summaryrefslogtreecommitdiff
path: root/sha1_name.c
blob: bf924178380c42a50b2fd7a02ff869dcc3ddff6a (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
#include "cache.h"
#include "tag.h"
#include "commit.h"
#include "tree.h"
#include "blob.h"
#include "tree-walk.h"
#include "refs.h"
#include "remote.h"

static int find_short_object_filename(int len, const char *name, unsigned char *sha1)
{
	struct alternate_object_database *alt;
	char hex[40];
	int found = 0;
	static struct alternate_object_database *fakeent;

	if (!fakeent) {
		const char *objdir = get_object_directory();
		int objdir_len = strlen(objdir);
		int entlen = objdir_len + 43;
		fakeent = xmalloc(sizeof(*fakeent) + entlen);
		memcpy(fakeent->base, objdir, objdir_len);
		fakeent->name = fakeent->base + objdir_len + 1;
		fakeent->name[-1] = '/';
	}
	fakeent->next = alt_odb_list;

	sprintf(hex, "%.2s", name);
	for (alt = fakeent; alt && found < 2; alt = alt->next) {
		struct dirent *de;
		DIR *dir;
		sprintf(alt->name, "%.2s/", name);
		dir = opendir(alt->base);
		if (!dir)
			continue;
		while ((de = readdir(dir)) != NULL) {
			if (strlen(de->d_name) != 38)
				continue;
			if (memcmp(de->d_name, name + 2, len - 2))
				continue;
			if (!found) {
				memcpy(hex + 2, de->d_name, 38);
				found++;
			}
			else if (memcmp(hex + 2, de->d_name, 38)) {
				found = 2;
				break;
			}
		}
		closedir(dir);
	}
	if (found == 1)
		return get_sha1_hex(hex, sha1) == 0;
	return found;
}

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 int find_short_packed_object(int len, const unsigned char *match, unsigned char *sha1)
{
	struct packed_git *p;
	const unsigned char *found_sha1 = NULL;
	int found = 0;

	prepare_packed_git();
	for (p = packed_git; p && found < 2; p = p->next) {
		uint32_t num, last;
		uint32_t first = 0;
		open_pack_index(p);
		num = p->num_objects;
		last = num;
		while (first < last) {
			uint32_t mid = (first + last) / 2;
			const unsigned char *now;
			int cmp;

			now = nth_packed_object_sha1(p, mid);
			cmp = hashcmp(match, now);
			if (!cmp) {
				first = mid;
				break;
			}
			if (cmp > 0) {
				first = mid+1;
				continue;
			}
			last = mid;
		}
		if (first < num) {
			const unsigned char *now, *next;
		       now = nth_packed_object_sha1(p, first);
			if (match_sha(len, match, now)) {
				next = nth_packed_object_sha1(p, first+1);
			       if (!next|| !match_sha(len, match, next)) {
					/* unique within this pack */
					if (!found) {
						found_sha1 = now;
						found++;
					}
					else if (hashcmp(found_sha1, now)) {
						found = 2;
						break;
					}
				}
				else {
					/* not even unique within this pack */
					found = 2;
					break;
				}
			}
		}
	}
	if (found == 1)
		hashcpy(sha1, found_sha1);
	return found;
}

#define SHORT_NAME_NOT_FOUND (-1)
#define SHORT_NAME_AMBIGUOUS (-2)

static int find_unique_short_object(int len, char *canonical,
				    unsigned char *res, unsigned char *sha1)
{
	int has_unpacked, has_packed;
	unsigned char unpacked_sha1[20], packed_sha1[20];

	prepare_alt_odb();
	has_unpacked = find_short_object_filename(len, canonical, unpacked_sha1);
	has_packed = find_short_packed_object(len, res, packed_sha1);
	if (!has_unpacked && !has_packed)
		return SHORT_NAME_NOT_FOUND;
	if (1 < has_unpacked || 1 < has_packed)
		return SHORT_NAME_AMBIGUOUS;
	if (has_unpacked != has_packed) {
		hashcpy(sha1, (has_packed ? packed_sha1 : unpacked_sha1));
		return 0;
	}
	/* Both have unique ones -- do they match? */
	if (hashcmp(packed_sha1, unpacked_sha1))
		return SHORT_NAME_AMBIGUOUS;
	hashcpy(sha1, packed_sha1);
	return 0;
}

