list-objects-filter: use BUG rather than die
[git] / commit-graph.c
1 #include "cache.h"
2 #include "config.h"
3 #include "dir.h"
4 #include "git-compat-util.h"
5 #include "lockfile.h"
6 #include "pack.h"
7 #include "packfile.h"
8 #include "commit.h"
9 #include "object.h"
10 #include "refs.h"
11 #include "revision.h"
12 #include "sha1-lookup.h"
13 #include "commit-graph.h"
14 #include "object-store.h"
15 #include "alloc.h"
16
17 #define GRAPH_SIGNATURE 0x43475048 /* "CGPH" */
18 #define GRAPH_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
19 #define GRAPH_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
20 #define GRAPH_CHUNKID_DATA 0x43444154 /* "CDAT" */
21 #define GRAPH_CHUNKID_LARGEEDGES 0x45444745 /* "EDGE" */
22
23 #define GRAPH_DATA_WIDTH 36
24
25 #define GRAPH_VERSION_1 0x1
26 #define GRAPH_VERSION GRAPH_VERSION_1
27
28 #define GRAPH_OID_VERSION_SHA1 1
29 #define GRAPH_OID_LEN_SHA1 GIT_SHA1_RAWSZ
30 #define GRAPH_OID_VERSION GRAPH_OID_VERSION_SHA1
31 #define GRAPH_OID_LEN GRAPH_OID_LEN_SHA1
32
33 #define GRAPH_OCTOPUS_EDGES_NEEDED 0x80000000
34 #define GRAPH_PARENT_MISSING 0x7fffffff
35 #define GRAPH_EDGE_LAST_MASK 0x7fffffff
36 #define GRAPH_PARENT_NONE 0x70000000
37
38 #define GRAPH_LAST_EDGE 0x80000000
39
40 #define GRAPH_HEADER_SIZE 8
41 #define GRAPH_FANOUT_SIZE (4 * 256)
42 #define GRAPH_CHUNKLOOKUP_WIDTH 12
43 #define GRAPH_MIN_SIZE (GRAPH_HEADER_SIZE + 4 * GRAPH_CHUNKLOOKUP_WIDTH \
44                         + GRAPH_FANOUT_SIZE + GRAPH_OID_LEN)
45
46 char *get_commit_graph_filename(const char *obj_dir)
47 {
48         return xstrfmt("%s/info/commit-graph", obj_dir);
49 }
50
51 static struct commit_graph *alloc_commit_graph(void)
52 {
53         struct commit_graph *g = xcalloc(1, sizeof(*g));
54         g->graph_fd = -1;
55
56         return g;
57 }
58
59 struct commit_graph *load_commit_graph_one(const char *graph_file)
60 {
61         void *graph_map;
62         const unsigned char *data, *chunk_lookup;
63         size_t graph_size;
64         struct stat st;
65         uint32_t i;
66         struct commit_graph *graph;
67         int fd = git_open(graph_file);
68         uint64_t last_chunk_offset;
69         uint32_t last_chunk_id;
70         uint32_t graph_signature;
71         unsigned char graph_version, hash_version;
72
73         if (fd < 0)
74                 return NULL;
75         if (fstat(fd, &st)) {
76                 close(fd);
77                 return NULL;
78         }
79         graph_size = xsize_t(st.st_size);
80
81         if (graph_size < GRAPH_MIN_SIZE) {
82                 close(fd);
83                 die("graph file %s is too small", graph_file);
84         }
85         graph_map = xmmap(NULL, graph_size, PROT_READ, MAP_PRIVATE, fd, 0);
86         data = (const unsigned char *)graph_map;
87
88         graph_signature = get_be32(data);
89         if (graph_signature != GRAPH_SIGNATURE) {
90                 error("graph signature %X does not match signature %X",
91                       graph_signature, GRAPH_SIGNATURE);
92                 goto cleanup_fail;
93         }
94
95         graph_version = *(unsigned char*)(data + 4);
96         if (graph_version != GRAPH_VERSION) {
97                 error("graph version %X does not match version %X",
98                       graph_version, GRAPH_VERSION);
99                 goto cleanup_fail;
100         }
101
102         hash_version = *(unsigned char*)(data + 5);
103         if (hash_version != GRAPH_OID_VERSION) {
104                 error("hash version %X does not match version %X",
105                       hash_version, GRAPH_OID_VERSION);
106                 goto cleanup_fail;
107         }
108
109         graph = alloc_commit_graph();
110
111         graph->hash_len = GRAPH_OID_LEN;
112         graph->num_chunks = *(unsigned char*)(data + 6);
113         graph->graph_fd = fd;
114         graph->data = graph_map;
115         graph->data_len = graph_size;
116
117         last_chunk_id = 0;
118         last_chunk_offset = 8;
119         chunk_lookup = data + 8;
