commit-graph.con commit Merge branch 'jc/clean-after-sanity-tests' (1840443)
   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 "revision.h"
  11#include "sha1-lookup.h"
  12#include "commit-graph.h"
  13#include "object-store.h"
  14
  15#define GRAPH_SIGNATURE 0x43475048 /* "CGPH" */
  16#define GRAPH_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
  17#define GRAPH_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
  18#define GRAPH_CHUNKID_DATA 0x43444154 /* "CDAT" */
  19#define GRAPH_CHUNKID_LARGEEDGES 0x45444745 /* "EDGE" */
  20
  21#define GRAPH_DATA_WIDTH 36
  22
  23#define GRAPH_VERSION_1 0x1
  24#define GRAPH_VERSION GRAPH_VERSION_1
  25
  26#define GRAPH_OID_VERSION_SHA1 1
  27#define GRAPH_OID_LEN_SHA1 GIT_SHA1_RAWSZ
  28#define GRAPH_OID_VERSION GRAPH_OID_VERSION_SHA1
  29#define GRAPH_OID_LEN GRAPH_OID_LEN_SHA1
  30
  31#define GRAPH_OCTOPUS_EDGES_NEEDED 0x80000000
  32#define GRAPH_PARENT_MISSING 0x7fffffff
  33#define GRAPH_EDGE_LAST_MASK 0x7fffffff
  34#define GRAPH_PARENT_NONE 0x70000000
  35
  36#define GRAPH_LAST_EDGE 0x80000000
  37
  38#define GRAPH_FANOUT_SIZE (4 * 256)
  39#define GRAPH_CHUNKLOOKUP_WIDTH 12
  40#define GRAPH_MIN_SIZE (5 * GRAPH_CHUNKLOOKUP_WIDTH + GRAPH_FANOUT_SIZE + \
  41                        GRAPH_OID_LEN + 8)
  42
  43char *get_commit_graph_filename(const char *obj_dir)
  44{
  45        return xstrfmt("%s/info/commit-graph", obj_dir);
  46}
  47
  48static struct commit_graph *alloc_commit_graph(void)
  49{
  50        struct commit_graph *g = xcalloc(1, sizeof(*g));
  51        g->graph_fd = -1;
  52
  53        return g;
  54}
  55
  56struct commit_graph *load_commit_graph_one(const char *graph_file)
  57{
  58        void *graph_map;
  59        const unsigned char *data, *chunk_lookup;
  60        size_t graph_size;
  61        struct stat st;
  62        uint32_t i;
  63        struct commit_graph *graph;
  64        int fd = git_open(graph_file);
  65        uint64_t last_chunk_offset;
  66        uint32_t last_chunk_id;
  67        uint32_t graph_signature;
  68        unsigned char graph_version, hash_version;
  69
  70        if (fd < 0)
  71                return NULL;
  72        if (fstat(fd, &st)) {
  73                close(fd);
  74                return NULL;
  75        }
  76        graph_size = xsize_t(st.st_size);
  77
  78        if (graph_size < GRAPH_MIN_SIZE) {
  79                close(fd);
  80                die("graph file %s is too small", graph_file);
  81        }
  82        graph_map = xmmap(NULL, graph_size, PROT_READ, MAP_PRIVATE, fd, 0);
  83        data = (const unsigned char *)graph_map;
  84
  85        graph_signature = get_be32(data);
  86        if (graph_signature != GRAPH_SIGNATURE) {
  87                error("graph signature %X does not match signature %X",
  88                      graph_signature, GRAPH_SIGNATURE);
  89                goto cleanup_fail;
  90        }
  91
  92        graph_version = *(unsigned char*)(data + 4);
  93        if (graph_version != GRAPH_VERSION) {
  94                error("graph version %X does not match version %X",
  95                      graph_version, GRAPH_VERSION);
  96                goto cleanup_fail;
  97        }
  98
  99        hash_version = *(unsigned char*)(data + 5);
 100        if (hash_version != GRAPH_OID_VERSION) {
 101                error("hash version %X does not match version %X",
 102                      hash_version, GRAPH_OID_VERSION);
 103                goto cleanup_fail;
 104        }
 105
 106        graph = alloc_commit_graph();
 107
 108        graph->hash_len = GRAPH_OID_LEN;
 109        graph->num_chunks = *(unsigned char*)(data + 6);
 110        graph->graph_fd = fd;
 111        graph->data = graph_map;
 112        graph->data_len = graph_size;
 113
 114        last_chunk_id = 0;
 115        last_chunk_offset = 8;
 116        chunk_lookup = data + 8;
 117        for (i = 0; i < graph->num_chunks; i++) {
 118                uint32_t chunk_id = get_be32(chunk_lookup + 0);
 119                uint64_t chunk_offset = get_be64(chunk_lookup + 4);
 120                int chunk_repeated = 0;
 121
 122                chunk_lookup += GRAPH_CHUNKLOOKUP_WIDTH;
 123
 124                if (chunk_offset > graph_size - GIT_MAX_RAWSZ) {
 125                        error("improper chunk offset %08x%08x", (uint32_t)(chunk_offset >> 32),
 126                              (uint32_t)chunk_offset);
 127                        goto cleanup_fail;
 128                }
 129
