commit.c

   1 #include "cache.h"
   2 #include "tag.h"
   3 #include "commit.h"
   4 #include "pkt-line.h"
   5 #include "utf8.h"
   6 #include "diff.h"
   7 #include "revision.h"
   8
   9 int save_commit_buffer = 1;
  10
  11 const char *commit_type = "commit";
  12
  13 static struct commit *check_commit(struct object *obj,
  14                                    const unsigned char *sha1,
  15                                    int quiet)
  16 {
  17         if (obj->type != OBJ_COMMIT) {
  18                 if (!quiet)
  19                         error("Object %s is a %s, not a commit",
  20                               sha1_to_hex(sha1), typename(obj->type));
  21                 return NULL;
  22         }
  23         return (struct commit *) obj;
  24 }
  25
  26 struct commit *lookup_commit_reference_gently(const unsigned char *sha1,
  27                                               int quiet)
  28 {
  29         struct object *obj = deref_tag(parse_object(sha1), NULL, 0);
  30
  31         if (!obj)
  32                 return NULL;
  33         return check_commit(obj, sha1, quiet);
  34 }
  35
  36 struct commit *lookup_commit_reference(const unsigned char *sha1)
  37 {
  38         return lookup_commit_reference_gently(sha1, 0);
  39 }
  40
  41 struct commit *lookup_commit(const unsigned char *sha1)
  42 {
  43         struct object *obj = lookup_object(sha1);
  44         if (!obj)
  45                 return create_object(sha1, OBJ_COMMIT, alloc_commit_node());
  46         if (!obj->type)
  47                 obj->type = OBJ_COMMIT;
  48         return check_commit(obj, sha1, 0);
  49 }
  50
  51 static unsigned long parse_commit_date(const char *buf, const char *tail)
  52 {
  53         const char *dateptr;
  54
  55         if (buf + 6 >= tail)
  56                 return 0;
  57         if (memcmp(buf, "author", 6))
  58                 return 0;
  59         while (buf < tail && *buf++ != '\n')
  60                 /* nada */;
  61         if (buf + 9 >= tail)
  62                 return 0;
  63         if (memcmp(buf, "committer", 9))
  64                 return 0;
  65         while (buf < tail && *buf++ != '>')
  66                 /* nada */;
  67         if (buf >= tail)
  68                 return 0;
  69         dateptr = buf;
  70         while (buf < tail && *buf++ != '\n')
  71                 /* nada */;
  72         if (buf >= tail)
  73                 return 0;
  74         /* dateptr < buf && buf[-1] == '\n', so strtoul will stop at buf-1 */
  75         return strtoul(dateptr, NULL, 10);
  76 }
  77
  78 static struct commit_graft **commit_graft;
  79 static int commit_graft_alloc, commit_graft_nr;
  80
  81 static int commit_graft_pos(const unsigned char *sha1)
  82 {
  83         int lo, hi;
  84         lo = 0;
  85         hi = commit_graft_nr;
  86         while (lo < hi) {
  87                 int mi = (lo + hi) / 2;
  88                 struct commit_graft *graft = commit_graft[mi];
  89                 int cmp = hashcmp(sha1, graft->sha1);
  90                 if (!cmp)
  91                         return mi;
  92                 if (cmp < 0)
  93                         hi = mi;
  94                 else
  95                         lo = mi + 1;
  96         }
  97         return -lo - 1;
  98 }
  99
 100 int register_commit_graft(struct commit_graft *graft, int ignore_dups)
 101 {
 102         int pos = commit_graft_pos(graft->sha1);
 103
 104         if (0 <= pos) {
 105                 if (ignore_dups)
 106                         free(graft);
 107                 else {
 108                         free(commit_graft[pos]);
 109                         commit_graft[pos] = graft;
 110                 }
 111                 return 1;
 112         }
 113         pos = -pos - 1;
 114         if (commit_graft_alloc <= ++commit_graft_nr) {
 115                 commit_graft_alloc = alloc_nr(commit_graft_alloc);
 116                 commit_graft = xrealloc(commit_graft,
 117                                         sizeof(*commit_graft) *
 118                                         commit_graft_alloc);
 119         }
 120         if (pos < commit_graft_nr)
 121                 memmove(commit_graft + pos + 1,
 122                         commit_graft + pos,
 123                         (commit_graft_nr - pos - 1) *
 124                         sizeof(*commit_graft));
 125         commit_graft[pos] = graft;
 126         return 0;
 127 }
 128
 129 struct commit_graft *read_graft_line(char *buf, int len)
 130 {
 131         /* The format is just "Commit Parent1 Parent2 ...\n" */
 132         int i;
 133         struct commit_graft *graft = NULL;
 134
 135         if (buf[len-1] == '\n')
 136                 buf[--len] = 0;
 137         if (buf[0] == '#' || buf[0] == '\0')
 138                 return NULL;
 139         if ((len + 1) % 41) {
 140         bad_graft_data:
