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 #include "notes.h"
   9
  10 int save_commit_buffer = 1;
  11
  12 const char *commit_type = "commit";
  13
  14 static struct commit *check_commit(struct object *obj,
  15                                    const unsigned char *sha1,
  16                                    int quiet)
  17 {
  18         if (obj->type != OBJ_COMMIT) {
  19                 if (!quiet)
  20                         error("Object %s is a %s, not a commit",
  21                               sha1_to_hex(sha1), typename(obj->type));
  22                 return NULL;
  23         }
  24         return (struct commit *) obj;
  25 }
  26
  27 struct commit *lookup_commit_reference_gently(const unsigned char *sha1,
  28                                               int quiet)
  29 {
  30         struct object *obj = deref_tag(parse_object(sha1), NULL, 0);
  31
  32         if (!obj)
  33                 return NULL;
  34         return check_commit(obj, sha1, quiet);
  35 }
  36
  37 struct commit *lookup_commit_reference(const unsigned char *sha1)
  38 {
  39         return lookup_commit_reference_gently(sha1, 0);
  40 }
  41
  42 struct commit *lookup_commit(const unsigned char *sha1)
  43 {
  44         struct object *obj = lookup_object(sha1);
  45         if (!obj)
  46                 return create_object(sha1, OBJ_COMMIT, alloc_commit_node());
  47         if (!obj->type)
  48                 obj->type = OBJ_COMMIT;
  49         return check_commit(obj, sha1, 0);
  50 }
  51
  52 static unsigned long parse_commit_date(const char *buf, const char *tail)
  53 {
  54         const char *dateptr;
  55
  56         if (buf + 6 >= tail)
  57                 return 0;
  58         if (memcmp(buf, "author", 6))
  59                 return 0;
  60         while (buf < tail && *buf++ != '\n')
  61                 /* nada */;
  62         if (buf + 9 >= tail)
  63                 return 0;
  64         if (memcmp(buf, "committer", 9))
  65                 return 0;
  66         while (buf < tail && *buf++ != '>')
  67                 /* nada */;
  68         if (buf >= tail)
  69                 return 0;
  70         dateptr = buf;
  71         while (buf < tail && *buf++ != '\n')
  72                 /* nada */;
  73         if (buf >= tail)
  74                 return 0;
  75         /* dateptr < buf && buf[-1] == '\n', so strtoul will stop at buf-1 */
  76         return strtoul(dateptr, NULL, 10);
  77 }
  78
  79 static struct commit_graft **commit_graft;
  80 static int commit_graft_alloc, commit_graft_nr;
  81
  82 static int commit_graft_pos(const unsigned char *sha1)
  83 {
  84         int lo, hi;
  85         lo = 0;
  86         hi = commit_graft_nr;
  87         while (lo < hi) {
  88                 int mi = (lo + hi) / 2;
  89                 struct commit_graft *graft = commit_graft[mi];
  90                 int cmp = hashcmp(sha1, graft->sha1);
  91                 if (!cmp)
  92                         return mi;
  93                 if (cmp < 0)
  94                         hi = mi;
  95                 else
  96                         lo = mi + 1;
  97         }
  98         return -lo - 1;
  99 }
 100
 101 int register_commit_graft(struct commit_graft *graft, int ignore_dups)
 102 {
 103         int pos = commit_graft_pos(graft->sha1);
 104
 105         if (0 <= pos) {
 106                 if (ignore_dups)
 107                         free(graft);
 108                 else {
 109                         free(commit_graft[pos]);
 110                         commit_graft[pos] = graft;
 111                 }
 112                 return 1;
 113         }
 114         pos = -pos - 1;
 115         if (commit_graft_alloc <= ++commit_graft_nr) {
 116                 commit_graft_alloc = alloc_nr(commit_graft_alloc);
 117                 commit_graft = xrealloc(commit_graft,
 118                                         sizeof(*commit_graft) *
 119                                         commit_graft_alloc);
 120         }
 121         if (pos < commit_graft_nr)
 122                 memmove(commit_graft + pos + 1,
 123                         commit_graft + pos,
 124                         (commit_graft_nr - pos - 1) *
 125                         sizeof(*commit_graft));
 126         commit_graft[pos] = graft;
 127         return 0;
 128 }
 129
 130 struct commit_graft *read_graft_line(char *buf, int len)
 131 {
 132         /* The format is just "Commit Parent1 Parent2 ...\n" */
 133         int i;
