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 for_each_commit_graft(each_commit_graft_fn fn, void *cb_data)
 218 {
 219         int i, ret;
 220         for (i = ret = 0; i < commit_graft_nr && !ret; i++)
 221                 ret = fn(commit_graft[i], cb_data);
 222         return ret;
 223 }
 224
 225 int write_shallow_commits(struct strbuf *out, int use_pack_protocol)
 226 {
 227         int i, count = 0;
 228         for (i = 0; i < commit_graft_nr; i++)
 229                 if (commit_graft[i]->nr_parent < 0) {
 230                         const char *hex =
 231                                 sha1_to_hex(commit_graft[i]->sha1);
 232                         count++;
 233                         if (use_pack_protocol)
 234                                 packet_buf_write(out, "shallow %s", hex);
 235                         else {
 236                                 strbuf_addstr(out, hex);
 237                                 strbuf_addch(out, '\n');
 238                         }
 239                 }
 240         return count;
 241 }
 242
 243 int unregister_shallow(const unsigned char *sha1)
 244 {
 245         int pos = commit_graft_pos(sha1);
 246         if (pos < 0)
 247                 return -1;
 248         if (pos + 1 < commit_graft_nr)
 249                 memmove(commit_graft + pos, commit_graft + pos + 1,
 250                                 sizeof(struct commit_graft *)
 251                                 * (commit_graft_nr - pos - 1));
 252         commit_graft_nr--;
 253         return 0;
 254 }
 255
 256 int parse_commit_buffer(struct commit *item, const void *buffer, unsigned long size)
 257 {
 258         const char *tail = buffer;
 259         const char *bufptr = buffer;
 260         unsigned char parent[20];
 261         struct commit_list **pptr;
 262         struct commit_graft *graft;
 263
 264         if (item->object.parsed)
 265                 return 0;
 266         item->object.parsed = 1;
 267         tail += size;
 268         if (tail <= bufptr + 46 || memcmp(bufptr, "tree ", 5) || bufptr[45] != '\n')
 269                 return error("bogus commit object %s", sha1_to_hex(item->object.sha1));
 270         if (get_sha1_hex(bufptr + 5, parent) < 0)
 271                 return error("bad tree pointer in commit %s",
 272                              sha1_to_hex(item->object.sha1));
 273         item->tree = lookup_tree(parent);
 274         bufptr += 46; /* "tree " + "hex sha1" + "\n" */
 275         pptr = &item->parents;
 276
 277         graft = lookup_commit_graft(item->object.sha1);
 278         while (bufptr + 48 < tail && !memcmp(bufptr, "parent ", 7)) {
 279                 struct commit *new_parent;
 280
 281                 if (tail <= bufptr + 48 ||
 282                     get_sha1_hex(bufptr + 7, parent) ||
 283                     bufptr[47] != '\n')
 284                         return error("bad parents in commit %s", sha1_to_hex(item->object.sha1));
 285                 bufptr += 48;
 286                 /*
 287                  * The clone is shallow if nr_parent < 0, and we must
 288                  * not traverse its real parents even when we unhide them.
 289                  */
 290                 if (graft && (graft->nr_parent < 0 || grafts_replace_parents))
 291                         continue;
 292                 new_parent = lookup_commit(parent);
 293                 if (new_parent)
 294                         pptr = &commit_list_insert(new_parent, pptr)->next;
 295         }
 296         if (graft) {
 297                 int i;
 298                 struct commit *new_parent;
 299                 for (i = 0; i < graft->nr_parent; i++) {
 300                         new_parent = lookup_commit(graft->parent[i]);
 301                         if (!new_parent)
 302                                 continue;
 303                         pptr = &commit_list_insert(new_parent, pptr)->next;
 304                 }
 305         }
 306         item->date = parse_commit_date(bufptr, tail);
 307
 308         return 0;
 309 }
 310
 311 int parse_commit(struct commit *item)
 312 {
 313         enum object_type type;
 314         void *buffer;
 315         unsigned long size;
 316         int ret;
 317
 318         if (!item)
 319                 return -1;
 320         if (item->object.parsed)
 321                 return 0;
 322         buffer = read_sha1_file(item->object.sha1, &type, &size);
 323         if (!buffer)
 324                 return error("Could not read %s",
 325                              sha1_to_hex(item->object.sha1));
 326         if (type != OBJ_COMMIT) {
 327                 free(buffer);
 328                 return error("Object %s not a commit",
 329                              sha1_to_hex(item->object.sha1));
 330         }
 331         ret = parse_commit_buffer(item, buffer, size);
 332         if (save_commit_buffer && !ret) {
 333                 item->buffer = buffer;
 334                 return 0;
 335         }
 336         free(buffer);
 337         return ret;
 338 }
 339
 340 int find_commit_subject(const char *commit_buffer, const char **subject)