 130                switch (chunk_id) {
 131                case GRAPH_CHUNKID_OIDFANOUT:
 132                        if (graph->chunk_oid_fanout)
 133                                chunk_repeated = 1;
 134                        else
 135                                graph->chunk_oid_fanout = (uint32_t*)(data + chunk_offset);
 136                        break;
 137
 138                case GRAPH_CHUNKID_OIDLOOKUP:
 139                        if (graph->chunk_oid_lookup)
 140                                chunk_repeated = 1;
 141                        else
 142                                graph->chunk_oid_lookup = data + chunk_offset;
 143                        break;
 144
 145                case GRAPH_CHUNKID_DATA:
 146                        if (graph->chunk_commit_data)
 147                                chunk_repeated = 1;
 148                        else
 149                                graph->chunk_commit_data = data + chunk_offset;
 150                        break;
 151
 152                case GRAPH_CHUNKID_LARGEEDGES:
 153                        if (graph->chunk_large_edges)
 154                                chunk_repeated = 1;
 155                        else
 156                                graph->chunk_large_edges = data + chunk_offset;
 157                        break;
 158                }
 159
 160                if (chunk_repeated) {
 161                        error("chunk id %08x appears multiple times", chunk_id);
 162                        goto cleanup_fail;
 163                }
 164
 165                if (last_chunk_id == GRAPH_CHUNKID_OIDLOOKUP)
 166                {
 167                        graph->num_commits = (chunk_offset - last_chunk_offset)
 168                                             / graph->hash_len;
 169                }
 170
 171                last_chunk_id = chunk_id;
 172                last_chunk_offset = chunk_offset;
 173        }
 174
 175        return graph;
 176
 177cleanup_fail:
 178        munmap(graph_map, graph_size);
 179        close(fd);
 180        exit(1);
 181}
 182
 183/* global storage */
 184static struct commit_graph *commit_graph = NULL;
 185
 186static void prepare_commit_graph_one(const char *obj_dir)
 187{
 188        char *graph_name;
 189
 190        if (commit_graph)
 191                return;
 192
 193        graph_name = get_commit_graph_filename(obj_dir);
 194        commit_graph = load_commit_graph_one(graph_name);
 195
 196        FREE_AND_NULL(graph_name);
 197}
 198
 199static int prepare_commit_graph_run_once = 0;
 200static void prepare_commit_graph(void)
 201{
 202        struct alternate_object_database *alt;
 203        char *obj_dir;
 204
 205        if (prepare_commit_graph_run_once)
 206                return;
 207        prepare_commit_graph_run_once = 1;
 208
 209        obj_dir = get_object_directory();
 210        prepare_commit_graph_one(obj_dir);
 211        prepare_alt_odb(the_repository);
 212        for (alt = the_repository->objects->alt_odb_list;
 213             !commit_graph && alt;
 214             alt = alt->next)
 215                prepare_commit_graph_one(alt->path);
 216}
 217
 218static void close_commit_graph(void)
 219{
 220        if (!commit_graph)
 221                return;
 222
 223        if (commit_graph->graph_fd >= 0) {
 224                munmap((void *)commit_graph->data, commit_graph->data_len);
 225                commit_graph->data = NULL;
 226                close(commit_graph->graph_fd);
 227        }
 228
 229        FREE_AND_NULL(commit_graph);
 230}
 231
 232static int bsearch_graph(struct commit_graph *g, struct object_id *oid, uint32_t *pos)
 233{
 234        return bsearch_hash(oid->hash, g->chunk_oid_fanout,
 235                            g->chunk_oid_lookup, g->hash_len, pos);
 236}
 237
 238static struct commit_list **insert_parent_or_die(struct commit_graph *g,
 239                                                 uint64_t pos,
 240                                                 struct commit_list **pptr)
 241{
 242        struct commit *c;
 243        struct object_id oid;
 244        hashcpy(oid.hash, g->chunk_oid_lookup + g->hash_len * pos);
 245        c = lookup_commit(&oid);
 246        if (!c)
 247                die("could not find commit %s", oid_to_hex(&oid));
 248        c->graph_pos = pos;
 249        return &commit_list_insert(c, pptr)->next;
 250}
 251
 252static void fill_commit_graph_info(struct commit *item, struct commit_graph *g, uint32_t pos)
 253{
