commit.con commit Documentation/merge subtree How-To: fix typo (59ab4eb)
   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
  10int save_commit_buffer = 1;
  11
  12const char *commit_type = "commit";
  13
  14static 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
  27struct 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
  37struct commit *lookup_commit_reference(const unsigned char *sha1)
  38{
  39        return lookup_commit_reference_gently(sha1, 0);
  40}
  41
  42struct 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
  52struct 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
  65static 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
  92static struct commit_graft **commit_graft;
  93static int commit_graft_alloc, commit_graft_nr;
  94
  95static 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
 114int 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
 143struct 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
 168bad_graft_data:
 169        error("bad graft data: %s", buf);
 170        free(graft);
 171        return NULL;
 172}
 173
 174static 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
 193static 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
 207struct 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
 217int 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
 235int 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
 248int parse_commit_buffer(struct commit *item, const void *buffer, unsigned long size)
 249{
 250        const char *tail = buffer;
 251        const 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
 303int 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
 332int 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
 351struct 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
 360unsigned 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
 368void 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
 377struct commit_list * 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
 391void commit_list_sort_by_date(struct commit_list **list)
 392{
 393        struct commit_list *ret = NULL;
 394        while (*list) {
 395                commit_list_insert_by_date((*list)->item, &ret);
 396                *list = (*list)->next;
 397        }
 398        *list = ret;
 399}
 400
 401struct 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                        commit_list_insert_by_date(commit, list);
 416                }
 417                parents = parents->next;
 418        }
 419        return ret;
 420}
 421
 422void 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
 443struct 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 */
 458void 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                commit_list_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                                        commit_list_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
 553static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);
 554
 555static 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
 567static 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        commit_list_insert_by_date(one, &list);
 591        for (i = 0; i < n; i++) {
 592                twos[i]->object.flags |= PARENT2;
 593                commit_list_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                                commit_list_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                        commit_list_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                        commit_list_insert_by_date(list->item, &result);
 636                free(list);
 637                list = next;
 638        }
 639        return result;
 640}
 641
 642struct 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
 669struct 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                        commit_list_insert_by_date(rslt[i], &result);
 729        }
 730        free(rslt);
 731        return result;
 732}
 733
 734struct 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
 740int 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
 755int 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
 775struct 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
 827static 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
 832int 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}