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_or_die(const unsigned char *sha1, const char *ref_name)
  43 {
  44         struct commit *c = lookup_commit_reference(sha1);
  45         if (!c)
  46                 die(_("could not parse %s"), ref_name);
  47         if (hashcmp(sha1, c->object.sha1)) {
  48                 warning(_("%s %s is not a commit!"),
  49                         ref_name, sha1_to_hex(sha1));
  50         }
  51         return c;
  52 }
  53
  54 struct commit *lookup_commit(const unsigned char *sha1)
  55 {
  56         struct object *obj = lookup_object(sha1);
  57         if (!obj)
  58                 return create_object(sha1, OBJ_COMMIT, alloc_commit_node());
  59         if (!obj->type)
  60                 obj->type = OBJ_COMMIT;
  61         return check_commit(obj, sha1, 0);
  62 }
  63
  64 struct commit *lookup_commit_reference_by_name(const char *name)
  65 {
  66         unsigned char sha1[20];
  67         struct commit *commit;
  68
  69         if (get_sha1(name, sha1))
  70                 return NULL;
  71         commit = lookup_commit_reference(sha1);
  72         if (!commit || parse_commit(commit))
  73                 return NULL;
  74         return commit;
  75 }
  76
  77 static unsigned long parse_commit_date(const char *buf, const char *tail)
  78 {
  79         const char *dateptr;
  80
  81         if (buf + 6 >= tail)
  82                 return 0;
  83         if (memcmp(buf, "author", 6))
  84                 return 0;
  85         while (buf < tail && *buf++ != '\n')
  86                 /* nada */;
  87         if (buf + 9 >= tail)
  88                 return 0;
  89         if (memcmp(buf, "committer", 9))
  90                 return 0;
  91         while (buf < tail && *buf++ != '>')
  92                 /* nada */;
  93         if (buf >= tail)
  94                 return 0;
  95         dateptr = buf;
  96         while (buf < tail && *buf++ != '\n')
  97                 /* nada */;
  98         if (buf >= tail)
  99                 return 0;
 100         /* dateptr < buf && buf[-1] == '\n', so strtoul will stop at buf-1 */
 101         return strtoul(dateptr, NULL, 10);
 102 }
 103
 104 static struct commit_graft **commit_graft;
 105 static int commit_graft_alloc, commit_graft_nr;
 106
 107 static int commit_graft_pos(const unsigned char *sha1)
 108 {
 109         int lo, hi;
 110         lo = 0;
 111         hi = commit_graft_nr;
 112         while (lo < hi) {
 113                 int mi = (lo + hi) / 2;
 114                 struct commit_graft *graft = commit_graft[mi];
 115                 int cmp = hashcmp(sha1, graft->sha1);
 116                 if (!cmp)
 117                         return mi;
 118                 if (cmp < 0)
 119                         hi = mi;
 120                 else
 121                         lo = mi + 1;
 122         }
 123         return -lo - 1;
 124 }
 125
 126 int register_commit_graft(struct commit_graft *graft, int ignore_dups)
 127 {
 128         int pos = commit_graft_pos(graft->sha1);
 129
 130         if (0 <= pos) {
 131                 if (ignore_dups)
 132                         free(graft);
 133                 else {
 134                         free(commit_graft[pos]);
 135                         commit_graft[pos] = graft;
 136                 }
 137                 return 1;
 138         }
 139         pos = -pos - 1;
 140         if (commit_graft_alloc <= ++commit_graft_nr) {
 141                 commit_graft_alloc = alloc_nr(commit_graft_alloc);
 142                 commit_graft = xrealloc(commit_graft,
 143                                         sizeof(*commit_graft) *
 144                                         commit_graft_alloc);
 145         }
 146         if (pos < commit_graft_nr)
 147                 memmove(commit_graft + pos + 1,
 148                         commit_graft + pos,
 149                         (commit_graft_nr - pos - 1) *
 150                         sizeof(*commit_graft));
 151         commit_graft[pos] = graft;
 152         return 0;
 153 }
 154
 155 struct commit_graft *read_graft_line(char *buf, int len)
 156 {
 157         /* The format is just "Commit Parent1 Parent2 ...\n" */
 158         int i;
 159         struct commit_graft *graft = NULL;
 160
 161         while (len && isspace(buf[len-1]))
 162                 buf[--len] = '\0';
 163         if (buf[0] == '#' || buf[0] == '\0')
 164                 return NULL;
 165         if ((len + 1) % 41)
