with smart server operations. See
RepositoryFormat.network_name() for more detail.
"""


format_registry = RepositoryFormatRegistry(network_format_registry)
"""Registry of formats, indexed by their BzrDirMetaFormat format string.

This can contain either format instances themselves, or classes/factories that
can be called to obtain one.
"""


#####################################################################
# Repository Formats

class RepositoryFormat(controldir.ControlComponentFormat):
    """A repository format.

    Formats provide four things:
     * An initialization routine to construct repository data on disk.
     * a optional format string which is used when the BzrDir supports
       versioned children.
     * an open routine which returns a Repository instance.
     * A network name for referring to the format in smart server RPC
       methods.

    There is one and only one Format subclass for each on-disk format. But
    there can be one Repository subclass that is used for several different
    formats. The _format attribute on a Repository instance can be used to
    determine the disk format.

    Formats are placed in a registry by their format string for reference
    during opening. These should be subclasses of RepositoryFormat for
    consistency.

    Once a format is deprecated, just deprecate the initialize and open
    methods on the format class. Do not deprecate the object, as the
    object may be created even when a repository instance hasn't been
    created.

    Common instance attributes:
    _matchingbzrdir - the bzrdir format that the repository format was
    originally written to work with. This can be used if manually
    constructing a bzrdir and repository, or more commonly for test suite
    parameterization.
    """

    # Set to True or False in derived classes. True indicates that the format
    # supports ghosts gracefully.
    supports_ghosts = None
    # Can this repository be given external locations to lookup additional
    # data. Set to True or False in derived classes.
    supports_external_lookups = None
    # Does this format support CHK bytestring lookups. Set to True or False in
    # derived classes.
    supports_chks = None
    # Should fetch trigger a reconcile after the fetch? Only needed for
    # some repository formats that can suffer internal inconsistencies.
    _fetch_reconcile = False
    # Does this format have < O(tree_size) delta generation. Used to hint what
    # code path for commit, amongst other things.
    fast_deltas = None
    # Does doing a pack operation compress data? Useful for the pack UI command
    # (so if there is one pack, the operation can still proceed because it may
    # help), and for fetching when data won't have come from the same
    # compressor.
    pack_compresses = False
    # Does the repository storage understand references to trees?
    supports_tree_reference = None
    # Is the format experimental ?
    experimental = False
    # Does this repository format escape funky characters, or does it create
    # files with similar names as the versioned files in its contents on disk
    # ?
    supports_funky_characters = None
    # Does this repository format support leaving locks?
    supports_leaving_lock = None
    # Does this format support the full VersionedFiles interface?
    supports_full_versioned_files = None
    # Does this format support signing revision signatures?
    supports_revision_signatures = True
    # Can the revision graph have incorrect parents?
    revision_graph_can_have_wrong_parents = None
    # Does this format support rich root data?
    rich_root_data = None
    # Does this format support explicitly versioned directories?
    supports_versioned_directories = None

    def __repr__(self):
        return "%s()" % self.__class__.__name__

    def __eq__(self, other):
        # format objects are generally stateless
        return isinstance(other, self.__class__)

    def __ne__(self, other):
        return not self == other

    @classmethod
    def find_format(klass, a_bzrdir):
        """Return the format for the repository object in a_bzrdir.

        This is used by bzr native formats that have a "format" file in
        the repository.  Other methods may be used by different types of
        control directory.
        """
        try:
            transport = a_bzrdir.get_repository_transport(None)
            format_string = transport.get_bytes("format")
            return format_registry.get(format_string)
        except errors.NoSuchFile:
            raise errors.NoRepositoryPresent(a_bzrdir)
        except KeyError:
            raise errors.UnknownFormatError(format=format_string,
                                            kind='repository')

    @classmethod
    @symbol_versioning.deprecated_method(symbol_versioning.deprecated_in((2, 4, 0)))
    def register_format(klass, format):
        format_registry.register(format)

    @classmethod
    @symbol_versioning.deprecated_method(symbol_versioning.deprecated_in((2, 4, 0)))
    def unregister_format(klass, format):
        format_registry.remove(format)

    @classmethod
    @symbol_versioning.deprecated_method(symbol_versioning.deprecated_in((2, 4, 0)))
    def get_default_format(klass):
        """Return the current default format."""
        return format_registry.get_default()

    def get_format_string(self):
        """Return the ASCII format string that identifies this format.

        Note that in pre format ?? repositories the format string is
        not permitted nor written to disk.
        """
        raise NotImplementedError(self.get_format_string)

    def get_format_description(self):
        """Return the short description for this format."""
        raise NotImplementedError(self.get_format_description)

    def initialize(self, a_bzrdir, shared=False):
        """Initialize a repository of this format in a_bzrdir.

