summaryrefslogtreecommitdiff
path: root/sha1-name.c
blob: a0fc1008ec4dfb8bdfb1ea0c447e12a1ecf703e2 (plain)
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
#include "cache.h"
#include "config.h"
#include "tag.h"
#include "commit.h"
#include "tree.h"
#include "blob.h"
#include "tree-walk.h"
#include "refs.h"
#include "remote.h"
#include "dir.h"
#include "sha1-array.h"
#include "packfile.h"
#include "object-store.h"
#include "repository.h"
#include "midx.h"
#include "commit-reach.h"
 
static int get_oid_oneline(const char *, struct object_id *, struct commit_list *);
 
typedef int (*disambiguate_hint_fn)(const struct object_id *, void *);
 
struct disambiguate_state {
	int len; /* length of prefix in hex chars */
	char hex_pfx[GIT_MAX_HEXSZ + 1];
	struct object_id bin_pfx;
 
	disambiguate_hint_fn fn;
	void *cb_data;
	struct object_id candidate;
	unsigned candidate_exists:1;
	unsigned candidate_checked:1;
	unsigned candidate_ok:1;
	unsigned disambiguate_fn_used:1;
	unsigned ambiguous:1;
	unsigned always_call_fn:1;
};
 
static void update_candidates(struct disambiguate_state *ds, const struct object_id *current)
{
	if (ds->always_call_fn) {
		ds->ambiguous = ds->fn(current, ds->cb_data) ? 1 : 0;
		return;
	}
	if (!ds->candidate_exists) {
		/* this is the first candidate */
		oidcpy(&ds->candidate, current);
		ds->candidate_exists = 1;
		return;
	} else if (oideq(&ds->candidate, current)) {
		/* the same as what we already have seen */
		return;
	}
 
	if (!ds->fn) {
		/* cannot disambiguate between ds->candidate and current */
		ds->ambiguous = 1;
		return;
	}
 
	if (!ds->candidate_checked) {
		ds->candidate_ok = ds->fn(&ds->candidate, ds->cb_data);
		ds->disambiguate_fn_used = 1;
		ds->candidate_checked = 1;
	}
 
	if (!ds->candidate_ok) {
		/* discard the candidate; we know it does not satisfy fn */
		oidcpy(&ds->candidate, current);
		ds->candidate_checked = 0;
		return;
	}
 
	/* if we reach this point, we know ds->candidate satisfies fn */
	if (ds->fn(current, ds->cb_data)) {
		/*
		 * if both current and candidate satisfy fn, we cannot
		 * disambiguate.
		 */
		ds->candidate_ok = 0;
		ds->ambiguous = 1;
	}
 
	/* otherwise, current can be discarded and candidate is still good */
}
 
static int match_sha(unsigned, const unsigned char *, const unsigned char *);
 
static void find_short_object_filename(struct disambiguate_state *ds)
{
	int subdir_nr = ds->bin_pfx.hash[0];
	struct object_directory *odb;
 
	for (odb = the_repository->objects->odb;
	     odb && !ds->ambiguous;
	     odb = odb->next) {
		int pos;
 
		odb_load_loose_cache(odb, subdir_nr);
		pos = oid_array_lookup(&odb->loose_objects_cache, &ds->bin_pfx);
		if (pos < 0)
			pos = -1 - pos;
		while (!ds->ambiguous && pos < odb->loose_objects_cache.nr) {
			const struct object_id *oid;
			oid = odb->loose_objects_cache.oid + pos;
			if (!match_sha(ds->len, ds->bin_pfx.hash, oid->hash))
				break;
			update_candidates(ds, oid);
			pos++;
		}
	}
}
 
static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
{
	do {
		if (*a != *b)
			return 0;
		a++;
		b++;
		len -= 2;
	} while (len > 1);
	if (len)
		if ((*a ^ *b) & 0xf0)
			return 0;
	return 1;
}
 
static void unique_in_midx(struct multi_pack_index *m,
			   struct disambiguate_state *ds)
{
	uint32_t num, i, first = 0;
	const struct object_id *current = NULL;
	num = m->num_objects;
 
	if (!num)
		return;
 
	bsearch_midx(&ds->bin_pfx, m, &first);
 
	/*
	 * At this point, "first" is the location of the lowest object
	 * with an object name that could match "bin_pfx".  See if we have
	 * 0, 1 or more objects that actually match(es).
	 */
	for (i = first; i < num && !ds->ambiguous; i++) {
		struct object_id oid;
		current = nth_midxed_object_oid(&oid, m, i);
		if (!match_sha(ds->len, ds->bin_pfx.hash, current->hash))
			break;
		update_candidates(ds, current);
	}
}
 
static void unique_in_pack(struct packed_git *p,
			   struct disambiguate_state *ds)
{
	uint32_t num, i, first = 0;
	const struct object_id *current = NULL;
 
	if (open_pack_index(p) || !p->num_objects)
		return;
 
	num = p->num_objects;
	bsearch_pack(&ds->bin_pfx, p, &first);
 
	/*
	 * At this point, "first" is the location of the lowest object
	 * with an object name that could match "bin_pfx".  See if we have
	 * 0, 1 or more objects that actually match(es).
	 */
	for (i = first; i < num && !ds->ambiguous; i++) {
		struct object_id oid;
		current = nth_packed_object_oid(&oid, p, i);
		if (!match_sha(ds->len, ds->bin_pfx.hash, current->hash))
			break;
		update_candidates(ds, current);
	}
}
 
static void find_short_packed_object(struct disambiguate_state *ds)
{
	struct multi_pack_index *m;
	struct packed_git *p;
 
	for (m = get_multi_pack_index(the_repository); m && !ds->ambiguous;
	     m = m->next)
		unique_in_midx(m, ds);
	for (p = get_packed_git(the_repository); p && !ds->ambiguous;
	     p = p->next)
		unique_in_pack(p, ds);
}
 
#define SHORT_NAME_NOT_FOUND (-1)
#define SHORT_NAME_AMBIGUOUS (-2)
 
static int finish_object_disambiguation(struct disambiguate_state *ds,
					struct object_id *oid)
{
	if (ds->ambiguous)
		return SHORT_NAME_AMBIGUOUS;
 
	if (!ds->candidate_exists)
		return SHORT_NAME_NOT_FOUND;
 
	if (!ds->candidate_checked)
		/*
		 * If this is the only candidate, there is no point
		 * calling the disambiguation hint callback.
		 *
		 * On the other hand, if the current candidate
		 * replaced an earlier candidate that did _not_ pass
		 * the disambiguation hint callback, then we do have
		 * more than one objects that match the short name
		 * given, so we should make sure this one matches;
		 * otherwise, if we discovered this one and the one
		 * that we previously discarded in the reverse order,
		 * we would end up showing different results in the
		 * same repository!
		 */
		ds->candidate_ok = (!ds->disambiguate_fn_used ||
				    ds->fn(&ds->candidate, ds->cb_data));
 
	if (!ds->candidate_ok)
		return SHORT_NAME_AMBIGUOUS;
 
	oidcpy(oid, &ds->candidate);
	return 0;
}
 
static int disambiguate_commit_only(const struct object_id *oid, void *cb_data_unused)
{
	int kind = oid_object_info(the_repository, oid, NULL);
	return kind == OBJ_COMMIT;
}
 
static int disambiguate_committish_only(const struct object_id *oid, void *cb_data_unused)
{
	struct object *obj;
	int kind;
 
	kind = oid_object_info(the_repository, oid, NULL);
	if (kind == OBJ_COMMIT)
		return 1;
	if (kind != OBJ_TAG)
		return 0;
 
