Andrew's git / gitweb.git / commit.c
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commit.con commit commit: factor out clear_commit_marks_for_object_array (86a0a40)
   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
 443void clear_commit_marks_for_object_array(struct object_array *a, unsigned mark)
 444{
 445        struct object *object;
 446        struct commit *commit;
 447        unsigned int i;
 448
 449        for (i = 0; i < a->nr; i++) {
 450                object = a->objects[i].item;
 451                commit = lookup_commit_reference_gently(object->sha1, 1);
 452                if (commit)
 453                        clear_commit_marks(commit, mark);
 454        }
 455}
 456
 457struct commit *pop_commit(struct commit_list **stack)
 458{
 459        struct commit_list *top = *stack;
 460        struct commit *item = top ? top->item : NULL;
 461
 462        if (top) {
 463                *stack = top->next;
 464                free(top);
 465        }
 466        return item;
 467}
 468
 469/*
 470 * Performs an in-place topological sort on the list supplied.
 471 */
 472void sort_in_topological_order(struct commit_list ** list, int lifo)
 473{
 474        struct commit_list *next, *orig = *list;
 475        struct commit_list *work, **insert;
 476        struct commit_list **pptr;
 477
 478        if (!orig)
 479                return;
 480        *list = NULL;
 481
 482        /* Mark them and clear the indegree */
 483        for (next = orig; next; next = next->next) {
 484                struct commit *commit = next->item;
 485                commit->indegree = 1;
 486        }
 487
 488        /* update the indegree */
 489        for (next = orig; next; next = next->next) {
 490                struct commit_list * parents = next->item->parents;
 491                while (parents) {
 492                        struct commit *parent = parents->item;
 493
 494                        if (parent->indegree)
 495                                parent->indegree++;
 496                        parents = parents->next;
 497                }
 498        }
 499
 500        /*
 501         * find the tips
 502         *
 503         * tips are nodes not reachable from any other node in the list
 504         *
 505         * the tips serve as a starting set for the work queue.
 506         */
 507        work = NULL;
 508        insert = &work;
 509        for (next = orig; next; next = next->next) {
 510                struct commit *commit = next->item;
 511
 512                if (commit->indegree == 1)
 513                        insert = &commit_list_insert(commit, insert)->next;
 514        }
 515
 516        /* process the list in topological order */
 517        if (!lifo)
 518                commit_list_sort_by_date(&work);
 519
 520        pptr = list;
 521        *list = NULL;
 522        while (work) {
 523                struct commit *commit;
 524                struct commit_list *parents, *work_item;
 525
 526                work_item = work;
 527                work = work_item->next;
 528                work_item->next = NULL;
 529
 530                commit = work_item->item;
 531                for (parents = commit->parents; parents ; parents = parents->next) {
 532                        struct commit *parent=parents->item;
 533
 534                        if (!parent->indegree)
 535                                continue;
 536
 537                        /*
 538                         * parents are only enqueued for emission
 539                         * when all their children have been emitted thereby
 540                         * guaranteeing topological order.
 541                         */
 542                        if (--parent->indegree == 1) {
 543                                if (!lifo)
 544                                        commit_list_insert_by_date(parent, &work);
 545                                else
 546                                        commit_list_insert(parent, &work);
 547                        }
 548                }
 549                /*
 550                 * work_item is a commit all of whose children
 551                 * have already been emitted. we can emit it now.
 552                 */
 553                commit->indegree = 0;
 554                *pptr = work_item;
 555                pptr = &work_item->next;
 556        }
 557}
 558
 559/* merge-base stuff */
 560
 561/* bits #0..15 in revision.h */
 562#define PARENT1         (1u<<16)
 563#define PARENT2         (1u<<17)
 564#define STALE           (1u<<18)
 565#define RESULT          (1u<<19)
 566
 567static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);
 568
 569static struct commit *interesting(struct commit_list *list)
 570{
 571        while (list) {
 572                struct commit *commit = list->item;
 573                list = list->next;
 574                if (commit->object.flags & STALE)
 575                        continue;
 576                return commit;
 577        }
 578        return NULL;
 579}
 580
 581static struct commit_list *merge_bases_many(struct commit *one, int n, struct commit **twos)
 582{
 583        struct commit_list *list = NULL;
 584        struct commit_list *result = NULL;
 585        int i;
 586
 587        for (i = 0; i < n; i++) {
 588                if (one == twos[i])
 589                        /*
 590                         * We do not mark this even with RESULT so we do not
 591                         * have to clean it up.
