commit-reach.c

   1 #include "cache.h"
   2 #include "commit.h"
   3 #include "commit-graph.h"
   4 #include "decorate.h"
   5 #include "prio-queue.h"
   6 #include "tree.h"
   7 #include "ref-filter.h"
   8 #include "revision.h"
   9 #include "tag.h"
  10 #include "commit-reach.h"
  11
  12 /* Remember to update object flag allocation in object.h */
  13 #define PARENT1         (1u<<16)
  14 #define PARENT2         (1u<<17)
  15 #define STALE           (1u<<18)
  16 #define RESULT          (1u<<19)
  17
  18 static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);
  19
  20 static int queue_has_nonstale(struct prio_queue *queue)
  21 {
  22         int i;
  23         for (i = 0; i < queue->nr; i++) {
  24                 struct commit *commit = queue->array[i].data;
  25                 if (!(commit->object.flags & STALE))
  26                         return 1;
  27         }
  28         return 0;
  29 }
  30
  31 /* all input commits in one and twos[] must have been parsed! */
  32 static struct commit_list *paint_down_to_common(struct repository *r,
  33                                                 struct commit *one, int n,
  34                                                 struct commit **twos,
  35                                                 int min_generation)
  36 {
  37         struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
  38         struct commit_list *result = NULL;
  39         int i;
  40         uint32_t last_gen = GENERATION_NUMBER_INFINITY;
  41
  42         if (!min_generation)
  43                 queue.compare = compare_commits_by_commit_date;
  44
  45         one->object.flags |= PARENT1;
  46         if (!n) {
  47                 commit_list_append(one, &result);
  48                 return result;
  49         }
  50         prio_queue_put(&queue, one);
  51
  52         for (i = 0; i < n; i++) {
  53                 twos[i]->object.flags |= PARENT2;
  54                 prio_queue_put(&queue, twos[i]);
  55         }
  56
  57         while (queue_has_nonstale(&queue)) {
  58                 struct commit *commit = prio_queue_get(&queue);
  59                 struct commit_list *parents;
  60                 int flags;
  61                 uint32_t generation = commit_graph_generation(commit);
  62
  63                 if (min_generation && generation > last_gen)
  64                         BUG("bad generation skip %8x > %8x at %s",
  65                             generation, last_gen,
  66                             oid_to_hex(&commit->object.oid));
  67                 last_gen = generation;
  68
  69                 if (generation < min_generation)
  70                         break;
  71
  72                 flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
  73                 if (flags == (PARENT1 | PARENT2)) {
  74                         if (!(commit->object.flags & RESULT)) {
  75                                 commit->object.flags |= RESULT;
  76                                 commit_list_insert_by_date(commit, &result);
  77                         }
  78                         /* Mark parents of a found merge stale */
  79                         flags |= STALE;
  80                 }
  81                 parents = commit->parents;
  82                 while (parents) {
  83                         struct commit *p = parents->item;
  84                         parents = parents->next;
  85                         if ((p->object.flags & flags) == flags)
  86                                 continue;
  87                         if (repo_parse_commit(r, p))
  88                                 return NULL;
  89                         p->object.flags |= flags;
  90                         prio_queue_put(&queue, p);
  91                 }
  92         }
  93
  94         clear_prio_queue(&queue);
  95         return result;
  96 }
  97
  98 static struct commit_list *merge_bases_many(struct repository *r,
  99                                             struct commit *one, int n,
 100                                             struct commit **twos)
 101 {
 102         struct commit_list *list = NULL;
 103         struct commit_list *result = NULL;
 104         int i;
 105
 106         for (i = 0; i < n; i++) {
 107                 if (one == twos[i])
 108                         /*
 109                          * We do not mark this even with RESULT so we do not
 110                          * have to clean it up.