 341 {
 342         const char *eol;
 343         const char *p = commit_buffer;
 344
 345         while (*p && (*p != '\n' || p[1] != '\n'))
 346                 p++;
 347         if (*p) {
 348                 p += 2;
 349                 for (eol = p; *eol && *eol != '\n'; eol++)
 350                         ; /* do nothing */
 351         } else
 352                 eol = p;
 353
 354         *subject = p;
 355
 356         return eol - p;
 357 }
 358
 359 struct commit_list *commit_list_insert(struct commit *item, struct commit_list **list_p)
 360 {
 361         struct commit_list *new_list = xmalloc(sizeof(struct commit_list));
 362         new_list->item = item;
 363         new_list->next = *list_p;
 364         *list_p = new_list;
 365         return new_list;
 366 }
 367
 368 unsigned commit_list_count(const struct commit_list *l)
 369 {
 370         unsigned c = 0;
 371         for (; l; l = l->next )
 372                 c++;
 373         return c;
 374 }
 375
 376 void free_commit_list(struct commit_list *list)
 377 {
 378         while (list) {
 379                 struct commit_list *temp = list;
 380                 list = temp->next;
 381                 free(temp);
 382         }
 383 }
 384
 385 struct commit_list * commit_list_insert_by_date(struct commit *item, struct commit_list **list)
 386 {
 387         struct commit_list **pp = list;
 388         struct commit_list *p;
 389         while ((p = *pp) != NULL) {
 390                 if (p->item->date < item->date) {
 391                         break;
 392                 }
 393                 pp = &p->next;
 394         }
 395         return commit_list_insert(item, pp);
 396 }
 397
 398
 399 void commit_list_sort_by_date(struct commit_list **list)
 400 {
 401         struct commit_list *ret = NULL;
 402         while (*list) {
 403                 commit_list_insert_by_date((*list)->item, &ret);
 404                 *list = (*list)->next;
 405         }
 406         *list = ret;
 407 }
 408
 409 struct commit *pop_most_recent_commit(struct commit_list **list,
 410                                       unsigned int mark)
 411 {
 412         struct commit *ret = (*list)->item;
 413         struct commit_list *parents = ret->parents;
 414         struct commit_list *old = *list;
 415
 416         *list = (*list)->next;
 417         free(old);
 418
 419         while (parents) {
 420                 struct commit *commit = parents->item;
 421                 if (!parse_commit(commit) && !(commit->object.flags & mark)) {
 422                         commit->object.flags |= mark;
 423                         commit_list_insert_by_date(commit, list);
 424                 }
 425                 parents = parents->next;
 426         }
 427         return ret;
 428 }
 429
 430 void clear_commit_marks(struct commit *commit, unsigned int mark)
 431 {
 432         while (commit) {
 433                 struct commit_list *parents;
 434
 435                 if (!(mark & commit->object.flags))
 436                         return;
 437
 438                 commit->object.flags &= ~mark;
 439
 440                 parents = commit->parents;
 441                 if (!parents)
 442                         return;
 443
 444                 while ((parents = parents->next))
 445                         clear_commit_marks(parents->item, mark);
 446
 447                 commit = commit->parents->item;
 448         }
 449 }
 450
 451 struct commit *pop_commit(struct commit_list **stack)
 452 {
 453         struct commit_list *top = *stack;
 454         struct commit *item = top ? top->item : NULL;
 455
 456         if (top) {
 457                 *stack = top->next;
 458                 free(top);
 459         }
 460         return item;
 461 }
 462
 463 /*
 464  * Performs an in-place topological sort on the list supplied.
 465  */
 466 void sort_in_topological_order(struct commit_list ** list, int lifo)
 467 {
 468         struct commit_list *next, *orig = *list;
 469         struct commit_list *work, **insert;
 470         struct commit_list **pptr;
 471
 472         if (!orig)
 473                 return;
 474         *list = NULL;
 475
 476         /* Mark them and clear the indegree */
 477         for (next = orig; next; next = next->next) {
 478                 struct commit *commit = next->item;
 479                 commit->indegree = 1;
 480         }
 481
 482         /* update the indegree */
 483         for (next = orig; next; next = next->next) {
 484                 struct commit_list * parents = next->item->parents;
 485                 while (parents) {
 486                         struct commit *parent = parents->item;
 487
 488                         if (parent->indegree)
 489                                 parent->indegree++;
 490                         parents = parents->next;
 491                 }
 492         }
 493
 494         /*
 495          * find the tips
 496          *
 497          * tips are nodes not reachable from any other node in the list
 498          *
 499          * the tips serve as a starting set for the work queue.