	/* We need to do this the hard way... */
	obj = deref_tag(the_repository, parse_object(the_repository, oid),
			NULL, 0);
	if (obj && obj->type == OBJ_COMMIT)
		return 1;
	return 0;
}
 
static int disambiguate_tree_only(const struct object_id *oid, void *cb_data_unused)
{
	int kind = oid_object_info(the_repository, oid, NULL);
	return kind == OBJ_TREE;
}
 
static int disambiguate_treeish_only(const struct object_id *oid, void *cb_data_unused)
{
	struct object *obj;
	int kind;
 
	kind = oid_object_info(the_repository, oid, NULL);
	if (kind == OBJ_TREE || kind == OBJ_COMMIT)
		return 1;
	if (kind != OBJ_TAG)
		return 0;
 
	/* We need to do this the hard way... */
	obj = deref_tag(the_repository, parse_object(the_repository, oid),
			NULL, 0);
	if (obj && (obj->type == OBJ_TREE || obj->type == OBJ_COMMIT))
		return 1;
	return 0;
}
 
static int disambiguate_blob_only(const struct object_id *oid, void *cb_data_unused)
{
	int kind = oid_object_info(the_repository, oid, NULL);
	return kind == OBJ_BLOB;
}
 
static disambiguate_hint_fn default_disambiguate_hint;
 
int set_disambiguate_hint_config(const char *var, const char *value)
{
	static const struct {
		const char *name;
		disambiguate_hint_fn fn;
	} hints[] = {
		{ "none", NULL },
		{ "commit", disambiguate_commit_only },
		{ "committish", disambiguate_committish_only },
		{ "tree", disambiguate_tree_only },
		{ "treeish", disambiguate_treeish_only },
		{ "blob", disambiguate_blob_only }
	};
	int i;
 
	if (!value)
		return config_error_nonbool(var);
 
	for (i = 0; i < ARRAY_SIZE(hints); i++) {
		if (!strcasecmp(value, hints[i].name)) {
			default_disambiguate_hint = hints[i].fn;
			return 0;
		}
	}
 
	return error("unknown hint type for '%s': %s", var, value);
}
 
static int init_object_disambiguation(const char *name, int len,
				      struct disambiguate_state *ds)
{
	int i;
 
	if (len < MINIMUM_ABBREV || len > the_hash_algo->hexsz)
		return -1;
 
	memset(ds, 0, sizeof(*ds));
 
	for (i = 0; i < len ;i++) {
		unsigned char c = name[i];
		unsigned char val;
		if (c >= '0' && c <= '9')
			val = c - '0';
		else if (c >= 'a' && c <= 'f')
			val = c - 'a' + 10;
		else if (c >= 'A' && c <='F') {
			val = c - 'A' + 10;
			c -= 'A' - 'a';
		}
		else
			return -1;
		ds->hex_pfx[i] = c;
		if (!(i & 1))
			val <<= 4;
		ds->bin_pfx.hash[i >> 1] |= val;
	}
 
	ds->len = len;
	ds->hex_pfx[len] = '\0';
	prepare_alt_odb(the_repository);
	return 0;
}
 
static int show_ambiguous_object(const struct object_id *oid, void *data)
{
	const struct disambiguate_state *ds = data;
	struct strbuf desc = STRBUF_INIT;
	int type;
 
	if (ds->fn && !ds->fn(oid, ds->cb_data))
		return 0;
 
	type = oid_object_info(the_repository, oid, NULL);
	if (type == OBJ_COMMIT) {
		struct commit *commit = lookup_commit(the_repository, oid);
		if (commit) {
			struct pretty_print_context pp = {0};
			pp.date_mode.type = DATE_SHORT;
			format_commit_message(commit, " %ad - %s", &desc, &pp);
		}
	} else if (type == OBJ_TAG) {
		struct tag *tag = lookup_tag(the_repository, oid);
		if (!parse_tag(tag) && tag->tag)
			strbuf_addf(&desc, " %s", tag->tag);
	}
 
	advise("  %s %s%s",
	       find_unique_abbrev(oid, DEFAULT_ABBREV),
	       type_name(type) ? type_name(type) : "unknown type",
	       desc.buf);
 
	strbuf_release(&desc);
	return 0;
}
 
static int collect_ambiguous(const struct object_id *oid, void *data)
{
	oid_array_append(data, oid);
	return 0;
}
 
static int sort_ambiguous(const void *a, const void *b)
{
	int a_type = oid_object_info(the_repository, a, NULL);
	int b_type = oid_object_info(the_repository, b, NULL);
	int a_type_sort;
	int b_type_sort;
 
	/*
	 * Sorts by hash within the same object type, just as
	 * oid_array_for_each_unique() would do.
	 */
	if (a_type == b_type)
		return oidcmp(a, b);
 
	/*
	 * Between object types show tags, then commits, and finally
	 * trees and blobs.
	 *
	 * The object_type enum is commit, tree, blob, tag, but we
	 * want tag, commit, tree blob. Cleverly (perhaps too
	 * cleverly) do that with modulus, since the enum assigns 1 to
	 * commit, so tag becomes 0.
	 */
	a_type_sort = a_type % 4;
	b_type_sort = b_type % 4;
	return a_type_sort > b_type_sort ? 1 : -1;
}
 
static int get_short_oid(const char *name, int len, struct object_id *oid,
			  unsigned flags)
{
	int status;
	struct disambiguate_state ds;
	int quietly = !!(flags & GET_OID_QUIETLY);
 
	if (init_object_disambiguation(name, len, &ds) < 0)
		return -1;
 
	if (HAS_MULTI_BITS(flags & GET_OID_DISAMBIGUATORS))
		BUG("multiple get_short_oid disambiguator flags");
 
	if (flags & GET_OID_COMMIT)
		ds.fn = disambiguate_commit_only;
	else if (flags & GET_OID_COMMITTISH)
		ds.fn = disambiguate_committish_only;
	else if (flags & GET_OID_TREE)
		ds.fn = disambiguate_tree_only;
	else if (flags & GET_OID_TREEISH)
		ds.fn = disambiguate_treeish_only;
	else if (flags & GET_OID_BLOB)
		ds.fn = disambiguate_blob_only;
	else
		ds.fn = default_disambiguate_hint;
 
	find_short_object_filename(&ds);
	find_short_packed_object(&ds);
	status = finish_object_disambiguation(&ds, oid);
 
	if (!quietly && (status == SHORT_NAME_AMBIGUOUS)) {
		struct oid_array collect = OID_ARRAY_INIT;
 
		error(_("short SHA1 %s is ambiguous"), ds.hex_pfx);
 
