git.oblomov.eu Git - git/blob - shallow.c

   1 #include "cache.h"
   2 #include "repository.h"
   3 #include "tempfile.h"
   4 #include "lockfile.h"
   5 #include "object-store.h"
   6 #include "commit.h"
   7 #include "tag.h"
   8 #include "pkt-line.h"
   9 #include "remote.h"
  10 #include "refs.h"
  11 #include "oid-array.h"
  12 #include "diff.h"
  13 #include "revision.h"
  14 #include "commit-slab.h"
  15 #include "list-objects.h"
  16 #include "commit-reach.h"
  17 #include "shallow.h"
  18
  19 void set_alternate_shallow_file(struct repository *r, const char *path, int override)
  20 {
  21         if (r->parsed_objects->is_shallow != -1)
  22                 BUG("is_repository_shallow must not be called before set_alternate_shallow_file");
  23         if (r->parsed_objects->alternate_shallow_file && !override)
  24                 return;
  25         free(r->parsed_objects->alternate_shallow_file);
  26         r->parsed_objects->alternate_shallow_file = xstrdup_or_null(path);
  27 }
  28
  29 int register_shallow(struct repository *r, const struct object_id *oid)
  30 {
  31         struct commit_graft *graft =
  32                 xmalloc(sizeof(struct commit_graft));
  33         struct commit *commit = lookup_commit(the_repository, oid);
  34
  35         oidcpy(&graft->oid, oid);
  36         graft->nr_parent = -1;
  37         if (commit && commit->object.parsed)
  38                 commit->parents = NULL;
  39         return register_commit_graft(r, graft, 0);
  40 }
  41
  42 int unregister_shallow(const struct object_id *oid)
  43 {
  44         int pos = commit_graft_pos(the_repository, oid->hash);
  45         if (pos < 0)
  46                 return -1;
  47         if (pos + 1 < the_repository->parsed_objects->grafts_nr)
  48                 MOVE_ARRAY(the_repository->parsed_objects->grafts + pos,
  49                            the_repository->parsed_objects->grafts + pos + 1,
  50                            the_repository->parsed_objects->grafts_nr - pos - 1);
  51         the_repository->parsed_objects->grafts_nr--;
  52         return 0;
  53 }
  54
  55 int is_repository_shallow(struct repository *r)
  56 {
  57         FILE *fp;
  58         char buf[1024];
  59         const char *path = r->parsed_objects->alternate_shallow_file;
  60
  61         if (r->parsed_objects->is_shallow >= 0)
  62                 return r->parsed_objects->is_shallow;
  63
  64         if (!path)
  65                 path = git_path_shallow(r);
  66         /*
  67          * fetch-pack sets '--shallow-file ""' as an indicator that no
  68          * shallow file should be used. We could just open it and it
  69          * will likely fail. But let's do an explicit check instead.
  70          */
  71         if (!*path || (fp = fopen(path, "r")) == NULL) {
  72                 stat_validity_clear(r->parsed_objects->shallow_stat);
  73                 r->parsed_objects->is_shallow = 0;
  74                 return r->parsed_objects->is_shallow;
  75         }
  76         stat_validity_update(r->parsed_objects->shallow_stat, fileno(fp));
  77         r->parsed_objects->is_shallow = 1;
  78
  79         while (fgets(buf, sizeof(buf), fp)) {
  80                 struct object_id oid;
  81                 if (get_oid_hex(buf, &oid))
  82                         die("bad shallow line: %s", buf);
  83                 register_shallow(r, &oid);
  84         }
  85         fclose(fp);
  86         return r->parsed_objects->is_shallow;
  87 }
  88
  89 static void reset_repository_shallow(struct repository *r)
  90 {
  91         r->parsed_objects->is_shallow = -1;
  92         stat_validity_clear(r->parsed_objects->shallow_stat);
  93 }
  94
  95 int commit_shallow_file(struct repository *r, struct shallow_lock *lk)
  96 {
  97         int res = commit_lock_file(&lk->lock);
  98         reset_repository_shallow(r);
  99         return res;
 100 }
 101
 102 void rollback_shallow_file(struct repository *r, struct shallow_lock *lk)
 103 {
 104         rollback_lock_file(&lk->lock);
 105         reset_repository_shallow(r);
 106 }
 107
 108 /*
 109  * TODO: use "int" elemtype instead of "int *" when/if commit-slab
 110  * supports a "valid" flag.
