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