 134         struct commit_graft *graft = NULL;
 135
 136         while (len && isspace(buf[len-1]))
 137                 buf[--len] = '\0';
 138         if (buf[0] == '#' || buf[0] == '\0')
 139                 return NULL;
 140         if ((len + 1) % 41)
 141                 goto bad_graft_data;
 142         i = (len + 1) / 41 - 1;
 143         graft = xmalloc(sizeof(*graft) + 20 * i);
 144         graft->nr_parent = i;
 145         if (get_sha1_hex(buf, graft->sha1))
 146                 goto bad_graft_data;
 147         for (i = 40; i < len; i += 41) {
 148                 if (buf[i] != ' ')
 149                         goto bad_graft_data;
 150                 if (get_sha1_hex(buf + i + 1, graft->parent[i/41]))
 151                         goto bad_graft_data;
 152         }
 153         return graft;
 154
 155 bad_graft_data:
 156         error("bad graft data: %s", buf);
 157         free(graft);
 158         return NULL;
 159 }
 160
 161 static int read_graft_file(const char *graft_file)
 162 {
 163         FILE *fp = fopen(graft_file, "r");
 164         char buf[1024];
 165         if (!fp)
 166                 return -1;
 167         while (fgets(buf, sizeof(buf), fp)) {
 168                 /* The format is just "Commit Parent1 Parent2 ...\n" */
 169                 int len = strlen(buf);
 170                 struct commit_graft *graft = read_graft_line(buf, len);
 171                 if (!graft)
 172                         continue;
 173                 if (register_commit_graft(graft, 1))
 174                         error("duplicate graft data: %s", buf);
 175         }
 176         fclose(fp);
 177         return 0;
 178 }
 179
 180 static void prepare_commit_graft(void)
 181 {
 182         static int commit_graft_prepared;
 183         char *graft_file;
 184
 185         if (commit_graft_prepared)
 186                 return;
 187         graft_file = get_graft_file();
 188         read_graft_file(graft_file);
 189         /* make sure shallows are read */
 190         is_repository_shallow();
 191         commit_graft_prepared = 1;
 192 }
 193
 194 struct commit_graft *lookup_commit_graft(const unsigned char *sha1)
 195 {
 196         int pos;
 197         prepare_commit_graft();
 198         pos = commit_graft_pos(sha1);
 199         if (pos < 0)
 200                 return NULL;
 201         return commit_graft[pos];
 202 }
 203
 204 int write_shallow_commits(struct strbuf *out, int use_pack_protocol)
 205 {
 206         int i, count = 0;
 207         for (i = 0; i < commit_graft_nr; i++)
 208                 if (commit_graft[i]->nr_parent < 0) {
 209                         const char *hex =
 210                                 sha1_to_hex(commit_graft[i]->sha1);
 211                         count++;
 212                         if (use_pack_protocol)
 213                                 packet_buf_write(out, "shallow %s", hex);
 214                         else {
 215                                 strbuf_addstr(out, hex);
 216                                 strbuf_addch(out, '\n');
 217                         }
 218                 }
 219         return count;
 220 }
 221
 222 int unregister_shallow(const unsigned char *sha1)
 223 {
 224         int pos = commit_graft_pos(sha1);
 225         if (pos < 0)
 226                 return -1;
 227         if (pos + 1 < commit_graft_nr)
 228                 memmove(commit_graft + pos, commit_graft + pos + 1,
 229                                 sizeof(struct commit_graft *)
 230                                 * (commit_graft_nr - pos - 1));
 231         commit_graft_nr--;
 232         return 0;
 233 }
 234
 235 int parse_commit_buffer(struct commit *item, void *buffer, unsigned long size)
 236 {
 237         char *tail = buffer;
 238         char *bufptr = buffer;
 239         unsigned char parent[20];
 240         struct commit_list **pptr;
 241         struct commit_graft *graft;
 242
 243         if (item->object.parsed)
 244                 return 0;
 245         item->object.parsed = 1;
 246         tail += size;
 247         if (tail <= bufptr + 46 || memcmp(bufptr, "tree ", 5) || bufptr[45] != '\n')
 248                 return error("bogus commit object %s", sha1_to_hex(item->object.sha1));
 249         if (get_sha1_hex(bufptr + 5, parent) < 0)
 250                 return error("bad tree pointer in commit %s",
 251                              sha1_to_hex(item->object.sha1));
 252         item->tree = lookup_tree(parent);
 253         bufptr += 46; /* "tree " + "hex sha1" + "\n" */