 111                          */
 112                         return commit_list_insert(one, &result);
 113         }
 114
 115         if (repo_parse_commit(r, one))
 116                 return NULL;
 117         for (i = 0; i < n; i++) {
 118                 if (repo_parse_commit(r, twos[i]))
 119                         return NULL;
 120         }
 121
 122         list = paint_down_to_common(r, one, n, twos, 0);
 123
 124         while (list) {
 125                 struct commit *commit = pop_commit(&list);
 126                 if (!(commit->object.flags & STALE))
 127                         commit_list_insert_by_date(commit, &result);
 128         }
 129         return result;
 130 }
 131
 132 struct commit_list *get_octopus_merge_bases(struct commit_list *in)
 133 {
 134         struct commit_list *i, *j, *k, *ret = NULL;
 135
 136         if (!in)
 137                 return ret;
 138
 139         commit_list_insert(in->item, &ret);
 140
 141         for (i = in->next; i; i = i->next) {
 142                 struct commit_list *new_commits = NULL, *end = NULL;
 143
 144                 for (j = ret; j; j = j->next) {
 145                         struct commit_list *bases;
 146                         bases = get_merge_bases(i->item, j->item);
 147                         if (!new_commits)
 148                                 new_commits = bases;
 149                         else
 150                                 end->next = bases;
 151                         for (k = bases; k; k = k->next)
 152                                 end = k;
 153                 }
 154                 ret = new_commits;
 155         }
 156         return ret;
 157 }
 158
 159 static int remove_redundant(struct repository *r, struct commit **array, int cnt)
 160 {
 161         /*
 162          * Some commit in the array may be an ancestor of
 163          * another commit.  Move such commit to the end of
 164          * the array, and return the number of commits that
 165          * are independent from each other.
 166          */
 167         struct commit **work;
 168         unsigned char *redundant;
 169         int *filled_index;
 170         int i, j, filled;
 171
 172         work = xcalloc(cnt, sizeof(*work));
 173         redundant = xcalloc(cnt, 1);
 174         ALLOC_ARRAY(filled_index, cnt - 1);
 175
 176         for (i = 0; i < cnt; i++)
 177                 repo_parse_commit(r, array[i]);
 178         for (i = 0; i < cnt; i++) {
 179                 struct commit_list *common;
 180                 uint32_t min_generation = commit_graph_generation(array[i]);
 181
 182                 if (redundant[i])
 183                         continue;
 184                 for (j = filled = 0; j < cnt; j++) {
 185                         uint32_t curr_generation;
 186                         if (i == j || redundant[j])
 187                                 continue;
 188                         filled_index[filled] = j;
 189                         work[filled++] = array[j];
 190
 191                         curr_generation = commit_graph_generation(array[j]);
 192                         if (curr_generation < min_generation)
 193                                 min_generation = curr_generation;
 194                 }
 195                 common = paint_down_to_common(r, array[i], filled,
 196                                               work, min_generation);
 197                 if (array[i]->object.flags & PARENT2)
 198                         redundant[i] = 1;
 199                 for (j = 0; j < filled; j++)
 200                         if (work[j]->object.flags & PARENT1)
 201                                 redundant[filled_index[j]] = 1;
 202                 clear_commit_marks(array[i], all_flags);
 203                 clear_commit_marks_many(filled, work, all_flags);
 204                 free_commit_list(common);
 205         }
 206
 207         /* Now collect the result */
 208         COPY_ARRAY(work, array, cnt);
 209         for (i = filled = 0; i < cnt; i++)
 210                 if (!redundant[i])
 211                         array[filled++] = work[i];
 212         for (j = filled, i = 0; i < cnt; i++)
 213                 if (redundant[i])
 214                         array[j++] = work[i];
 215         free(work);
 216         free(redundant);
 217         free(filled_index);
 218         return filled;
 219 }
 220
 221 static struct commit_list *get_merge_bases_many_0(struct repository *r,
 222                                                   struct commit *one,
 223                                                   int n,
 224                                                   struct commit **twos,
 225                                                   int cleanup)
 226 {
 227         struct commit_list *list;
 228         struct commit **rslt;