120         for (i = 0; i < graph->num_chunks; i++) {
121                 uint32_t chunk_id = get_be32(chunk_lookup + 0);
122                 uint64_t chunk_offset = get_be64(chunk_lookup + 4);
123                 int chunk_repeated = 0;
124
125                 chunk_lookup += GRAPH_CHUNKLOOKUP_WIDTH;
126
127                 if (chunk_offset > graph_size - GIT_MAX_RAWSZ) {
128                         error("improper chunk offset %08x%08x", (uint32_t)(chunk_offset >> 32),
129                               (uint32_t)chunk_offset);
130                         goto cleanup_fail;
131                 }
132
133                 switch (chunk_id) {
134                 case GRAPH_CHUNKID_OIDFANOUT:
135                         if (graph->chunk_oid_fanout)
136                                 chunk_repeated = 1;
137                         else
138                                 graph->chunk_oid_fanout = (uint32_t*)(data + chunk_offset);
139                         break;
140
141                 case GRAPH_CHUNKID_OIDLOOKUP:
142                         if (graph->chunk_oid_lookup)
143                                 chunk_repeated = 1;
144                         else
145                                 graph->chunk_oid_lookup = data + chunk_offset;
146                         break;
147
148                 case GRAPH_CHUNKID_DATA:
149                         if (graph->chunk_commit_data)
150                                 chunk_repeated = 1;
151                         else
152                                 graph->chunk_commit_data = data + chunk_offset;
153                         break;
154
155                 case GRAPH_CHUNKID_LARGEEDGES:
156                         if (graph->chunk_large_edges)
157                                 chunk_repeated = 1;
158                         else
159                                 graph->chunk_large_edges = data + chunk_offset;
160                         break;
161                 }
162
163                 if (chunk_repeated) {
164                         error("chunk id %08x appears multiple times", chunk_id);
165                         goto cleanup_fail;
166                 }
167
168                 if (last_chunk_id == GRAPH_CHUNKID_OIDLOOKUP)
169                 {
170                         graph->num_commits = (chunk_offset - last_chunk_offset)
171                                              / graph->hash_len;
172                 }
173
174                 last_chunk_id = chunk_id;
175                 last_chunk_offset = chunk_offset;
176         }
177
178         return graph;
179
180 cleanup_fail:
181         munmap(graph_map, graph_size);
182         close(fd);
183         exit(1);
184 }
185
186 static void prepare_commit_graph_one(struct repository *r, const char *obj_dir)
187 {
188         char *graph_name;
189
190         if (r->objects->commit_graph)
191                 return;
192
193         graph_name = get_commit_graph_filename(obj_dir);
194         r->objects->commit_graph =
195                 load_commit_graph_one(graph_name);
196
197         FREE_AND_NULL(graph_name);
198 }
199
200 /*
201  * Return 1 if commit_graph is non-NULL, and 0 otherwise.
202  *
203  * On the first invocation, this function attemps to load the commit
204  * graph if the_repository is configured to have one.
205  */
206 static int prepare_commit_graph(struct repository *r)
207 {
208         struct alternate_object_database *alt;
209         char *obj_dir;
210         int config_value;
211
212         if (r->objects->commit_graph_attempted)
213                 return !!r->objects->commit_graph;
214         r->objects->commit_graph_attempted = 1;
215
216         if (repo_config_get_bool(r, "core.commitgraph", &config_value) ||
217             !config_value)
218                 /*
219                  * This repository is not configured to use commit graphs, so
220                  * do not load one. (But report commit_graph_attempted anyway
221                  * so that commit graph loading is not attempted again for this
222                  * repository.)