 254        const unsigned char *commit_data = g->chunk_commit_data + GRAPH_DATA_WIDTH * pos;
 255        item->graph_pos = pos;
 256        item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
 257}
 258
 259static int fill_commit_in_graph(struct commit *item, struct commit_graph *g, uint32_t pos)
 260{
 261        uint32_t edge_value;
 262        uint32_t *parent_data_ptr;
 263        uint64_t date_low, date_high;
 264        struct commit_list **pptr;
 265        const unsigned char *commit_data = g->chunk_commit_data + (g->hash_len + 16) * pos;
 266
 267        item->object.parsed = 1;
 268        item->graph_pos = pos;
 269
 270        item->maybe_tree = NULL;
 271
 272        date_high = get_be32(commit_data + g->hash_len + 8) & 0x3;
 273        date_low = get_be32(commit_data + g->hash_len + 12);
 274        item->date = (timestamp_t)((date_high << 32) | date_low);
 275
 276        item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
 277
 278        pptr = &item->parents;
 279
 280        edge_value = get_be32(commit_data + g->hash_len);
 281        if (edge_value == GRAPH_PARENT_NONE)
 282                return 1;
 283        pptr = insert_parent_or_die(g, edge_value, pptr);
 284
 285        edge_value = get_be32(commit_data + g->hash_len + 4);
 286        if (edge_value == GRAPH_PARENT_NONE)
 287                return 1;
 288        if (!(edge_value & GRAPH_OCTOPUS_EDGES_NEEDED)) {
 289                pptr = insert_parent_or_die(g, edge_value, pptr);
 290                return 1;
 291        }
 292
 293        parent_data_ptr = (uint32_t*)(g->chunk_large_edges +
 294                          4 * (uint64_t)(edge_value & GRAPH_EDGE_LAST_MASK));
 295        do {
 296                edge_value = get_be32(parent_data_ptr);
 297                pptr = insert_parent_or_die(g,
 298                                            edge_value & GRAPH_EDGE_LAST_MASK,
 299                                            pptr);
 300                parent_data_ptr++;
 301        } while (!(edge_value & GRAPH_LAST_EDGE));
 302
 303        return 1;
 304}
 305
 306static int find_commit_in_graph(struct commit *item, struct commit_graph *g, uint32_t *pos)
 307{
 308        if (item->graph_pos != COMMIT_NOT_FROM_GRAPH) {
 309                *pos = item->graph_pos;
 310                return 1;
 311        } else {
 312                return bsearch_graph(g, &(item->object.oid), pos);
 313        }
 314}
 315
 316int parse_commit_in_graph(struct commit *item)
 317{
 318        uint32_t pos;
 319
 320        if (!core_commit_graph)
 321                return 0;
 322        if (item->object.parsed)
 323                return 1;
 324        prepare_commit_graph();
 325        if (commit_graph && find_commit_in_graph(item, commit_graph, &pos))
 326                return fill_commit_in_graph(item, commit_graph, pos);
 327        return 0;
 328}
 329
 330void load_commit_graph_info(struct commit *item)
 331{
 332        uint32_t pos;
 333        if (!core_commit_graph)
 334                return;
 335        prepare_commit_graph();
 336        if (commit_graph && find_commit_in_graph(item, commit_graph, &pos))
 337                fill_commit_graph_info(item, commit_graph, pos);
 338}
 339
 340static struct tree *load_tree_for_commit(struct commit_graph *g, struct commit *c)
 341{
 342        struct object_id oid;
 343        const unsigned char *commit_data = g->chunk_commit_data +
 344                                           GRAPH_DATA_WIDTH * (c->graph_pos);
 345
 346        hashcpy(oid.hash, commit_data);
 347        c->maybe_tree = lookup_tree(&oid);
 348
 349        return c->maybe_tree;
 350}
 351
 352struct tree *get_commit_tree_in_graph(const struct commit *c)
 353{
 354        if (c->maybe_tree)
 355                return c->maybe_tree;
 356        if (c->graph_pos == COMMIT_NOT_FROM_GRAPH)
 357                BUG("get_commit_tree_in_graph called from non-commit-graph commit");
 358
 359        return load_tree_for_commit(commit_graph, (struct commit *)c);
 360}
 361
 362static void write_graph_chunk_fanout(struct hashfile *f,
 363                                     struct commit **commits,
 364                                     int nr_commits)
 365{
 366        int i, count = 0;
 367        struct commit **list = commits;
 368
 369        /*
 370         * Write the first-level table (the list is sorted,
 371         * but we use a 256-entry lookup to be able to avoid
 372         * having to do eight extra binary search iterations).