 500          */
 501         work = NULL;
 502         insert = &work;
 503         for (next = orig; next; next = next->next) {
 504                 struct commit *commit = next->item;
 505
 506                 if (commit->indegree == 1)
 507                         insert = &commit_list_insert(commit, insert)->next;
 508         }
 509
 510         /* process the list in topological order */
 511         if (!lifo)
 512                 commit_list_sort_by_date(&work);
 513
 514         pptr = list;
 515         *list = NULL;
 516         while (work) {
 517                 struct commit *commit;
 518                 struct commit_list *parents, *work_item;
 519
 520                 work_item = work;
 521                 work = work_item->next;
 522                 work_item->next = NULL;
 523
 524                 commit = work_item->item;
 525                 for (parents = commit->parents; parents ; parents = parents->next) {
 526                         struct commit *parent=parents->item;
 527
 528                         if (!parent->indegree)
 529                                 continue;
 530
 531                         /*
 532                          * parents are only enqueued for emission
 533                          * when all their children have been emitted thereby
 534                          * guaranteeing topological order.
 535                          */
 536                         if (--parent->indegree == 1) {
 537                                 if (!lifo)
 538                                         commit_list_insert_by_date(parent, &work);
 539                                 else
 540                                         commit_list_insert(parent, &work);
 541                         }
 542                 }
 543                 /*
 544                  * work_item is a commit all of whose children
 545                  * have already been emitted. we can emit it now.
 546                  */
 547                 commit->indegree = 0;
 548                 *pptr = work_item;
 549                 pptr = &work_item->next;
 550         }
 551 }
 552
 553 /* merge-base stuff */
 554
 555 /* bits #0..15 in revision.h */
 556 #define PARENT1         (1u<<16)
 557 #define PARENT2         (1u<<17)
 558 #define STALE           (1u<<18)
 559 #define RESULT          (1u<<19)
 560
 561 static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);
 562
 563 static struct commit *interesting(struct commit_list *list)
 564 {
 565         while (list) {
 566                 struct commit *commit = list->item;
 567                 list = list->next;
 568                 if (commit->object.flags & STALE)
 569                         continue;
 570                 return commit;
 571         }
 572         return NULL;
 573 }
 574
 575 static struct commit_list *merge_bases_many(struct commit *one, int n, struct commit **twos)
 576 {
 577         struct commit_list *list = NULL;
 578         struct commit_list *result = NULL;
 579         int i;
 580
 581         for (i = 0; i < n; i++) {
 582                 if (one == twos[i])
 583                         /*
 584                          * We do not mark this even with RESULT so we do not
 585                          * have to clean it up.
 586                          */
 587                         return commit_list_insert(one, &result);
 588         }
 589
 590         if (parse_commit(one))
 591                 return NULL;
 592         for (i = 0; i < n; i++) {
 593                 if (parse_commit(twos[i]))
 594                         return NULL;
 595         }
 596
 597         one->object.flags |= PARENT1;
 598         commit_list_insert_by_date(one, &list);
 599         for (i = 0; i < n; i++) {
 600                 twos[i]->object.flags |= PARENT2;
 601                 commit_list_insert_by_date(twos[i], &list);
 602         }
 603
 604         while (interesting(list)) {
 605                 struct commit *commit;
 606                 struct commit_list *parents;
 607                 struct commit_list *next;
 608                 int flags;
 609
 610                 commit = list->item;
 611                 next = list->next;
 612                 free(list);
 613                 list = next;
 614
 615                 flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
 616                 if (flags == (PARENT1 | PARENT2)) {
 617                         if (!(commit->object.flags & RESULT)) {
 618                                 commit->object.flags |= RESULT;
 619                                 commit_list_insert_by_date(commit, &result);
 620                         }
 621                         /* Mark parents of a found merge stale */
 622                         flags |= STALE;
 623                 }
 624                 parents = commit->parents;
 625                 while (parents) {
 626                         struct commit *p = parents->item;
 627                         parents = parents->next;
 628                         if ((p->object.flags & flags) == flags)
 629                                 continue;
 630                         if (parse_commit(p))