		/*
		 * We may still have ambiguity if we simply saw a series of
		 * candidates that did not satisfy our hint function. In
		 * that case, we still want to show them, so disable the hint
		 * function entirely.
		 */
		if (!ds.ambiguous)
			ds.fn = NULL;
 
		advise(_("The candidates are:"));
		for_each_abbrev(ds.hex_pfx, collect_ambiguous, &collect);
		QSORT(collect.oid, collect.nr, sort_ambiguous);
 
		if (oid_array_for_each(&collect, show_ambiguous_object, &ds))
			BUG("show_ambiguous_object shouldn't return non-zero");
		oid_array_clear(&collect);
	}
 
	return status;
}
 
int for_each_abbrev(const char *prefix, each_abbrev_fn fn, void *cb_data)
{
	struct oid_array collect = OID_ARRAY_INIT;
	struct disambiguate_state ds;
	int ret;
 
	if (init_object_disambiguation(prefix, strlen(prefix), &ds) < 0)
		return -1;
 
	ds.always_call_fn = 1;
	ds.fn = collect_ambiguous;
	ds.cb_data = &collect;
	find_short_object_filename(&ds);
	find_short_packed_object(&ds);
 
	ret = oid_array_for_each_unique(&collect, fn, cb_data);
	oid_array_clear(&collect);
	return ret;
}
 
/*
 * Return the slot of the most-significant bit set in "val". There are various
 * ways to do this quickly with fls() or __builtin_clzl(), but speed is
 * probably not a big deal here.
 */
static unsigned msb(unsigned long val)
{
	unsigned r = 0;
	while (val >>= 1)
		r++;
	return r;
}
 
struct min_abbrev_data {
	unsigned int init_len;
	unsigned int cur_len;
	char *hex;
	const struct object_id *oid;
};
 
static inline char get_hex_char_from_oid(const struct object_id *oid,
					 unsigned int pos)
{
	static const char hex[] = "0123456789abcdef";
 
	if ((pos & 1) == 0)
		return hex[oid->hash[pos >> 1] >> 4];
	else
		return hex[oid->hash[pos >> 1] & 0xf];
}
 
static int extend_abbrev_len(const struct object_id *oid, void *cb_data)
{
	struct min_abbrev_data *mad = cb_data;
 
	unsigned int i = mad->init_len;
	while (mad->hex[i] && mad->hex[i] == get_hex_char_from_oid(oid, i))
		i++;
 
	if (i < GIT_MAX_RAWSZ && i >= mad->cur_len)
		mad->cur_len = i + 1;
 
	return 0;
}
 
static void find_abbrev_len_for_midx(struct multi_pack_index *m,
				     struct min_abbrev_data *mad)
{
	int match = 0;
	uint32_t num, first = 0;
	struct object_id oid;
	const struct object_id *mad_oid;
 
	if (!m->num_objects)
		return;
 
	num = m->num_objects;
	mad_oid = mad->oid;
	match = bsearch_midx(mad_oid, m, &first);
 
	/*
	 * first is now the position in the packfile where we would insert
	 * mad->hash if it does not exist (or the position of mad->hash if
	 * it does exist). Hence, we consider a maximum of two objects
	 * nearby for the abbreviation length.
	 */
	mad->init_len = 0;
	if (!match) {
		if (nth_midxed_object_oid(&oid, m, first))
			extend_abbrev_len(&oid, mad);
	} else if (first < num - 1) {
		if (nth_midxed_object_oid(&oid, m, first + 1))
			extend_abbrev_len(&oid, mad);
	}
	if (first > 0) {
		if (nth_midxed_object_oid(&oid, m, first - 1))
			extend_abbrev_len(&oid, mad);
	}
	mad->init_len = mad->cur_len;
}
 
static void find_abbrev_len_for_pack(struct packed_git *p,
				     struct min_abbrev_data *mad)
{
	int match = 0;
	uint32_t num, first = 0;
	struct object_id oid;
	const struct object_id *mad_oid;
 
	if (open_pack_index(p) || !p->num_objects)
		return;
 
	num = p->num_objects;
	mad_oid = mad->oid;
	match = bsearch_pack(mad_oid, p, &first);
 
	/*
	 * first is now the position in the packfile where we would insert
	 * mad->hash if it does not exist (or the position of mad->hash if
	 * it does exist). Hence, we consider a maximum of two objects
	 * nearby for the abbreviation length.
	 */
	mad->init_len = 0;
	if (!match) {
		if (nth_packed_object_oid(&oid, p, first))
			extend_abbrev_len(&oid, mad);
	} else if (first < num - 1) {
		if (nth_packed_object_oid(&oid, p, first + 1))
			extend_abbrev_len(&oid, mad);
	}
	if (first > 0) {
		if (nth_packed_object_oid(&oid, p, first - 1))
			extend_abbrev_len(&oid, mad);
	}
	mad->init_len = mad->cur_len;
}
 
static void find_abbrev_len_packed(struct min_abbrev_data *mad)
{
	struct multi_pack_index *m;
	struct packed_git *p;
 
	for (m = get_multi_pack_index(the_repository); m; m = m->next)
		find_abbrev_len_for_midx(m, mad);
	for (p = get_packed_git(the_repository); p; p = p->next)
		find_abbrev_len_for_pack(p, mad);
}
 
int find_unique_abbrev_r(char *hex, const struct object_id *oid, int len)
{
	struct disambiguate_state ds;
	struct min_abbrev_data mad;
	struct object_id oid_ret;
	const unsigned hexsz = the_hash_algo->hexsz;
 
	if (len < 0) {
		unsigned long count = approximate_object_count();
		/*
		 * Add one because the MSB only tells us the highest bit set,
		 * not including the value of all the _other_ bits (so "15"
		 * is only one off of 2^4, but the MSB is the 3rd bit.
		 */
		len = msb(count) + 1;
		/*
		 * We now know we have on the order of 2^len objects, which
		 * expects a collision at 2^(len/2). But we also care about hex
		 * chars, not bits, and there are 4 bits per hex. So all
		 * together we need to divide by 2 and round up.
		 */
		len = DIV_ROUND_UP(len, 2);
		/*
		 * For very small repos, we stick with our regular fallback.
		 */
		if (len < FALLBACK_DEFAULT_ABBREV)
			len = FALLBACK_DEFAULT_ABBREV;
	}
 
	oid_to_hex_r(hex, oid);
	if (len == hexsz || !len)
		return hexsz;
 
	mad.init_len = len;
	mad.cur_len = len;
	mad.hex = hex;
	mad.oid = oid;
 
	find_abbrev_len_packed(&mad);
 