 373         */
 374        for (i = 0; i < 256; i++) {
 375                while (count < nr_commits) {
 376                        if ((*list)->object.oid.hash[0] != i)
 377                                break;
 378                        count++;
 379                        list++;
 380                }
 381
 382                hashwrite_be32(f, count);
 383        }
 384}
 385
 386static void write_graph_chunk_oids(struct hashfile *f, int hash_len,
 387                                   struct commit **commits, int nr_commits)
 388{
 389        struct commit **list = commits;
 390        int count;
 391        for (count = 0; count < nr_commits; count++, list++)
 392                hashwrite(f, (*list)->object.oid.hash, (int)hash_len);
 393}
 394
 395static const unsigned char *commit_to_sha1(size_t index, void *table)
 396{
 397        struct commit **commits = table;
 398        return commits[index]->object.oid.hash;
 399}
 400
 401static void write_graph_chunk_data(struct hashfile *f, int hash_len,
 402                                   struct commit **commits, int nr_commits)
 403{
 404        struct commit **list = commits;
 405        struct commit **last = commits + nr_commits;
 406        uint32_t num_extra_edges = 0;
 407
 408        while (list < last) {
 409                struct commit_list *parent;
 410                int edge_value;
 411                uint32_t packedDate[2];
 412
 413                parse_commit(*list);
 414                hashwrite(f, get_commit_tree_oid(*list)->hash, hash_len);
 415
 416                parent = (*list)->parents;
 417
 418                if (!parent)
 419                        edge_value = GRAPH_PARENT_NONE;
 420                else {
 421                        edge_value = sha1_pos(parent->item->object.oid.hash,
 422                                              commits,
 423                                              nr_commits,
 424                                              commit_to_sha1);
 425
 426                        if (edge_value < 0)
 427                                edge_value = GRAPH_PARENT_MISSING;
 428                }
 429
 430                hashwrite_be32(f, edge_value);
 431
 432                if (parent)
 433                        parent = parent->next;
 434
 435                if (!parent)
 436                        edge_value = GRAPH_PARENT_NONE;
 437                else if (parent->next)
 438                        edge_value = GRAPH_OCTOPUS_EDGES_NEEDED | num_extra_edges;
 439                else {
 440                        edge_value = sha1_pos(parent->item->object.oid.hash,
 441                                              commits,
 442                                              nr_commits,
 443                                              commit_to_sha1);
 444                        if (edge_value < 0)
 445                                edge_value = GRAPH_PARENT_MISSING;
 446                }
 447
 448                hashwrite_be32(f, edge_value);
 449
 450                if (edge_value & GRAPH_OCTOPUS_EDGES_NEEDED) {
 451                        do {
 452                                num_extra_edges++;
 453                                parent = parent->next;
 454                        } while (parent);
 455                }
 456
 457                if (sizeof((*list)->date) > 4)
 458                        packedDate[0] = htonl(((*list)->date >> 32) & 0x3);
 459                else
 460                        packedDate[0] = 0;
 461
 462                packedDate[0] |= htonl((*list)->generation << 2);
 463
 464                packedDate[1] = htonl((*list)->date);
 465                hashwrite(f, packedDate, 8);
 466
 467                list++;
 468        }
 469}
 470
 471static void write_graph_chunk_large_edges(struct hashfile *f,
 472                                          struct commit **commits,
 473                                          int nr_commits)