static int get_short_sha1(const char *name, int len, unsigned char *sha1,
			  int quietly)
{
	int i, status;
	char canonical[40];
	unsigned char res[20];

	if (len < MINIMUM_ABBREV || len > 40)
		return -1;
	hashclr(res);
	memset(canonical, 'x', 40);
	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;
		canonical[i] = c;
		if (!(i & 1))
			val <<= 4;
		res[i >> 1] |= val;
	}

	status = find_unique_short_object(i, canonical, res, sha1);
	if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
		return error("short SHA1 %.*s is ambiguous.", len, canonical);
	return status;
}

const char *find_unique_abbrev(const unsigned char *sha1, int len)
{
	int status, exists;
	static char hex[41];

	exists = has_sha1_file(sha1);
	memcpy(hex, sha1_to_hex(sha1), 40);
	if (len == 40 || !len)
		return hex;
	while (len < 40) {
		unsigned char sha1_ret[20];
		status = get_short_sha1(hex, len, sha1_ret, 1);
		if (exists
		    ? !status
		    : status == SHORT_NAME_NOT_FOUND) {
			hex[len] = 0;
			return hex;
		}
		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;
}

/*
 * *string and *len will only be substituted, and *string returned (for
 * later free()ing) if the string passed in is a magic short-hand form
 * to name a branch.
 */
static char *substitute_branch_name(const char **string, int *len)
{
	struct strbuf buf = STRBUF_INIT;
	int ret = interpret_branch_name(*string, &buf);

	if (ret == *len) {
		size_t size;
		*string = strbuf_detach(&buf, &size);
		*len = size;
		return (char *)*string;
	}

	return NULL;
}

int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
{
	char *last_branch = substitute_branch_name(&str, &len);
	const char **p, *r;
	int refs_found = 0;

	*ref = NULL;
	for (p = ref_rev_parse_rules; *p; p++) {
		char fullref[PATH_MAX];
		unsigned char sha1_from_ref[20];
		unsigned char *this_result;
		int flag;

		this_result = refs_found ? sha1_from_ref : sha1;
		mksnpath(fullref, sizeof(fullref), *p, len, str);
		r = resolve_ref(fullref, this_result, 1, &flag);
		if (r) {
			if (!refs_found++)
				*ref = xstrdup(r);
			if (!warn_ambiguous_refs)
				break;
		} else if ((flag & REF_ISSYMREF) && strcmp(fullref, "HEAD"))
			warning("ignoring dangling symref %s.", fullref);
	}
	free(last_branch);
	return refs_found;
}

int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
{
	char *last_branch = substitute_branch_name(&str, &len);
	const char **p;
	int logs_found = 0;

	*log = NULL;
	for (p = ref_rev_parse_rules; *p; p++) {
		struct stat st;
		unsigned char hash[20];
		char path[PATH_MAX];
		const char *ref, *it;

		mksnpath(path, sizeof(path), *p, len, str);
		ref = resolve_ref(path, hash, 1, NULL);
		if (!ref)
			continue;
		if (!stat(git_path("logs/%s", path), &st) &&
		    S_ISREG(st.st_mode))
			it = path;
		else if (strcmp(ref, path) &&
			 !stat(git_path("logs/%s", ref), &st) &&
			 S_ISREG(st.st_mode))
			it = ref;
		else
			continue;
		if (!logs_found++) {
			*log = xstrdup(it);
			hashcpy(sha1, hash);
		}
		if (!warn_ambiguous_refs)
			break;
	}
	free(last_branch);
	return logs_found;
}

static inline int upstream_mark(const char *string, int len)
{
	const char *suffix[] = { "@{upstream}", "@{u}" };
	int i;

	for (i = 0; i < ARRAY_SIZE(suffix); i++) {
		int suffix_len = strlen(suffix[i]);
		if (suffix_len <= len
		    && !memcmp(string, suffix[i], suffix_len))
			return suffix_len;
	}
	return 0;
}

static int get_sha1_1(const char *name, int len, unsigned char *sha1);

static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
{
	static const char *warning = "warning: refname '%.*s' is ambiguous.\n";
	char *real_ref = NULL;
	int refs_found = 0;
	int at, reflog_len;