 229         struct commit_list *result;
 230         int cnt, i;
 231
 232         result = merge_bases_many(r, one, n, twos);
 233         for (i = 0; i < n; i++) {
 234                 if (one == twos[i])
 235                         return result;
 236         }
 237         if (!result || !result->next) {
 238                 if (cleanup) {
 239                         clear_commit_marks(one, all_flags);
 240                         clear_commit_marks_many(n, twos, all_flags);
 241                 }
 242                 return result;
 243         }
 244
 245         /* There are more than one */
 246         cnt = commit_list_count(result);
 247         rslt = xcalloc(cnt, sizeof(*rslt));
 248         for (list = result, i = 0; list; list = list->next)
 249                 rslt[i++] = list->item;
 250         free_commit_list(result);
 251
 252         clear_commit_marks(one, all_flags);
 253         clear_commit_marks_many(n, twos, all_flags);
 254
 255         cnt = remove_redundant(r, rslt, cnt);
 256         result = NULL;
 257         for (i = 0; i < cnt; i++)
 258                 commit_list_insert_by_date(rslt[i], &result);
 259         free(rslt);
 260         return result;
 261 }
 262
 263 struct commit_list *repo_get_merge_bases_many(struct repository *r,
 264                                               struct commit *one,
 265                                               int n,
 266                                               struct commit **twos)
 267 {
 268         return get_merge_bases_many_0(r, one, n, twos, 1);
 269 }
 270
 271 struct commit_list *repo_get_merge_bases_many_dirty(struct repository *r,
 272                                                     struct commit *one,
 273                                                     int n,
 274                                                     struct commit **twos)
 275 {
 276         return get_merge_bases_many_0(r, one, n, twos, 0);
 277 }
 278
 279 struct commit_list *repo_get_merge_bases(struct repository *r,
 280                                          struct commit *one,
 281                                          struct commit *two)
 282 {
 283         return get_merge_bases_many_0(r, one, 1, &two, 1);
 284 }
 285
 286 /*
 287  * Is "commit" a descendant of one of the elements on the "with_commit" list?
 288  */
 289 int is_descendant_of(struct commit *commit, struct commit_list *with_commit)
 290 {
 291         if (!with_commit)
 292                 return 1;
 293
 294         if (generation_numbers_enabled(the_repository)) {
 295                 struct commit_list *from_list = NULL;
 296                 int result;
 297                 commit_list_insert(commit, &from_list);
 298                 result = can_all_from_reach(from_list, with_commit, 0);
 299                 free_commit_list(from_list);
 300                 return result;
 301         } else {
 302                 while (with_commit) {
 303                         struct commit *other;
 304
 305                         other = with_commit->item;
 306                         with_commit = with_commit->next;
 307                         if (in_merge_bases(other, commit))
 308                                 return 1;
 309                 }
 310                 return 0;
 311         }
 312 }
 313
 314 /*
 315  * Is "commit" an ancestor of one of the "references"?
 316  */
 317 int repo_in_merge_bases_many(struct repository *r, struct commit *commit,
 318                              int nr_reference, struct commit **reference)
 319 {
 320         struct commit_list *bases;
 321         int ret = 0, i;
 322         uint32_t generation, min_generation = GENERATION_NUMBER_INFINITY;
 323
 324         if (repo_parse_commit(r, commit))
 325                 return ret;
 326         for (i = 0; i < nr_reference; i++) {
 327                 if (repo_parse_commit(r, reference[i]))
 328                         return ret;
 329
 330                 generation = commit_graph_generation(reference[i]);
 331                 if (generation < min_generation)
 332                         min_generation = generation;
 333         }
 334
 335         generation = commit_graph_generation(commit);
 336         if (generation > min_generation)
 337                 return ret;
 338
 339         bases = paint_down_to_common(r, commit,
 340                                      nr_reference, reference,
 341                                      generation);
 342         if (commit->object.flags & PARENT2)
 343                 ret = 1;
 344         clear_commit_marks(commit, all_flags);
 345         clear_commit_marks_many(nr_reference, reference, all_flags);
 346         free_commit_list(bases);
 347         return ret;
 348 }
 349
 350 /*
 351  * Is "commit" an ancestor of (i.e. reachable from) the "reference"?