 254         pptr = &item->parents;
 255
 256         graft = lookup_commit_graft(item->object.sha1);
 257         while (bufptr + 48 < tail && !memcmp(bufptr, "parent ", 7)) {
 258                 struct commit *new_parent;
 259
 260                 if (tail <= bufptr + 48 ||
 261                     get_sha1_hex(bufptr + 7, parent) ||
 262                     bufptr[47] != '\n')
 263                         return error("bad parents in commit %s", sha1_to_hex(item->object.sha1));
 264                 bufptr += 48;
 265                 /*
 266                  * The clone is shallow if nr_parent < 0, and we must
 267                  * not traverse its real parents even when we unhide them.
 268                  */
 269                 if (graft && (graft->nr_parent < 0 || grafts_replace_parents))
 270                         continue;
 271                 new_parent = lookup_commit(parent);
 272                 if (new_parent)
 273                         pptr = &commit_list_insert(new_parent, pptr)->next;
 274         }
 275         if (graft) {
 276                 int i;
 277                 struct commit *new_parent;
 278                 for (i = 0; i < graft->nr_parent; i++) {
 279                         new_parent = lookup_commit(graft->parent[i]);
 280                         if (!new_parent)
 281                                 continue;
 282                         pptr = &commit_list_insert(new_parent, pptr)->next;
 283                 }
 284         }
 285         item->date = parse_commit_date(bufptr, tail);
 286
 287         return 0;
 288 }
 289
 290 int parse_commit(struct commit *item)
 291 {
 292         enum object_type type;
 293         void *buffer;
 294         unsigned long size;
 295         int ret;
 296
 297         if (!item)
 298                 return -1;
 299         if (item->object.parsed)
 300                 return 0;
 301         buffer = read_sha1_file(item->object.sha1, &type, &size);
 302         if (!buffer)
 303                 return error("Could not read %s",
 304                              sha1_to_hex(item->object.sha1));
 305         if (type != OBJ_COMMIT) {
 306                 free(buffer);
 307                 return error("Object %s not a commit",
 308                              sha1_to_hex(item->object.sha1));
 309         }
 310         ret = parse_commit_buffer(item, buffer, size);
 311         if (save_commit_buffer && !ret) {
 312                 item->buffer = buffer;
 313                 return 0;
 314         }
 315         free(buffer);
 316         return ret;
 317 }
 318
 319 int find_commit_subject(const char *commit_buffer, const char **subject)
 320 {
 321         const char *eol;
 322         const char *p = commit_buffer;
 323
 324         while (*p && (*p != '\n' || p[1] != '\n'))
 325                 p++;
 326         if (*p) {
 327                 p += 2;
 328                 for (eol = p; *eol && *eol != '\n'; eol++)
 329                         ; /* do nothing */
 330         } else
 331                 eol = p;
 332
 333         *subject = p;
 334
 335         return eol - p;
 336 }
 337
 338 struct commit_list *commit_list_insert(struct commit *item, struct commit_list **list_p)
 339 {
 340         struct commit_list *new_list = xmalloc(sizeof(struct commit_list));
 341         new_list->item = item;
 342         new_list->next = *list_p;
 343         *list_p = new_list;
 344         return new_list;
 345 }
 346
 347 unsigned commit_list_count(const struct commit_list *l)
 348 {
 349         unsigned c = 0;
 350         for (; l; l = l->next )
 351                 c++;
 352         return c;
 353 }
 354
 355 void free_commit_list(struct commit_list *list)
 356 {
 357         while (list) {
 358                 struct commit_list *temp = list;
 359                 list = temp->next;
 360                 free(temp);
 361         }
 362 }
 363
 364 struct commit_list * insert_by_date(struct commit *item, struct commit_list **list)
 365 {
 366         struct commit_list **pp = list;
 367         struct commit_list *p;
 368         while ((p = *pp) != NULL) {
 369                 if (p->item->date < item->date) {
 370                         break;
 371                 }
 372                 pp = &p->next;
 373         }
 374         return commit_list_insert(item, pp);
 375 }
 376
 377
 378 void sort_by_date(struct commit_list **list)
 379 {
 380         struct commit_list *ret = NULL;
 381         while (*list) {
 382                 insert_by_date((*list)->item, &ret);