	if (init_object_disambiguation(hex, mad.cur_len, &ds) < 0)
		return -1;
 
	ds.fn = extend_abbrev_len;
	ds.always_call_fn = 1;
	ds.cb_data = (void *)&mad;
 
	find_short_object_filename(&ds);
	(void)finish_object_disambiguation(&ds, &oid_ret);
 
	hex[mad.cur_len] = 0;
	return mad.cur_len;
}
 
const char *find_unique_abbrev(const struct object_id *oid, int len)
{
	static int bufno;
	static char hexbuffer[4][GIT_MAX_HEXSZ + 1];
	char *hex = hexbuffer[bufno];
	bufno = (bufno + 1) % ARRAY_SIZE(hexbuffer);
	find_unique_abbrev_r(hex, oid, len);
	return hex;
}
 
static int ambiguous_path(const char *path, int len)
{
	int slash = 1;
	int cnt;
 
	for (cnt = 0; cnt < len; cnt++) {
		switch (*path++) {
		case '\0':
			break;
		case '/':
			if (slash)
				break;
			slash = 1;
			continue;
		case '.':
			continue;
		default:
			slash = 0;
			continue;
		}
		break;
	}
	return slash;
}
 
static inline int at_mark(const char *string, int len,
			  const char **suffix, int nr)
{
	int i;
 
	for (i = 0; i < nr; i++) {
		int suffix_len = strlen(suffix[i]);
		if (suffix_len <= len
		    && !strncasecmp(string, suffix[i], suffix_len))
			return suffix_len;
	}
	return 0;
}
 
static inline int upstream_mark(const char *string, int len)
{
	const char *suffix[] = { "@{upstream}", "@{u}" };
	return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
}
 
static inline int push_mark(const char *string, int len)
{
	const char *suffix[] = { "@{push}" };
	return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
}
 
static int get_oid_1(const char *name, int len, struct object_id *oid, unsigned lookup_flags);
static int interpret_nth_prior_checkout(const char *name, int namelen, struct strbuf *buf);
 
static int get_oid_basic(const char *str, int len, struct object_id *oid,
			  unsigned int flags)
{
	static const char *warn_msg = "refname '%.*s' is ambiguous.";
	static const char *object_name_msg = N_(
	"Git normally never creates a ref that ends with 40 hex characters\n"
	"because it will be ignored when you just specify 40-hex. These refs\n"
	"may be created by mistake. For example,\n"
	"\n"
	"  git checkout -b $br $(git rev-parse ...)\n"
	"\n"
	"where \"$br\" is somehow empty and a 40-hex ref is created. Please\n"
	"examine these refs and maybe delete them. Turn this message off by\n"
	"running \"git config advice.objectNameWarning false\"");
	struct object_id tmp_oid;
	char *real_ref = NULL;
	int refs_found = 0;
	int at, reflog_len, nth_prior = 0;
 
	if (len == the_hash_algo->hexsz && !get_oid_hex(str, oid)) {
		if (warn_ambiguous_refs && warn_on_object_refname_ambiguity) {
			refs_found = dwim_ref(str, len, &tmp_oid, &real_ref);
			if (refs_found > 0) {
				warning(warn_msg, len, str);
				if (advice_object_name_warning)
					fprintf(stderr, "%s\n", _(object_name_msg));
			}
			free(real_ref);
		}
		return 0;
	}
 
	/* basic@{time or number or -number} format to query ref-log */
	reflog_len = at = 0;
	if (len && str[len-1] == '}') {
		for (at = len-4; at >= 0; at--) {
			if (str[at] == '@' && str[at+1] == '{') {
				if (str[at+2] == '-') {
					if (at != 0)
						/* @{-N} not at start */
						return -1;
					nth_prior = 1;
					continue;
				}
				if (!upstream_mark(str + at, len - at) &&
				    !push_mark(str + at, len - at)) {
					reflog_len = (len-1) - (at+2);
					len = at;
				}
				break;
			}
		}
	}
 
	/* Accept only unambiguous ref paths. */
	if (len && ambiguous_path(str, len))
		return -1;
 
	if (nth_prior) {
		struct strbuf buf = STRBUF_INIT;
		int detached;
 
		if (interpret_nth_prior_checkout(str, len, &buf) > 0) {
			detached = (buf.len == the_hash_algo->hexsz && !get_oid_hex(buf.buf, oid));
			strbuf_release(&buf);
			if (detached)
				return 0;
		}
	}
 
	if (!len && reflog_len)
		/* allow "@{...}" to mean the current branch reflog */
		refs_found = dwim_ref("HEAD", 4, oid, &real_ref);
	else if (reflog_len)
		refs_found = dwim_log(str, len, oid, &real_ref);
	else
		refs_found = dwim_ref(str, len, oid, &real_ref);
 
	if (!refs_found)
		return -1;
 
	if (warn_ambiguous_refs && !(flags & GET_OID_QUIETLY) &&
	    (refs_found > 1 ||
	     !get_short_oid(str, len, &tmp_oid, GET_OID_QUIETLY)))
		warning(warn_msg, len, str);
 
	if (reflog_len) {
		int nth, i;
		timestamp_t at_time;
		timestamp_t co_time;
		int co_tz, co_cnt;
 
		/* Is it asking for N-th entry, or approxidate? */
		for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
			char ch = str[at+2+i];
			if ('0' <= ch && ch <= '9')
				nth = nth * 10 + ch - '0';
			else
				nth = -1;
		}
		if (100000000 <= nth) {
			at_time = nth;
			nth = -1;
		} else if (0 <= nth)
			at_time = 0;
		else {
			int errors = 0;
			char *tmp = xstrndup(str + at + 2, reflog_len);
			at_time = approxidate_careful(tmp, &errors);
			free(tmp);
			if (errors) {
				free(real_ref);
				return -1;
			}
		}
		if (read_ref_at(real_ref, flags, at_time, nth, oid, NULL,
				&co_time, &co_tz, &co_cnt)) {
			if (!len) {
				if (starts_with(real_ref, "refs/heads/")) {
					str = real_ref + 11;
					len = strlen(real_ref + 11);
				} else {
					/* detached HEAD */
					str = "HEAD";
					len = 4;
				}
			}
			if (at_time) {
				if (!(flags & GET_OID_QUIETLY)) {
					warning("Log for '%.*s' only goes "
						"back to %s.", len, str,
						show_date(co_time, co_tz, DATE_MODE(RFC2822)));
				}
			} else {
				if (flags & GET_OID_QUIETLY) {
					exit(128);
				}
				die("Log for '%.*s' only has %d entries.",
				    len, str, co_cnt);
			}
		}
	}
 
	free(real_ref);
	return 0;
}
 
static int get_parent(const char *name, int len,
		      struct object_id *result, int idx)
{
	struct object_id oid;
	int ret = get_oid_1(name, len, &oid, GET_OID_COMMITTISH);
	struct commit *commit;
	struct commit_list *p;
 