 352  */
 353 int repo_in_merge_bases(struct repository *r,
 354                         struct commit *commit,
 355                         struct commit *reference)
 356 {
 357         return repo_in_merge_bases_many(r, commit, 1, &reference);
 358 }
 359
 360 struct commit_list *reduce_heads(struct commit_list *heads)
 361 {
 362         struct commit_list *p;
 363         struct commit_list *result = NULL, **tail = &result;
 364         struct commit **array;
 365         int num_head, i;
 366
 367         if (!heads)
 368                 return NULL;
 369
 370         /* Uniquify */
 371         for (p = heads; p; p = p->next)
 372                 p->item->object.flags &= ~STALE;
 373         for (p = heads, num_head = 0; p; p = p->next) {
 374                 if (p->item->object.flags & STALE)
 375                         continue;
 376                 p->item->object.flags |= STALE;
 377                 num_head++;
 378         }
 379         array = xcalloc(num_head, sizeof(*array));
 380         for (p = heads, i = 0; p; p = p->next) {
 381                 if (p->item->object.flags & STALE) {
 382                         array[i++] = p->item;
 383                         p->item->object.flags &= ~STALE;
 384                 }
 385         }
 386         num_head = remove_redundant(the_repository, array, num_head);
 387         for (i = 0; i < num_head; i++)
 388                 tail = &commit_list_insert(array[i], tail)->next;
 389         free(array);
 390         return result;
 391 }
 392
 393 void reduce_heads_replace(struct commit_list **heads)
 394 {
 395         struct commit_list *result = reduce_heads(*heads);
 396         free_commit_list(*heads);
 397         *heads = result;
 398 }
 399
 400 int ref_newer(const struct object_id *new_oid, const struct object_id *old_oid)
 401 {
 402         struct object *o;
 403         struct commit *old_commit, *new_commit;
 404         struct commit_list *old_commit_list = NULL;
 405
 406         /*
 407          * Both new_commit and old_commit must be commit-ish and new_commit is descendant of
 408          * old_commit.  Otherwise we require --force.
 409          */
 410         o = deref_tag(the_repository, parse_object(the_repository, old_oid),
 411                       NULL, 0);
 412         if (!o || o->type != OBJ_COMMIT)
 413                 return 0;
 414         old_commit = (struct commit *) o;
 415
 416         o = deref_tag(the_repository, parse_object(the_repository, new_oid),
 417                       NULL, 0);
 418         if (!o || o->type != OBJ_COMMIT)
 419                 return 0;
 420         new_commit = (struct commit *) o;
 421
 422         if (parse_commit(new_commit) < 0)
 423                 return 0;
 424
 425         commit_list_insert(old_commit, &old_commit_list);
 426         return is_descendant_of(new_commit, old_commit_list);
 427 }
 428
 429 /*
 430  * Mimicking the real stack, this stack lives on the heap, avoiding stack
 431  * overflows.
 432  *
 433  * At each recursion step, the stack items points to the commits whose
 434  * ancestors are to be inspected.
 435  */
 436 struct contains_stack {
 437         int nr, alloc;
 438         struct contains_stack_entry {
 439                 struct commit *commit;
 440                 struct commit_list *parents;
 441         } *contains_stack;
 442 };
 443
 444 static int in_commit_list(const struct commit_list *want, struct commit *c)
 445 {
 446         for (; want; want = want->next)
 447                 if (oideq(&want->item->object.oid, &c->object.oid))
 448                         return 1;
 449         return 0;
 450 }
 451
 452 /*
 453  * Test whether the candidate is contained in the list.
 454  * Do not recurse to find out, though, but return -1 if inconclusive.