 111  */
 112 define_commit_slab(commit_depth, int *);
 113 static void free_depth_in_slab(int **ptr)
 114 {
 115         FREE_AND_NULL(*ptr);
 116 }
 117 struct commit_list *get_shallow_commits(struct object_array *heads, int depth,
 118                 int shallow_flag, int not_shallow_flag)
 119 {
 120         int i = 0, cur_depth = 0;
 121         struct commit_list *result = NULL;
 122         struct object_array stack = OBJECT_ARRAY_INIT;
 123         struct commit *commit = NULL;
 124         struct commit_graft *graft;
 125         struct commit_depth depths;
 126
 127         init_commit_depth(&depths);
 128         while (commit || i < heads->nr || stack.nr) {
 129                 struct commit_list *p;
 130                 if (!commit) {
 131                         if (i < heads->nr) {
 132                                 int **depth_slot;
 133                                 commit = (struct commit *)
 134                                         deref_tag(the_repository,
 135                                                   heads->objects[i++].item,
 136                                                   NULL, 0);
 137                                 if (!commit || commit->object.type != OBJ_COMMIT) {
 138                                         commit = NULL;
 139                                         continue;
 140                                 }
 141                                 depth_slot = commit_depth_at(&depths, commit);
 142                                 if (!*depth_slot)
 143                                         *depth_slot = xmalloc(sizeof(int));
 144                                 **depth_slot = 0;
 145                                 cur_depth = 0;
 146                         } else {
 147                                 commit = (struct commit *)
 148                                         object_array_pop(&stack);
 149                                 cur_depth = **commit_depth_at(&depths, commit);
 150                         }
 151                 }
 152                 parse_commit_or_die(commit);
 153                 cur_depth++;
 154                 if ((depth != INFINITE_DEPTH && cur_depth >= depth) ||
 155                     (is_repository_shallow(the_repository) && !commit->parents &&
 156                      (graft = lookup_commit_graft(the_repository, &commit->object.oid)) != NULL &&
 157                      graft->nr_parent < 0)) {
 158                         commit_list_insert(commit, &result);
 159                         commit->object.flags |= shallow_flag;
 160                         commit = NULL;
 161                         continue;
 162                 }
 163                 commit->object.flags |= not_shallow_flag;
 164                 for (p = commit->parents, commit = NULL; p; p = p->next) {
 165                         int **depth_slot = commit_depth_at(&depths, p->item);
 166                         if (!*depth_slot) {
 167                                 *depth_slot = xmalloc(sizeof(int));
 168                                 **depth_slot = cur_depth;
 169                         } else {
 170                                 if (cur_depth >= **depth_slot)
 171                                         continue;
 172                                 **depth_slot = cur_depth;
 173                         }
 174                         if (p->next)
 175                                 add_object_array(&p->item->object,
 176                                                 NULL, &stack);
 177                         else {
 178                                 commit = p->item;
 179                                 cur_depth = **commit_depth_at(&depths, commit);
 180                         }
 181                 }
 182         }
 183         deep_clear_commit_depth(&depths, free_depth_in_slab);
 184
 185         return result;
 186 }
 187
 188 static void show_commit(struct commit *commit, void *data)
 189 {
 190         commit_list_insert(commit, data);
 191 }
 192
 193 /*
 194  * Given rev-list arguments, run rev-list. All reachable commits
 195  * except border ones are marked with not_shallow_flag. Border commits
 196  * are marked with shallow_flag. The list of border/shallow commits
 197  * are also returned.
 198  */
 199 struct commit_list *get_shallow_commits_by_rev_list(int ac, const char **av,
 200                                                     int shallow_flag,
 201                                                     int not_shallow_flag)
 202 {
 203         struct commit_list *result = NULL, *p;
 204         struct commit_list *not_shallow_list = NULL;
 205         struct rev_info revs;
 206         int both_flags = shallow_flag | not_shallow_flag;
 207
 208         /*
 209          * SHALLOW (excluded) and NOT_SHALLOW (included) should not be
 210          * set at this point. But better be safe than sorry.