223                  */
224                 return 0;
225
226         obj_dir = r->objects->objectdir;
227         prepare_commit_graph_one(r, obj_dir);
228         prepare_alt_odb(r);
229         for (alt = r->objects->alt_odb_list;
230              !r->objects->commit_graph && alt;
231              alt = alt->next)
232                 prepare_commit_graph_one(r, alt->path);
233         return !!r->objects->commit_graph;
234 }
235
236 static void close_commit_graph(void)
237 {
238         free_commit_graph(the_repository->objects->commit_graph);
239         the_repository->objects->commit_graph = NULL;
240 }
241
242 static int bsearch_graph(struct commit_graph *g, struct object_id *oid, uint32_t *pos)
243 {
244         return bsearch_hash(oid->hash, g->chunk_oid_fanout,
245                             g->chunk_oid_lookup, g->hash_len, pos);
246 }
247
248 static struct commit_list **insert_parent_or_die(struct commit_graph *g,
249                                                  uint64_t pos,
250                                                  struct commit_list **pptr)
251 {
252         struct commit *c;
253         struct object_id oid;
254
255         if (pos >= g->num_commits)
256                 die("invalid parent position %"PRIu64, pos);
257
258         hashcpy(oid.hash, g->chunk_oid_lookup + g->hash_len * pos);
259         c = lookup_commit(the_repository, &oid);
260         if (!c)
261                 die("could not find commit %s", oid_to_hex(&oid));
262         c->graph_pos = pos;
263         return &commit_list_insert(c, pptr)->next;
264 }
265
266 static void fill_commit_graph_info(struct commit *item, struct commit_graph *g, uint32_t pos)
267 {
268         const unsigned char *commit_data = g->chunk_commit_data + GRAPH_DATA_WIDTH * pos;
269         item->graph_pos = pos;
270         item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
271 }
272
273 static int fill_commit_in_graph(struct commit *item, struct commit_graph *g, uint32_t pos)
274 {
275         uint32_t edge_value;
276         uint32_t *parent_data_ptr;
277         uint64_t date_low, date_high;
278         struct commit_list **pptr;
279         const unsigned char *commit_data = g->chunk_commit_data + (g->hash_len + 16) * pos;
280
281         item->object.parsed = 1;
282         item->graph_pos = pos;
283
284         item->maybe_tree = NULL;
285
286         date_high = get_be32(commit_data + g->hash_len + 8) & 0x3;
287         date_low = get_be32(commit_data + g->hash_len + 12);
288         item->date = (timestamp_t)((date_high << 32) | date_low);
289
290         item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
291
292         pptr = &item->parents;
293
294         edge_value = get_be32(commit_data + g->hash_len);
295         if (edge_value == GRAPH_PARENT_NONE)
296                 return 1;
297         pptr = insert_parent_or_die(g, edge_value, pptr);
298
299         edge_value = get_be32(commit_data + g->hash_len + 4);
300         if (edge_value == GRAPH_PARENT_NONE)
301                 return 1;
302         if (!(edge_value & GRAPH_OCTOPUS_EDGES_NEEDED)) {
303                 pptr = insert_parent_or_die(g, edge_value, pptr);
304                 return 1;
305         }
306
307         parent_data_ptr = (uint32_t*)(g->chunk_large_edges +
308                           4 * (uint64_t)(edge_value & GRAPH_EDGE_LAST_MASK));
309         do {
310                 edge_value = get_be32(parent_data_ptr);
311                 pptr = insert_parent_or_die(g,
312                                             edge_value & GRAPH_EDGE_LAST_MASK,
313                                             pptr);
314                 parent_data_ptr++;
315         } while (!(edge_value & GRAPH_LAST_EDGE));
316
317         return 1;
318 }
319
320 static int find_commit_in_graph(struct commit *item, struct commit_graph *g, uint32_t *pos)
321 {
322         if (item->graph_pos != COMMIT_NOT_FROM_GRAPH) {
323                 *pos = item->graph_pos;
324                 return 1;
325         } else {
326                 return bsearch_graph(g, &(item->object.oid), pos);
327         }
328 }
329
330 static int parse_commit_in_graph_one(struct commit_graph *g, struct commit *item)
331 {
332         uint32_t pos;
333
334         if (item->object.parsed)
335                 return 1;
336
337         if (find_commit_in_graph(item, g, &pos))
338                 return fill_commit_in_graph(item, g, pos);
339
340         return 0;
341 }
342
343 int parse_commit_in_graph(struct repository *r, struct commit *item)
344 {
345         if (!prepare_commit_graph(r))
346                 return 0;
347         return parse_commit_in_graph_one(r->objects->commit_graph, item);
348 }
349
350 void load_commit_graph_info(struct repository *r, struct commit *item)
351 {
352         uint32_t pos;
353         if (!prepare_commit_graph(r))
354                 return;
355         if (find_commit_in_graph(item, r->objects->commit_graph, &pos))
356                 fill_commit_graph_info(item, r->objects->commit_graph, pos);
357 }
358
359 static struct tree *load_tree_for_commit(struct commit_graph *g, struct commit *c)
360 {
361         struct object_id oid;
362         const unsigned char *commit_data = g->chunk_commit_data +
363                                            GRAPH_DATA_WIDTH * (c->graph_pos);
364
365         hashcpy(oid.hash, commit_data);
366         c->maybe_tree = lookup_tree(the_repository, &oid);
367
368         return c->maybe_tree;
369 }
370
371 static struct tree *get_commit_tree_in_graph_one(struct commit_graph *g,
372                                                  const struct commit *c)
373 {
374         if (c->maybe_tree)
375                 return c->maybe_tree;
376         if (c->graph_pos == COMMIT_NOT_FROM_GRAPH)
377                 BUG("get_commit_tree_in_graph_one called from non-commit-graph commit");
378
379         return load_tree_for_commit(g, (struct commit *)c);
380 }
381
382 struct tree *get_commit_tree_in_graph(struct repository *r, const struct commit *c)
383 {
384         return get_commit_tree_in_graph_one(r->objects->commit_graph, c);
385 }
386
387 static void write_graph_chunk_fanout(struct hashfile *f,
388                                      struct commit **commits,
389                                      int nr_commits)
390 {
391         int i, count = 0;
392         struct commit **list = commits;
393
394         /*
395          * Write the first-level table (the list is sorted,
396          * but we use a 256-entry lookup to be able to avoid
397          * having to do eight extra binary search iterations).
