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                                                 timestamp_t 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         timestamp_t last_gen = GENERATION_NUMBER_INFINITY;
  41
  42         if (!min_generation && !corrected_commit_dates_enabled(r))
  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                 timestamp_t generation = commit_graph_generation(commit);
  62
  63                 if (min_generation && generation > last_gen)
  64                         BUG("bad generation skip %"PRItime" > %"PRItime" 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                 timestamp_t min_generation = commit_graph_generation(array[i]);
 181
 182                 if (redundant[i])
 183                         continue;
 184                 for (j = filled = 0; j < cnt; j++) {
 185                         timestamp_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 repo_is_descendant_of(struct repository *r,
 290                           struct commit *commit,
 291                           struct commit_list *with_commit)
 292 {
 293         if (!with_commit)
 294                 return 1;
 295
 296         if (generation_numbers_enabled(the_repository)) {
 297                 struct commit_list *from_list = NULL;
 298                 int result;
 299                 commit_list_insert(commit, &from_list);
 300                 result = can_all_from_reach(from_list, with_commit, 0);
 301                 free_commit_list(from_list);
 302                 return result;
 303         } else {
 304                 while (with_commit) {
 305                         struct commit *other;
 306
 307                         other = with_commit->item;
 308                         with_commit = with_commit->next;
 309                         if (repo_in_merge_bases_many(r, other, 1, &commit))
 310                                 return 1;
 311                 }
 312                 return 0;
 313         }
 314 }
 315
 316 /*
 317  * Is "commit" an ancestor of one of the "references"?
 318  */
 319 int repo_in_merge_bases_many(struct repository *r, struct commit *commit,
 320                              int nr_reference, struct commit **reference)
 321 {
 322         struct commit_list *bases;
 323         int ret = 0, i;
 324         timestamp_t generation, max_generation = GENERATION_NUMBER_ZERO;
 325
 326         if (repo_parse_commit(r, commit))
 327                 return ret;
 328         for (i = 0; i < nr_reference; i++) {
 329                 if (repo_parse_commit(r, reference[i]))
 330                         return ret;
 331
 332                 generation = commit_graph_generation(reference[i]);
 333                 if (generation > max_generation)
 334                         max_generation = generation;
 335         }
 336
 337         generation = commit_graph_generation(commit);
 338         if (generation > max_generation)
 339                 return ret;
 340
 341         bases = paint_down_to_common(r, commit,
 342                                      nr_reference, reference,
 343                                      generation);
 344         if (commit->object.flags & PARENT2)
 345                 ret = 1;
 346         clear_commit_marks(commit, all_flags);
 347         clear_commit_marks_many(nr_reference, reference, all_flags);
 348         free_commit_list(bases);
 349         return ret;
 350 }
 351
 352 /*
 353  * Is "commit" an ancestor of (i.e. reachable from) the "reference"?
 354  */
 355 int repo_in_merge_bases(struct repository *r,
 356                         struct commit *commit,
 357                         struct commit *reference)
 358 {
 359         int res;
 360         struct commit_list *list = NULL;
 361         struct commit_list **next = &list;
 362
 363         next = commit_list_append(commit, next);
 364         res = repo_is_descendant_of(r, reference, list);
 365         free_commit_list(list);
 366
 367         return res;
 368 }
 369
 370 struct commit_list *reduce_heads(struct commit_list *heads)
 371 {
 372         struct commit_list *p;
 373         struct commit_list *result = NULL, **tail = &result;
 374         struct commit **array;
 375         int num_head, i;
 376
 377         if (!heads)
 378                 return NULL;
 379
 380         /* Uniquify */
 381         for (p = heads; p; p = p->next)
 382                 p->item->object.flags &= ~STALE;
 383         for (p = heads, num_head = 0; p; p = p->next) {
 384                 if (p->item->object.flags & STALE)
 385                         continue;
 386                 p->item->object.flags |= STALE;
 387                 num_head++;
 388         }
 389         array = xcalloc(num_head, sizeof(*array));
 390         for (p = heads, i = 0; p; p = p->next) {
 391                 if (p->item->object.flags & STALE) {
 392                         array[i++] = p->item;
 393                         p->item->object.flags &= ~STALE;
 394                 }
 395         }
 396         num_head = remove_redundant(the_repository, array, num_head);
 397         for (i = 0; i < num_head; i++)
 398                 tail = &commit_list_insert(array[i], tail)->next;
 399         free(array);
 400         return result;
 401 }
 402
 403 void reduce_heads_replace(struct commit_list **heads)
 404 {
 405         struct commit_list *result = reduce_heads(*heads);
 406         free_commit_list(*heads);
 407         *heads = result;
 408 }
 409
 410 int ref_newer(const struct object_id *new_oid, const struct object_id *old_oid)
 411 {
 412         struct object *o;
 413         struct commit *old_commit, *new_commit;
 414         struct commit_list *old_commit_list = NULL;
 415         int ret;
 416
 417         /*
 418          * Both new_commit and old_commit must be commit-ish and new_commit is descendant of
 419          * old_commit.  Otherwise we require --force.