 166                 goto bad_graft_data;
 167         i = (len + 1) / 41 - 1;
 168         graft = xmalloc(sizeof(*graft) + 20 * i);
 169         graft->nr_parent = i;
 170         if (get_sha1_hex(buf, graft->sha1))
 171                 goto bad_graft_data;
 172         for (i = 40; i < len; i += 41) {
 173                 if (buf[i] != ' ')
 174                         goto bad_graft_data;
 175                 if (get_sha1_hex(buf + i + 1, graft->parent[i/41]))
 176                         goto bad_graft_data;
 177         }
 178         return graft;
 179
 180 bad_graft_data:
 181         error("bad graft data: %s", buf);
 182         free(graft);
 183         return NULL;
 184 }
 185
 186 static int read_graft_file(const char *graft_file)
 187 {
 188         FILE *fp = fopen(graft_file, "r");
 189         char buf[1024];
 190         if (!fp)
 191                 return -1;
 192         while (fgets(buf, sizeof(buf), fp)) {
 193                 /* The format is just "Commit Parent1 Parent2 ...\n" */
 194                 int len = strlen(buf);
 195                 struct commit_graft *graft = read_graft_line(buf, len);
 196                 if (!graft)
 197                         continue;
 198                 if (register_commit_graft(graft, 1))
 199                         error("duplicate graft data: %s", buf);
 200         }
 201         fclose(fp);
 202         return 0;
 203 }
 204
 205 static void prepare_commit_graft(void)
 206 {
 207         static int commit_graft_prepared;
 208         char *graft_file;
 209
 210         if (commit_graft_prepared)
 211                 return;
 212         graft_file = get_graft_file();
 213         read_graft_file(graft_file);
 214         /* make sure shallows are read */
 215         is_repository_shallow();
 216         commit_graft_prepared = 1;
 217 }
 218
 219 struct commit_graft *lookup_commit_graft(const unsigned char *sha1)
 220 {
 221         int pos;
 222         prepare_commit_graft();
 223         pos = commit_graft_pos(sha1);
 224         if (pos < 0)
 225                 return NULL;
 226         return commit_graft[pos];
 227 }
 228
 229 int for_each_commit_graft(each_commit_graft_fn fn, void *cb_data)
 230 {
 231         int i, ret;
 232         for (i = ret = 0; i < commit_graft_nr && !ret; i++)
 233                 ret = fn(commit_graft[i], cb_data);
 234         return ret;
 235 }
 236
 237 int unregister_shallow(const unsigned char *sha1)
 238 {
 239         int pos = commit_graft_pos(sha1);
 240         if (pos < 0)
 241                 return -1;
 242         if (pos + 1 < commit_graft_nr)
 243                 memmove(commit_graft + pos, commit_graft + pos + 1,
 244                                 sizeof(struct commit_graft *)
 245                                 * (commit_graft_nr - pos - 1));
 246         commit_graft_nr--;
 247         return 0;
 248 }
 249
 250 int parse_commit_buffer(struct commit *item, const void *buffer, unsigned long size)
 251 {
 252         const char *tail = buffer;
 253         const char *bufptr = buffer;
 254         unsigned char parent[20];
 255         struct commit_list **pptr;
 256         struct commit_graft *graft;
 257
 258         if (item->object.parsed)
 259                 return 0;
 260         item->object.parsed = 1;
 261         tail += size;
 262         if (tail <= bufptr + 46 || memcmp(bufptr, "tree ", 5) || bufptr[45] != '\n')
 263                 return error("bogus commit object %s", sha1_to_hex(item->object.sha1));
 264         if (get_sha1_hex(bufptr + 5, parent) < 0)
 265                 return error("bad tree pointer in commit %s",
 266                              sha1_to_hex(item->object.sha1));
 267         item->tree = lookup_tree(parent);
 268         bufptr += 46; /* "tree " + "hex sha1" + "\n" */
 269         pptr = &item->parents;
 270
 271         graft = lookup_commit_graft(item->object.sha1);
 272         while (bufptr + 48 < tail && !memcmp(bufptr, "parent ", 7)) {
 273                 struct commit *new_parent;
 274
 275                 if (tail <= bufptr + 48 ||
 276                     get_sha1_hex(bufptr + 7, parent) ||
 277                     bufptr[47] != '\n')
 278                         return error("bad parents in commit %s", sha1_to_hex(item->object.sha1));
 279                 bufptr += 48;
 280                 /*
 281                  * The clone is shallow if nr_parent < 0, and we must
 282                  * not traverse its real parents even when we unhide them.