 383                 *list = (*list)->next;
 384         }
 385         *list = ret;
 386 }
 387
 388 struct commit *pop_most_recent_commit(struct commit_list **list,
 389                                       unsigned int mark)
 390 {
 391         struct commit *ret = (*list)->item;
 392         struct commit_list *parents = ret->parents;
 393         struct commit_list *old = *list;
 394
 395         *list = (*list)->next;
 396         free(old);
 397
 398         while (parents) {
 399                 struct commit *commit = parents->item;
 400                 if (!parse_commit(commit) && !(commit->object.flags & mark)) {
 401                         commit->object.flags |= mark;
 402                         insert_by_date(commit, list);
 403                 }
 404                 parents = parents->next;
 405         }
 406         return ret;
 407 }
 408
 409 void clear_commit_marks(struct commit *commit, unsigned int mark)
 410 {
 411         while (commit) {
 412                 struct commit_list *parents;
 413
 414                 if (!(mark & commit->object.flags))
 415                         return;
 416
 417                 commit->object.flags &= ~mark;
 418
 419                 parents = commit->parents;
 420                 if (!parents)
 421                         return;
 422
 423                 while ((parents = parents->next))
 424                         clear_commit_marks(parents->item, mark);
 425
 426                 commit = commit->parents->item;
 427         }
 428 }
 429
 430 struct commit *pop_commit(struct commit_list **stack)
 431 {
 432         struct commit_list *top = *stack;
 433         struct commit *item = top ? top->item : NULL;
 434
 435         if (top) {
 436                 *stack = top->next;
 437                 free(top);
 438         }
 439         return item;
 440 }
 441
 442 /*
 443  * Performs an in-place topological sort on the list supplied.
 444  */
 445 void sort_in_topological_order(struct commit_list ** list, int lifo)
 446 {
 447         struct commit_list *next, *orig = *list;
 448         struct commit_list *work, **insert;
 449         struct commit_list **pptr;
 450
 451         if (!orig)
 452                 return;
 453         *list = NULL;
 454
 455         /* Mark them and clear the indegree */
 456         for (next = orig; next; next = next->next) {
 457                 struct commit *commit = next->item;
 458                 commit->indegree = 1;
 459         }
 460
 461         /* update the indegree */
 462         for (next = orig; next; next = next->next) {
 463                 struct commit_list * parents = next->item->parents;
 464                 while (parents) {
 465                         struct commit *parent = parents->item;
 466
 467                         if (parent->indegree)
 468                                 parent->indegree++;
 469                         parents = parents->next;
 470                 }
 471         }
 472
 473         /*
 474          * find the tips
 475          *
 476          * tips are nodes not reachable from any other node in the list
 477          *
 478          * the tips serve as a starting set for the work queue.
 479          */
 480         work = NULL;
 481         insert = &work;
 482         for (next = orig; next; next = next->next) {
 483                 struct commit *commit = next->item;
 484
 485                 if (commit->indegree == 1)
 486                         insert = &commit_list_insert(commit, insert)->next;
 487         }
 488
 489         /* process the list in topological order */
 490         if (!lifo)
 491                 sort_by_date(&work);
 492
 493         pptr = list;
 494         *list = NULL;
 495         while (work) {
 496                 struct commit *commit;
 497                 struct commit_list *parents, *work_item;
 498
 499                 work_item = work;
 500                 work = work_item->next;
 501                 work_item->next = NULL;
 502
 503                 commit = work_item->item;
 504                 for (parents = commit->parents; parents ; parents = parents->next) {
 505                         struct commit *parent=parents->item;
 506
 507                         if (!parent->indegree)
 508                                 continue;
 509
 510                         /*
 511                          * parents are only enqueued for emission
 512                          * when all their children have been emitted thereby
 513                          * guaranteeing topological order.