 211          */
 212         clear_object_flags(both_flags);
 213
 214         is_repository_shallow(the_repository); /* make sure shallows are read */
 215
 216         repo_init_revisions(the_repository, &revs, NULL);
 217         save_commit_buffer = 0;
 218         setup_revisions(ac, av, &revs, NULL);
 219
 220         if (prepare_revision_walk(&revs))
 221                 die("revision walk setup failed");
 222         traverse_commit_list(&revs, show_commit, NULL, &not_shallow_list);
 223
 224         if (!not_shallow_list)
 225                 die("no commits selected for shallow requests");
 226
 227         /* Mark all reachable commits as NOT_SHALLOW */
 228         for (p = not_shallow_list; p; p = p->next)
 229                 p->item->object.flags |= not_shallow_flag;
 230
 231         /*
 232          * mark border commits SHALLOW + NOT_SHALLOW.
 233          * We cannot clear NOT_SHALLOW right now. Imagine border
 234          * commit A is processed first, then commit B, whose parent is
 235          * A, later. If NOT_SHALLOW on A is cleared at step 1, B
 236          * itself is considered border at step 2, which is incorrect.
 237          */
 238         for (p = not_shallow_list; p; p = p->next) {
 239                 struct commit *c = p->item;
 240                 struct commit_list *parent;
 241
 242                 if (parse_commit(c))
 243                         die("unable to parse commit %s",
 244                             oid_to_hex(&c->object.oid));
 245
 246                 for (parent = c->parents; parent; parent = parent->next)
 247                         if (!(parent->item->object.flags & not_shallow_flag)) {
 248                                 c->object.flags |= shallow_flag;
 249                                 commit_list_insert(c, &result);
 250                                 break;
 251                         }
 252         }
 253         free_commit_list(not_shallow_list);
 254
 255         /*
 256          * Now we can clean up NOT_SHALLOW on border commits. Having
 257          * both flags set can confuse the caller.
 258          */
 259         for (p = result; p; p = p->next) {
 260                 struct object *o = &p->item->object;
 261                 if ((o->flags & both_flags) == both_flags)
 262                         o->flags &= ~not_shallow_flag;
 263         }
 264         return result;
 265 }
 266
 267 static void check_shallow_file_for_update(struct repository *r)
 268 {
 269         if (r->parsed_objects->is_shallow == -1)
 270                 BUG("shallow must be initialized by now");
 271
 272         if (!stat_validity_check(r->parsed_objects->shallow_stat,
 273                                  git_path_shallow(r)))
 274                 die("shallow file has changed since we read it");
 275 }
 276
 277 #define SEEN_ONLY 1
 278 #define VERBOSE   2
 279 #define QUICK 4
 280
 281 struct write_shallow_data {
 282         struct strbuf *out;
 283         int use_pack_protocol;
 284         int count;
 285         unsigned flags;
 286 };
 287
 288 static int write_one_shallow(const struct commit_graft *graft, void *cb_data)
 289 {
 290         struct write_shallow_data *data = cb_data;
 291         const char *hex = oid_to_hex(&graft->oid);
 292         if (graft->nr_parent != -1)
 293                 return 0;
 294         if (data->flags & QUICK) {
 295                 if (!has_object_file(&graft->oid))
 296                         return 0;
 297         } else if (data->flags & SEEN_ONLY) {
 298                 struct commit *c = lookup_commit(the_repository, &graft->oid);
 299                 if (!c || !(c->object.flags & SEEN)) {
 300                         if (data->flags & VERBOSE)
 301                                 printf("Removing %s from .git/shallow\n",
 302                                        oid_to_hex(&c->object.oid));
 303                         return 0;
 304                 }
 305         }
 306         data->count++;
 307         if (data->use_pack_protocol)
 308                 packet_buf_write(data->out, "shallow %s", hex);