 420          */
 421         o = deref_tag(the_repository, parse_object(the_repository, old_oid),
 422                       NULL, 0);
 423         if (!o || o->type != OBJ_COMMIT)
 424                 return 0;
 425         old_commit = (struct commit *) o;
 426
 427         o = deref_tag(the_repository, parse_object(the_repository, new_oid),
 428                       NULL, 0);
 429         if (!o || o->type != OBJ_COMMIT)
 430                 return 0;
 431         new_commit = (struct commit *) o;
 432
 433         if (parse_commit(new_commit) < 0)
 434                 return 0;
 435
 436         commit_list_insert(old_commit, &old_commit_list);
 437         ret = repo_is_descendant_of(the_repository,
 438                                     new_commit, old_commit_list);
 439         free_commit_list(old_commit_list);
 440         return ret;
 441 }
 442
 443 /*
 444  * Mimicking the real stack, this stack lives on the heap, avoiding stack
 445  * overflows.
 446  *
 447  * At each recursion step, the stack items points to the commits whose
 448  * ancestors are to be inspected.
 449  */
 450 struct contains_stack {
 451         int nr, alloc;
 452         struct contains_stack_entry {
 453                 struct commit *commit;
 454                 struct commit_list *parents;
 455         } *contains_stack;
 456 };
 457
 458 static int in_commit_list(const struct commit_list *want, struct commit *c)
 459 {
 460         for (; want; want = want->next)
 461                 if (oideq(&want->item->object.oid, &c->object.oid))
 462                         return 1;
 463         return 0;
 464 }
 465
 466 /*
 467  * Test whether the candidate is contained in the list.
 468  * Do not recurse to find out, though, but return -1 if inconclusive.
 469  */
 470 static enum contains_result contains_test(struct commit *candidate,
 471                                           const struct commit_list *want,
 472                                           struct contains_cache *cache,
 473                                           timestamp_t cutoff)
 474 {
 475         enum contains_result *cached = contains_cache_at(cache, candidate);
 476
 477         /* If we already have the answer cached, return that. */
 478         if (*cached)
 479                 return *cached;
 480
 481         /* or are we it? */
 482         if (in_commit_list(want, candidate)) {
 483                 *cached = CONTAINS_YES;
 484                 return CONTAINS_YES;
 485         }
 486
 487         /* Otherwise, we don't know; prepare to recurse */
 488         parse_commit_or_die(candidate);
 489
 490         if (commit_graph_generation(candidate) < cutoff)
 491                 return CONTAINS_NO;
 492
 493         return CONTAINS_UNKNOWN;
 494 }
 495
 496 static void push_to_contains_stack(struct commit *candidate, struct contains_stack *contains_stack)
 497 {
 498         ALLOC_GROW(contains_stack->contains_stack, contains_stack->nr + 1, contains_stack->alloc);
 499         contains_stack->contains_stack[contains_stack->nr].commit = candidate;
 500         contains_stack->contains_stack[contains_stack->nr++].parents = candidate->parents;
 501 }
 502
 503 static enum contains_result contains_tag_algo(struct commit *candidate,
 504                                               const struct commit_list *want,
 505                                               struct contains_cache *cache)
 506 {
 507         struct contains_stack contains_stack = { 0, 0, NULL };
 508         enum contains_result result;
 509         timestamp_t cutoff = GENERATION_NUMBER_INFINITY;
 510         const struct commit_list *p;
 511
 512         for (p = want; p; p = p->next) {
 513                 timestamp_t generation;
 514                 struct commit *c = p->item;
 515                 load_commit_graph_info(the_repository, c);
 516                 generation = commit_graph_generation(c);
 517                 if (generation < cutoff)
 518                         cutoff = generation;
 519         }
 520
 521         result = contains_test(candidate, want, cache, cutoff);
 522         if (result != CONTAINS_UNKNOWN)
 523                 return result;
 524
 525         push_to_contains_stack(candidate, &contains_stack);
 526         while (contains_stack.nr) {
 527                 struct contains_stack_entry *entry = &contains_stack.contains_stack[contains_stack.nr - 1];
 528                 struct commit *commit = entry->commit;
 529                 struct commit_list *parents = entry->parents;
 530
 531                 if (!parents) {
 532                         *contains_cache_at(cache, commit) = CONTAINS_NO;
 533                         contains_stack.nr--;
 534                 }
 535                 /*
 536                  * If we just popped the stack, parents->item has been marked,
 537                  * therefore contains_test will return a meaningful yes/no.