	if (ret)
		return ret;
	commit = lookup_commit_reference(the_repository, &oid);
	if (parse_commit(commit))
		return -1;
	if (!idx) {
		oidcpy(result, &commit->object.oid);
		return 0;
	}
	p = commit->parents;
	while (p) {
		if (!--idx) {
			oidcpy(result, &p->item->object.oid);
			return 0;
		}
		p = p->next;
	}
	return -1;
}
 
static int get_nth_ancestor(const char *name, int len,
			    struct object_id *result, int generation)
{
	struct object_id oid;
	struct commit *commit;
	int ret;
 
	ret = get_oid_1(name, len, &oid, GET_OID_COMMITTISH);
	if (ret)
		return ret;
	commit = lookup_commit_reference(the_repository, &oid);
	if (!commit)
		return -1;
 
	while (generation--) {
		if (parse_commit(commit) || !commit->parents)
			return -1;
		commit = commit->parents->item;
	}
	oidcpy(result, &commit->object.oid);
	return 0;
}
 
struct object *peel_to_type(const char *name, int namelen,
			    struct object *o, enum object_type expected_type)
{
	if (name && !namelen)
		namelen = strlen(name);
	while (1) {
		if (!o || (!o->parsed && !parse_object(the_repository, &o->oid)))
			return NULL;
		if (expected_type == OBJ_ANY || o->type == expected_type)
			return o;
		if (o->type == OBJ_TAG)
			o = ((struct tag*) o)->tagged;
		else if (o->type == OBJ_COMMIT)
			o = &(get_commit_tree(((struct commit *)o))->object);
		else {
			if (name)
				error("%.*s: expected %s type, but the object "
				      "dereferences to %s type",
				      namelen, name, type_name(expected_type),
				      type_name(o->type));
			return NULL;
		}
	}
}
 
static int peel_onion(const char *name, int len, struct object_id *oid,
		      unsigned lookup_flags)
{
	struct object_id outer;
	const char *sp;
	unsigned int expected_type = 0;
	struct object *o;
 
	/*
	 * "ref^{type}" dereferences ref repeatedly until you cannot
	 * dereference anymore, or you get an object of given type,
	 * whichever comes first.  "ref^{}" means just dereference
	 * tags until you get a non-tag.  "ref^0" is a shorthand for
	 * "ref^{commit}".  "commit^{tree}" could be used to find the
	 * top-level tree of the given commit.
	 */
	if (len < 4 || name[len-1] != '}')
		return -1;
 
	for (sp = name + len - 1; name <= sp; sp--) {
		int ch = *sp;
		if (ch == '{' && name < sp && sp[-1] == '^')
			break;
	}
	if (sp <= name)
		return -1;
 
	sp++; /* beginning of type name, or closing brace for empty */
	if (starts_with(sp, "commit}"))
		expected_type = OBJ_COMMIT;
	else if (starts_with(sp, "tag}"))
		expected_type = OBJ_TAG;
	else if (starts_with(sp, "tree}"))
		expected_type = OBJ_TREE;
	else if (starts_with(sp, "blob}"))
		expected_type = OBJ_BLOB;
	else if (starts_with(sp, "object}"))
		expected_type = OBJ_ANY;
	else if (sp[0] == '}')
		expected_type = OBJ_NONE;
	else if (sp[0] == '/')
		expected_type = OBJ_COMMIT;
	else
		return -1;
 
	lookup_flags &= ~GET_OID_DISAMBIGUATORS;
	if (expected_type == OBJ_COMMIT)
		lookup_flags |= GET_OID_COMMITTISH;
	else if (expected_type == OBJ_TREE)
		lookup_flags |= GET_OID_TREEISH;
 
	if (get_oid_1(name, sp - name - 2, &outer, lookup_flags))
		return -1;
 
	o = parse_object(the_repository, &outer);
	if (!o)
		return -1;
	if (!expected_type) {
		o = deref_tag(the_repository, o, name, sp - name - 2);
		if (!o || (!o->parsed && !parse_object(the_repository, &o->oid)))
			return -1;
		oidcpy(oid, &o->oid);
		return 0;
	}
 
	/*
	 * At this point, the syntax look correct, so
	 * if we do not get the needed object, we should
	 * barf.
	 */
	o = peel_to_type(name, len, o, expected_type);
	if (!o)
		return -1;
 
	oidcpy(oid, &o->oid);
	if (sp[0] == '/') {
		/* "$commit^{/foo}" */
		char *prefix;
		int ret;
		struct commit_list *list = NULL;
 
		/*
		 * $commit^{/}. Some regex implementation may reject.
		 * We don't need regex anyway. '' pattern always matches.
		 */
		if (sp[1] == '}')
			return 0;
 
		prefix = xstrndup(sp + 1, name + len - 1 - (sp + 1));
		commit_list_insert((struct commit *)o, &list);
		ret = get_oid_oneline(prefix, oid, list);
		free(prefix);
		return ret;
	}
	return 0;
}
 
static int get_describe_name(const char *name, int len, struct object_id *oid)
{
	const char *cp;
	unsigned flags = GET_OID_QUIETLY | GET_OID_COMMIT;
 
	for (cp = name + len - 1; name + 2 <= cp; cp--) {
		char ch = *cp;
		if (!isxdigit(ch)) {
			/* We must be looking at g in "SOMETHING-g"
			 * for it to be describe output.
			 */
			if (ch == 'g' && cp[-1] == '-') {
				cp++;
				len -= cp - name;
				return get_short_oid(cp, len, oid, flags);
			}
		}
	}
	return -1;
}
 
static int get_oid_1(const char *name, int len, struct object_id *oid, unsigned lookup_flags)
{
	int ret, has_suffix;
	const char *cp;
 
	/*
	 * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
	 */
	has_suffix = 0;
	for (cp = name + len - 1; name <= cp; cp--) {
		int ch = *cp;
		if ('0' <= ch && ch <= '9')
			continue;
		if (ch == '~' || ch == '^')
			has_suffix = ch;
		break;
	}
 
	if (has_suffix) {
		int num = 0;
		int len1 = cp - name;
		cp++;
		while (cp < name + len)
			num = num * 10 + *cp++ - '0';
		if (!num && len1 == len - 1)
			num = 1;
		if (has_suffix == '^')
			return get_parent(name, len1, oid, num);
		/* else if (has_suffix == '~') -- goes without saying */
		return get_nth_ancestor(name, len1, oid, num);
	}
 
	ret = peel_onion(name, len, oid, lookup_flags);
	if (!ret)
		return 0;
 
	ret = get_oid_basic(name, len, oid, lookup_flags);
	if (!ret)
		return 0;
 
	/* It could be describe output that is "SOMETHING-gXXXX" */
	ret = get_describe_name(name, len, oid);
	if (!ret)
		return 0;
 
	return get_short_oid(name, len, oid, lookup_flags);
}
 
/*
 * This interprets names like ':/Initial revision of "git"' by searching
 * through history and returning the first commit whose message starts
 * the given regular expression.
 *
 * For negative-matching, prefix the pattern-part with '!-', like: ':/!-WIP'.
 *
 * For a literal '!' character at the beginning of a pattern, you have to repeat
 * that, like: ':/!!foo'
 *
 * For future extension, all other sequences beginning with ':/!' are reserved.
 */
 