 592                         */
 593                        return commit_list_insert(one, &result);
 594        }
 595
 596        if (parse_commit(one))
 597                return NULL;
 598        for (i = 0; i < n; i++) {
 599                if (parse_commit(twos[i]))
 600                        return NULL;
 601        }
 602
 603        one->object.flags |= PARENT1;
 604        commit_list_insert_by_date(one, &list);
 605        for (i = 0; i < n; i++) {
 606                twos[i]->object.flags |= PARENT2;
 607                commit_list_insert_by_date(twos[i], &list);
 608        }
 609
 610        while (interesting(list)) {
 611                struct commit *commit;
 612                struct commit_list *parents;
 613                struct commit_list *next;
 614                int flags;
 615
 616                commit = list->item;
 617                next = list->next;
 618                free(list);
 619                list = next;
 620
 621                flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
 622                if (flags == (PARENT1 | PARENT2)) {
 623                        if (!(commit->object.flags & RESULT)) {
 624                                commit->object.flags |= RESULT;
 625                                commit_list_insert_by_date(commit, &result);
 626                        }
 627                        /* Mark parents of a found merge stale */
 628                        flags |= STALE;
 629                }
 630                parents = commit->parents;
 631                while (parents) {
 632                        struct commit *p = parents->item;
 633                        parents = parents->next;
 634                        if ((p->object.flags & flags) == flags)
 635                                continue;
 636                        if (parse_commit(p))
 637                                return NULL;
 638                        p->object.flags |= flags;
 639                        commit_list_insert_by_date(p, &list);
 640                }
 641        }
 642
 643        /* Clean up the result to remove stale ones */
 644        free_commit_list(list);
 645        list = result; result = NULL;
 646        while (list) {
 647                struct commit_list *next = list->next;
 648                if (!(list->item->object.flags & STALE))
 649                        commit_list_insert_by_date(list->item, &result);
 650                free(list);
 651                list = next;
 652        }
 653        return result;
 654}
 655
 656struct commit_list *get_octopus_merge_bases(struct commit_list *in)
 657{
 658        struct commit_list *i, *j, *k, *ret = NULL;
 659        struct commit_list **pptr = &ret;
 660
 661        for (i = in; i; i = i->next) {
 662                if (!ret)
 663                        pptr = &commit_list_insert(i->item, pptr)->next;
 664                else {
 665                        struct commit_list *new = NULL, *end = NULL;
 666
 667                        for (j = ret; j; j = j->next) {
 668                                struct commit_list *bases;
 669                                bases = get_merge_bases(i->item, j->item, 1);
 670                                if (!new)
 671                                        new = bases;
 672                                else
 673                                        end->next = bases;
 674                                for (k = bases; k; k = k->next)
 675                                        end = k;
 676                        }
 677                        ret = new;
 678                }
 679        }
 680        return ret;
 681}
 682
 683struct commit_list *get_merge_bases_many(struct commit *one,
 684                                         int n,
 685                                         struct commit **twos,
 686                                         int cleanup)
 687{
 688        struct commit_list *list;
 689        struct commit **rslt;
 690        struct commit_list *result;
 691        int cnt, i, j;
 692
 693        result = merge_bases_many(one, n, twos);
 694        for (i = 0; i < n; i++) {
 695                if (one == twos[i])
 696                        return result;
 697        }
 698        if (!result || !result->next) {
 699                if (cleanup) {
 700                        clear_commit_marks(one, all_flags);
 701                        for (i = 0; i < n; i++)
 702                                clear_commit_marks(twos[i], all_flags);
 703                }
 704                return result;
 705        }
 706
 707        /* There are more than one */
 708        cnt = 0;
 709        list = result;
 710        while (list) {
 711                list = list->next;
 712                cnt++;
 713        }
 714        rslt = xcalloc(cnt, sizeof(*rslt));
 715        for (list = result, i = 0; list; list = list->next)
 716                rslt[i++] = list->item;
 717        free_commit_list(result);
 718
 719        clear_commit_marks(one, all_flags);
 720        for (i = 0; i < n; i++)
 721                clear_commit_marks(twos[i], all_flags);