 309         else {
 310                 strbuf_addstr(data->out, hex);
 311                 strbuf_addch(data->out, '\n');
 312         }
 313         return 0;
 314 }
 315
 316 static int write_shallow_commits_1(struct strbuf *out, int use_pack_protocol,
 317                                    const struct oid_array *extra,
 318                                    unsigned flags)
 319 {
 320         struct write_shallow_data data;
 321         int i;
 322         data.out = out;
 323         data.use_pack_protocol = use_pack_protocol;
 324         data.count = 0;
 325         data.flags = flags;
 326         for_each_commit_graft(write_one_shallow, &data);
 327         if (!extra)
 328                 return data.count;
 329         for (i = 0; i < extra->nr; i++) {
 330                 strbuf_addstr(out, oid_to_hex(extra->oid + i));
 331                 strbuf_addch(out, '\n');
 332                 data.count++;
 333         }
 334         return data.count;
 335 }
 336
 337 int write_shallow_commits(struct strbuf *out, int use_pack_protocol,
 338                           const struct oid_array *extra)
 339 {
 340         return write_shallow_commits_1(out, use_pack_protocol, extra, 0);
 341 }
 342
 343 const char *setup_temporary_shallow(const struct oid_array *extra)
 344 {
 345         struct tempfile *temp;
 346         struct strbuf sb = STRBUF_INIT;
 347
 348         if (write_shallow_commits(&sb, 0, extra)) {
 349                 temp = xmks_tempfile(git_path("shallow_XXXXXX"));
 350
 351                 if (write_in_full(temp->fd, sb.buf, sb.len) < 0 ||
 352                     close_tempfile_gently(temp) < 0)
 353                         die_errno("failed to write to %s",
 354                                   get_tempfile_path(temp));
 355                 strbuf_release(&sb);
 356                 return get_tempfile_path(temp);
 357         }
 358         /*
 359          * is_repository_shallow() sees empty string as "no shallow
 360          * file".
 361          */
 362         return "";
 363 }
 364
 365 void setup_alternate_shallow(struct shallow_lock *shallow_lock,
 366                              const char **alternate_shallow_file,
 367                              const struct oid_array *extra)
 368 {
 369         struct strbuf sb = STRBUF_INIT;
 370         int fd;
 371
 372         fd = hold_lock_file_for_update(&shallow_lock->lock,
 373                                        git_path_shallow(the_repository),
 374                                        LOCK_DIE_ON_ERROR);
 375         check_shallow_file_for_update(the_repository);
 376         if (write_shallow_commits(&sb, 0, extra)) {
 377                 if (write_in_full(fd, sb.buf, sb.len) < 0)
 378                         die_errno("failed to write to %s",
 379                                   get_lock_file_path(&shallow_lock->lock));
 380                 *alternate_shallow_file = get_lock_file_path(&shallow_lock->lock);
 381         } else
 382                 /*
 383                  * is_repository_shallow() sees empty string as "no
 384                  * shallow file".
 385                  */
 386                 *alternate_shallow_file = "";
 387         strbuf_release(&sb);
 388 }
 389
 390 static int advertise_shallow_grafts_cb(const struct commit_graft *graft, void *cb)
 391 {
 392         int fd = *(int *)cb;
 393         if (graft->nr_parent == -1)
 394                 packet_write_fmt(fd, "shallow %s\n", oid_to_hex(&graft->oid));
 395         return 0;
 396 }
 397
 398 void advertise_shallow_grafts(int fd)
 399 {
 400         if (!is_repository_shallow(the_repository))
 401                 return;
 402         for_each_commit_graft(advertise_shallow_grafts_cb, &fd);
 403 }
 404
 405 /*
 406  * mark_reachable_objects() should have been run prior to this and all
 407  * reachable commits marked as "SEEN", except when quick_prune is non-zero,
 408  * in which case lines are excised from the shallow file if they refer to
 409  * commits that do not exist (any longer).