/* Remember to update object flag allocation in object.h */
#define ONELINE_SEEN (1u<<20)
 
static int handle_one_ref(const char *path, const struct object_id *oid,
			  int flag, void *cb_data)
{
	struct commit_list **list = cb_data;
	struct object *object = parse_object(the_repository, oid);
	if (!object)
		return 0;
	if (object->type == OBJ_TAG) {
		object = deref_tag(the_repository, object, path,
				   strlen(path));
		if (!object)
			return 0;
	}
	if (object->type != OBJ_COMMIT)
		return 0;
	commit_list_insert((struct commit *)object, list);
	return 0;
}
 
static int get_oid_oneline(const char *prefix, struct object_id *oid,
			    struct commit_list *list)
{
	struct commit_list *backup = NULL, *l;
	int found = 0;
	int negative = 0;
	regex_t regex;
 
	if (prefix[0] == '!') {
		prefix++;
 
		if (prefix[0] == '-') {
			prefix++;
			negative = 1;
		} else if (prefix[0] != '!') {
			return -1;
		}
	}
 
	if (regcomp(&regex, prefix, REG_EXTENDED))
		return -1;
 
	for (l = list; l; l = l->next) {
		l->item->object.flags |= ONELINE_SEEN;
		commit_list_insert(l->item, &backup);
	}
	while (list) {
		const char *p, *buf;
		struct commit *commit;
		int matches;
 
		commit = pop_most_recent_commit(&list, ONELINE_SEEN);
		if (!parse_object(the_repository, &commit->object.oid))
			continue;
		buf = get_commit_buffer(commit, NULL);
		p = strstr(buf, "\n\n");
		matches = negative ^ (p && !regexec(&regex, p + 2, 0, NULL, 0));
		unuse_commit_buffer(commit, buf);
 
		if (matches) {
			oidcpy(oid, &commit->object.oid);
			found = 1;
			break;
		}
	}
	regfree(&regex);
	free_commit_list(list);
	for (l = backup; l; l = l->next)
		clear_commit_marks(l->item, ONELINE_SEEN);
	free_commit_list(backup);
	return found ? 0 : -1;
}
 
struct grab_nth_branch_switch_cbdata {
	int remaining;
	struct strbuf buf;
};
 
static int grab_nth_branch_switch(struct object_id *ooid, struct object_id *noid,
				  const char *email, timestamp_t timestamp, int tz,
				  const char *message, void *cb_data)
{
	struct grab_nth_branch_switch_cbdata *cb = cb_data;
	const char *match = NULL, *target = NULL;
	size_t len;
 
	if (skip_prefix(message, "checkout: moving from ", &match))
		target = strstr(match, " to ");
 
	if (!match || !target)
		return 0;
	if (--(cb->remaining) == 0) {
		len = target - match;
		strbuf_reset(&cb->buf);
		strbuf_add(&cb->buf, match, len);
		return 1; /* we are done */
	}
	return 0;
}
 
/*
 * Parse @{-N} syntax, return the number of characters parsed
 * if successful; otherwise signal an error with negative value.
 */
static int interpret_nth_prior_checkout(const char *name, int namelen,
					struct strbuf *buf)
{
	long nth;
	int retval;
	struct grab_nth_branch_switch_cbdata cb;
	const char *brace;
	char *num_end;
 
	if (namelen < 4)
		return -1;
	if (name[0] != '@' || name[1] != '{' || name[2] != '-')
		return -1;
	brace = memchr(name, '}', namelen);
	if (!brace)
		return -1;
	nth = strtol(name + 3, &num_end, 10);
	if (num_end != brace)
		return -1;
	if (nth <= 0)
		return -1;
	cb.remaining = nth;
	strbuf_init(&cb.buf, 20);
 
	retval = 0;
	if (0 < for_each_reflog_ent_reverse("HEAD", grab_nth_branch_switch, &cb)) {
		strbuf_reset(buf);
		strbuf_addbuf(buf, &cb.buf);
		retval = brace - name + 1;
	}
 
	strbuf_release(&cb.buf);
	return retval;
}
 
int get_oid_mb(const char *name, struct object_id *oid)
{
	struct commit *one, *two;
	struct commit_list *mbs;
	struct object_id oid_tmp;
	const char *dots;
	int st;
 
	dots = strstr(name, "...");
	if (!dots)
		return get_oid(name, oid);
	if (dots == name)
		st = get_oid("HEAD", &oid_tmp);
	else {
		struct strbuf sb;
		strbuf_init(&sb, dots - name);
		strbuf_add(&sb, name, dots - name);
		st = get_oid_committish(sb.buf, &oid_tmp);
		strbuf_release(&sb);
	}
	if (st)
		return st;
	one = lookup_commit_reference_gently(the_repository, &oid_tmp, 0);
	if (!one)
		return -1;
 
	if (get_oid_committish(dots[3] ? (dots + 3) : "HEAD", &oid_tmp))
		return -1;
	two = lookup_commit_reference_gently(the_repository, &oid_tmp, 0);
	if (!two)
		return -1;
	mbs = get_merge_bases(one, two);
	if (!mbs || mbs->next)
		st = -1;
	else {
		st = 0;
		oidcpy(oid, &mbs->item->object.oid);
	}
	free_commit_list(mbs);
	return st;
}
 
/* parse @something syntax, when 'something' is not {.*} */
static int interpret_empty_at(const char *name, int namelen, int len, struct strbuf *buf)
{
	const char *next;
 
	if (len || name[1] == '{')
		return -1;
 
	/* make sure it's a single @, or @@{.*}, not @foo */
	next = memchr(name + len + 1, '@', namelen - len - 1);
	if (next && next[1] != '{')
		return -1;
	if (!next)
		next = name + namelen;
	if (next != name + 1)
		return -1;
 
	strbuf_reset(buf);
	strbuf_add(buf, "HEAD", 4);
	return 1;
}
 
static int reinterpret(const char *name, int namelen, int len,
		       struct strbuf *buf, unsigned allowed)
{
	/* we have extra data, which might need further processing */
	struct strbuf tmp = STRBUF_INIT;
	int used = buf->len;
	int ret;
 
	strbuf_add(buf, name + len, namelen - len);
	ret = interpret_branch_name(buf->buf, buf->len, &tmp, allowed);
	/* that data was not interpreted, remove our cruft */
	if (ret < 0) {
		strbuf_setlen(buf, used);
		return len;
	}
	strbuf_reset(buf);
	strbuf_addbuf(buf, &tmp);
	strbuf_release(&tmp);
	/* tweak for size of {-N} versus expanded ref name */
	return ret - used + len;
}
 