 455  */
 456 static enum contains_result contains_test(struct commit *candidate,
 457                                           const struct commit_list *want,
 458                                           struct contains_cache *cache,
 459                                           uint32_t cutoff)
 460 {
 461         enum contains_result *cached = contains_cache_at(cache, candidate);
 462
 463         /* If we already have the answer cached, return that. */
 464         if (*cached)
 465                 return *cached;
 466
 467         /* or are we it? */
 468         if (in_commit_list(want, candidate)) {
 469                 *cached = CONTAINS_YES;
 470                 return CONTAINS_YES;
 471         }
 472
 473         /* Otherwise, we don't know; prepare to recurse */
 474         parse_commit_or_die(candidate);
 475
 476         if (commit_graph_generation(candidate) < cutoff)
 477                 return CONTAINS_NO;
 478
 479         return CONTAINS_UNKNOWN;
 480 }
 481
 482 static void push_to_contains_stack(struct commit *candidate, struct contains_stack *contains_stack)
 483 {
 484         ALLOC_GROW(contains_stack->contains_stack, contains_stack->nr + 1, contains_stack->alloc);
 485         contains_stack->contains_stack[contains_stack->nr].commit = candidate;
 486         contains_stack->contains_stack[contains_stack->nr++].parents = candidate->parents;
 487 }
 488
 489 static enum contains_result contains_tag_algo(struct commit *candidate,
 490                                               const struct commit_list *want,
 491                                               struct contains_cache *cache)
 492 {
 493         struct contains_stack contains_stack = { 0, 0, NULL };
 494         enum contains_result result;
 495         uint32_t cutoff = GENERATION_NUMBER_INFINITY;
 496         const struct commit_list *p;
 497
 498         for (p = want; p; p = p->next) {
 499                 uint32_t generation;
 500                 struct commit *c = p->item;
 501                 load_commit_graph_info(the_repository, c);
 502                 generation = commit_graph_generation(c);
 503                 if (generation < cutoff)
 504                         cutoff = generation;
 505         }
 506
 507         result = contains_test(candidate, want, cache, cutoff);
 508         if (result != CONTAINS_UNKNOWN)
 509                 return result;
 510
 511         push_to_contains_stack(candidate, &contains_stack);
 512         while (contains_stack.nr) {
 513                 struct contains_stack_entry *entry = &contains_stack.contains_stack[contains_stack.nr - 1];
 514                 struct commit *commit = entry->commit;
 515                 struct commit_list *parents = entry->parents;
 516
 517                 if (!parents) {
 518                         *contains_cache_at(cache, commit) = CONTAINS_NO;
 519                         contains_stack.nr--;
 520                 }
 521                 /*
 522                  * If we just popped the stack, parents->item has been marked,
 523                  * therefore contains_test will return a meaningful yes/no.
 524                  */
 525                 else switch (contains_test(parents->item, want, cache, cutoff)) {
 526                 case CONTAINS_YES:
 527                         *contains_cache_at(cache, commit) = CONTAINS_YES;
 528                         contains_stack.nr--;
 529                         break;
 530                 case CONTAINS_NO:
 531                         entry->parents = parents->next;
 532                         break;
 533                 case CONTAINS_UNKNOWN:
 534                         push_to_contains_stack(parents->item, &contains_stack);
 535                         break;
 536                 }
 537         }
 538         free(contains_stack.contains_stack);
 539         return contains_test(candidate, want, cache, cutoff);
 540 }
 541
 542 int commit_contains(struct ref_filter *filter, struct commit *commit,
 543                     struct commit_list *list, struct contains_cache *cache)
 544 {
 545         if (filter->with_commit_tag_algo)
 546                 return contains_tag_algo(commit, list, cache) == CONTAINS_YES;
 547         return is_descendant_of(commit, list);
 548 }
 549
 550 static int compare_commits_by_gen(const void *_a, const void *_b)
 551 {
 552         const struct commit *a = *(const struct commit * const *)_a;
 553         const struct commit *b = *(const struct commit * const *)_b;
 554
 555         uint32_t generation_a = commit_graph_generation(a);
 556         uint32_t generation_b = commit_graph_generation(b);
 557
 558         if (generation_a < generation_b)
 559                 return -1;
 560         if (generation_a > generation_b)