 283                  */
 284                 if (graft && (graft->nr_parent < 0 || grafts_replace_parents))
 285                         continue;
 286                 new_parent = lookup_commit(parent);
 287                 if (new_parent)
 288                         pptr = &commit_list_insert(new_parent, pptr)->next;
 289         }
 290         if (graft) {
 291                 int i;
 292                 struct commit *new_parent;
 293                 for (i = 0; i < graft->nr_parent; i++) {
 294                         new_parent = lookup_commit(graft->parent[i]);
 295                         if (!new_parent)
 296                                 continue;
 297                         pptr = &commit_list_insert(new_parent, pptr)->next;
 298                 }
 299         }
 300         item->date = parse_commit_date(bufptr, tail);
 301
 302         return 0;
 303 }
 304
 305 int parse_commit(struct commit *item)
 306 {
 307         enum object_type type;
 308         void *buffer;
 309         unsigned long size;
 310         int ret;
 311
 312         if (!item)
 313                 return -1;
 314         if (item->object.parsed)
 315                 return 0;
 316         buffer = read_sha1_file(item->object.sha1, &type, &size);
 317         if (!buffer)
 318                 return error("Could not read %s",
 319                              sha1_to_hex(item->object.sha1));
 320         if (type != OBJ_COMMIT) {
 321                 free(buffer);
 322                 return error("Object %s not a commit",
 323                              sha1_to_hex(item->object.sha1));
 324         }
 325         ret = parse_commit_buffer(item, buffer, size);
 326         if (save_commit_buffer && !ret) {
 327                 item->buffer = buffer;
 328                 return 0;
 329         }
 330         free(buffer);
 331         return ret;
 332 }
 333
 334 int find_commit_subject(const char *commit_buffer, const char **subject)
 335 {
 336         const char *eol;
 337         const char *p = commit_buffer;
 338
 339         while (*p && (*p != '\n' || p[1] != '\n'))
 340                 p++;
 341         if (*p) {
 342                 p += 2;
 343                 for (eol = p; *eol && *eol != '\n'; eol++)
 344                         ; /* do nothing */
 345         } else
 346                 eol = p;
 347
 348         *subject = p;
 349
 350         return eol - p;
 351 }
 352
 353 struct commit_list *commit_list_insert(struct commit *item, struct commit_list **list_p)
 354 {
 355         struct commit_list *new_list = xmalloc(sizeof(struct commit_list));
 356         new_list->item = item;
 357         new_list->next = *list_p;
 358         *list_p = new_list;
 359         return new_list;
 360 }
 361
 362 unsigned commit_list_count(const struct commit_list *l)
 363 {
 364         unsigned c = 0;
 365         for (; l; l = l->next )
 366                 c++;
 367         return c;
 368 }
 369
 370 void free_commit_list(struct commit_list *list)
 371 {
 372         while (list) {
 373                 struct commit_list *temp = list;
 374                 list = temp->next;
 375                 free(temp);
 376         }
 377 }
 378
 379 struct commit_list * commit_list_insert_by_date(struct commit *item, struct commit_list **list)
 380 {
 381         struct commit_list **pp = list;
 382         struct commit_list *p;
 383         while ((p = *pp) != NULL) {
 384                 if (p->item->date < item->date) {
 385                         break;
 386                 }
 387                 pp = &p->next;
 388         }
 389         return commit_list_insert(item, pp);
 390 }
 391
 392
 393 void commit_list_sort_by_date(struct commit_list **list)
 394 {
 395         struct commit_list *ret = NULL;
 396         while (*list) {
 397                 commit_list_insert_by_date((*list)->item, &ret);
 398                 *list = (*list)->next;
 399         }
 400         *list = ret;
 401 }
 402
 403 struct commit *pop_most_recent_commit(struct commit_list **list,
 404                                       unsigned int mark)
 405 {
 406         struct commit *ret = (*list)->item;
 407         struct commit_list *parents = ret->parents;