	if (len == 40 && !get_sha1_hex(str, sha1))
		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-2; at >= 0; at--) {
			if (str[at] == '@' && str[at+1] == '{') {
				if (!upstream_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 (!len && reflog_len) {
		struct strbuf buf = STRBUF_INIT;
		int ret;
		/* try the @{-N} syntax for n-th checkout */
		ret = interpret_branch_name(str+at, &buf);
		if (ret > 0) {
			/* substitute this branch name and restart */
			return get_sha1_1(buf.buf, buf.len, sha1);
		} else if (ret == 0) {
			return -1;
		}
		/* allow "@{...}" to mean the current branch reflog */
		refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
	} else if (reflog_len)
		refs_found = dwim_log(str, len, sha1, &real_ref);
	else
		refs_found = dwim_ref(str, len, sha1, &real_ref);

	if (!refs_found)
		return -1;

	if (warn_ambiguous_refs && refs_found > 1)
		fprintf(stderr, warning, len, str);

	if (reflog_len) {
		int nth, i;
		unsigned long at_time;
		unsigned long co_time;
		int co_tz, co_cnt;

		/* a @{-N} placed anywhere except the start is an error */
		if (str[at+2] == '-')
			return -1;

		/* 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)
				return -1;
		}
		if (read_ref_at(real_ref, at_time, nth, sha1, NULL,
				&co_time, &co_tz, &co_cnt)) {
			if (at_time)
				fprintf(stderr,
					"warning: Log for '%.*s' only goes "
					"back to %s.\n", len, str,
					show_date(co_time, co_tz, DATE_RFC2822));
			else
				fprintf(stderr,
					"warning: Log for '%.*s' only has "
					"%d entries.\n", len, str, co_cnt);
		}
	}

	free(real_ref);
	return 0;
}

static int get_parent(const char *name, int len,
		      unsigned char *result, int idx)
{
	unsigned char sha1[20];
	int ret = get_sha1_1(name, len, sha1);
	struct commit *commit;
	struct commit_list *p;

	if (ret)
		return ret;
	commit = lookup_commit_reference(sha1);
	if (!commit)
		return -1;
	if (parse_commit(commit))
		return -1;
	if (!idx) {
		hashcpy(result, commit->object.sha1);
		return 0;
	}
	p = commit->parents;
	while (p) {
		if (!--idx) {
			hashcpy(result, p->item->object.sha1);
			return 0;
		}
		p = p->next;
	}
	return -1;
}

static int get_nth_ancestor(const char *name, int len,
			    unsigned char *result, int generation)
{
	unsigned char sha1[20];
	struct commit *commit;
	int ret;

	ret = get_sha1_1(name, len, sha1);
	if (ret)
		return ret;
	commit = lookup_commit_reference(sha1);
	if (!commit)
		return -1;

	while (generation--) {
		if (parse_commit(commit) || !commit->parents)
			return -1;
		commit = commit->parents->item;
	}
	hashcpy(result, commit->object.sha1);
	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);
	if (!o) {
		unsigned char sha1[20];
		if (get_sha1_1(name, namelen, sha1))
			return NULL;
		o = parse_object(sha1);
	}
	while (1) {
		if (!o || (!o->parsed && !parse_object(o->sha1)))
			return NULL;
		if (o->type == expected_type)
			return o;
		if (o->type == OBJ_TAG)
			o = ((struct tag*) o)->tagged;
		else if (o->type == OBJ_COMMIT)
			o = &(((struct commit *) o)->tree->object);
		else {
			if (name)
				error("%.*s: expected %s type, but the object "
				      "dereferences to %s type",
				      namelen, name, typename(expected_type),
				      typename(o->type));
			return NULL;
		}
	}
}

static int peel_onion(const char *name, int len, unsigned char *sha1)
{
	unsigned char outer[20];
	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 (!strncmp(commit_type, sp, 6) && sp[6] == '}')
		expected_type = OBJ_COMMIT;
	else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
		expected_type = OBJ_TREE;
	else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')
		expected_type = OBJ_BLOB;
	else if (sp[0] == '}')
		expected_type = OBJ_NONE;
	else
		return -1;

	if (get_sha1_1(name, sp - name - 2, outer))
		return -1;