398          */
399         for (i = 0; i < 256; i++) {
400                 while (count < nr_commits) {
401                         if ((*list)->object.oid.hash[0] != i)
402                                 break;
403                         count++;
404                         list++;
405                 }
406
407                 hashwrite_be32(f, count);
408         }
409 }
410
411 static void write_graph_chunk_oids(struct hashfile *f, int hash_len,
412                                    struct commit **commits, int nr_commits)
413 {
414         struct commit **list = commits;
415         int count;
416         for (count = 0; count < nr_commits; count++, list++)
417                 hashwrite(f, (*list)->object.oid.hash, (int)hash_len);
418 }
419
420 static const unsigned char *commit_to_sha1(size_t index, void *table)
421 {
422         struct commit **commits = table;
423         return commits[index]->object.oid.hash;
424 }
425
426 static void write_graph_chunk_data(struct hashfile *f, int hash_len,
427                                    struct commit **commits, int nr_commits)
428 {
429         struct commit **list = commits;
430         struct commit **last = commits + nr_commits;
431         uint32_t num_extra_edges = 0;
432
433         while (list < last) {
434                 struct commit_list *parent;
435                 int edge_value;
436                 uint32_t packedDate[2];
437
438                 parse_commit(*list);
439                 hashwrite(f, get_commit_tree_oid(*list)->hash, hash_len);
440
441                 parent = (*list)->parents;
442
443                 if (!parent)
444                         edge_value = GRAPH_PARENT_NONE;
445                 else {
446                         edge_value = sha1_pos(parent->item->object.oid.hash,
447                                               commits,
448                                               nr_commits,
449                                               commit_to_sha1);
450
451                         if (edge_value < 0)
452                                 edge_value = GRAPH_PARENT_MISSING;
453                 }
454
455                 hashwrite_be32(f, edge_value);
456
457                 if (parent)
458                         parent = parent->next;
459
460                 if (!parent)
461                         edge_value = GRAPH_PARENT_NONE;
462                 else if (parent->next)
463                         edge_value = GRAPH_OCTOPUS_EDGES_NEEDED | num_extra_edges;
464                 else {
465                         edge_value = sha1_pos(parent->item->object.oid.hash,
466                                               commits,
467                                               nr_commits,
468                                               commit_to_sha1);
469                         if (edge_value < 0)
470                                 edge_value = GRAPH_PARENT_MISSING;
471                 }
472
473                 hashwrite_be32(f, edge_value);
474
475                 if (edge_value & GRAPH_OCTOPUS_EDGES_NEEDED) {
476                         do {
477                                 num_extra_edges++;
478                                 parent = parent->next;
479                         } while (parent);
480                 }
481
482                 if (sizeof((*list)->date) > 4)
483                         packedDate[0] = htonl(((*list)->date >> 32) & 0x3);
484                 else
485                         packedDate[0] = 0;
486
487                 packedDate[0] |= htonl((*list)->generation << 2);
488
489                 packedDate[1] = htonl((*list)->date);
490                 hashwrite(f, packedDate, 8);
491
492                 list++;
493         }
494 }
495
496 static void write_graph_chunk_large_edges(struct hashfile *f,
497                                           struct commit **commits,
498                                           int nr_commits)
499 {
500         struct commit **list = commits;
501         struct commit **last = commits + nr_commits;
502         struct commit_list *parent;
503
504         while (list < last) {
505                 int num_parents = 0;
506                 for (parent = (*list)->parents; num_parents < 3 && parent;
507                      parent = parent->next)
508                         num_parents++;
509
510                 if (num_parents <= 2) {
511                         list++;
512                         continue;
513                 }
514
515                 /* Since num_parents > 2, this initializer is safe. */
516                 for (parent = (*list)->parents->next; parent; parent = parent->next) {
517                         int edge_value = sha1_pos(parent->item->object.oid.hash,
518                                                   commits,
519                                                   nr_commits,
520                                                   commit_to_sha1);
521
522                         if (edge_value < 0)
523                                 edge_value = GRAPH_PARENT_MISSING;
524                         else if (!parent->next)
525                                 edge_value |= GRAPH_LAST_EDGE;
526
527                         hashwrite_be32(f, edge_value);
528                 }
529
530                 list++;
531         }
532 }
533
534 static int commit_compare(const void *_a, const void *_b)
535 {
536         const struct object_id *a = (const struct object_id *)_a;