 514                          */
 515                         if (--parent->indegree == 1) {
 516                                 if (!lifo)
 517                                         insert_by_date(parent, &work);
 518                                 else
 519                                         commit_list_insert(parent, &work);
 520                         }
 521                 }
 522                 /*
 523                  * work_item is a commit all of whose children
 524                  * have already been emitted. we can emit it now.
 525                  */
 526                 commit->indegree = 0;
 527                 *pptr = work_item;
 528                 pptr = &work_item->next;
 529         }
 530 }
 531
 532 /* merge-base stuff */
 533
 534 /* bits #0..15 in revision.h */
 535 #define PARENT1         (1u<<16)
 536 #define PARENT2         (1u<<17)
 537 #define STALE           (1u<<18)
 538 #define RESULT          (1u<<19)
 539
 540 static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);
 541
 542 static struct commit *interesting(struct commit_list *list)
 543 {
 544         while (list) {
 545                 struct commit *commit = list->item;
 546                 list = list->next;
 547                 if (commit->object.flags & STALE)
 548                         continue;
 549                 return commit;
 550         }
 551         return NULL;
 552 }
 553
 554 static struct commit_list *merge_bases_many(struct commit *one, int n, struct commit **twos)
 555 {
 556         struct commit_list *list = NULL;
 557         struct commit_list *result = NULL;
 558         int i;
 559
 560         for (i = 0; i < n; i++) {
 561                 if (one == twos[i])
 562                         /*
 563                          * We do not mark this even with RESULT so we do not
 564                          * have to clean it up.
 565                          */
 566                         return commit_list_insert(one, &result);
 567         }
 568
 569         if (parse_commit(one))
 570                 return NULL;
 571         for (i = 0; i < n; i++) {
 572                 if (parse_commit(twos[i]))
 573                         return NULL;
 574         }
 575
 576         one->object.flags |= PARENT1;
 577         insert_by_date(one, &list);
 578         for (i = 0; i < n; i++) {
 579                 twos[i]->object.flags |= PARENT2;
 580                 insert_by_date(twos[i], &list);
 581         }
 582
 583         while (interesting(list)) {
 584                 struct commit *commit;
 585                 struct commit_list *parents;
 586                 struct commit_list *next;
 587                 int flags;
 588
 589                 commit = list->item;
 590                 next = list->next;
 591                 free(list);
 592                 list = next;
 593
 594                 flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
 595                 if (flags == (PARENT1 | PARENT2)) {
 596                         if (!(commit->object.flags & RESULT)) {
 597                                 commit->object.flags |= RESULT;
 598                                 insert_by_date(commit, &result);
 599                         }
 600                         /* Mark parents of a found merge stale */
 601                         flags |= STALE;
 602                 }
 603                 parents = commit->parents;
 604                 while (parents) {
 605                         struct commit *p = parents->item;
 606                         parents = parents->next;
 607                         if ((p->object.flags & flags) == flags)
 608                                 continue;
 609                         if (parse_commit(p))
 610                                 return NULL;
 611                         p->object.flags |= flags;
 612                         insert_by_date(p, &list);
 613                 }
 614         }
 615
 616         /* Clean up the result to remove stale ones */
 617         free_commit_list(list);
 618         list = result; result = NULL;
 619         while (list) {
 620                 struct commit_list *next = list->next;
 621                 if (!(list->item->object.flags & STALE))
 622                         insert_by_date(list->item, &result);
 623                 free(list);
 624                 list = next;
 625         }
 626         return result;
 627 }
 628
 629 struct commit_list *get_octopus_merge_bases(struct commit_list *in)
 630 {
 631         struct commit_list *i, *j, *k, *ret = NULL;
 632         struct commit_list **pptr = &ret;
 633
 634         for (i = in; i; i = i->next) {
 635                 if (!ret)