 141                 error("bad graft data: %s", buf);
 142                 free(graft);
 143                 return NULL;
 144         }
 145         i = (len + 1) / 41 - 1;
 146         graft = xmalloc(sizeof(*graft) + 20 * i);
 147         graft->nr_parent = i;
 148         if (get_sha1_hex(buf, graft->sha1))
 149                 goto bad_graft_data;
 150         for (i = 40; i < len; i += 41) {
 151                 if (buf[i] != ' ')
 152                         goto bad_graft_data;
 153                 if (get_sha1_hex(buf + i + 1, graft->parent[i/41]))
 154                         goto bad_graft_data;
 155         }
 156         return graft;
 157 }
 158
 159 static int read_graft_file(const char *graft_file)
 160 {
 161         FILE *fp = fopen(graft_file, "r");
 162         char buf[1024];
 163         if (!fp)
 164                 return -1;
 165         while (fgets(buf, sizeof(buf), fp)) {
 166                 /* The format is just "Commit Parent1 Parent2 ...\n" */
 167                 int len = strlen(buf);
 168                 struct commit_graft *graft = read_graft_line(buf, len);
 169                 if (!graft)
 170                         continue;
 171                 if (register_commit_graft(graft, 1))
 172                         error("duplicate graft data: %s", buf);
 173         }
 174         fclose(fp);
 175         return 0;
 176 }
 177
 178 static void prepare_commit_graft(void)
 179 {
 180         static int commit_graft_prepared;
 181         char *graft_file;
 182
 183         if (commit_graft_prepared)
 184                 return;
 185         graft_file = get_graft_file();
 186         read_graft_file(graft_file);
 187         /* make sure shallows are read */
 188         is_repository_shallow();
 189         commit_graft_prepared = 1;
 190 }
 191
 192 struct commit_graft *lookup_commit_graft(const unsigned char *sha1)
 193 {
 194         int pos;
 195         prepare_commit_graft();
 196         pos = commit_graft_pos(sha1);
 197         if (pos < 0)
 198                 return NULL;
 199         return commit_graft[pos];
 200 }
 201
 202 int write_shallow_commits(struct strbuf *out, int use_pack_protocol)
 203 {
 204         int i, count = 0;
 205         for (i = 0; i < commit_graft_nr; i++)
 206                 if (commit_graft[i]->nr_parent < 0) {
 207                         const char *hex =
 208                                 sha1_to_hex(commit_graft[i]->sha1);
 209                         count++;
 210                         if (use_pack_protocol)
 211                                 packet_buf_write(out, "shallow %s", hex);
 212                         else {
 213                                 strbuf_addstr(out, hex);
 214                                 strbuf_addch(out, '\n');
 215                         }
 216                 }
 217         return count;
 218 }
 219
 220 int unregister_shallow(const unsigned char *sha1)
 221 {
 222         int pos = commit_graft_pos(sha1);
 223         if (pos < 0)
 224                 return -1;
 225         if (pos + 1 < commit_graft_nr)
 226                 memcpy(commit_graft + pos, commit_graft + pos + 1,
 227                                 sizeof(struct commit_graft *)
 228                                 * (commit_graft_nr - pos - 1));
 229         commit_graft_nr--;
 230         return 0;
 231 }
 232
 233 int parse_commit_buffer(struct commit *item, void *buffer, unsigned long size)
 234 {
 235         char *tail = buffer;
 236         char *bufptr = buffer;
 237         unsigned char parent[20];
 238         struct commit_list **pptr;
 239         struct commit_graft *graft;
 240
 241         if (item->object.parsed)
 242                 return 0;
 243         item->object.parsed = 1;
 244         tail += size;
 245         if (tail <= bufptr + 46 || memcmp(bufptr, "tree ", 5) || bufptr[45] != '\n')
 246                 return error("bogus commit object %s", sha1_to_hex(item->object.sha1));
 247         if (get_sha1_hex(bufptr + 5, parent) < 0)
 248                 return error("bad tree pointer in commit %s",
 249                              sha1_to_hex(item->object.sha1));
 250         item->tree = lookup_tree(parent);
 251         bufptr += 46; /* "tree " + "hex sha1" + "\n" */
 252         pptr = &item->parents;
 253
 254         graft = lookup_commit_graft(item->object.sha1);
 255         while (bufptr + 48 < tail && !memcmp(bufptr, "parent ", 7)) {
 256                 struct commit *new_parent;
 257
 258                 if (tail <= bufptr + 48 ||
 259                     get_sha1_hex(bufptr + 7, parent) ||
 260                     bufptr[47] != '\n')
 261                         return error("bad parents in commit %s", sha1_to_hex(item->object.sha1));
 262                 bufptr += 48;
 263                 /*
 264                  * The clone is shallow if nr_parent < 0, and we must
 265                  * not traverse its real parents even when we unhide them.