537         const struct object_id *b = (const struct object_id *)_b;
538         return oidcmp(a, b);
539 }
540
541 struct packed_commit_list {
542         struct commit **list;
543         int nr;
544         int alloc;
545 };
546
547 struct packed_oid_list {
548         struct object_id *list;
549         int nr;
550         int alloc;
551 };
552
553 static int add_packed_commits(const struct object_id *oid,
554                               struct packed_git *pack,
555                               uint32_t pos,
556                               void *data)
557 {
558         struct packed_oid_list *list = (struct packed_oid_list*)data;
559         enum object_type type;
560         off_t offset = nth_packed_object_offset(pack, pos);
561         struct object_info oi = OBJECT_INFO_INIT;
562
563         oi.typep = &type;
564         if (packed_object_info(the_repository, pack, offset, &oi) < 0)
565                 die("unable to get type of object %s", oid_to_hex(oid));
566
567         if (type != OBJ_COMMIT)
568                 return 0;
569
570         ALLOC_GROW(list->list, list->nr + 1, list->alloc);
571         oidcpy(&(list->list[list->nr]), oid);
572         list->nr++;
573
574         return 0;
575 }
576
577 static void add_missing_parents(struct packed_oid_list *oids, struct commit *commit)
578 {
579         struct commit_list *parent;
580         for (parent = commit->parents; parent; parent = parent->next) {
581                 if (!(parent->item->object.flags & UNINTERESTING)) {
582                         ALLOC_GROW(oids->list, oids->nr + 1, oids->alloc);
583                         oidcpy(&oids->list[oids->nr], &(parent->item->object.oid));
584                         oids->nr++;
585                         parent->item->object.flags |= UNINTERESTING;
586                 }
587         }
588 }
589
590 static void close_reachable(struct packed_oid_list *oids)
591 {
592         int i;
593         struct commit *commit;
594
595         for (i = 0; i < oids->nr; i++) {
596                 commit = lookup_commit(the_repository, &oids->list[i]);
597                 if (commit)
598                         commit->object.flags |= UNINTERESTING;
599         }
600
601         /*
602          * As this loop runs, oids->nr may grow, but not more
603          * than the number of missing commits in the reachable
604          * closure.
605          */
606         for (i = 0; i < oids->nr; i++) {
607                 commit = lookup_commit(the_repository, &oids->list[i]);
608
609                 if (commit && !parse_commit(commit))
610                         add_missing_parents(oids, commit);
611         }
612
613         for (i = 0; i < oids->nr; i++) {
614                 commit = lookup_commit(the_repository, &oids->list[i]);
615
616                 if (commit)
617                         commit->object.flags &= ~UNINTERESTING;
618         }
619 }
620
621 static void compute_generation_numbers(struct packed_commit_list* commits)
622 {
623         int i;
624         struct commit_list *list = NULL;
625
626         for (i = 0; i < commits->nr; i++) {
627                 if (commits->list[i]->generation != GENERATION_NUMBER_INFINITY &&
628                     commits->list[i]->generation != GENERATION_NUMBER_ZERO)
629                         continue;
630
631                 commit_list_insert(commits->list[i], &list);
632                 while (list) {
633                         struct commit *current = list->item;
634                         struct commit_list *parent;
635                         int all_parents_computed = 1;
636                         uint32_t max_generation = 0;
637
638                         for (parent = current->parents; parent; parent = parent->next) {
639                                 if (parent->item->generation == GENERATION_NUMBER_INFINITY ||
640                                     parent->item->generation == GENERATION_NUMBER_ZERO) {
641                                         all_parents_computed = 0;
642                                         commit_list_insert(parent->item, &list);
643                                         break;
644                                 } else if (parent->item->generation > max_generation) {
645                                         max_generation = parent->item->generation;
646                                 }
647                         }
648
649                         if (all_parents_computed) {
650                                 current->generation = max_generation + 1;
651                                 pop_commit(&list);
652
653                                 if (current->generation > GENERATION_NUMBER_MAX)
654                                         current->generation = GENERATION_NUMBER_MAX;
655                         }
656                 }
657         }
658 }
659
660 static int add_ref_to_list(const char *refname,
661                            const struct object_id *oid,
662                            int flags, void *cb_data)
663 {
664         struct string_list *list = (struct string_list *)cb_data;
665
666         string_list_append(list, oid_to_hex(oid));
667         return 0;
668 }
669
670 void write_commit_graph_reachable(const char *obj_dir, int append)
671 {
672         struct string_list list;
673
674         string_list_init(&list, 1);
675         for_each_ref(add_ref_to_list, &list);
676         write_commit_graph(obj_dir, NULL, &list, append);