 474{
 475        struct commit **list = commits;
 476        struct commit **last = commits + nr_commits;
 477        struct commit_list *parent;
 478
 479        while (list < last) {
 480                int num_parents = 0;
 481                for (parent = (*list)->parents; num_parents < 3 && parent;
 482                     parent = parent->next)
 483                        num_parents++;
 484
 485                if (num_parents <= 2) {
 486                        list++;
 487                        continue;
 488                }
 489
 490                /* Since num_parents > 2, this initializer is safe. */
 491                for (parent = (*list)->parents->next; parent; parent = parent->next) {
 492                        int edge_value = sha1_pos(parent->item->object.oid.hash,
 493                                                  commits,
 494                                                  nr_commits,
 495                                                  commit_to_sha1);
 496
 497                        if (edge_value < 0)
 498                                edge_value = GRAPH_PARENT_MISSING;
 499                        else if (!parent->next)
 500                                edge_value |= GRAPH_LAST_EDGE;
 501
 502                        hashwrite_be32(f, edge_value);
 503                }
 504
 505                list++;
 506        }
 507}
 508
 509static int commit_compare(const void *_a, const void *_b)
 510{
 511        const struct object_id *a = (const struct object_id *)_a;
 512        const struct object_id *b = (const struct object_id *)_b;
 513        return oidcmp(a, b);
 514}
 515
 516struct packed_commit_list {
 517        struct commit **list;
 518        int nr;
 519        int alloc;
 520};
 521
 522struct packed_oid_list {
 523        struct object_id *list;
 524        int nr;
 525        int alloc;
 526};
 527
 528static int add_packed_commits(const struct object_id *oid,
 529                              struct packed_git *pack,
 530                              uint32_t pos,
 531                              void *data)
 532{
 533        struct packed_oid_list *list = (struct packed_oid_list*)data;
 534        enum object_type type;
 535        off_t offset = nth_packed_object_offset(pack, pos);
 536        struct object_info oi = OBJECT_INFO_INIT;
 537
 538        oi.typep = &type;
 539        if (packed_object_info(the_repository, pack, offset, &oi) < 0)
 540                die("unable to get type of object %s", oid_to_hex(oid));
 541
 542        if (type != OBJ_COMMIT)
 543                return 0;
 544
 545        ALLOC_GROW(list->list, list->nr + 1, list->alloc);
 546        oidcpy(&(list->list[list->nr]), oid);
 547        list->nr++;
 548
 549        return 0;
 550}
 551
 552static void add_missing_parents(struct packed_oid_list *oids, struct commit *commit)
 553{
 554        struct commit_list *parent;
 555        for (parent = commit->parents; parent; parent = parent->next) {
 556                if (!(parent->item->object.flags & UNINTERESTING)) {
 557                        ALLOC_GROW(oids->list, oids->nr + 1, oids->alloc);
 558                        oidcpy(&oids->list[oids->nr], &(parent->item->object.oid));
 559                        oids->nr++;
 560                        parent->item->object.flags |= UNINTERESTING;
 561                }
 562        }
 563}
 564
 565static void close_reachable(struct packed_oid_list *oids)
 566{
 567        int i;
 568        struct commit *commit;
 569
 570        for (i = 0; i < oids->nr; i++) {
 571                commit = lookup_commit(&oids->list[i]);
 572                if (commit)
 573                        commit->object.flags |= UNINTERESTING;
 574        }
 575
 576        /*
 577         * As this loop runs, oids->nr may grow, but not more
 578         * than the number of missing commits in the reachable
 579         * closure.