	o = parse_object(outer);
	if (!o)
		return -1;
	if (!expected_type) {
		o = deref_tag(o, name, sp - name - 2);
		if (!o || (!o->parsed && !parse_object(o->sha1)))
			return -1;
		hashcpy(sha1, o->sha1);
	}
	else {
		/*
		 * 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) {
			hashcpy(sha1, o->sha1);
			return 0;
		}
		return -1;
	}
	return 0;
}

static int get_describe_name(const char *name, int len, unsigned char *sha1)
{
	const char *cp;

	for (cp = name + len - 1; name + 2 <= cp; cp--) {
		char ch = *cp;
		if (hexval(ch) & ~0377) {
			/* 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_sha1(cp, len, sha1, 1);
			}
		}
	}
	return -1;
}

static int get_sha1_1(const char *name, int len, unsigned char *sha1)
{
	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, sha1, num);
		/* else if (has_suffix == '~') -- goes without saying */
		return get_nth_ancestor(name, len1, sha1, num);
	}

	ret = peel_onion(name, len, sha1);
	if (!ret)
		return 0;

	ret = get_sha1_basic(name, len, sha1);
	if (!ret)
		return 0;

	/* It could be describe output that is "SOMETHING-gXXXX" */
	ret = get_describe_name(name, len, sha1);
	if (!ret)
		return 0;

	return get_short_sha1(name, len, sha1, 0);
}

static int handle_one_ref(const char *path,
		const unsigned char *sha1, int flag, void *cb_data)
{
	struct commit_list **list = cb_data;
	struct object *object = parse_object(sha1);
	if (!object)
		return 0;
	if (object->type == OBJ_TAG) {
		object = deref_tag(object, path, strlen(path));
		if (!object)
			return 0;
	}
	if (object->type != OBJ_COMMIT)
		return 0;
	insert_by_date((struct commit *)object, list);
	return 0;
}

/*
 * This interprets names like ':/Initial revision of "git"' by searching
 * through history and returning the first commit whose message starts
 * with the given string.
 *
 * For future extension, ':/!' is reserved. If you want to match a message
 * beginning with a '!', you have to repeat the exclamation mark.
 */

#define ONELINE_SEEN (1u<<20)
static int get_sha1_oneline(const char *prefix, unsigned char *sha1)
{
	struct commit_list *list = NULL, *backup = NULL, *l;
	int retval = -1;
	char *temp_commit_buffer = NULL;

	if (prefix[0] == '!') {
		if (prefix[1] != '!')
			die ("Invalid search pattern: %s", prefix);
		prefix++;
	}
	for_each_ref(handle_one_ref, &list);
	for (l = list; l; l = l->next)
		commit_list_insert(l->item, &backup);
	while (list) {
		char *p;
		struct commit *commit;
		enum object_type type;
		unsigned long size;

		commit = pop_most_recent_commit(&list, ONELINE_SEEN);
		if (!parse_object(commit->object.sha1))
			continue;
		free(temp_commit_buffer);
		if (commit->buffer)
			p = commit->buffer;
		else {
			p = read_sha1_file(commit->object.sha1, &type, &size);
			if (!p)
				continue;
			temp_commit_buffer = p;
		}
		if (!(p = strstr(p, "\n\n")))
			continue;
		if (!prefixcmp(p + 2, prefix)) {
			hashcpy(sha1, commit->object.sha1);
			retval = 0;
			break;
		}
	}
	free(temp_commit_buffer);
	free_commit_list(list);
	for (l = backup; l; l = l->next)
		clear_commit_marks(l->item, ONELINE_SEEN);
	return retval;
}

struct grab_nth_branch_switch_cbdata {
	long cnt, alloc;
	struct strbuf *buf;
};

static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
				  const char *email, unsigned long 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;
	int nth;

	if (!prefixcmp(message, "checkout: moving from ")) {
		match = message + strlen("checkout: moving from ");
		target = strstr(match, " to ");
	}

	if (!match || !target)
		return 0;

	len = target - match;
	nth = cb->cnt++ % cb->alloc;
	strbuf_reset(&cb->buf[nth]);
	strbuf_add(&cb->buf[nth], match, len);
	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, struct strbuf *buf)
{
	long nth;
	int i, retval;
	struct grab_nth_branch_switch_cbdata cb;
	const char *brace;
	char *num_end;