 266                  */
 267                 if (graft && (graft->nr_parent < 0 || grafts_replace_parents))
 268                         continue;
 269                 new_parent = lookup_commit(parent);
 270                 if (new_parent)
 271                         pptr = &commit_list_insert(new_parent, pptr)->next;
 272         }
 273         if (graft) {
 274                 int i;
 275                 struct commit *new_parent;
 276                 for (i = 0; i < graft->nr_parent; i++) {
 277                         new_parent = lookup_commit(graft->parent[i]);
 278                         if (!new_parent)
 279                                 continue;
 280                         pptr = &commit_list_insert(new_parent, pptr)->next;
 281                 }
 282         }
 283         item->date = parse_commit_date(bufptr, tail);
 284
 285         return 0;
 286 }
 287
 288 int parse_commit(struct commit *item)
 289 {
 290         enum object_type type;
 291         void *buffer;
 292         unsigned long size;
 293         int ret;
 294
 295         if (!item)
 296                 return -1;
 297         if (item->object.parsed)
 298                 return 0;
 299         buffer = read_sha1_file(item->object.sha1, &type, &size);
 300         if (!buffer)
 301                 return error("Could not read %s",
 302                              sha1_to_hex(item->object.sha1));
 303         if (type != OBJ_COMMIT) {
 304                 free(buffer);
 305                 return error("Object %s not a commit",
 306                              sha1_to_hex(item->object.sha1));
 307         }
 308         ret = parse_commit_buffer(item, buffer, size);
 309         if (save_commit_buffer && !ret) {
 310                 item->buffer = buffer;
 311                 return 0;
 312         }
 313         free(buffer);
 314         return ret;
 315 }
 316
 317 struct commit_list *commit_list_insert(struct commit *item, struct commit_list **list_p)
 318 {
 319         struct commit_list *new_list = xmalloc(sizeof(struct commit_list));
 320         new_list->item = item;
 321         new_list->next = *list_p;
 322         *list_p = new_list;
 323         return new_list;
 324 }
 325
 326 unsigned commit_list_count(const struct commit_list *l)
 327 {
 328         unsigned c = 0;
 329         for (; l; l = l->next )
 330                 c++;
 331         return c;
 332 }
 333
 334 void free_commit_list(struct commit_list *list)
 335 {
 336         while (list) {
 337                 struct commit_list *temp = list;
 338                 list = temp->next;
 339                 free(temp);
 340         }
 341 }
 342
 343 struct commit_list * insert_by_date(struct commit *item, struct commit_list **list)
 344 {
 345         struct commit_list **pp = list;
 346         struct commit_list *p;
 347         while ((p = *pp) != NULL) {
 348                 if (p->item->date < item->date) {
 349                         break;
 350                 }
 351                 pp = &p->next;
 352         }
 353         return commit_list_insert(item, pp);
 354 }
 355
 356
 357 void sort_by_date(struct commit_list **list)
 358 {
 359         struct commit_list *ret = NULL;
 360         while (*list) {
 361                 insert_by_date((*list)->item, &ret);
 362                 *list = (*list)->next;
 363         }
 364         *list = ret;
 365 }
 366
 367 struct commit *pop_most_recent_commit(struct commit_list **list,
 368                                       unsigned int mark)
 369 {
 370         struct commit *ret = (*list)->item;
 371         struct commit_list *parents = ret->parents;
 372         struct commit_list *old = *list;
 373
 374         *list = (*list)->next;
 375         free(old);
 376
 377         while (parents) {
 378                 struct commit *commit = parents->item;
 379                 if (!parse_commit(commit) && !(commit->object.flags & mark)) {
 380                         commit->object.flags |= mark;
 381                         insert_by_date(commit, list);
 382                 }
 383                 parents = parents->next;
 384         }
 385         return ret;
 386 }
 387