static void set_shortened_ref(struct strbuf *buf, const char *ref)
{
	char *s = shorten_unambiguous_ref(ref, 0);
	strbuf_reset(buf);
	strbuf_addstr(buf, s);
	free(s);
}
 
static int branch_interpret_allowed(const char *refname, unsigned allowed)
{
	if (!allowed)
		return 1;
 
	if ((allowed & INTERPRET_BRANCH_LOCAL) &&
	    starts_with(refname, "refs/heads/"))
		return 1;
	if ((allowed & INTERPRET_BRANCH_REMOTE) &&
	    starts_with(refname, "refs/remotes/"))
		return 1;
 
	return 0;
}
 
static int interpret_branch_mark(const char *name, int namelen,
				 int at, struct strbuf *buf,
				 int (*get_mark)(const char *, int),
				 const char *(*get_data)(struct branch *,
							 struct strbuf *),
				 unsigned allowed)
{
	int len;
	struct branch *branch;
	struct strbuf err = STRBUF_INIT;
	const char *value;
 
	len = get_mark(name + at, namelen - at);
	if (!len)
		return -1;
 
	if (memchr(name, ':', at))
		return -1;
 
	if (at) {
		char *name_str = xmemdupz(name, at);
		branch = branch_get(name_str);
		free(name_str);
	} else
		branch = branch_get(NULL);
 
	value = get_data(branch, &err);
	if (!value)
		die("%s", err.buf);
 
	if (!branch_interpret_allowed(value, allowed))
		return -1;
 
	set_shortened_ref(buf, value);
	return len + at;
}
 
int interpret_branch_name(const char *name, int namelen, struct strbuf *buf,
			  unsigned allowed)
{
	char *at;
	const char *start;
	int len;
 
	if (!namelen)
		namelen = strlen(name);
 
	if (!allowed || (allowed & INTERPRET_BRANCH_LOCAL)) {
		len = interpret_nth_prior_checkout(name, namelen, buf);
		if (!len) {
			return len; /* syntax Ok, not enough switches */
		} else if (len > 0) {
			if (len == namelen)
				return len; /* consumed all */
			else
				return reinterpret(name, namelen, len, buf, allowed);
		}
	}
 
	for (start = name;
	     (at = memchr(start, '@', namelen - (start - name)));
	     start = at + 1) {
 
		if (!allowed || (allowed & INTERPRET_BRANCH_HEAD)) {
			len = interpret_empty_at(name, namelen, at - name, buf);
			if (len > 0)
				return reinterpret(name, namelen, len, buf,
						   allowed);
		}
 
		len = interpret_branch_mark(name, namelen, at - name, buf,
					    upstream_mark, branch_get_upstream,
					    allowed);
		if (len > 0)
			return len;
 
		len = interpret_branch_mark(name, namelen, at - name, buf,
					    push_mark, branch_get_push,
					    allowed);
		if (len > 0)
			return len;
	}
 
	return -1;
}
 
void strbuf_branchname(struct strbuf *sb, const char *name, unsigned allowed)
{
	int len = strlen(name);
	int used = interpret_branch_name(name, len, sb, allowed);
 
	if (used < 0)
		used = 0;
	strbuf_add(sb, name + used, len - used);
}
 
int strbuf_check_branch_ref(struct strbuf *sb, const char *name)
{
	if (startup_info->have_repository)
		strbuf_branchname(sb, name, INTERPRET_BRANCH_LOCAL);
	else
		strbuf_addstr(sb, name);
 
	/*
	 * This splice must be done even if we end up rejecting the
	 * name; builtin/branch.c::copy_or_rename_branch() still wants
	 * to see what the name expanded to so that "branch -m" can be
	 * used as a tool to correct earlier mistakes.
	 */
	strbuf_splice(sb, 0, 0, "refs/heads/", 11);
 
	if (*name == '-' ||
	    !strcmp(sb->buf, "refs/heads/HEAD"))
		return -1;
 
	return check_refname_format(sb->buf, 0);
}
 
/*
 * This is like "get_oid_basic()", except it allows "object ID expressions",
 * notably "xyz^" for "parent of xyz"
 */
int get_oid(const char *name, struct object_id *oid)
{
	struct object_context unused;
	return get_oid_with_context(name, 0, oid, &unused);
}
 
 
/*
 * Many callers know that the user meant to name a commit-ish by
 * syntactical positions where the object name appears.  Calling this
 * function allows the machinery to disambiguate shorter-than-unique
 * abbreviated object names between commit-ish and others.
 *
 * Note that this does NOT error out when the named object is not a
 * commit-ish. It is merely to give a hint to the disambiguation
 * machinery.
 */
int get_oid_committish(const char *name, struct object_id *oid)
{
	struct object_context unused;
	return get_oid_with_context(name, GET_OID_COMMITTISH,
				    oid, &unused);
}
 
int get_oid_treeish(const char *name, struct object_id *oid)
{
	struct object_context unused;
	return get_oid_with_context(name, GET_OID_TREEISH,
				    oid, &unused);
}
 
int get_oid_commit(const char *name, struct object_id *oid)
{
	struct object_context unused;
	return get_oid_with_context(name, GET_OID_COMMIT,
				    oid, &unused);
}
 
int get_oid_tree(const char *name, struct object_id *oid)
{
	struct object_context unused;
	return get_oid_with_context(name, GET_OID_TREE,
				    oid, &unused);
}
 
int get_oid_blob(const char *name, struct object_id *oid)
{
	struct object_context unused;
	return get_oid_with_context(name, GET_OID_BLOB,
				    oid, &unused);
}
 
/* Must be called only when object_name:filename doesn't exist. */
static void diagnose_invalid_oid_path(const char *prefix,
				      const char *filename,
				      const struct object_id *tree_oid,
				      const char *object_name,
				      int object_name_len)
{
	struct object_id oid;
	unsigned mode;
 
	if (!prefix)
		prefix = "";
 
	if (file_exists(filename))
		die("Path '%s' exists on disk, but not in '%.*s'.",
		    filename, object_name_len, object_name);
	if (is_missing_file_error(errno)) {
		char *fullname = xstrfmt("%s%s", prefix, filename);
 
		if (!get_tree_entry(tree_oid, fullname, &oid, &mode)) {
			die("Path '%s' exists, but not '%s'.\n"
			    "Did you mean '%.*s:%s' aka '%.*s:./%s'?",
			    fullname,
			    filename,
			    object_name_len, object_name,
			    fullname,
			    object_name_len, object_name,
			    filename);
		}
		die("Path '%s' does not exist in '%.*s'",
		    filename, object_name_len, object_name);
	}
}
 
/* Must be called only when :stage:filename doesn't exist. */
static void diagnose_invalid_index_path(int stage,
					const char *prefix,
					const char *filename)
{
	const struct cache_entry *ce;
	int pos;
	unsigned namelen = strlen(filename);
	struct strbuf fullname = STRBUF_INIT;
 
	if (!prefix)
		prefix = "";
 