 408         struct commit_list *old = *list;
 409
 410         *list = (*list)->next;
 411         free(old);
 412
 413         while (parents) {
 414                 struct commit *commit = parents->item;
 415                 if (!parse_commit(commit) && !(commit->object.flags & mark)) {
 416                         commit->object.flags |= mark;
 417                         commit_list_insert_by_date(commit, list);
 418                 }
 419                 parents = parents->next;
 420         }
 421         return ret;
 422 }
 423
 424 void clear_commit_marks(struct commit *commit, unsigned int mark)
 425 {
 426         while (commit) {
 427                 struct commit_list *parents;
 428
 429                 if (!(mark & commit->object.flags))
 430                         return;
 431
 432                 commit->object.flags &= ~mark;
 433
 434                 parents = commit->parents;
 435                 if (!parents)
 436                         return;
 437
 438                 while ((parents = parents->next))
 439                         clear_commit_marks(parents->item, mark);
 440
 441                 commit = commit->parents->item;
 442         }
 443 }
 444
 445 struct commit *pop_commit(struct commit_list **stack)
 446 {
 447         struct commit_list *top = *stack;
 448         struct commit *item = top ? top->item : NULL;
 449
 450         if (top) {
 451                 *stack = top->next;
 452                 free(top);
 453         }
 454         return item;
 455 }
 456
 457 /*
 458  * Performs an in-place topological sort on the list supplied.
 459  */
 460 void sort_in_topological_order(struct commit_list ** list, int lifo)
 461 {
 462         struct commit_list *next, *orig = *list;
 463         struct commit_list *work, **insert;
 464         struct commit_list **pptr;
 465
 466         if (!orig)
 467                 return;
 468         *list = NULL;
 469
 470         /* Mark them and clear the indegree */
 471         for (next = orig; next; next = next->next) {
 472                 struct commit *commit = next->item;
 473                 commit->indegree = 1;
 474         }
 475
 476         /* update the indegree */
 477         for (next = orig; next; next = next->next) {
 478                 struct commit_list * parents = next->item->parents;
 479                 while (parents) {
 480                         struct commit *parent = parents->item;
 481
 482                         if (parent->indegree)
 483                                 parent->indegree++;
 484                         parents = parents->next;
 485                 }
 486         }
 487
 488         /*
 489          * find the tips
 490          *
 491          * tips are nodes not reachable from any other node in the list
 492          *
 493          * the tips serve as a starting set for the work queue.
 494          */
 495         work = NULL;
 496         insert = &work;
 497         for (next = orig; next; next = next->next) {
 498                 struct commit *commit = next->item;
 499
 500                 if (commit->indegree == 1)
 501                         insert = &commit_list_insert(commit, insert)->next;
 502         }
 503
 504         /* process the list in topological order */
 505         if (!lifo)
 506                 commit_list_sort_by_date(&work);
 507
 508         pptr = list;
 509         *list = NULL;
 510         while (work) {
 511                 struct commit *commit;
 512                 struct commit_list *parents, *work_item;
 513
 514                 work_item = work;
 515                 work = work_item->next;
 516                 work_item->next = NULL;
 517
 518                 commit = work_item->item;
 519                 for (parents = commit->parents; parents ; parents = parents->next) {
 520                         struct commit *parent = parents->item;
 521
 522                         if (!parent->indegree)
 523                                 continue;
 524
 525                         /*
 526                          * parents are only enqueued for emission
 527                          * when all their children have been emitted thereby
 528                          * guaranteeing topological order.