 580         */
 581        for (i = 0; i < oids->nr; i++) {
 582                commit = lookup_commit(&oids->list[i]);
 583
 584                if (commit && !parse_commit(commit))
 585                        add_missing_parents(oids, commit);
 586        }
 587
 588        for (i = 0; i < oids->nr; i++) {
 589                commit = lookup_commit(&oids->list[i]);
 590
 591                if (commit)
 592                        commit->object.flags &= ~UNINTERESTING;
 593        }
 594}
 595
 596static void compute_generation_numbers(struct packed_commit_list* commits)
 597{
 598        int i;
 599        struct commit_list *list = NULL;
 600
 601        for (i = 0; i < commits->nr; i++) {
 602                if (commits->list[i]->generation != GENERATION_NUMBER_INFINITY &&
 603                    commits->list[i]->generation != GENERATION_NUMBER_ZERO)
 604                        continue;
 605
 606                commit_list_insert(commits->list[i], &list);
 607                while (list) {
 608                        struct commit *current = list->item;
 609                        struct commit_list *parent;
 610                        int all_parents_computed = 1;
 611                        uint32_t max_generation = 0;
 612
 613                        for (parent = current->parents; parent; parent = parent->next) {
 614                                if (parent->item->generation == GENERATION_NUMBER_INFINITY ||
 615                                    parent->item->generation == GENERATION_NUMBER_ZERO) {
 616                                        all_parents_computed = 0;
 617                                        commit_list_insert(parent->item, &list);
 618                                        break;
 619                                } else if (parent->item->generation > max_generation) {
 620                                        max_generation = parent->item->generation;
 621                                }
 622                        }
 623
 624                        if (all_parents_computed) {
 625                                current->generation = max_generation + 1;
 626                                pop_commit(&list);
 627
 628                                if (current->generation > GENERATION_NUMBER_MAX)
 629                                        current->generation = GENERATION_NUMBER_MAX;
 630                        }
 631                }
 632        }
 633}
 634
 635void write_commit_graph(const char *obj_dir,
 636                        const char **pack_indexes,
 637                        int nr_packs,
 638                        const char **commit_hex,
 639                        int nr_commits,
 640                        int append)
 641{
 642        struct packed_oid_list oids;
 643        struct packed_commit_list commits;
 644        struct hashfile *f;
 645        uint32_t i, count_distinct = 0;
 646        char *graph_name;
 647        struct lock_file lk = LOCK_INIT;
 648        uint32_t chunk_ids[5];
 649        uint64_t chunk_offsets[5];
 650        int num_chunks;
 651        int num_extra_edges;
 652        struct commit_list *parent;
 653
 654        oids.nr = 0;
 655        oids.alloc = approximate_object_count() / 4;
 656
 657        if (append) {
 658                prepare_commit_graph_one(obj_dir);
 659                if (commit_graph)
 660                        oids.alloc += commit_graph->num_commits;
 661        }
 662
 663        if (oids.alloc < 1024)
 664                oids.alloc = 1024;
 665        ALLOC_ARRAY(oids.list, oids.alloc);
 666
 667        if (append && commit_graph) {
 668                for (i = 0; i < commit_graph->num_commits; i++) {
 669                        const unsigned char *hash = commit_graph->chunk_oid_lookup +
 670                                commit_graph->hash_len * i;
 671                        hashcpy(oids.list[oids.nr++].hash, hash);
 672                }
 673        }
 674
 675        if (pack_indexes) {
 676                struct strbuf packname = STRBUF_INIT;
 677                int dirlen;
 678                strbuf_addf(&packname, "%s/pack/", obj_dir);
 679                dirlen = packname.len;
 680                for (i = 0; i < nr_packs; i++) {
 681                        struct packed_git *p;
 682                        strbuf_setlen(&packname, dirlen);
 683                        strbuf_addstr(&packname, pack_indexes[i]);
 684                        p = add_packed_git(packname.buf, packname.len, 1);
 685                        if (!p)
 686                                die("error adding pack %s", packname.buf);
 687                        if (open_pack_index(p))
 688                                die("error opening index for %s", packname.buf);
 689                        for_each_object_in_pack(p, add_packed_commits, &oids);