	/* Wrong stage number? */
	pos = cache_name_pos(filename, namelen);
	if (pos < 0)
		pos = -pos - 1;
	if (pos < active_nr) {
		ce = active_cache[pos];
		if (ce_namelen(ce) == namelen &&
		    !memcmp(ce->name, filename, namelen))
			die("Path '%s' is in the index, but not at stage %d.\n"
			    "Did you mean ':%d:%s'?",
			    filename, stage,
			    ce_stage(ce), filename);
	}
 
	/* Confusion between relative and absolute filenames? */
	strbuf_addstr(&fullname, prefix);
	strbuf_addstr(&fullname, filename);
	pos = cache_name_pos(fullname.buf, fullname.len);
	if (pos < 0)
		pos = -pos - 1;
	if (pos < active_nr) {
		ce = active_cache[pos];
		if (ce_namelen(ce) == fullname.len &&
		    !memcmp(ce->name, fullname.buf, fullname.len))
			die("Path '%s' is in the index, but not '%s'.\n"
			    "Did you mean ':%d:%s' aka ':%d:./%s'?",
			    fullname.buf, filename,
			    ce_stage(ce), fullname.buf,
			    ce_stage(ce), filename);
	}
 
	if (file_exists(filename))
		die("Path '%s' exists on disk, but not in the index.", filename);
	if (is_missing_file_error(errno))
		die("Path '%s' does not exist (neither on disk nor in the index).",
		    filename);
 
	strbuf_release(&fullname);
}
 
 
static char *resolve_relative_path(const char *rel)
{
	if (!starts_with(rel, "./") && !starts_with(rel, "../"))
		return NULL;
 
	if (!is_inside_work_tree())
		die("relative path syntax can't be used outside working tree.");
 
	/* die() inside prefix_path() if resolved path is outside worktree */
	return prefix_path(startup_info->prefix,
			   startup_info->prefix ? strlen(startup_info->prefix) : 0,
			   rel);
}
 
static int get_oid_with_context_1(const char *name,
				  unsigned flags,
				  const char *prefix,
				  struct object_id *oid,
				  struct object_context *oc)
{
	int ret, bracket_depth;
	int namelen = strlen(name);
	const char *cp;
	int only_to_die = flags & GET_OID_ONLY_TO_DIE;
 
	if (only_to_die)
		flags |= GET_OID_QUIETLY;
 
	memset(oc, 0, sizeof(*oc));
	oc->mode = S_IFINVALID;
	strbuf_init(&oc->symlink_path, 0);
	ret = get_oid_1(name, namelen, oid, flags);
	if (!ret)
		return ret;
	/*
	 * sha1:path --> object name of path in ent sha1
	 * :path -> object name of absolute path in index
	 * :./path -> object name of path relative to cwd in index
	 * :[0-3]:path -> object name of path in index at stage
	 * :/foo -> recent commit matching foo
	 */
	if (name[0] == ':') {
		int stage = 0;
		const struct cache_entry *ce;
		char *new_path = NULL;
		int pos;
		if (!only_to_die && namelen > 2 && name[1] == '/') {
			struct commit_list *list = NULL;
 
			for_each_ref(handle_one_ref, &list);
			head_ref(handle_one_ref, &list);
			commit_list_sort_by_date(&list);
			return get_oid_oneline(name + 2, oid, list);
		}
		if (namelen < 3 ||
		    name[2] != ':' ||
		    name[1] < '0' || '3' < name[1])
			cp = name + 1;
		else {
			stage = name[1] - '0';
			cp = name + 3;
		}
		new_path = resolve_relative_path(cp);
		if (!new_path) {
			namelen = namelen - (cp - name);
		} else {
			cp = new_path;
			namelen = strlen(cp);
		}
 
		if (flags & GET_OID_RECORD_PATH)
			oc->path = xstrdup(cp);
 
		if (!the_index.cache)
			repo_read_index(the_repository);
		pos = index_name_pos(&the_index, cp, namelen);
		if (pos < 0)
			pos = -pos - 1;
		while (pos < active_nr) {
			ce = active_cache[pos];
			if (ce_namelen(ce) != namelen ||
			    memcmp(ce->name, cp, namelen))
				break;
			if (ce_stage(ce) == stage) {
				oidcpy(oid, &ce->oid);
				oc->mode = ce->ce_mode;
				free(new_path);
				return 0;
			}
			pos++;
		}
		if (only_to_die && name[1] && name[1] != '/')
			diagnose_invalid_index_path(stage, prefix, cp);
		free(new_path);
		return -1;
	}
	for (cp = name, bracket_depth = 0; *cp; cp++) {
		if (*cp == '{')
			bracket_depth++;
		else if (bracket_depth && *cp == '}')
			bracket_depth--;
		else if (!bracket_depth && *cp == ':')
			break;
	}
	if (*cp == ':') {
		struct object_id tree_oid;
		int len = cp - name;
		unsigned sub_flags = flags;
 
		sub_flags &= ~GET_OID_DISAMBIGUATORS;
		sub_flags |= GET_OID_TREEISH;
 
		if (!get_oid_1(name, len, &tree_oid, sub_flags)) {
			const char *filename = cp+1;
			char *new_filename = NULL;
 
			new_filename = resolve_relative_path(filename);
			if (new_filename)
				filename = new_filename;
			if (flags & GET_OID_FOLLOW_SYMLINKS) {
				ret = get_tree_entry_follow_symlinks(&tree_oid,
					filename, oid, &oc->symlink_path,
					&oc->mode);
			} else {
				ret = get_tree_entry(&tree_oid, filename, oid,
						     &oc->mode);
				if (ret && only_to_die) {
					diagnose_invalid_oid_path(prefix,
								   filename,
								   &tree_oid,
								   name, len);
				}
			}
			if (flags & GET_OID_RECORD_PATH)
				oc->path = xstrdup(filename);
 
			free(new_filename);
			return ret;
		} else {
			if (only_to_die)
				die("Invalid object name '%.*s'.", len, name);
		}
	}
	return ret;
}
 
/*
 * Call this function when you know "name" given by the end user must
 * name an object but it doesn't; the function _may_ die with a better
 * diagnostic message than "no such object 'name'", e.g. "Path 'doc' does not
 * exist in 'HEAD'" when given "HEAD:doc", or it may return in which case
 * you have a chance to diagnose the error further.
 */
void maybe_die_on_misspelt_object_name(const char *name, const char *prefix)
{
	struct object_context oc;
	struct object_id oid;
	get_oid_with_context_1(name, GET_OID_ONLY_TO_DIE, prefix, &oid, &oc);
}
 
int get_oid_with_context(const char *str, unsigned flags, struct object_id *oid, struct object_context *oc)
{
	if (flags & GET_OID_FOLLOW_SYMLINKS && flags & GET_OID_ONLY_TO_DIE)
		BUG("incompatible flags for get_sha1_with_context");
	return get_oid_with_context_1(str, flags, NULL, oid, oc);
}