 538                  */
 539                 else switch (contains_test(parents->item, want, cache, cutoff)) {
 540                 case CONTAINS_YES:
 541                         *contains_cache_at(cache, commit) = CONTAINS_YES;
 542                         contains_stack.nr--;
 543                         break;
 544                 case CONTAINS_NO:
 545                         entry->parents = parents->next;
 546                         break;
 547                 case CONTAINS_UNKNOWN:
 548                         push_to_contains_stack(parents->item, &contains_stack);
 549                         break;
 550                 }
 551         }
 552         free(contains_stack.contains_stack);
 553         return contains_test(candidate, want, cache, cutoff);
 554 }
 555
 556 int commit_contains(struct ref_filter *filter, struct commit *commit,
 557                     struct commit_list *list, struct contains_cache *cache)
 558 {
 559         if (filter->with_commit_tag_algo)
 560                 return contains_tag_algo(commit, list, cache) == CONTAINS_YES;
 561         return repo_is_descendant_of(the_repository, commit, list);
 562 }
 563
 564 static int compare_commits_by_gen(const void *_a, const void *_b)
 565 {
 566         const struct commit *a = *(const struct commit * const *)_a;
 567         const struct commit *b = *(const struct commit * const *)_b;
 568
 569         timestamp_t generation_a = commit_graph_generation(a);
 570         timestamp_t generation_b = commit_graph_generation(b);
 571
 572         if (generation_a < generation_b)
 573                 return -1;
 574         if (generation_a > generation_b)
 575                 return 1;
 576         return 0;
 577 }
 578
 579 int can_all_from_reach_with_flag(struct object_array *from,
 580                                  unsigned int with_flag,
 581                                  unsigned int assign_flag,
 582                                  time_t min_commit_date,
 583                                  timestamp_t min_generation)
 584 {
 585         struct commit **list = NULL;
 586         int i;
 587         int nr_commits;
 588         int result = 1;
 589
 590         ALLOC_ARRAY(list, from->nr);
 591         nr_commits = 0;
 592         for (i = 0; i < from->nr; i++) {
 593                 struct object *from_one = from->objects[i].item;
 594
 595                 if (!from_one || from_one->flags & assign_flag)
 596                         continue;
 597
 598                 from_one = deref_tag(the_repository, from_one,
 599                                      "a from object", 0);
 600                 if (!from_one || from_one->type != OBJ_COMMIT) {
 601                         /*
 602                          * no way to tell if this is reachable by
 603                          * looking at the ancestry chain alone, so
 604                          * leave a note to ourselves not to worry about
 605                          * this object anymore.
 606                          */
 607                         from->objects[i].item->flags |= assign_flag;
 608                         continue;
 609                 }
 610
 611                 list[nr_commits] = (struct commit *)from_one;
 612                 if (parse_commit(list[nr_commits]) ||
 613                     commit_graph_generation(list[nr_commits]) < min_generation) {
 614                         result = 0;
 615                         goto cleanup;
 616                 }
 617
 618                 nr_commits++;
 619         }
 620
 621         QSORT(list, nr_commits, compare_commits_by_gen);
 622
 623         for (i = 0; i < nr_commits; i++) {
 624                 /* DFS from list[i] */
 625                 struct commit_list *stack = NULL;
 626
 627                 list[i]->object.flags |= assign_flag;
 628                 commit_list_insert(list[i], &stack);
 629
 630                 while (stack) {
 631                         struct commit_list *parent;
 632
 633                         if (stack->item->object.flags & (with_flag | RESULT)) {
 634                                 pop_commit(&stack);
 635                                 if (stack)
 636                                         stack->item->object.flags |= RESULT;
 637                                 continue;
 638                         }
 639
 640                         for (parent = stack->item->parents; parent; parent = parent->next) {
 641                                 if (parent->item->object.flags & (with_flag | RESULT))
 642                                         stack->item->object.flags |= RESULT;
 643
 644                                 if (!(parent->item->object.flags & assign_flag)) {
 645                                         parent->item->object.flags |= assign_flag;
 646
 647                                         if (parse_commit(parent->item) ||
 648                                             parent->item->date < min_commit_date ||
 649                                             commit_graph_generation(parent->item) < min_generation)
 650                                                 continue;
 651
 652                                         commit_list_insert(parent->item, &stack);
 653                                         break;
 654                                 }
 655                         }
 656
 657                         if (!parent)
 658                                 pop_commit(&stack);
 659                 }
 660
 661                 if (!(list[i]->object.flags & (with_flag | RESULT))) {
 662                         result = 0;
