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