 561                 return 1;
 562         return 0;
 563 }
 564
 565 int can_all_from_reach_with_flag(struct object_array *from,
 566                                  unsigned int with_flag,
 567                                  unsigned int assign_flag,
 568                                  time_t min_commit_date,
 569                                  uint32_t min_generation)
 570 {
 571         struct commit **list = NULL;
 572         int i;
 573         int nr_commits;
 574         int result = 1;
 575
 576         ALLOC_ARRAY(list, from->nr);
 577         nr_commits = 0;
 578         for (i = 0; i < from->nr; i++) {
 579                 struct object *from_one = from->objects[i].item;
 580
 581                 if (!from_one || from_one->flags & assign_flag)
 582                         continue;
 583
 584                 from_one = deref_tag(the_repository, from_one,
 585                                      "a from object", 0);
 586                 if (!from_one || from_one->type != OBJ_COMMIT) {
 587                         /*
 588                          * no way to tell if this is reachable by
 589                          * looking at the ancestry chain alone, so
 590                          * leave a note to ourselves not to worry about
 591                          * this object anymore.
 592                          */
 593                         from->objects[i].item->flags |= assign_flag;
 594                         continue;
 595                 }
 596
 597                 list[nr_commits] = (struct commit *)from_one;
 598                 if (parse_commit(list[nr_commits]) ||
 599                     commit_graph_generation(list[nr_commits]) < min_generation) {
 600                         result = 0;
 601                         goto cleanup;
 602                 }
 603
 604                 nr_commits++;
 605         }
 606
 607         QSORT(list, nr_commits, compare_commits_by_gen);
 608
 609         for (i = 0; i < nr_commits; i++) {
 610                 /* DFS from list[i] */
 611                 struct commit_list *stack = NULL;
 612
 613                 list[i]->object.flags |= assign_flag;
 614                 commit_list_insert(list[i], &stack);
 615
 616                 while (stack) {
 617                         struct commit_list *parent;
 618
 619                         if (stack->item->object.flags & (with_flag | RESULT)) {
 620                                 pop_commit(&stack);
 621                                 if (stack)
 622                                         stack->item->object.flags |= RESULT;
 623                                 continue;
 624                         }
 625
 626                         for (parent = stack->item->parents; parent; parent = parent->next) {
 627                                 if (parent->item->object.flags & (with_flag | RESULT))
 628                                         stack->item->object.flags |= RESULT;
 629
 630                                 if (!(parent->item->object.flags & assign_flag)) {
 631                                         parent->item->object.flags |= assign_flag;
 632
 633                                         if (parse_commit(parent->item) ||
 634                                             parent->item->date < min_commit_date ||
 635                                             commit_graph_generation(parent->item) < min_generation)
 636                                                 continue;
 637
 638                                         commit_list_insert(parent->item, &stack);
 639                                         break;
 640                                 }
 641                         }
 642
 643                         if (!parent)
 644                                 pop_commit(&stack);
 645                 }
 646
 647                 if (!(list[i]->object.flags & (with_flag | RESULT))) {
 648                         result = 0;
 649                         goto cleanup;
 650                 }
 651         }
 652
 653 cleanup:
 654         clear_commit_marks_many(nr_commits, list, RESULT | assign_flag);
 655         free(list);
 656
 657         for (i = 0; i < from->nr; i++)
 658                 from->objects[i].item->flags &= ~assign_flag;
 659
 660         return result;
 661 }
 662
 663 int can_all_from_reach(struct commit_list *from, struct commit_list *to,
 664                        int cutoff_by_min_date)
 665 {
 666         struct object_array from_objs = OBJECT_ARRAY_INIT;
 667         time_t min_commit_date = cutoff_by_min_date ? from->item->date : 0;
 668         struct commit_list *from_iter = from, *to_iter = to;
 669         int result;
 670         uint32_t min_generation = GENERATION_NUMBER_INFINITY;
 671