 388 void clear_commit_marks(struct commit *commit, unsigned int mark)
 389 {
 390         while (commit) {
 391                 struct commit_list *parents;
 392
 393                 if (!(mark & commit->object.flags))
 394                         return;
 395
 396                 commit->object.flags &= ~mark;
 397
 398                 parents = commit->parents;
 399                 if (!parents)
 400                         return;
 401
 402                 while ((parents = parents->next))
 403                         clear_commit_marks(parents->item, mark);
 404
 405                 commit = commit->parents->item;
 406         }
 407 }
 408
 409 struct commit *pop_commit(struct commit_list **stack)
 410 {
 411         struct commit_list *top = *stack;
 412         struct commit *item = top ? top->item : NULL;
 413
 414         if (top) {
 415                 *stack = top->next;
 416                 free(top);
 417         }
 418         return item;
 419 }
 420
 421 /*
 422  * Performs an in-place topological sort on the list supplied.
 423  */
 424 void sort_in_topological_order(struct commit_list ** list, int lifo)
 425 {
 426         struct commit_list *next, *orig = *list;
 427         struct commit_list *work, **insert;
 428         struct commit_list **pptr;
 429
 430         if (!orig)
 431                 return;
 432         *list = NULL;
 433
 434         /* Mark them and clear the indegree */
 435         for (next = orig; next; next = next->next) {
 436                 struct commit *commit = next->item;
 437                 commit->indegree = 1;
 438         }
 439
 440         /* update the indegree */
 441         for (next = orig; next; next = next->next) {
 442                 struct commit_list * parents = next->item->parents;
 443                 while (parents) {
 444                         struct commit *parent = parents->item;
 445
 446                         if (parent->indegree)
 447                                 parent->indegree++;
 448                         parents = parents->next;
 449                 }
 450         }
 451
 452         /*
 453          * find the tips
 454          *
 455          * tips are nodes not reachable from any other node in the list
 456          *
 457          * the tips serve as a starting set for the work queue.
 458          */
 459         work = NULL;
 460         insert = &work;
 461         for (next = orig; next; next = next->next) {
 462                 struct commit *commit = next->item;
 463
 464                 if (commit->indegree == 1)
 465                         insert = &commit_list_insert(commit, insert)->next;
 466         }
 467
 468         /* process the list in topological order */
 469         if (!lifo)
 470                 sort_by_date(&work);
 471
 472         pptr = list;
 473         *list = NULL;
 474         while (work) {
 475                 struct commit *commit;
 476                 struct commit_list *parents, *work_item;
 477
 478                 work_item = work;
 479                 work = work_item->next;
 480                 work_item->next = NULL;
 481
 482                 commit = work_item->item;
 483                 for (parents = commit->parents; parents ; parents = parents->next) {
 484                         struct commit *parent=parents->item;
 485
 486                         if (!parent->indegree)
 487                                 continue;
 488
 489                         /*
 490                          * parents are only enqueued for emission
 491                          * when all their children have been emitted thereby
 492                          * guaranteeing topological order.
 493                          */
 494                         if (--parent->indegree == 1) {
 495                                 if (!lifo)
 496                                         insert_by_date(parent, &work);
 497                                 else
 498                                         commit_list_insert(parent, &work);
 499                         }
 500                 }
 501                 /*
 502                  * work_item is a commit all of whose children
 503                  * have already been emitted. we can emit it now.