	if (name[0] != '@' || name[1] != '{' || name[2] != '-')
		return -1;
	brace = strchr(name, '}');
	if (!brace)
		return -1;
	nth = strtol(name+3, &num_end, 10);
	if (num_end != brace)
		return -1;
	if (nth <= 0)
		return -1;
	cb.alloc = nth;
	cb.buf = xmalloc(nth * sizeof(struct strbuf));
	for (i = 0; i < nth; i++)
		strbuf_init(&cb.buf[i], 20);
	cb.cnt = 0;
	retval = 0;
	for_each_recent_reflog_ent("HEAD", grab_nth_branch_switch, 40960, &cb);
	if (cb.cnt < nth) {
		cb.cnt = 0;
		for_each_reflog_ent("HEAD", grab_nth_branch_switch, &cb);
	}
	if (cb.cnt < nth)
		goto release_return;
	i = cb.cnt % nth;
	strbuf_reset(buf);
	strbuf_add(buf, cb.buf[i].buf, cb.buf[i].len);
	retval = brace-name+1;

release_return:
	for (i = 0; i < nth; i++)
		strbuf_release(&cb.buf[i]);
	free(cb.buf);

	return retval;
}

int get_sha1_mb(const char *name, unsigned char *sha1)
{
	struct commit *one, *two;
	struct commit_list *mbs;
	unsigned char sha1_tmp[20];
	const char *dots;
	int st;

	dots = strstr(name, "...");
	if (!dots)
		return get_sha1(name, sha1);
	if (dots == name)
		st = get_sha1("HEAD", sha1_tmp);
	else {
		struct strbuf sb;
		strbuf_init(&sb, dots - name);
		strbuf_add(&sb, name, dots - name);
		st = get_sha1(sb.buf, sha1_tmp);
		strbuf_release(&sb);
	}
	if (st)
		return st;
	one = lookup_commit_reference_gently(sha1_tmp, 0);
	if (!one)
		return -1;

	if (get_sha1(dots[3] ? (dots + 3) : "HEAD", sha1_tmp))
		return -1;
	two = lookup_commit_reference_gently(sha1_tmp, 0);
	if (!two)
		return -1;
	mbs = get_merge_bases(one, two, 1);
	if (!mbs || mbs->next)
		st = -1;
	else {
		st = 0;
		hashcpy(sha1, mbs->item->object.sha1);
	}
	free_commit_list(mbs);
	return st;
}

/*
 * This reads short-hand syntax that not only evaluates to a commit
 * object name, but also can act as if the end user spelled the name
 * of the branch from the command line.
 *
 * - "@{-N}" finds the name of the Nth previous branch we were on, and
 *   places the name of the branch in the given buf and returns the
 *   number of characters parsed if successful.
 *
 * - "<branch>@{upstream}" finds the name of the other ref that
 *   <branch> is configured to merge with (missing <branch> defaults
 *   to the current branch), and places the name of the branch in the
 *   given buf and returns the number of characters parsed if
 *   successful.
 *
 * If the input is not of the accepted format, it returns a negative
 * number to signal an error.
 *
 * If the input was ok but there are not N branch switches in the
 * reflog, it returns 0.
 */
int interpret_branch_name(const char *name, struct strbuf *buf)
{
	char *cp;
	struct branch *upstream;
	int namelen = strlen(name);
	int len = interpret_nth_prior_checkout(name, buf);
	int tmp_len;

	if (!len)
		return len; /* syntax Ok, not enough switches */
	if (0 < len && len == namelen)
		return len; /* consumed all */
	else if (0 < len) {
		/* 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, &tmp);
		/* 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;
	}

	cp = strchr(name, '@');
	if (!cp)
		return -1;
	tmp_len = upstream_mark(cp, namelen - (cp - name));
	if (!tmp_len)
		return -1;
	len = cp + tmp_len - name;
	cp = xstrndup(name, cp - name);
	upstream = branch_get(*cp ? cp : NULL);
	if (!upstream
	    || !upstream->merge
	    || !upstream->merge[0]->dst)
		return error("No upstream branch found for '%s'", cp);
	free(cp);
	cp = shorten_unambiguous_ref(upstream->merge[0]->dst, 0);
	strbuf_reset(buf);
	strbuf_addstr(buf, cp);
	free(cp);
	return len;
}