677 }
678
679 void write_commit_graph(const char *obj_dir,
680                         struct string_list *pack_indexes,
681                         struct string_list *commit_hex,
682                         int append)
683 {
684         struct packed_oid_list oids;
685         struct packed_commit_list commits;
686         struct hashfile *f;
687         uint32_t i, count_distinct = 0;
688         char *graph_name;
689         struct lock_file lk = LOCK_INIT;
690         uint32_t chunk_ids[5];
691         uint64_t chunk_offsets[5];
692         int num_chunks;
693         int num_extra_edges;
694         struct commit_list *parent;
695
696         oids.nr = 0;
697         oids.alloc = approximate_object_count() / 4;
698
699         if (append) {
700                 prepare_commit_graph_one(the_repository, obj_dir);
701                 if (the_repository->objects->commit_graph)
702                         oids.alloc += the_repository->objects->commit_graph->num_commits;
703         }
704
705         if (oids.alloc < 1024)
706                 oids.alloc = 1024;
707         ALLOC_ARRAY(oids.list, oids.alloc);
708
709         if (append && the_repository->objects->commit_graph) {
710                 struct commit_graph *commit_graph =
711                         the_repository->objects->commit_graph;
712                 for (i = 0; i < commit_graph->num_commits; i++) {
713                         const unsigned char *hash = commit_graph->chunk_oid_lookup +
714                                 commit_graph->hash_len * i;
715                         hashcpy(oids.list[oids.nr++].hash, hash);
716                 }
717         }
718
719         if (pack_indexes) {
720                 struct strbuf packname = STRBUF_INIT;
721                 int dirlen;
722                 strbuf_addf(&packname, "%s/pack/", obj_dir);
723                 dirlen = packname.len;
724                 for (i = 0; i < pack_indexes->nr; i++) {
725                         struct packed_git *p;
726                         strbuf_setlen(&packname, dirlen);
727                         strbuf_addstr(&packname, pack_indexes->items[i].string);
728                         p = add_packed_git(packname.buf, packname.len, 1);
729                         if (!p)
730                                 die("error adding pack %s", packname.buf);
731                         if (open_pack_index(p))
732                                 die("error opening index for %s", packname.buf);
733                         for_each_object_in_pack(p, add_packed_commits, &oids);
734                         close_pack(p);
735                 }
736                 strbuf_release(&packname);
737         }
738
739         if (commit_hex) {
740                 for (i = 0; i < commit_hex->nr; i++) {
741                         const char *end;
742                         struct object_id oid;
743                         struct commit *result;
744
745                         if (commit_hex->items[i].string &&
746                             parse_oid_hex(commit_hex->items[i].string, &oid, &end))
747                                 continue;
748
749                         result = lookup_commit_reference_gently(the_repository, &oid, 1);
750
751                         if (result) {
752                                 ALLOC_GROW(oids.list, oids.nr + 1, oids.alloc);
753                                 oidcpy(&oids.list[oids.nr], &(result->object.oid));
754                                 oids.nr++;
755                         }
756                 }
757         }
758
759         if (!pack_indexes && !commit_hex)
760                 for_each_packed_object(add_packed_commits, &oids, 0);
761
762         close_reachable(&oids);
763
764         QSORT(oids.list, oids.nr, commit_compare);
765
766         count_distinct = 1;
767         for (i = 1; i < oids.nr; i++) {
768                 if (oidcmp(&oids.list[i-1], &oids.list[i]))
769                         count_distinct++;
770         }
771
772         if (count_distinct >= GRAPH_PARENT_MISSING)
773                 die(_("the commit graph format cannot write %d commits"), count_distinct);
774
775         commits.nr = 0;
776         commits.alloc = count_distinct;
777         ALLOC_ARRAY(commits.list, commits.alloc);
778
779         num_extra_edges = 0;
780         for (i = 0; i < oids.nr; i++) {
781                 int num_parents = 0;
782                 if (i > 0 && !oidcmp(&oids.list[i-1], &oids.list[i]))
783                         continue;
784
785                 commits.list[commits.nr] = lookup_commit(the_repository, &oids.list[i]);
786                 parse_commit(commits.list[commits.nr]);
787
788                 for (parent = commits.list[commits.nr]->parents;
789                      parent; parent = parent->next)
790                         num_parents++;
791
792                 if (num_parents > 2)
793                         num_extra_edges += num_parents - 1;
794
795                 commits.nr++;
796         }
797         num_chunks = num_extra_edges ? 4 : 3;
798
799         if (commits.nr >= GRAPH_PARENT_MISSING)
800                 die(_("too many commits to write graph"));
801
802         compute_generation_numbers(&commits);
803
804         graph_name = get_commit_graph_filename(obj_dir);
805         if (safe_create_leading_directories(graph_name))
806                 die_errno(_("unable to create leading directories of %s"),