 636                         pptr = &commit_list_insert(i->item, pptr)->next;
 637                 else {
 638                         struct commit_list *new = NULL, *end = NULL;
 639
 640                         for (j = ret; j; j = j->next) {
 641                                 struct commit_list *bases;
 642                                 bases = get_merge_bases(i->item, j->item, 1);
 643                                 if (!new)
 644                                         new = bases;
 645                                 else
 646                                         end->next = bases;
 647                                 for (k = bases; k; k = k->next)
 648                                         end = k;
 649                         }
 650                         ret = new;
 651                 }
 652         }
 653         return ret;
 654 }
 655
 656 struct commit_list *get_merge_bases_many(struct commit *one,
 657                                          int n,
 658                                          struct commit **twos,
 659                                          int cleanup)
 660 {
 661         struct commit_list *list;
 662         struct commit **rslt;
 663         struct commit_list *result;
 664         int cnt, i, j;
 665
 666         result = merge_bases_many(one, n, twos);
 667         for (i = 0; i < n; i++) {
 668                 if (one == twos[i])
 669                         return result;
 670         }
 671         if (!result || !result->next) {
 672                 if (cleanup) {
 673                         clear_commit_marks(one, all_flags);
 674                         for (i = 0; i < n; i++)
 675                                 clear_commit_marks(twos[i], all_flags);
 676                 }
 677                 return result;
 678         }
 679
 680         /* There are more than one */
 681         cnt = 0;
 682         list = result;
 683         while (list) {
 684                 list = list->next;
 685                 cnt++;
 686         }
 687         rslt = xcalloc(cnt, sizeof(*rslt));
 688         for (list = result, i = 0; list; list = list->next)
 689                 rslt[i++] = list->item;
 690         free_commit_list(result);
 691
 692         clear_commit_marks(one, all_flags);
 693         for (i = 0; i < n; i++)
 694                 clear_commit_marks(twos[i], all_flags);
 695         for (i = 0; i < cnt - 1; i++) {
 696                 for (j = i+1; j < cnt; j++) {
 697                         if (!rslt[i] || !rslt[j])
 698                                 continue;
 699                         result = merge_bases_many(rslt[i], 1, &rslt[j]);
 700                         clear_commit_marks(rslt[i], all_flags);
 701                         clear_commit_marks(rslt[j], all_flags);
 702                         for (list = result; list; list = list->next) {
 703                                 if (rslt[i] == list->item)
 704                                         rslt[i] = NULL;
 705                                 if (rslt[j] == list->item)
 706                                         rslt[j] = NULL;
 707                         }
 708                 }
 709         }
 710
 711         /* Surviving ones in rslt[] are the independent results */
 712         result = NULL;
 713         for (i = 0; i < cnt; i++) {
 714                 if (rslt[i])
 715                         insert_by_date(rslt[i], &result);
 716         }
 717         free(rslt);
 718         return result;
 719 }
 720
 721 struct commit_list *get_merge_bases(struct commit *one, struct commit *two,
 722                                     int cleanup)
 723 {
 724         return get_merge_bases_many(one, 1, &two, cleanup);
 725 }
 726
 727 int is_descendant_of(struct commit *commit, struct commit_list *with_commit)
 728 {
 729         if (!with_commit)
 730                 return 1;
 731         while (with_commit) {
 732                 struct commit *other;
 733
 734                 other = with_commit->item;
 735                 with_commit = with_commit->next;
 736                 if (in_merge_bases(other, &commit, 1))
 737                         return 1;
 738         }
 739         return 0;
 740 }
 741
 742 int in_merge_bases(struct commit *commit, struct commit **reference, int num)
 743 {
 744         struct commit_list *bases, *b;
 745         int ret = 0;
 746
 747         if (num == 1)
 748                 bases = get_merge_bases(commit, *reference, 1);
 749         else
 750                 die("not yet");
 751         for (b = bases; b; b = b->next) {
 752                 if (!hashcmp(commit->object.sha1, b->item->object.sha1)) {
 753                         ret = 1;