 663                         goto cleanup;
 664                 }
 665         }
 666
 667 cleanup:
 668         clear_commit_marks_many(nr_commits, list, RESULT | assign_flag);
 669         free(list);
 670
 671         for (i = 0; i < from->nr; i++)
 672                 from->objects[i].item->flags &= ~assign_flag;
 673
 674         return result;
 675 }
 676
 677 int can_all_from_reach(struct commit_list *from, struct commit_list *to,
 678                        int cutoff_by_min_date)
 679 {
 680         struct object_array from_objs = OBJECT_ARRAY_INIT;
 681         time_t min_commit_date = cutoff_by_min_date ? from->item->date : 0;
 682         struct commit_list *from_iter = from, *to_iter = to;
 683         int result;
 684         timestamp_t min_generation = GENERATION_NUMBER_INFINITY;
 685
 686         while (from_iter) {
 687                 add_object_array(&from_iter->item->object, NULL, &from_objs);
 688
 689                 if (!parse_commit(from_iter->item)) {
 690                         timestamp_t generation;
 691                         if (from_iter->item->date < min_commit_date)
 692                                 min_commit_date = from_iter->item->date;
 693
 694                         generation = commit_graph_generation(from_iter->item);
 695                         if (generation < min_generation)
 696                                 min_generation = generation;
 697                 }
 698
 699                 from_iter = from_iter->next;
 700         }
 701
 702         while (to_iter) {
 703                 if (!parse_commit(to_iter->item)) {
 704                         timestamp_t generation;
 705                         if (to_iter->item->date < min_commit_date)
 706                                 min_commit_date = to_iter->item->date;
 707
 708                         generation = commit_graph_generation(to_iter->item);
 709                         if (generation < min_generation)
 710                                 min_generation = generation;
 711                 }
 712
 713                 to_iter->item->object.flags |= PARENT2;
 714
 715                 to_iter = to_iter->next;
 716         }
 717
 718         result = can_all_from_reach_with_flag(&from_objs, PARENT2, PARENT1,
 719                                               min_commit_date, min_generation);
 720
 721         while (from) {
 722                 clear_commit_marks(from->item, PARENT1);
 723                 from = from->next;
 724         }
 725
 726         while (to) {
 727                 clear_commit_marks(to->item, PARENT2);
 728                 to = to->next;
 729         }
 730
 731         object_array_clear(&from_objs);
 732         return result;
 733 }
 734
 735 struct commit_list *get_reachable_subset(struct commit **from, int nr_from,
 736                                          struct commit **to, int nr_to,
 737                                          unsigned int reachable_flag)
 738 {
 739         struct commit **item;
 740         struct commit *current;
 741         struct commit_list *found_commits = NULL;
 742         struct commit **to_last = to + nr_to;
 743         struct commit **from_last = from + nr_from;
 744         timestamp_t min_generation = GENERATION_NUMBER_INFINITY;
 745         int num_to_find = 0;
 746
 747         struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
 748
 749         for (item = to; item < to_last; item++) {
 750                 timestamp_t generation;
 751                 struct commit *c = *item;
 752
 753                 parse_commit(c);
 754                 generation = commit_graph_generation(c);
 755                 if (generation < min_generation)
 756                         min_generation = generation;
 757
 758                 if (!(c->object.flags & PARENT1)) {
 759                         c->object.flags |= PARENT1;
 760                         num_to_find++;
 761                 }
 762         }
 763
 764         for (item = from; item < from_last; item++) {
 765                 struct commit *c = *item;
 766                 if (!(c->object.flags & PARENT2)) {
 767                         c->object.flags |= PARENT2;
 768                         parse_commit(c);
 769
 770                         prio_queue_put(&queue, *item);
 771                 }
 772         }
 773
 774         while (num_to_find && (current = prio_queue_get(&queue)) != NULL) {
 775                 struct commit_list *parents;
 776
 777                 if (current->object.flags & PARENT1) {
 778                         current->object.flags &= ~PARENT1;
 779                         current->object.flags |= reachable_flag;
 780                         commit_list_insert(current, &found_commits);
 781                         num_to_find--;
 782                 }
 783
 784                 for (parents = current->parents; parents; parents = parents->next) {
 785                         struct commit *p = parents->item;
 786
 787                         parse_commit(p);
 788
 789                         if (commit_graph_generation(p) < min_generation)
 790                                 continue;
 791
 792                         if (p->object.flags & PARENT2)
 793                                 continue;
 794
 795                         p->object.flags |= PARENT2;
 796                         prio_queue_put(&queue, p);
 797                 }
 798         }
 799
 800         clear_commit_marks_many(nr_to, to, PARENT1);
 801         clear_commit_marks_many(nr_from, from, PARENT2);
 802
 803         return found_commits;
 804 }