807                           graph_name);
808
809         hold_lock_file_for_update(&lk, graph_name, LOCK_DIE_ON_ERROR);
810         f = hashfd(lk.tempfile->fd, lk.tempfile->filename.buf);
811
812         hashwrite_be32(f, GRAPH_SIGNATURE);
813
814         hashwrite_u8(f, GRAPH_VERSION);
815         hashwrite_u8(f, GRAPH_OID_VERSION);
816         hashwrite_u8(f, num_chunks);
817         hashwrite_u8(f, 0); /* unused padding byte */
818
819         chunk_ids[0] = GRAPH_CHUNKID_OIDFANOUT;
820         chunk_ids[1] = GRAPH_CHUNKID_OIDLOOKUP;
821         chunk_ids[2] = GRAPH_CHUNKID_DATA;
822         if (num_extra_edges)
823                 chunk_ids[3] = GRAPH_CHUNKID_LARGEEDGES;
824         else
825                 chunk_ids[3] = 0;
826         chunk_ids[4] = 0;
827
828         chunk_offsets[0] = 8 + (num_chunks + 1) * GRAPH_CHUNKLOOKUP_WIDTH;
829         chunk_offsets[1] = chunk_offsets[0] + GRAPH_FANOUT_SIZE;
830         chunk_offsets[2] = chunk_offsets[1] + GRAPH_OID_LEN * commits.nr;
831         chunk_offsets[3] = chunk_offsets[2] + (GRAPH_OID_LEN + 16) * commits.nr;
832         chunk_offsets[4] = chunk_offsets[3] + 4 * num_extra_edges;
833
834         for (i = 0; i <= num_chunks; i++) {
835                 uint32_t chunk_write[3];
836
837                 chunk_write[0] = htonl(chunk_ids[i]);
838                 chunk_write[1] = htonl(chunk_offsets[i] >> 32);
839                 chunk_write[2] = htonl(chunk_offsets[i] & 0xffffffff);
840                 hashwrite(f, chunk_write, 12);
841         }
842
843         write_graph_chunk_fanout(f, commits.list, commits.nr);
844         write_graph_chunk_oids(f, GRAPH_OID_LEN, commits.list, commits.nr);
845         write_graph_chunk_data(f, GRAPH_OID_LEN, commits.list, commits.nr);
846         write_graph_chunk_large_edges(f, commits.list, commits.nr);
847
848         close_commit_graph();
849         finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_FSYNC);
850         commit_lock_file(&lk);
851
852         free(oids.list);
853         oids.alloc = 0;
854         oids.nr = 0;
855 }
856
857 #define VERIFY_COMMIT_GRAPH_ERROR_HASH 2
858 static int verify_commit_graph_error;
859
860 static void graph_report(const char *fmt, ...)
861 {
862         va_list ap;
863
864         verify_commit_graph_error = 1;
865         va_start(ap, fmt);
866         vfprintf(stderr, fmt, ap);
867         fprintf(stderr, "\n");
868         va_end(ap);
869 }
870
871 #define GENERATION_ZERO_EXISTS 1
872 #define GENERATION_NUMBER_EXISTS 2
873
874 int verify_commit_graph(struct repository *r, struct commit_graph *g)
875 {
876         uint32_t i, cur_fanout_pos = 0;
877         struct object_id prev_oid, cur_oid, checksum;
878         int generation_zero = 0;
879         struct hashfile *f;
880         int devnull;
881
882         if (!g) {
883                 graph_report("no commit-graph file loaded");
884                 return 1;
885         }
886
887         verify_commit_graph_error = 0;
888
889         if (!g->chunk_oid_fanout)
890                 graph_report("commit-graph is missing the OID Fanout chunk");
891         if (!g->chunk_oid_lookup)
892                 graph_report("commit-graph is missing the OID Lookup chunk");
893         if (!g->chunk_commit_data)
894                 graph_report("commit-graph is missing the Commit Data chunk");
895
896         if (verify_commit_graph_error)
897                 return verify_commit_graph_error;
898
899         devnull = open("/dev/null", O_WRONLY);
900         f = hashfd(devnull, NULL);
901         hashwrite(f, g->data, g->data_len - g->hash_len);
902         finalize_hashfile(f, checksum.hash, CSUM_CLOSE);
903         if (hashcmp(checksum.hash, g->data + g->data_len - g->hash_len)) {
904                 graph_report(_("the commit-graph file has incorrect checksum and is likely corrupt"));
905                 verify_commit_graph_error = VERIFY_COMMIT_GRAPH_ERROR_HASH;
906         }
907
908         for (i = 0; i < g->num_commits; i++) {
909                 struct commit *graph_commit;
910
911                 hashcpy(cur_oid.hash, g->chunk_oid_lookup + g->hash_len * i);
912
913                 if (i && oidcmp(&prev_oid, &cur_oid) >= 0)
914                         graph_report("commit-graph has incorrect OID order: %s then %s",
915                                      oid_to_hex(&prev_oid),
916                                      oid_to_hex(&cur_oid));
917
918                 oidcpy(&prev_oid, &cur_oid);
919
920                 while (cur_oid.hash[0] > cur_fanout_pos) {
921                         uint32_t fanout_value = get_be32(g->chunk_oid_fanout + cur_fanout_pos);
922
923                         if (i != fanout_value)
924                                 graph_report("commit-graph has incorrect fanout value: fanout[%d] = %u != %u",
925                                              cur_fanout_pos, fanout_value, i);
926                         cur_fanout_pos++;
927                 }
928
929                 graph_commit = lookup_commit(r, &cur_oid);
930                 if (!parse_commit_in_graph_one(g, graph_commit))
931                         graph_report("failed to parse %s from commit-graph",
932                                      oid_to_hex(&cur_oid));
933         }
934
935         while (cur_fanout_pos < 256) {
936                 uint32_t fanout_value = get_be32(g->chunk_oid_fanout + cur_fanout_pos);
937
938                 if (g->num_commits != fanout_value)