 529                          */
 530                         if (--parent->indegree == 1) {
 531                                 if (!lifo)
 532                                         commit_list_insert_by_date(parent, &work);
 533                                 else
 534                                         commit_list_insert(parent, &work);
 535                         }
 536                 }
 537                 /*
 538                  * work_item is a commit all of whose children
 539                  * have already been emitted. we can emit it now.
 540                  */
 541                 commit->indegree = 0;
 542                 *pptr = work_item;
 543                 pptr = &work_item->next;
 544         }
 545 }
 546
 547 /* merge-base stuff */
 548
 549 /* bits #0..15 in revision.h */
 550 #define PARENT1         (1u<<16)
 551 #define PARENT2         (1u<<17)
 552 #define STALE           (1u<<18)
 553 #define RESULT          (1u<<19)
 554
 555 static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);
 556
 557 static struct commit *interesting(struct commit_list *list)
 558 {
 559         while (list) {
 560                 struct commit *commit = list->item;
 561                 list = list->next;
 562                 if (commit->object.flags & STALE)
 563                         continue;
 564                 return commit;
 565         }
 566         return NULL;
 567 }
 568
 569 static struct commit_list *merge_bases_many(struct commit *one, int n, struct commit **twos)
 570 {
 571         struct commit_list *list = NULL;
 572         struct commit_list *result = NULL;
 573         int i;
 574
 575         for (i = 0; i < n; i++) {
 576                 if (one == twos[i])
 577                         /*
 578                          * We do not mark this even with RESULT so we do not
 579                          * have to clean it up.
 580                          */
 581                         return commit_list_insert(one, &result);
 582         }
 583
 584         if (parse_commit(one))
 585                 return NULL;
 586         for (i = 0; i < n; i++) {
 587                 if (parse_commit(twos[i]))
 588                         return NULL;
 589         }
 590
 591         one->object.flags |= PARENT1;
 592         commit_list_insert_by_date(one, &list);
 593         for (i = 0; i < n; i++) {
 594                 twos[i]->object.flags |= PARENT2;
 595                 commit_list_insert_by_date(twos[i], &list);
 596         }
 597
 598         while (interesting(list)) {
 599                 struct commit *commit;
 600                 struct commit_list *parents;
 601                 struct commit_list *next;
 602                 int flags;
 603
 604                 commit = list->item;
 605                 next = list->next;
 606                 free(list);
 607                 list = next;
 608
 609                 flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
 610                 if (flags == (PARENT1 | PARENT2)) {
 611                         if (!(commit->object.flags & RESULT)) {
 612                                 commit->object.flags |= RESULT;
 613                                 commit_list_insert_by_date(commit, &result);
 614                         }
 615                         /* Mark parents of a found merge stale */
 616                         flags |= STALE;
 617                 }
 618                 parents = commit->parents;
 619                 while (parents) {
 620                         struct commit *p = parents->item;
 621                         parents = parents->next;
 622                         if ((p->object.flags & flags) == flags)
 623                                 continue;
 624                         if (parse_commit(p))
 625                                 return NULL;
 626                         p->object.flags |= flags;
 627                         commit_list_insert_by_date(p, &list);
 628                 }
 629         }
 630
 631         /* Clean up the result to remove stale ones */
 632         free_commit_list(list);
 633         list = result; result = NULL;
 634         while (list) {
 635                 struct commit_list *next = list->next;
 636                 if (!(list->item->object.flags & STALE))
 637                         commit_list_insert_by_date(list->item, &result);
 638                 free(list);
 639                 list = next;
 640         }
 641         return result;
 642 }
 643
 644 struct commit_list *get_octopus_merge_bases(struct commit_list *in)
 645 {
 646         struct commit_list *i, *j, *k, *ret = NULL;
 647         struct commit_list **pptr = &ret;
 648
 649         for (i = in; i; i = i->next) {