        :param a_bzrdir: The bzrdir to put the new repository in it.
        :param shared: The repository should be initialized as a sharable one.
        :returns: The new repository object.

        This may raise UninitializableFormat if shared repository are not
        compatible the a_bzrdir.
        """
        raise NotImplementedError(self.initialize)

    def is_supported(self):
        """Is this format supported?

        Supported formats must be initializable and openable.
        Unsupported formats may not support initialization or committing or
        some other features depending on the reason for not being supported.
        """
        return True

    def is_deprecated(self):
        """Is this format deprecated?

        Deprecated formats may trigger a user-visible warning recommending
        the user to upgrade. They are still fully supported.
        """
        return False

    def network_name(self):
        """A simple byte string uniquely identifying this format for RPC calls.

        MetaDir repository formats use their disk format string to identify the
        repository over the wire. All in one formats such as bzr < 0.8, and
        foreign formats like svn/git and hg should use some marker which is
        unique and immutable.
        """
        raise NotImplementedError(self.network_name)

    def check_conversion_target(self, target_format):
        if self.rich_root_data and not target_format.rich_root_data:
            raise errors.BadConversionTarget(
                'Does not support rich root data.', target_format,
                from_format=self)
        if (self.supports_tree_reference and 
            not getattr(target_format, 'supports_tree_reference', False)):
            raise errors.BadConversionTarget(
                'Does not support nested trees', target_format,
                from_format=self)

    def open(self, a_bzrdir, _found=False):
        """Return an instance of this format for the bzrdir a_bzrdir.

        _found is a private parameter, do not use it.
        """
        raise NotImplementedError(self.open)

    def _run_post_repo_init_hooks(self, repository, a_bzrdir, shared):
        from bzrlib.bzrdir import BzrDir, RepoInitHookParams
        hooks = BzrDir.hooks['post_repo_init']
        if not hooks:
            return
        params = RepoInitHookParams(repository, self, a_bzrdir, shared)
        for hook in hooks:
            hook(params)


class MetaDirRepositoryFormat(RepositoryFormat):
    """Common base class for the new repositories using the metadir layout."""

    rich_root_data = False
    supports_tree_reference = False
    supports_external_lookups = False
    supports_leaving_lock = True

    @property
    def _matchingbzrdir(self):
        matching = bzrdir.BzrDirMetaFormat1()
        matching.repository_format = self
        return matching

    def __init__(self):
        super(MetaDirRepositoryFormat, self).__init__()

    def _create_control_files(self, a_bzrdir):
        """Create the required files and the initial control_files object."""
        # FIXME: RBC 20060125 don't peek under the covers
        # NB: no need to escape relative paths that are url safe.
        repository_transport = a_bzrdir.get_repository_transport(self)
        control_files = lockable_files.LockableFiles(repository_transport,
                                'lock', lockdir.LockDir)
        control_files.create_lock()
        return control_files

    def _upload_blank_content(self, a_bzrdir, dirs, files, utf8_files, shared):
        """Upload the initial blank content."""
        control_files = self._create_control_files(a_bzrdir)
        control_files.lock_write()
        transport = control_files._transport
        if shared == True:
            utf8_files += [('shared-storage', '')]
        try:
            transport.mkdir_multi(dirs, mode=a_bzrdir._get_dir_mode())
            for (filename, content_stream) in files:
                transport.put_file(filename, content_stream,
                    mode=a_bzrdir._get_file_mode())
            for (filename, content_bytes) in utf8_files:
                transport.put_bytes_non_atomic(filename, content_bytes,
                    mode=a_bzrdir._get_file_mode())
        finally:
            control_files.unlock()

    def network_name(self):
        """Metadir formats have matching disk and network format strings."""
        return self.get_format_string()


# formats which have no format string are not discoverable or independently
# creatable on disk, so are not registered in format_registry.  They're
# all in bzrlib.repofmt.knitreponow.  When an instance of one of these is
# needed, it's constructed directly by the BzrDir.  Non-native formats where
# the repository is not separately opened are similar.

format_registry.register_lazy(
    'Bazaar-NG Knit Repository Format 1',
    'bzrlib.repofmt.knitrepo',
    'RepositoryFormatKnit1',
    )

format_registry.register_lazy(
    'Bazaar Knit Repository Format 3 (bzr 0.15)\n',
    'bzrlib.repofmt.knitrepo',
    'RepositoryFormatKnit3',
    )

format_registry.register_lazy(
    'Bazaar Knit Repository Format 4 (bzr 1.0)\n',
    'bzrlib.repofmt.knitrepo',
    'RepositoryFormatKnit4',
    )