 410  */
 411 void prune_shallow(unsigned options)
 412 {
 413         struct shallow_lock shallow_lock = SHALLOW_LOCK_INIT;
 414         struct strbuf sb = STRBUF_INIT;
 415         unsigned flags = SEEN_ONLY;
 416         int fd;
 417
 418         if (options & PRUNE_QUICK)
 419                 flags |= QUICK;
 420
 421         if (options & PRUNE_SHOW_ONLY) {
 422                 flags |= VERBOSE;
 423                 write_shallow_commits_1(&sb, 0, NULL, flags);
 424                 strbuf_release(&sb);
 425                 return;
 426         }
 427         fd = hold_lock_file_for_update(&shallow_lock.lock,
 428                                        git_path_shallow(the_repository),
 429                                        LOCK_DIE_ON_ERROR);
 430         check_shallow_file_for_update(the_repository);
 431         if (write_shallow_commits_1(&sb, 0, NULL, flags)) {
 432                 if (write_in_full(fd, sb.buf, sb.len) < 0)
 433                         die_errno("failed to write to %s",
 434                                   get_lock_file_path(&shallow_lock.lock));
 435                 commit_shallow_file(the_repository, &shallow_lock);
 436         } else {
 437                 unlink(git_path_shallow(the_repository));
 438                 rollback_shallow_file(the_repository, &shallow_lock);
 439         }
 440         strbuf_release(&sb);
 441 }
 442
 443 struct trace_key trace_shallow = TRACE_KEY_INIT(SHALLOW);
 444
 445 /*
 446  * Step 1, split sender shallow commits into "ours" and "theirs"
 447  * Step 2, clean "ours" based on .git/shallow
 448  */
 449 void prepare_shallow_info(struct shallow_info *info, struct oid_array *sa)
 450 {
 451         int i;
 452         trace_printf_key(&trace_shallow, "shallow: prepare_shallow_info\n");
 453         memset(info, 0, sizeof(*info));
 454         info->shallow = sa;
 455         if (!sa)
 456                 return;
 457         ALLOC_ARRAY(info->ours, sa->nr);
 458         ALLOC_ARRAY(info->theirs, sa->nr);
 459         for (i = 0; i < sa->nr; i++) {
 460                 if (has_object_file(sa->oid + i)) {
 461                         struct commit_graft *graft;
 462                         graft = lookup_commit_graft(the_repository,
 463                                                     &sa->oid[i]);
 464                         if (graft && graft->nr_parent < 0)
 465                                 continue;
 466                         info->ours[info->nr_ours++] = i;
 467                 } else
 468                         info->theirs[info->nr_theirs++] = i;
 469         }
 470 }
 471
 472 void clear_shallow_info(struct shallow_info *info)
 473 {
 474         free(info->ours);
 475         free(info->theirs);
 476 }
 477
 478 /* Step 4, remove non-existent ones in "theirs" after getting the pack */
 479
 480 void remove_nonexistent_theirs_shallow(struct shallow_info *info)
 481 {
 482         struct object_id *oid = info->shallow->oid;
 483         int i, dst;
 484         trace_printf_key(&trace_shallow, "shallow: remove_nonexistent_theirs_shallow\n");
 485         for (i = dst = 0; i < info->nr_theirs; i++) {
 486                 if (i != dst)
 487                         info->theirs[dst] = info->theirs[i];
 488                 if (has_object_file(oid + info->theirs[i]))
 489                         dst++;
 490         }
 491         info->nr_theirs = dst;
 492 }
 493
 494 define_commit_slab(ref_bitmap, uint32_t *);
 495
 496 #define POOL_SIZE (512 * 1024)
 497
 498 struct paint_info {
 499         struct ref_bitmap ref_bitmap;
 500         unsigned nr_bits;
 501         char **pools;
 502         char *free, *end;
 503         unsigned pool_count;
 504 };
 505
 506 static uint32_t *paint_alloc(struct paint_info *info)
 507 {
 508         unsigned nr = DIV_ROUND_UP(info->nr_bits, 32);
 509         unsigned size = nr * sizeof(uint32_t);
 510         void *p;
 511         if (!info->pool_count || size > info->end - info->free) {
 512                 if (size > POOL_SIZE)
 513                         BUG("pool size too small for %d in paint_alloc()",
 514                             size);
 515                 info->pool_count++;
 516                 REALLOC_ARRAY(info->pools, info->pool_count);
 517                 info->free = xmalloc(POOL_SIZE);
 518                 info->pools[info->pool_count - 1] = info->free;
 519                 info->end = info->free + POOL_SIZE;
 520         }
 521         p = info->free;
 522         info->free += size;
 523         return p;
 524 }
 525
 526 /*
 527  * Given a commit SHA-1, walk down to parents until either SEEN,
 528  * UNINTERESTING or BOTTOM is hit. Set the id-th bit in ref_bitmap for
 529  * all walked commits.