 650                 if (!ret)
 651                         pptr = &commit_list_insert(i->item, pptr)->next;
 652                 else {
 653                         struct commit_list *new = NULL, *end = NULL;
 654
 655                         for (j = ret; j; j = j->next) {
 656                                 struct commit_list *bases;
 657                                 bases = get_merge_bases(i->item, j->item, 1);
 658                                 if (!new)
 659                                         new = bases;
 660                                 else
 661                                         end->next = bases;
 662                                 for (k = bases; k; k = k->next)
 663                                         end = k;
 664                         }
 665                         ret = new;
 666                 }
 667         }
 668         return ret;
 669 }
 670
 671 struct commit_list *get_merge_bases_many(struct commit *one,
 672                                          int n,
 673                                          struct commit **twos,
 674                                          int cleanup)
 675 {
 676         struct commit_list *list;
 677         struct commit **rslt;
 678         struct commit_list *result;
 679         int cnt, i, j;
 680
 681         result = merge_bases_many(one, n, twos);
 682         for (i = 0; i < n; i++) {
 683                 if (one == twos[i])
 684                         return result;
 685         }
 686         if (!result || !result->next) {
 687                 if (cleanup) {
 688                         clear_commit_marks(one, all_flags);
 689                         for (i = 0; i < n; i++)
 690                                 clear_commit_marks(twos[i], all_flags);
 691                 }
 692                 return result;
 693         }
 694
 695         /* There are more than one */
 696         cnt = 0;
 697         list = result;
 698         while (list) {
 699                 list = list->next;
 700                 cnt++;
 701         }
 702         rslt = xcalloc(cnt, sizeof(*rslt));
 703         for (list = result, i = 0; list; list = list->next)
 704                 rslt[i++] = list->item;
 705         free_commit_list(result);
 706
 707         clear_commit_marks(one, all_flags);
 708         for (i = 0; i < n; i++)
 709                 clear_commit_marks(twos[i], all_flags);
 710         for (i = 0; i < cnt - 1; i++) {
 711                 for (j = i+1; j < cnt; j++) {
 712                         if (!rslt[i] || !rslt[j])
 713                                 continue;
 714                         result = merge_bases_many(rslt[i], 1, &rslt[j]);
 715                         clear_commit_marks(rslt[i], all_flags);
 716                         clear_commit_marks(rslt[j], all_flags);
 717                         for (list = result; list; list = list->next) {
 718                                 if (rslt[i] == list->item)
 719                                         rslt[i] = NULL;
 720                                 if (rslt[j] == list->item)
 721                                         rslt[j] = NULL;
 722                         }
 723                 }
 724         }
 725
 726         /* Surviving ones in rslt[] are the independent results */
 727         result = NULL;
 728         for (i = 0; i < cnt; i++) {
 729                 if (rslt[i])
 730                         commit_list_insert_by_date(rslt[i], &result);
 731         }
 732         free(rslt);
 733         return result;
 734 }
 735
 736 struct commit_list *get_merge_bases(struct commit *one, struct commit *two,
 737                                     int cleanup)
 738 {
 739         return get_merge_bases_many(one, 1, &two, cleanup);
 740 }
 741
 742 int is_descendant_of(struct commit *commit, struct commit_list *with_commit)
 743 {
 744         if (!with_commit)
 745                 return 1;
 746         while (with_commit) {
 747                 struct commit *other;
 748
 749                 other = with_commit->item;
 750                 with_commit = with_commit->next;
 751                 if (in_merge_bases(other, &commit, 1))
 752                         return 1;
 753         }
 754         return 0;
 755 }
 756
 757 int in_merge_bases(struct commit *commit, struct commit **reference, int num)
 758 {
 759         struct commit_list *bases, *b;
 760         int ret = 0;
 761
 762         if (num == 1)
 763                 bases = get_merge_bases(commit, *reference, 1);
 764         else
 765                 die("not yet");
 766         for (b = bases; b; b = b->next) {
 767                 if (!hashcmp(commit->object.sha1, b->item->object.sha1)) {