# Pack-based formats. There is one format for pre-subtrees, and one for
# post-subtrees to allow ease of testing.
# NOTE: These are experimental in 0.92. Stable in 1.0 and above
format_registry.register_lazy(
    'Bazaar pack repository format 1 (needs bzr 0.92)\n',
    'bzrlib.repofmt.knitpack_repo',
    'RepositoryFormatKnitPack1',
    )
format_registry.register_lazy(
    'Bazaar pack repository format 1 with subtree support (needs bzr 0.92)\n',
    'bzrlib.repofmt.knitpack_repo',
    'RepositoryFormatKnitPack3',
    )
format_registry.register_lazy(
    'Bazaar pack repository format 1 with rich root (needs bzr 1.0)\n',
    'bzrlib.repofmt.knitpack_repo',
    'RepositoryFormatKnitPack4',
    )
format_registry.register_lazy(
    'Bazaar RepositoryFormatKnitPack5 (bzr 1.6)\n',
    'bzrlib.repofmt.knitpack_repo',
    'RepositoryFormatKnitPack5',
    )
format_registry.register_lazy(
    'Bazaar RepositoryFormatKnitPack5RichRoot (bzr 1.6.1)\n',
    'bzrlib.repofmt.knitpack_repo',
    'RepositoryFormatKnitPack5RichRoot',
    )
format_registry.register_lazy(
    'Bazaar RepositoryFormatKnitPack5RichRoot (bzr 1.6)\n',
    'bzrlib.repofmt.knitpack_repo',
    'RepositoryFormatKnitPack5RichRootBroken',
    )
format_registry.register_lazy(
    'Bazaar RepositoryFormatKnitPack6 (bzr 1.9)\n',
    'bzrlib.repofmt.knitpack_repo',
    'RepositoryFormatKnitPack6',
    )
format_registry.register_lazy(
    'Bazaar RepositoryFormatKnitPack6RichRoot (bzr 1.9)\n',
    'bzrlib.repofmt.knitpack_repo',
    'RepositoryFormatKnitPack6RichRoot',
    )
format_registry.register_lazy(
    'Bazaar repository format 2a (needs bzr 1.16 or later)\n',
    'bzrlib.repofmt.groupcompress_repo',
    'RepositoryFormat2a',
    )

# Development formats.
# Check their docstrings to see if/when they are obsolete.
format_registry.register_lazy(
    ("Bazaar development format 2 with subtree support "
        "(needs bzr.dev from before 1.8)\n"),
    'bzrlib.repofmt.knitpack_repo',
    'RepositoryFormatPackDevelopment2Subtree',
    )
format_registry.register_lazy(
    'Bazaar development format 8\n',
    'bzrlib.repofmt.groupcompress_repo',
    'RepositoryFormat2aSubtree',
    )


class InterRepository(InterObject):
    """This class represents operations taking place between two repositories.

    Its instances have methods like copy_content and fetch, and contain
    references to the source and target repositories these operations can be
    carried out on.

    Often we will provide convenience methods on 'repository' which carry out
    operations with another repository - they will always forward to
    InterRepository.get(other).method_name(parameters).
    """

    _optimisers = []
    """The available optimised InterRepository types."""

    @needs_write_lock
    def copy_content(self, revision_id=None):
        """Make a complete copy of the content in self into destination.

        This is a destructive operation! Do not use it on existing
        repositories.

        :param revision_id: Only copy the content needed to construct
                            revision_id and its parents.
        """
        try:
            self.target.set_make_working_trees(self.source.make_working_trees())
        except NotImplementedError:
            pass
        self.target.fetch(self.source, revision_id=revision_id)

    @needs_write_lock
    def fetch(self, revision_id=None, find_ghosts=False,
            fetch_spec=None):
        """Fetch the content required to construct revision_id.

        The content is copied from self.source to self.target.

        :param revision_id: if None all content is copied, if NULL_REVISION no
                            content is copied.
        :return: None.
        """
        raise NotImplementedError(self.fetch)

    @needs_read_lock
    def search_missing_revision_ids(self,
            revision_id=symbol_versioning.DEPRECATED_PARAMETER,
            find_ghosts=True, revision_ids=None, if_present_ids=None,
            limit=None):
        """Return the revision ids that source has that target does not.