 530  */
 531 static void paint_down(struct paint_info *info, const struct object_id *oid,
 532                        unsigned int id)
 533 {
 534         unsigned int i, nr;
 535         struct commit_list *head = NULL;
 536         int bitmap_nr = DIV_ROUND_UP(info->nr_bits, 32);
 537         size_t bitmap_size = st_mult(sizeof(uint32_t), bitmap_nr);
 538         struct commit *c = lookup_commit_reference_gently(the_repository, oid,
 539                                                           1);
 540         uint32_t *tmp; /* to be freed before return */
 541         uint32_t *bitmap;
 542
 543         if (!c)
 544                 return;
 545
 546         tmp = xmalloc(bitmap_size);
 547         bitmap = paint_alloc(info);
 548         memset(bitmap, 0, bitmap_size);
 549         bitmap[id / 32] |= (1U << (id % 32));
 550         commit_list_insert(c, &head);
 551         while (head) {
 552                 struct commit_list *p;
 553                 struct commit *c = pop_commit(&head);
 554                 uint32_t **refs = ref_bitmap_at(&info->ref_bitmap, c);
 555
 556                 /* XXX check "UNINTERESTING" from pack bitmaps if available */
 557                 if (c->object.flags & (SEEN | UNINTERESTING))
 558                         continue;
 559                 else
 560                         c->object.flags |= SEEN;
 561
 562                 if (*refs == NULL)
 563                         *refs = bitmap;
 564                 else {
 565                         memcpy(tmp, *refs, bitmap_size);
 566                         for (i = 0; i < bitmap_nr; i++)
 567                                 tmp[i] |= bitmap[i];
 568                         if (memcmp(tmp, *refs, bitmap_size)) {
 569                                 *refs = paint_alloc(info);
 570                                 memcpy(*refs, tmp, bitmap_size);
 571                         }
 572                 }
 573
 574                 if (c->object.flags & BOTTOM)
 575                         continue;
 576
 577                 if (parse_commit(c))
 578                         die("unable to parse commit %s",
 579                             oid_to_hex(&c->object.oid));
 580
 581                 for (p = c->parents; p; p = p->next) {
 582                         if (p->item->object.flags & SEEN)
 583                                 continue;
 584                         commit_list_insert(p->item, &head);
 585                 }
 586         }
 587
 588         nr = get_max_object_index();
 589         for (i = 0; i < nr; i++) {
 590                 struct object *o = get_indexed_object(i);
 591                 if (o && o->type == OBJ_COMMIT)
 592                         o->flags &= ~SEEN;
 593         }
 594
 595         free(tmp);
 596 }
 597
 598 static int mark_uninteresting(const char *refname, const struct object_id *oid,
 599                               int flags, void *cb_data)
 600 {
 601         struct commit *commit = lookup_commit_reference_gently(the_repository,
 602                                                                oid, 1);
 603         if (!commit)
 604                 return 0;
 605         commit->object.flags |= UNINTERESTING;
 606         mark_parents_uninteresting(commit);
 607         return 0;
 608 }
 609
 610 static void post_assign_shallow(struct shallow_info *info,
 611                                 struct ref_bitmap *ref_bitmap,
 612                                 int *ref_status);
 613 /*
 614  * Step 6(+7), associate shallow commits with new refs
 615  *
 616  * info->ref must be initialized before calling this function.
 617  *
 618  * If used is not NULL, it's an array of info->shallow->nr
 619  * bitmaps. The n-th bit set in the m-th bitmap if ref[n] needs the
 620  * m-th shallow commit from info->shallow.