/*
 * This is like "get_sha1_basic()", except it allows "sha1 expressions",
 * notably "xyz^" for "parent of xyz"
 */
int get_sha1(const char *name, unsigned char *sha1)
{
	unsigned unused;
	return get_sha1_with_mode(name, sha1, &unused);
}

/* Must be called only when object_name:filename doesn't exist. */
static void diagnose_invalid_sha1_path(const char *prefix,
				       const char *filename,
				       const unsigned char *tree_sha1,
				       const char *object_name)
{
	struct stat st;
	unsigned char sha1[20];
	unsigned mode;

	if (!prefix)
		prefix = "";

	if (!lstat(filename, &st))
		die("Path '%s' exists on disk, but not in '%s'.",
		    filename, object_name);
	if (errno == ENOENT || errno == ENOTDIR) {
		char *fullname = xmalloc(strlen(filename)
					     + strlen(prefix) + 1);
		strcpy(fullname, prefix);
		strcat(fullname, filename);

		if (!get_tree_entry(tree_sha1, fullname,
				    sha1, &mode)) {
			die("Path '%s' exists, but not '%s'.\n"
			    "Did you mean '%s:%s'?",
			    fullname,
			    filename,
			    object_name,
			    fullname);
		}
		die("Path '%s' does not exist in '%s'",
		    filename, 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)
{
	struct stat st;
	struct cache_entry *ce;
	int pos;
	unsigned namelen = strlen(filename);
	unsigned fullnamelen;
	char *fullname;

	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? */
	fullnamelen = namelen + strlen(prefix);
	fullname = xmalloc(fullnamelen + 1);
	strcpy(fullname, prefix);
	strcat(fullname, filename);
	pos = cache_name_pos(fullname, fullnamelen);
	if (pos < 0)
		pos = -pos - 1;
	if (pos < active_nr) {
		ce = active_cache[pos];
		if (ce_namelen(ce) == fullnamelen &&
		    !memcmp(ce->name, fullname, fullnamelen))
			die("Path '%s' is in the index, but not '%s'.\n"
			    "Did you mean ':%d:%s'?",
			    fullname, filename,
			    ce_stage(ce), fullname);
	}

	if (!lstat(filename, &st))
		die("Path '%s' exists on disk, but not in the index.", filename);
	if (errno == ENOENT || errno == ENOTDIR)
		die("Path '%s' does not exist (neither on disk nor in the index).",
		    filename);

	free(fullname);
}


int get_sha1_with_mode_1(const char *name, unsigned char *sha1, unsigned *mode, int gently, const char *prefix)
{
	int ret, bracket_depth;
	int namelen = strlen(name);
	const char *cp;

	*mode = S_IFINVALID;
	ret = get_sha1_1(name, namelen, sha1);
	if (!ret)
		return ret;
	/* sha1:path --> object name of path in ent sha1
	 * :path -> object name of path in index
	 * :[0-3]:path -> object name of path in index at stage
	 */
	if (name[0] == ':') {
		int stage = 0;
		struct cache_entry *ce;
		int pos;
		if (namelen > 2 && name[1] == '/')
			return get_sha1_oneline(name + 2, sha1);
		if (namelen < 3 ||
		    name[2] != ':' ||
		    name[1] < '0' || '3' < name[1])
			cp = name + 1;
		else {
			stage = name[1] - '0';
			cp = name + 3;
		}
		namelen = namelen - (cp - name);
		if (!active_cache)
			read_cache();
		pos = cache_name_pos(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) {
				hashcpy(sha1, ce->sha1);
				*mode = ce->ce_mode;
				return 0;
			}
			pos++;
		}
		if (!gently)
			diagnose_invalid_index_path(stage, prefix, cp);
		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 == ':') {
		unsigned char tree_sha1[20];
		char *object_name = NULL;
		if (!gently) {
			object_name = xmalloc(cp-name+1);
			strncpy(object_name, name, cp-name);
			object_name[cp-name] = '\0';
		}
		if (!get_sha1_1(name, cp-name, tree_sha1)) {
			const char *filename = cp+1;
			ret = get_tree_entry(tree_sha1, filename, sha1, mode);
			if (!gently) {
				diagnose_invalid_sha1_path(prefix, filename,
							   tree_sha1, object_name);
				free(object_name);
			}
			return ret;
		} else {
			if (!gently)
				die("Invalid object name '%s'.", object_name);
		}
	}
	return ret;
}