        :param revision_id: only return revision ids included by this
            revision_id.
        :param revision_ids: return revision ids included by these
            revision_ids.  NoSuchRevision will be raised if any of these
            revisions are not present.
        :param if_present_ids: like revision_ids, but will not cause
            NoSuchRevision if any of these are absent, instead they will simply
            not be in the result.  This is useful for e.g. finding revisions
            to fetch for tags, which may reference absent revisions.
        :param find_ghosts: If True find missing revisions in deep history
            rather than just finding the surface difference.
        :param limit: Maximum number of revisions to return, topologically
            ordered
        :return: A bzrlib.graph.SearchResult.
        """
        raise NotImplementedError(self.search_missing_revision_ids)

    @staticmethod
    def _same_model(source, target):
        """True if source and target have the same data representation.

        Note: this is always called on the base class; overriding it in a
        subclass will have no effect.
        """
        try:
            InterRepository._assert_same_model(source, target)
            return True
        except errors.IncompatibleRepositories, e:
            return False

    @staticmethod
    def _assert_same_model(source, target):
        """Raise an exception if two repositories do not use the same model.
        """
        if source.supports_rich_root() != target.supports_rich_root():
            raise errors.IncompatibleRepositories(source, target,
                "different rich-root support")
        if source._serializer != target._serializer:
            raise errors.IncompatibleRepositories(source, target,
                "different serializers")


class CopyConverter(object):
    """A repository conversion tool which just performs a copy of the content.

    This is slow but quite reliable.
    """

    def __init__(self, target_format):
        """Create a CopyConverter.

        :param target_format: The format the resulting repository should be.
        """
        self.target_format = target_format

    def convert(self, repo, pb):
        """Perform the conversion of to_convert, giving feedback via pb.

        :param to_convert: The disk object to convert.
        :param pb: a progress bar to use for progress information.
        """
        pb = ui.ui_factory.nested_progress_bar()
        self.count = 0
        self.total = 4
        # this is only useful with metadir layouts - separated repo content.
        # trigger an assertion if not such
        repo._format.get_format_string()
        self.repo_dir = repo.bzrdir
        pb.update('Moving repository to repository.backup')
        self.repo_dir.transport.move('repository', 'repository.backup')
        backup_transport =  self.repo_dir.transport.clone('repository.backup')
        repo._format.check_conversion_target(self.target_format)
        self.source_repo = repo._format.open(self.repo_dir,
            _found=True,
            _override_transport=backup_transport)
        pb.update('Creating new repository')
        converted = self.target_format.initialize(self.repo_dir,
                                                  self.source_repo.is_shared())
        converted.lock_write()
        try:
            pb.update('Copying content')
            self.source_repo.copy_content_into(converted)
        finally:
            converted.unlock()
        pb.update('Deleting old repository content')
        self.repo_dir.transport.delete_tree('repository.backup')
        ui.ui_factory.note('repository converted')
        pb.finished()


def _strip_NULL_ghosts(revision_graph):
    """Also don't use this. more compatibility code for unmigrated clients."""
    # Filter ghosts, and null:
    if _mod_revision.NULL_REVISION in revision_graph:
        del revision_graph[_mod_revision.NULL_REVISION]
    for key, parents in revision_graph.items():
        revision_graph[key] = tuple(parent for parent in parents if parent
            in revision_graph)
    return revision_graph


def _iter_for_revno(repo, partial_history_cache, stop_index=None,
                    stop_revision=None):
    """Extend the partial history to include a given index

    If a stop_index is supplied, stop when that index has been reached.
    If a stop_revision is supplied, stop when that revision is
    encountered.  Otherwise, stop when the beginning of history is
    reached.

    :param stop_index: The index which should be present.  When it is
        present, history extension will stop.
    :param stop_revision: The revision id which should be present.  When
        it is encountered, history extension will stop.
    """
    start_revision = partial_history_cache[-1]
    graph = repo.get_graph()
    iterator = graph.iter_lefthand_ancestry(start_revision,
        (_mod_revision.NULL_REVISION,))
    try:
        # skip the last revision in the list
        iterator.next()
        while True:
            if (stop_index is not None and
                len(partial_history_cache) > stop_index):
                break
            if partial_history_cache[-1] == stop_revision:
                break
            revision_id = iterator.next()
            partial_history_cache.append(revision_id)
    except StopIteration:
        # No more history
        return


class _LazyListJoin(object):
    """An iterable yielding the contents of many lists as one list.

    Each iterator made from this will reflect the current contents of the lists
    at the time the iterator is made.
    
    This is used by Repository's _make_parents_provider implementation so that
    it is safe to do::

      pp = repo._make_parents_provider()      # uses a list of fallback repos
      pp.add_fallback_repository(other_repo)  # appends to that list
      result = pp.get_parent_map(...)
      # The result will include revs from other_repo
    """

    def __init__(self, *list_parts):
        self.list_parts = list_parts

    def __iter__(self):
        full_list = []
        for list_part in self.list_parts:
            full_list.extend(list_part)
        return iter(full_list)