 621  *
 622  * If used is NULL, "ours" and "theirs" are updated. And if ref_status
 623  * is not NULL it's an array of ref->nr ints. ref_status[i] is true if
 624  * the ref needs some shallow commits from either info->ours or
 625  * info->theirs.
 626  */
 627 void assign_shallow_commits_to_refs(struct shallow_info *info,
 628                                     uint32_t **used, int *ref_status)
 629 {
 630         struct object_id *oid = info->shallow->oid;
 631         struct oid_array *ref = info->ref;
 632         unsigned int i, nr;
 633         int *shallow, nr_shallow = 0;
 634         struct paint_info pi;
 635
 636         trace_printf_key(&trace_shallow, "shallow: assign_shallow_commits_to_refs\n");
 637         ALLOC_ARRAY(shallow, info->nr_ours + info->nr_theirs);
 638         for (i = 0; i < info->nr_ours; i++)
 639                 shallow[nr_shallow++] = info->ours[i];
 640         for (i = 0; i < info->nr_theirs; i++)
 641                 shallow[nr_shallow++] = info->theirs[i];
 642
 643         /*
 644          * Prepare the commit graph to track what refs can reach what
 645          * (new) shallow commits.
 646          */
 647         nr = get_max_object_index();
 648         for (i = 0; i < nr; i++) {
 649                 struct object *o = get_indexed_object(i);
 650                 if (!o || o->type != OBJ_COMMIT)
 651                         continue;
 652
 653                 o->flags &= ~(UNINTERESTING | BOTTOM | SEEN);
 654         }
 655
 656         memset(&pi, 0, sizeof(pi));
 657         init_ref_bitmap(&pi.ref_bitmap);
 658         pi.nr_bits = ref->nr;
 659
 660         /*
 661          * "--not --all" to cut short the traversal if new refs
 662          * connect to old refs. If not (e.g. force ref updates) it'll
 663          * have to go down to the current shallow commits.
 664          */
 665         head_ref(mark_uninteresting, NULL);
 666         for_each_ref(mark_uninteresting, NULL);
 667
 668         /* Mark potential bottoms so we won't go out of bound */
 669         for (i = 0; i < nr_shallow; i++) {
 670                 struct commit *c = lookup_commit(the_repository,
 671                                                  &oid[shallow[i]]);
 672                 c->object.flags |= BOTTOM;
 673         }
 674
 675         for (i = 0; i < ref->nr; i++)
 676                 paint_down(&pi, ref->oid + i, i);
 677
 678         if (used) {
 679                 int bitmap_size = DIV_ROUND_UP(pi.nr_bits, 32) * sizeof(uint32_t);
 680                 memset(used, 0, sizeof(*used) * info->shallow->nr);
 681                 for (i = 0; i < nr_shallow; i++) {
 682                         const struct commit *c = lookup_commit(the_repository,
 683                                                                &oid[shallow[i]]);
 684                         uint32_t **map = ref_bitmap_at(&pi.ref_bitmap, c);
 685                         if (*map)
 686                                 used[shallow[i]] = xmemdupz(*map, bitmap_size);
 687                 }
 688                 /*
 689                  * unreachable shallow commits are not removed from
 690                  * "ours" and "theirs". The user is supposed to run
 691                  * step 7 on every ref separately and not trust "ours"
 692                  * and "theirs" any more.