 631                                 return NULL;
 632                         p->object.flags |= flags;
 633                         commit_list_insert_by_date(p, &list);
 634                 }
 635         }
 636
 637         /* Clean up the result to remove stale ones */
 638         free_commit_list(list);
 639         list = result; result = NULL;
 640         while (list) {
 641                 struct commit_list *next = list->next;
 642                 if (!(list->item->object.flags & STALE))
 643                         commit_list_insert_by_date(list->item, &result);
 644                 free(list);
 645                 list = next;
 646         }
 647         return result;
 648 }
 649
 650 struct commit_list *get_octopus_merge_bases(struct commit_list *in)
 651 {
 652         struct commit_list *i, *j, *k, *ret = NULL;
 653         struct commit_list **pptr = &ret;
 654
 655         for (i = in; i; i = i->next) {
 656                 if (!ret)
 657                         pptr = &commit_list_insert(i->item, pptr)->next;
 658                 else {
 659                         struct commit_list *new = NULL, *end = NULL;
 660
 661                         for (j = ret; j; j = j->next) {
 662                                 struct commit_list *bases;
 663                                 bases = get_merge_bases(i->item, j->item, 1);
 664                                 if (!new)
 665                                         new = bases;
 666                                 else
 667                                         end->next = bases;
 668                                 for (k = bases; k; k = k->next)
 669                                         end = k;
 670                         }
 671                         ret = new;
 672                 }
 673         }
 674         return ret;
 675 }
 676
 677 struct commit_list *get_merge_bases_many(struct commit *one,
 678                                          int n,
 679                                          struct commit **twos,
 680                                          int cleanup)
 681 {
 682         struct commit_list *list;
 683         struct commit **rslt;
 684         struct commit_list *result;
 685         int cnt, i, j;
 686
 687         result = merge_bases_many(one, n, twos);
 688         for (i = 0; i < n; i++) {
 689                 if (one == twos[i])
 690                         return result;
 691         }
 692         if (!result || !result->next) {
 693                 if (cleanup) {
 694                         clear_commit_marks(one, all_flags);
 695                         for (i = 0; i < n; i++)
 696                                 clear_commit_marks(twos[i], all_flags);
 697                 }
 698                 return result;
 699         }
 700
 701         /* There are more than one */
 702         cnt = 0;
 703         list = result;
 704         while (list) {
 705                 list = list->next;
 706                 cnt++;
 707         }
 708         rslt = xcalloc(cnt, sizeof(*rslt));
 709         for (list = result, i = 0; list; list = list->next)
 710                 rslt[i++] = list->item;
 711         free_commit_list(result);
 712
 713         clear_commit_marks(one, all_flags);
 714         for (i = 0; i < n; i++)
 715                 clear_commit_marks(twos[i], all_flags);
 716         for (i = 0; i < cnt - 1; i++) {
 717                 for (j = i+1; j < cnt; j++) {
 718                         if (!rslt[i] || !rslt[j])
 719                                 continue;
 720                         result = merge_bases_many(rslt[i], 1, &rslt[j]);
 721                         clear_commit_marks(rslt[i], all_flags);
 722                         clear_commit_marks(rslt[j], all_flags);
 723                         for (list = result; list; list = list->next) {
 724                                 if (rslt[i] == list->item)
 725                                         rslt[i] = NULL;
 726                                 if (rslt[j] == list->item)
 727                                         rslt[j] = NULL;
 728                         }
 729                 }
 730         }
 731
 732         /* Surviving ones in rslt[] are the independent results */
 733         result = NULL;
 734         for (i = 0; i < cnt; i++) {
 735                 if (rslt[i])
 736                         commit_list_insert_by_date(rslt[i], &result);
 737         }
 738         free(rslt);
 739         return result;
 740 }
 741
 742 struct commit_list *get_merge_bases(struct commit *one, struct commit *two,
 743                                     int cleanup)
 744 {
 745         return get_merge_bases_many(one, 1, &two, cleanup);
 746 }
 747
 748 int is_descendant_of(struct commit *commit, struct commit_list *with_commit)
 749 {
 750         if (!with_commit)
 751                 return 1;
 752         while (with_commit) {
 753                 struct commit *other;
 754
 755                 other = with_commit->item;
 756                 with_commit = with_commit->next;
 757                 if (in_merge_bases(other, &commit, 1))
 758                         return 1;
 759         }
 760         return 0;
 761 }