 672         while (from_iter) {
 673                 add_object_array(&from_iter->item->object, NULL, &from_objs);
 674
 675                 if (!parse_commit(from_iter->item)) {
 676                         uint32_t generation;
 677                         if (from_iter->item->date < min_commit_date)
 678                                 min_commit_date = from_iter->item->date;
 679
 680                         generation = commit_graph_generation(from_iter->item);
 681                         if (generation < min_generation)
 682                                 min_generation = generation;
 683                 }
 684
 685                 from_iter = from_iter->next;
 686         }
 687
 688         while (to_iter) {
 689                 if (!parse_commit(to_iter->item)) {
 690                         uint32_t generation;
 691                         if (to_iter->item->date < min_commit_date)
 692                                 min_commit_date = to_iter->item->date;
 693
 694                         generation = commit_graph_generation(to_iter->item);
 695                         if (generation < min_generation)
 696                                 min_generation = generation;
 697                 }
 698
 699                 to_iter->item->object.flags |= PARENT2;
 700
 701                 to_iter = to_iter->next;
 702         }
 703
 704         result = can_all_from_reach_with_flag(&from_objs, PARENT2, PARENT1,
 705                                               min_commit_date, min_generation);
 706
 707         while (from) {
 708                 clear_commit_marks(from->item, PARENT1);
 709                 from = from->next;
 710         }
 711
 712         while (to) {
 713                 clear_commit_marks(to->item, PARENT2);
 714                 to = to->next;
 715         }
 716
 717         object_array_clear(&from_objs);
 718         return result;
 719 }
 720
 721 struct commit_list *get_reachable_subset(struct commit **from, int nr_from,
 722                                          struct commit **to, int nr_to,
 723                                          unsigned int reachable_flag)
 724 {
 725         struct commit **item;
 726         struct commit *current;
 727         struct commit_list *found_commits = NULL;
 728         struct commit **to_last = to + nr_to;
 729         struct commit **from_last = from + nr_from;
 730         uint32_t min_generation = GENERATION_NUMBER_INFINITY;
 731         int num_to_find = 0;
 732
 733         struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
 734
 735         for (item = to; item < to_last; item++) {
 736                 uint32_t generation;
 737                 struct commit *c = *item;
 738
 739                 parse_commit(c);
 740                 generation = commit_graph_generation(c);
 741                 if (generation < min_generation)
 742                         min_generation = generation;
 743
 744                 if (!(c->object.flags & PARENT1)) {
 745                         c->object.flags |= PARENT1;
 746                         num_to_find++;
 747                 }
 748         }
 749
 750         for (item = from; item < from_last; item++) {
 751                 struct commit *c = *item;
 752                 if (!(c->object.flags & PARENT2)) {
 753                         c->object.flags |= PARENT2;
 754                         parse_commit(c);
 755
 756                         prio_queue_put(&queue, *item);
 757                 }
 758         }
 759
 760         while (num_to_find && (current = prio_queue_get(&queue)) != NULL) {
 761                 struct commit_list *parents;
 762
 763                 if (current->object.flags & PARENT1) {
 764                         current->object.flags &= ~PARENT1;
 765                         current->object.flags |= reachable_flag;
 766                         commit_list_insert(current, &found_commits);
 767                         num_to_find--;
 768                 }
 769
 770                 for (parents = current->parents; parents; parents = parents->next) {
 771                         struct commit *p = parents->item;
 772
 773                         parse_commit(p);
 774
 775                         if (commit_graph_generation(p) < min_generation)
 776                                 continue;
 777
 778                         if (p->object.flags & PARENT2)
 779                                 continue;
 780
 781                         p->object.flags |= PARENT2;
 782                         prio_queue_put(&queue, p);
 783                 }
 784         }
 785
 786         clear_commit_marks_many(nr_to, to, PARENT1);
 787         clear_commit_marks_many(nr_from, from, PARENT2);
 788
 789         return found_commits;
 790 }