 690                        close_pack(p);
 691                }
 692                strbuf_release(&packname);
 693        }
 694
 695        if (commit_hex) {
 696                for (i = 0; i < nr_commits; i++) {
 697                        const char *end;
 698                        struct object_id oid;
 699                        struct commit *result;
 700
 701                        if (commit_hex[i] && parse_oid_hex(commit_hex[i], &oid, &end))
 702                                continue;
 703
 704                        result = lookup_commit_reference_gently(&oid, 1);
 705
 706                        if (result) {
 707                                ALLOC_GROW(oids.list, oids.nr + 1, oids.alloc);
 708                                oidcpy(&oids.list[oids.nr], &(result->object.oid));
 709                                oids.nr++;
 710                        }
 711                }
 712        }
 713
 714        if (!pack_indexes && !commit_hex)
 715                for_each_packed_object(add_packed_commits, &oids, 0);
 716
 717        close_reachable(&oids);
 718
 719        QSORT(oids.list, oids.nr, commit_compare);
 720
 721        count_distinct = 1;
 722        for (i = 1; i < oids.nr; i++) {
 723                if (oidcmp(&oids.list[i-1], &oids.list[i]))
 724                        count_distinct++;
 725        }
 726
 727        if (count_distinct >= GRAPH_PARENT_MISSING)
 728                die(_("the commit graph format cannot write %d commits"), count_distinct);
 729
 730        commits.nr = 0;
 731        commits.alloc = count_distinct;
 732        ALLOC_ARRAY(commits.list, commits.alloc);
 733
 734        num_extra_edges = 0;
 735        for (i = 0; i < oids.nr; i++) {
 736                int num_parents = 0;
 737                if (i > 0 && !oidcmp(&oids.list[i-1], &oids.list[i]))
 738                        continue;
 739
 740                commits.list[commits.nr] = lookup_commit(&oids.list[i]);
 741                parse_commit(commits.list[commits.nr]);
 742
 743                for (parent = commits.list[commits.nr]->parents;
 744                     parent; parent = parent->next)
 745                        num_parents++;
 746
 747                if (num_parents > 2)
 748                        num_extra_edges += num_parents - 1;
 749
 750                commits.nr++;
 751        }
 752        num_chunks = num_extra_edges ? 4 : 3;
 753
 754        if (commits.nr >= GRAPH_PARENT_MISSING)
 755                die(_("too many commits to write graph"));
 756
 757        compute_generation_numbers(&commits);
 758
 759        graph_name = get_commit_graph_filename(obj_dir);
 760        if (safe_create_leading_directories(graph_name))
 761                die_errno(_("unable to create leading directories of %s"),
 762                          graph_name);
 763
 764        hold_lock_file_for_update(&lk, graph_name, LOCK_DIE_ON_ERROR);
 765        f = hashfd(lk.tempfile->fd, lk.tempfile->filename.buf);
 766
 767        hashwrite_be32(f, GRAPH_SIGNATURE);
 768
 769        hashwrite_u8(f, GRAPH_VERSION);
 770        hashwrite_u8(f, GRAPH_OID_VERSION);
 771        hashwrite_u8(f, num_chunks);
 772        hashwrite_u8(f, 0); /* unused padding byte */
 773
 774        chunk_ids[0] = GRAPH_CHUNKID_OIDFANOUT;
 775        chunk_ids[1] = GRAPH_CHUNKID_OIDLOOKUP;
 776        chunk_ids[2] = GRAPH_CHUNKID_DATA;
 777        if (num_extra_edges)
 778                chunk_ids[3] = GRAPH_CHUNKID_LARGEEDGES;
 779        else
 780                chunk_ids[3] = 0;
 781        chunk_ids[4] = 0;
 782
 783        chunk_offsets[0] = 8 + (num_chunks + 1) * GRAPH_CHUNKLOOKUP_WIDTH;
 784        chunk_offsets[1] = chunk_offsets[0] + GRAPH_FANOUT_SIZE;
 785        chunk_offsets[2] = chunk_offsets[1] + GRAPH_OID_LEN * commits.nr;
 786        chunk_offsets[3] = chunk_offsets[2] + (GRAPH_OID_LEN + 16) * commits.nr;
 787        chunk_offsets[4] = chunk_offsets[3] + 4 * num_extra_edges;
 788
 789        for (i = 0; i <= num_chunks; i++) {
 790                uint32_t chunk_write[3];
 791
 792                chunk_write[0] = htonl(chunk_ids[i]);
 793                chunk_write[1] = htonl(chunk_offsets[i] >> 32);
 794                chunk_write[2] = htonl(chunk_offsets[i] & 0xffffffff);
 795                hashwrite(f, chunk_write, 12);
 796        }
 797
 798        write_graph_chunk_fanout(f, commits.list, commits.nr);
 799        write_graph_chunk_oids(f, GRAPH_OID_LEN, commits.list, commits.nr);
 800        write_graph_chunk_data(f, GRAPH_OID_LEN, commits.list, commits.nr);
 801        write_graph_chunk_large_edges(f, commits.list, commits.nr);
 802
 803        close_commit_graph();
 804        finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_FSYNC);
 805        commit_lock_file(&lk);
 806
 807        free(oids.list);
 808        oids.alloc = 0;
 809        oids.nr = 0;
 810}