 762
 763 int in_merge_bases(struct commit *commit, struct commit **reference, int num)
 764 {
 765         struct commit_list *bases, *b;
 766         int ret = 0;
 767
 768         if (num == 1)
 769                 bases = get_merge_bases(commit, *reference, 1);
 770         else
 771                 die("not yet");
 772         for (b = bases; b; b = b->next) {
 773                 if (!hashcmp(commit->object.sha1, b->item->object.sha1)) {
 774                         ret = 1;
 775                         break;
 776                 }
 777         }
 778
 779         free_commit_list(bases);
 780         return ret;
 781 }
 782
 783 struct commit_list *reduce_heads(struct commit_list *heads)
 784 {
 785         struct commit_list *p;
 786         struct commit_list *result = NULL, **tail = &result;
 787         struct commit **other;
 788         size_t num_head, num_other;
 789
 790         if (!heads)
 791                 return NULL;
 792
 793         /* Avoid unnecessary reallocations */
 794         for (p = heads, num_head = 0; p; p = p->next)
 795                 num_head++;
 796         other = xcalloc(sizeof(*other), num_head);
 797
 798         /* For each commit, see if it can be reached by others */
 799         for (p = heads; p; p = p->next) {
 800                 struct commit_list *q, *base;
 801
 802                 /* Do we already have this in the result? */
 803                 for (q = result; q; q = q->next)
 804                         if (p->item == q->item)
 805                                 break;
 806                 if (q)
 807                         continue;
 808
 809                 num_other = 0;
 810                 for (q = heads; q; q = q->next) {
 811                         if (p->item == q->item)
 812                                 continue;
 813                         other[num_other++] = q->item;
 814                 }
 815                 if (num_other)
 816                         base = get_merge_bases_many(p->item, num_other, other, 1);
 817                 else
 818                         base = NULL;
 819                 /*
 820                  * If p->item does not have anything common with other
 821                  * commits, there won't be any merge base.  If it is
 822                  * reachable from some of the others, p->item will be
 823                  * the merge base.  If its history is connected with
 824                  * others, but p->item is not reachable by others, we
 825                  * will get something other than p->item back.
 826                  */
 827                 if (!base || (base->item != p->item))
 828                         tail = &(commit_list_insert(p->item, tail)->next);
 829                 free_commit_list(base);
 830         }
 831         free(other);
 832         return result;
 833 }
 834
 835 static const char commit_utf8_warn[] =
 836 "Warning: commit message does not conform to UTF-8.\n"
 837 "You may want to amend it after fixing the message, or set the config\n"
 838 "variable i18n.commitencoding to the encoding your project uses.\n";
 839
 840 int commit_tree(const char *msg, unsigned char *tree,
 841                 struct commit_list *parents, unsigned char *ret,
 842                 const char *author)
 843 {
 844         int result;
 845         int encoding_is_utf8;
 846         struct strbuf buffer;
 847
 848         assert_sha1_type(tree, OBJ_TREE);
 849
 850         /* Not having i18n.commitencoding is the same as having utf-8 */
 851         encoding_is_utf8 = is_encoding_utf8(git_commit_encoding);
 852
 853         strbuf_init(&buffer, 8192); /* should avoid reallocs for the headers */
 854         strbuf_addf(&buffer, "tree %s\n", sha1_to_hex(tree));
 855
 856         /*
 857          * NOTE! This ordering means that the same exact tree merged with a
 858          * different order of parents will be a _different_ changeset even
 859          * if everything else stays the same.
 860          */
 861         while (parents) {
 862                 struct commit_list *next = parents->next;
 863                 strbuf_addf(&buffer, "parent %s\n",
 864                         sha1_to_hex(parents->item->object.sha1));
 865                 free(parents);
 866                 parents = next;
 867         }
 868
 869         /* Person/date information */
 870         if (!author)
 871                 author = git_author_info(IDENT_ERROR_ON_NO_NAME);
 872         strbuf_addf(&buffer, "author %s\n", author);
 873         strbuf_addf(&buffer, "committer %s\n", git_committer_info(IDENT_ERROR_ON_NO_NAME));
 874         if (!encoding_is_utf8)
 875                 strbuf_addf(&buffer, "encoding %s\n", git_commit_encoding);
 876         strbuf_addch(&buffer, '\n');
 877
 878         /* And add the comment */
 879         strbuf_addstr(&buffer, msg);
 880
 881         /* And check the encoding */
 882         if (encoding_is_utf8 && !is_utf8(buffer.buf))
 883                 fprintf(stderr, commit_utf8_warn);
 884
 885         result = write_sha1_file(buffer.buf, buffer.len, commit_type, ret);
 886         strbuf_release(&buffer);
 887         return result;
 888 }