 504                  */
 505                 commit->indegree = 0;
 506                 *pptr = work_item;
 507                 pptr = &work_item->next;
 508         }
 509 }
 510
 511 /* merge-base stuff */
 512
 513 /* bits #0..15 in revision.h */
 514 #define PARENT1         (1u<<16)
 515 #define PARENT2         (1u<<17)
 516 #define STALE           (1u<<18)
 517 #define RESULT          (1u<<19)
 518
 519 static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);
 520
 521 static struct commit *interesting(struct commit_list *list)
 522 {
 523         while (list) {
 524                 struct commit *commit = list->item;
 525                 list = list->next;
 526                 if (commit->object.flags & STALE)
 527                         continue;
 528                 return commit;
 529         }
 530         return NULL;
 531 }
 532
 533 static struct commit_list *merge_bases_many(struct commit *one, int n, struct commit **twos)
 534 {
 535         struct commit_list *list = NULL;
 536         struct commit_list *result = NULL;
 537         int i;
 538
 539         for (i = 0; i < n; i++) {
 540                 if (one == twos[i])
 541                         /*
 542                          * We do not mark this even with RESULT so we do not
 543                          * have to clean it up.
 544                          */
 545                         return commit_list_insert(one, &result);
 546         }
 547
 548         if (parse_commit(one))
 549                 return NULL;
 550         for (i = 0; i < n; i++) {
 551                 if (parse_commit(twos[i]))
 552                         return NULL;
 553         }
 554
 555         one->object.flags |= PARENT1;
 556         insert_by_date(one, &list);
 557         for (i = 0; i < n; i++) {
 558                 twos[i]->object.flags |= PARENT2;
 559                 insert_by_date(twos[i], &list);
 560         }
 561
 562         while (interesting(list)) {
 563                 struct commit *commit;
 564                 struct commit_list *parents;
 565                 struct commit_list *next;
 566                 int flags;
 567
 568                 commit = list->item;
 569                 next = list->next;
 570                 free(list);
 571                 list = next;
 572
 573                 flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
 574                 if (flags == (PARENT1 | PARENT2)) {
 575                         if (!(commit->object.flags & RESULT)) {
 576                                 commit->object.flags |= RESULT;
 577                                 insert_by_date(commit, &result);
 578                         }
 579                         /* Mark parents of a found merge stale */
 580                         flags |= STALE;
 581                 }
 582                 parents = commit->parents;
 583                 while (parents) {
 584                         struct commit *p = parents->item;
 585                         parents = parents->next;
 586                         if ((p->object.flags & flags) == flags)
 587                                 continue;
 588                         if (parse_commit(p))
 589                                 return NULL;
 590                         p->object.flags |= flags;
 591                         insert_by_date(p, &list);
 592                 }
 593         }
 594
 595         /* Clean up the result to remove stale ones */
 596         free_commit_list(list);
 597         list = result; result = NULL;
 598         while (list) {
 599                 struct commit_list *next = list->next;
 600                 if (!(list->item->object.flags & STALE))
 601                         insert_by_date(list->item, &result);
 602                 free(list);
 603                 list = next;
 604         }
 605         return result;
 606 }
 607
 608 struct commit_list *get_octopus_merge_bases(struct commit_list *in)
 609 {
 610         struct commit_list *i, *j, *k, *ret = NULL;
 611         struct commit_list **pptr = &ret;
 612
 613         for (i = in; i; i = i->next) {
 614                 if (!ret)
 615                         pptr = &commit_list_insert(i->item, pptr)->next;
 616                 else {
 617                         struct commit_list *new = NULL, *end = NULL;
 618
 619                         for (j = ret; j; j = j->next) {
 620                                 struct commit_list *bases;
 621                                 bases = get_merge_bases(i->item, j->item, 1);
 622                                 if (!new)
 623                                         new = bases;
 624                                 else
 625                                         end->next = bases;
 626                                 for (k = bases; k; k = k->next)
 627                                         end = k;
 628                         }
 629                         ret = new;
 630                 }
 631         }
 632         return ret;
 633 }
 634
 635 struct commit_list *get_merge_bases_many(struct commit *one,
 636                                          int n,
 637                                          struct commit **twos,
 638                                          int cleanup)
 639 {
 640         struct commit_list *list;
 641         struct commit **rslt;
 642         struct commit_list *result;
 643         int cnt, i, j;
 644
 645         result = merge_bases_many(one, n, twos);
 646         for (i = 0; i < n; i++) {
 647                 if (one == twos[i])
 648                         return result;
 649         }