 754                         break;
 755                 }
 756         }
 757
 758         free_commit_list(bases);
 759         return ret;
 760 }
 761
 762 struct commit_list *reduce_heads(struct commit_list *heads)
 763 {
 764         struct commit_list *p;
 765         struct commit_list *result = NULL, **tail = &result;
 766         struct commit **other;
 767         size_t num_head, num_other;
 768
 769         if (!heads)
 770                 return NULL;
 771
 772         /* Avoid unnecessary reallocations */
 773         for (p = heads, num_head = 0; p; p = p->next)
 774                 num_head++;
 775         other = xcalloc(sizeof(*other), num_head);
 776
 777         /* For each commit, see if it can be reached by others */
 778         for (p = heads; p; p = p->next) {
 779                 struct commit_list *q, *base;
 780
 781                 /* Do we already have this in the result? */
 782                 for (q = result; q; q = q->next)
 783                         if (p->item == q->item)
 784                                 break;
 785                 if (q)
 786                         continue;
 787
 788                 num_other = 0;
 789                 for (q = heads; q; q = q->next) {
 790                         if (p->item == q->item)
 791                                 continue;
 792                         other[num_other++] = q->item;
 793                 }
 794                 if (num_other)
 795                         base = get_merge_bases_many(p->item, num_other, other, 1);
 796                 else
 797                         base = NULL;
 798                 /*
 799                  * If p->item does not have anything common with other
 800                  * commits, there won't be any merge base.  If it is
 801                  * reachable from some of the others, p->item will be
 802                  * the merge base.  If its history is connected with
 803                  * others, but p->item is not reachable by others, we
 804                  * will get something other than p->item back.
 805                  */
 806                 if (!base || (base->item != p->item))
 807                         tail = &(commit_list_insert(p->item, tail)->next);
 808                 free_commit_list(base);
 809         }
 810         free(other);
 811         return result;
 812 }
 813
 814 static const char commit_utf8_warn[] =
 815 "Warning: commit message does not conform to UTF-8.\n"
 816 "You may want to amend it after fixing the message, or set the config\n"
 817 "variable i18n.commitencoding to the encoding your project uses.\n";
 818
 819 int commit_tree(const char *msg, unsigned char *tree,
 820                 struct commit_list *parents, unsigned char *ret,
 821                 const char *author)
 822 {
 823         int result;
 824         int encoding_is_utf8;
 825         struct strbuf buffer;
 826
 827         assert_sha1_type(tree, OBJ_TREE);
 828
 829         /* Not having i18n.commitencoding is the same as having utf-8 */
 830         encoding_is_utf8 = is_encoding_utf8(git_commit_encoding);
 831
 832         strbuf_init(&buffer, 8192); /* should avoid reallocs for the headers */
 833         strbuf_addf(&buffer, "tree %s\n", sha1_to_hex(tree));
 834
 835         /*
 836          * NOTE! This ordering means that the same exact tree merged with a
 837          * different order of parents will be a _different_ changeset even
 838          * if everything else stays the same.
 839          */
 840         while (parents) {
 841                 struct commit_list *next = parents->next;
 842                 strbuf_addf(&buffer, "parent %s\n",
 843                         sha1_to_hex(parents->item->object.sha1));
 844                 free(parents);
 845                 parents = next;
 846         }
 847
 848         /* Person/date information */
 849         if (!author)
 850                 author = git_author_info(IDENT_ERROR_ON_NO_NAME);
 851         strbuf_addf(&buffer, "author %s\n", author);
 852         strbuf_addf(&buffer, "committer %s\n", git_committer_info(IDENT_ERROR_ON_NO_NAME));
 853         if (!encoding_is_utf8)
 854                 strbuf_addf(&buffer, "encoding %s\n", git_commit_encoding);
 855         strbuf_addch(&buffer, '\n');
 856
 857         /* And add the comment */
 858         strbuf_addstr(&buffer, msg);
 859
 860         /* And check the encoding */
 861         if (encoding_is_utf8 && !is_utf8(buffer.buf))
 862                 fprintf(stderr, commit_utf8_warn);
 863
 864         result = write_sha1_file(buffer.buf, buffer.len, commit_type, ret);
 865         strbuf_release(&buffer);
 866         return result;
 867 }