 768                         ret = 1;
 769                         break;
 770                 }
 771         }
 772
 773         free_commit_list(bases);
 774         return ret;
 775 }
 776
 777 struct commit_list *reduce_heads(struct commit_list *heads)
 778 {
 779         struct commit_list *p;
 780         struct commit_list *result = NULL, **tail = &result;
 781         struct commit **other;
 782         size_t num_head, num_other;
 783
 784         if (!heads)
 785                 return NULL;
 786
 787         /* Avoid unnecessary reallocations */
 788         for (p = heads, num_head = 0; p; p = p->next)
 789                 num_head++;
 790         other = xcalloc(sizeof(*other), num_head);
 791
 792         /* For each commit, see if it can be reached by others */
 793         for (p = heads; p; p = p->next) {
 794                 struct commit_list *q, *base;
 795
 796                 /* Do we already have this in the result? */
 797                 for (q = result; q; q = q->next)
 798                         if (p->item == q->item)
 799                                 break;
 800                 if (q)
 801                         continue;
 802
 803                 num_other = 0;
 804                 for (q = heads; q; q = q->next) {
 805                         if (p->item == q->item)
 806                                 continue;
 807                         other[num_other++] = q->item;
 808                 }
 809                 if (num_other)
 810                         base = get_merge_bases_many(p->item, num_other, other, 1);
 811                 else
 812                         base = NULL;
 813                 /*
 814                  * If p->item does not have anything common with other
 815                  * commits, there won't be any merge base.  If it is
 816                  * reachable from some of the others, p->item will be
 817                  * the merge base.  If its history is connected with
 818                  * others, but p->item is not reachable by others, we
 819                  * will get something other than p->item back.
 820                  */
 821                 if (!base || (base->item != p->item))
 822                         tail = &(commit_list_insert(p->item, tail)->next);
 823                 free_commit_list(base);
 824         }
 825         free(other);
 826         return result;
 827 }
 828
 829 static const char commit_utf8_warn[] =
 830 "Warning: commit message does not conform to UTF-8.\n"
 831 "You may want to amend it after fixing the message, or set the config\n"
 832 "variable i18n.commitencoding to the encoding your project uses.\n";
 833
 834 int commit_tree(const char *msg, unsigned char *tree,
 835                 struct commit_list *parents, unsigned char *ret,
 836                 const char *author)
 837 {
 838         int result;
 839         int encoding_is_utf8;
 840         struct strbuf buffer;
 841
 842         assert_sha1_type(tree, OBJ_TREE);
 843
 844         /* Not having i18n.commitencoding is the same as having utf-8 */
 845         encoding_is_utf8 = is_encoding_utf8(git_commit_encoding);
 846
 847         strbuf_init(&buffer, 8192); /* should avoid reallocs for the headers */
 848         strbuf_addf(&buffer, "tree %s\n", sha1_to_hex(tree));
 849
 850         /*
 851          * NOTE! This ordering means that the same exact tree merged with a
 852          * different order of parents will be a _different_ changeset even
 853          * if everything else stays the same.
 854          */
 855         while (parents) {
 856                 struct commit_list *next = parents->next;
 857                 strbuf_addf(&buffer, "parent %s\n",
 858                         sha1_to_hex(parents->item->object.sha1));
 859                 free(parents);
 860                 parents = next;
 861         }
 862
 863         /* Person/date information */
 864         if (!author)
 865                 author = git_author_info(IDENT_ERROR_ON_NO_NAME);
 866         strbuf_addf(&buffer, "author %s\n", author);
 867         strbuf_addf(&buffer, "committer %s\n", git_committer_info(IDENT_ERROR_ON_NO_NAME));
 868         if (!encoding_is_utf8)
 869                 strbuf_addf(&buffer, "encoding %s\n", git_commit_encoding);
 870         strbuf_addch(&buffer, '\n');
 871
 872         /* And add the comment */
 873         strbuf_addstr(&buffer, msg);
 874
 875         /* And check the encoding */
 876         if (encoding_is_utf8 && !is_utf8(buffer.buf))
 877                 fprintf(stderr, commit_utf8_warn);
 878
 879         result = write_sha1_file(buffer.buf, buffer.len, commit_type, ret);
 880         strbuf_release(&buffer);
 881         return result;
 882 }