 650         if (!result || !result->next) {
 651                 if (cleanup) {
 652                         clear_commit_marks(one, all_flags);
 653                         for (i = 0; i < n; i++)
 654                                 clear_commit_marks(twos[i], all_flags);
 655                 }
 656                 return result;
 657         }
 658
 659         /* There are more than one */
 660         cnt = 0;
 661         list = result;
 662         while (list) {
 663                 list = list->next;
 664                 cnt++;
 665         }
 666         rslt = xcalloc(cnt, sizeof(*rslt));
 667         for (list = result, i = 0; list; list = list->next)
 668                 rslt[i++] = list->item;
 669         free_commit_list(result);
 670
 671         clear_commit_marks(one, all_flags);
 672         for (i = 0; i < n; i++)
 673                 clear_commit_marks(twos[i], all_flags);
 674         for (i = 0; i < cnt - 1; i++) {
 675                 for (j = i+1; j < cnt; j++) {
 676                         if (!rslt[i] || !rslt[j])
 677                                 continue;
 678                         result = merge_bases_many(rslt[i], 1, &rslt[j]);
 679                         clear_commit_marks(rslt[i], all_flags);
 680                         clear_commit_marks(rslt[j], all_flags);
 681                         for (list = result; list; list = list->next) {
 682                                 if (rslt[i] == list->item)
 683                                         rslt[i] = NULL;
 684                                 if (rslt[j] == list->item)
 685                                         rslt[j] = NULL;
 686                         }
 687                 }
 688         }
 689
 690         /* Surviving ones in rslt[] are the independent results */
 691         result = NULL;
 692         for (i = 0; i < cnt; i++) {
 693                 if (rslt[i])
 694                         insert_by_date(rslt[i], &result);
 695         }
 696         free(rslt);
 697         return result;
 698 }
 699
 700 struct commit_list *get_merge_bases(struct commit *one, struct commit *two,
 701                                     int cleanup)
 702 {
 703         return get_merge_bases_many(one, 1, &two, cleanup);
 704 }
 705
 706 int is_descendant_of(struct commit *commit, struct commit_list *with_commit)
 707 {
 708         if (!with_commit)
 709                 return 1;
 710         while (with_commit) {
 711                 struct commit *other;
 712
 713                 other = with_commit->item;
 714                 with_commit = with_commit->next;
 715                 if (in_merge_bases(other, &commit, 1))
 716                         return 1;
 717         }
 718         return 0;
 719 }
 720
 721 int in_merge_bases(struct commit *commit, struct commit **reference, int num)
 722 {
 723         struct commit_list *bases, *b;
 724         int ret = 0;
 725
 726         if (num == 1)
 727                 bases = get_merge_bases(commit, *reference, 1);
 728         else
 729                 die("not yet");
 730         for (b = bases; b; b = b->next) {
 731                 if (!hashcmp(commit->object.sha1, b->item->object.sha1)) {
 732                         ret = 1;
 733                         break;
 734                 }
 735         }
 736
 737         free_commit_list(bases);
 738         return ret;
 739 }
 740
 741 struct commit_list *reduce_heads(struct commit_list *heads)
 742 {
 743         struct commit_list *p;
 744         struct commit_list *result = NULL, **tail = &result;
 745         struct commit **other;
 746         size_t num_head, num_other;
 747
 748         if (!heads)
 749                 return NULL;
 750
 751         /* Avoid unnecessary reallocations */
 752         for (p = heads, num_head = 0; p; p = p->next)
 753                 num_head++;
 754         other = xcalloc(sizeof(*other), num_head);
 755
 756         /* For each commit, see if it can be reached by others */
 757         for (p = heads; p; p = p->next) {
 758                 struct commit_list *q, *base;
 759
 760                 /* Do we already have this in the result? */
 761                 for (q = result; q; q = q->next)
 762                         if (p->item == q->item)
 763                                 break;
 764                 if (q)
 765                         continue;
 766
 767                 num_other = 0;
 768                 for (q = heads; q; q = q->next) {
 769                         if (p->item == q->item)
 770                                 continue;
 771                         other[num_other++] = q->item;
 772                 }
 773                 if (num_other)
 774                         base = get_merge_bases_many(p->item, num_other, other, 1);
 775                 else
 776                         base = NULL;
 777                 /*
 778                  * If p->item does not have anything common with other
 779                  * commits, there won't be any merge base.  If it is
 780                  * reachable from some of the others, p->item will be
 781                  * the merge base.  If its history is connected with
 782                  * others, but p->item is not reachable by others, we
 783                  * will get something other than p->item back.
 784                  */
 785                 if (!base || (base->item != p->item))
 786                         tail = &(commit_list_insert(p->item, tail)->next);
 787                 free_commit_list(base);
 788         }
 789         free(other);
 790         return result;
 791 }