939                         graph_report("commit-graph has incorrect fanout value: fanout[%d] = %u != %u",
940                                      cur_fanout_pos, fanout_value, i);
941
942                 cur_fanout_pos++;
943         }
944
945         if (verify_commit_graph_error & ~VERIFY_COMMIT_GRAPH_ERROR_HASH)
946                 return verify_commit_graph_error;
947
948         for (i = 0; i < g->num_commits; i++) {
949                 struct commit *graph_commit, *odb_commit;
950                 struct commit_list *graph_parents, *odb_parents;
951                 uint32_t max_generation = 0;
952
953                 hashcpy(cur_oid.hash, g->chunk_oid_lookup + g->hash_len * i);
954
955                 graph_commit = lookup_commit(r, &cur_oid);
956                 odb_commit = (struct commit *)create_object(r, cur_oid.hash, alloc_commit_node(r));
957                 if (parse_commit_internal(odb_commit, 0, 0)) {
958                         graph_report("failed to parse %s from object database",
959                                      oid_to_hex(&cur_oid));
960                         continue;
961                 }
962
963                 if (oidcmp(&get_commit_tree_in_graph_one(g, graph_commit)->object.oid,
964                            get_commit_tree_oid(odb_commit)))
965                         graph_report("root tree OID for commit %s in commit-graph is %s != %s",
966                                      oid_to_hex(&cur_oid),
967                                      oid_to_hex(get_commit_tree_oid(graph_commit)),
968                                      oid_to_hex(get_commit_tree_oid(odb_commit)));
969
970                 graph_parents = graph_commit->parents;
971                 odb_parents = odb_commit->parents;
972
973                 while (graph_parents) {
974                         if (odb_parents == NULL) {
975                                 graph_report("commit-graph parent list for commit %s is too long",
976                                              oid_to_hex(&cur_oid));
977                                 break;
978                         }
979
980                         if (oidcmp(&graph_parents->item->object.oid, &odb_parents->item->object.oid))
981                                 graph_report("commit-graph parent for %s is %s != %s",
982                                              oid_to_hex(&cur_oid),
983                                              oid_to_hex(&graph_parents->item->object.oid),
984                                              oid_to_hex(&odb_parents->item->object.oid));
985
986                         if (graph_parents->item->generation > max_generation)
987                                 max_generation = graph_parents->item->generation;
988
989                         graph_parents = graph_parents->next;
990                         odb_parents = odb_parents->next;
991                 }
992
993                 if (odb_parents != NULL)
994                         graph_report("commit-graph parent list for commit %s terminates early",
995                                      oid_to_hex(&cur_oid));
996
997                 if (!graph_commit->generation) {
998                         if (generation_zero == GENERATION_NUMBER_EXISTS)
999                                 graph_report("commit-graph has generation number zero for commit %s, but non-zero elsewhere",
1000                                              oid_to_hex(&cur_oid));
1001                         generation_zero = GENERATION_ZERO_EXISTS;
1002                 } else if (generation_zero == GENERATION_ZERO_EXISTS)
1003                         graph_report("commit-graph has non-zero generation number for commit %s, but zero elsewhere",
1004                                      oid_to_hex(&cur_oid));
1005
1006                 if (generation_zero == GENERATION_ZERO_EXISTS)
1007                         continue;
1008
1009                 /*
1010                  * If one of our parents has generation GENERATION_NUMBER_MAX, then
1011                  * our generation is also GENERATION_NUMBER_MAX. Decrement to avoid
1012                  * extra logic in the following condition.
1013                  */
1014                 if (max_generation == GENERATION_NUMBER_MAX)
1015                         max_generation--;
1016
1017                 if (graph_commit->generation != max_generation + 1)
1018                         graph_report("commit-graph generation for commit %s is %u != %u",
1019                                      oid_to_hex(&cur_oid),
1020                                      graph_commit->generation,
1021                                      max_generation + 1);
1022
1023                 if (graph_commit->date != odb_commit->date)
1024                         graph_report("commit date for commit %s in commit-graph is %"PRItime" != %"PRItime,
1025                                      oid_to_hex(&cur_oid),
1026                                      graph_commit->date,
1027                                      odb_commit->date);
1028         }
1029
1030         return verify_commit_graph_error;
1031 }
1032
1033 void free_commit_graph(struct commit_graph *g)
1034 {
1035         if (!g)
1036                 return;
1037         if (g->graph_fd >= 0) {
1038                 munmap((void *)g->data, g->data_len);
1039                 g->data = NULL;
1040                 close(g->graph_fd);
1041         }
1042         free(g);
1043 }