 693                  */
 694         } else
 695                 post_assign_shallow(info, &pi.ref_bitmap, ref_status);
 696
 697         clear_ref_bitmap(&pi.ref_bitmap);
 698         for (i = 0; i < pi.pool_count; i++)
 699                 free(pi.pools[i]);
 700         free(pi.pools);
 701         free(shallow);
 702 }
 703
 704 struct commit_array {
 705         struct commit **commits;
 706         int nr, alloc;
 707 };
 708
 709 static int add_ref(const char *refname, const struct object_id *oid,
 710                    int flags, void *cb_data)
 711 {
 712         struct commit_array *ca = cb_data;
 713         ALLOC_GROW(ca->commits, ca->nr + 1, ca->alloc);
 714         ca->commits[ca->nr] = lookup_commit_reference_gently(the_repository,
 715                                                              oid, 1);
 716         if (ca->commits[ca->nr])
 717                 ca->nr++;
 718         return 0;
 719 }
 720
 721 static void update_refstatus(int *ref_status, int nr, uint32_t *bitmap)
 722 {
 723         unsigned int i;
 724         if (!ref_status)
 725                 return;
 726         for (i = 0; i < nr; i++)
 727                 if (bitmap[i / 32] & (1U << (i % 32)))
 728                         ref_status[i]++;
 729 }
 730
 731 /*
 732  * Step 7, reachability test on "ours" at commit level
 733  */
 734 static void post_assign_shallow(struct shallow_info *info,
 735                                 struct ref_bitmap *ref_bitmap,
 736                                 int *ref_status)
 737 {
 738         struct object_id *oid = info->shallow->oid;
 739         struct commit *c;
 740         uint32_t **bitmap;
 741         int dst, i, j;
 742         int bitmap_nr = DIV_ROUND_UP(info->ref->nr, 32);
 743         struct commit_array ca;
 744
 745         trace_printf_key(&trace_shallow, "shallow: post_assign_shallow\n");
 746         if (ref_status)
 747                 memset(ref_status, 0, sizeof(*ref_status) * info->ref->nr);
 748
 749         /* Remove unreachable shallow commits from "theirs" */
 750         for (i = dst = 0; i < info->nr_theirs; i++) {
 751                 if (i != dst)
 752                         info->theirs[dst] = info->theirs[i];
 753                 c = lookup_commit(the_repository, &oid[info->theirs[i]]);
 754                 bitmap = ref_bitmap_at(ref_bitmap, c);
 755                 if (!*bitmap)
 756                         continue;
 757                 for (j = 0; j < bitmap_nr; j++)
 758                         if (bitmap[0][j]) {
 759                                 update_refstatus(ref_status, info->ref->nr, *bitmap);
 760                                 dst++;
 761                                 break;
 762                         }
 763         }
 764         info->nr_theirs = dst;
 765
 766         memset(&ca, 0, sizeof(ca));
 767         head_ref(add_ref, &ca);
 768         for_each_ref(add_ref, &ca);
 769
 770         /* Remove unreachable shallow commits from "ours" */
 771         for (i = dst = 0; i < info->nr_ours; i++) {
 772                 if (i != dst)
 773                         info->ours[dst] = info->ours[i];
 774                 c = lookup_commit(the_repository, &oid[info->ours[i]]);
 775                 bitmap = ref_bitmap_at(ref_bitmap, c);
 776                 if (!*bitmap)
 777                         continue;
 778                 for (j = 0; j < bitmap_nr; j++)
 779                         if (bitmap[0][j] &&
 780                             /* Step 7, reachability test at commit level */
 781                             !in_merge_bases_many(c, ca.nr, ca.commits)) {
 782                                 update_refstatus(ref_status, info->ref->nr, *bitmap);
 783                                 dst++;
 784                                 break;
 785                         }
 786         }
 787         info->nr_ours = dst;
 788
 789         free(ca.commits);
 790 }
 791
 792 /* (Delayed) step 7, reachability test at commit level */
 793 int delayed_reachability_test(struct shallow_info *si, int c)
 794 {
 795         if (si->need_reachability_test[c]) {
 796                 struct commit *commit = lookup_commit(the_repository,
 797                                                       &si->shallow->oid[c]);
 798
 799                 if (!si->commits) {
 800                         struct commit_array ca;
 801
 802                         memset(&ca, 0, sizeof(ca));
 803                         head_ref(add_ref, &ca);
 804                         for_each_ref(add_ref, &ca);
 805                         si->commits = ca.commits;
 806                         si->nr_commits = ca.nr;
 807                 }
 808
 809                 si->reachable[c] = in_merge_bases_many(commit,
 810                                                        si->nr_commits,
 811                                                        si->commits);
 812                 si->need_reachability_test[c] = 0;
 813         }
 814         return si->reachable[c];
 815 }