 722        for (i = 0; i < cnt - 1; i++) {
 723                for (j = i+1; j < cnt; j++) {
 724                        if (!rslt[i] || !rslt[j])
 725                                continue;
 726                        result = merge_bases_many(rslt[i], 1, &rslt[j]);
 727                        clear_commit_marks(rslt[i], all_flags);
 728                        clear_commit_marks(rslt[j], all_flags);
 729                        for (list = result; list; list = list->next) {
 730                                if (rslt[i] == list->item)
 731                                        rslt[i] = NULL;
 732                                if (rslt[j] == list->item)
 733                                        rslt[j] = NULL;
 734                        }
 735                }
 736        }
 737
 738        /* Surviving ones in rslt[] are the independent results */
 739        result = NULL;
 740        for (i = 0; i < cnt; i++) {
 741                if (rslt[i])
 742                        commit_list_insert_by_date(rslt[i], &result);
 743        }
 744        free(rslt);
 745        return result;
 746}
 747
 748struct commit_list *get_merge_bases(struct commit *one, struct commit *two,
 749                                    int cleanup)
 750{
 751        return get_merge_bases_many(one, 1, &two, cleanup);
 752}
 753
 754int is_descendant_of(struct commit *commit, struct commit_list *with_commit)
 755{
 756        if (!with_commit)
 757                return 1;
 758        while (with_commit) {
 759                struct commit *other;
 760
 761                other = with_commit->item;
 762                with_commit = with_commit->next;
 763                if (in_merge_bases(other, &commit, 1))
 764                        return 1;
 765        }
 766        return 0;
 767}
 768
 769int in_merge_bases(struct commit *commit, struct commit **reference, int num)
 770{
 771        struct commit_list *bases, *b;
 772        int ret = 0;
 773
 774        if (num == 1)
 775                bases = get_merge_bases(commit, *reference, 1);
 776        else
 777                die("not yet");
 778        for (b = bases; b; b = b->next) {
 779                if (!hashcmp(commit->object.sha1, b->item->object.sha1)) {
 780                        ret = 1;
 781                        break;
 782                }
 783        }
 784
 785        free_commit_list(bases);
 786        return ret;
 787}
 788
 789struct commit_list *reduce_heads(struct commit_list *heads)
 790{
 791        struct commit_list *p;
 792        struct commit_list *result = NULL, **tail = &result;
 793        struct commit **other;
 794        size_t num_head, num_other;
 795
 796        if (!heads)
 797                return NULL;
 798
 799        /* Avoid unnecessary reallocations */
 800        for (p = heads, num_head = 0; p; p = p->next)
 801                num_head++;
 802        other = xcalloc(sizeof(*other), num_head);
 803
 804        /* For each commit, see if it can be reached by others */
 805        for (p = heads; p; p = p->next) {
 806                struct commit_list *q, *base;
 807
 808                /* Do we already have this in the result? */
 809                for (q = result; q; q = q->next)
 810                        if (p->item == q->item)
 811                                break;
 812                if (q)
 813                        continue;
 814
 815                num_other = 0;
 816                for (q = heads; q; q = q->next) {
 817                        if (p->item == q->item)
 818                                continue;
 819                        other[num_other++] = q->item;
 820                }
 821                if (num_other)
 822                        base = get_merge_bases_many(p->item, num_other, other, 1);
 823                else
 824                        base = NULL;
 825                /*
 826                 * If p->item does not have anything common with other
 827                 * commits, there won't be any merge base.  If it is
 828                 * reachable from some of the others, p->item will be
 829                 * the merge base.  If its history is connected with
 830                 * others, but p->item is not reachable by others, we
 831                 * will get something other than p->item back.
 832                 */
 833                if (!base || (base->item != p->item))
 834                        tail = &(commit_list_insert(p->item, tail)->next);
 835                free_commit_list(base);
 836        }
 837        free(other);
 838        return result;
 839}
 840
 841static const char commit_utf8_warn[] =
 842"Warning: commit message does not conform to UTF-8.\n"
 843"You may want to amend it after fixing the message, or set the config\n"
 844"variable i18n.commitencoding to the encoding your project uses.\n";
 845
 846int commit_tree(const char *msg, unsigned char *tree,
 847                struct commit_list *parents, unsigned char *ret,
 848                const char *author)
 849{
 850        int result;
 851        int encoding_is_utf8;
 852        struct strbuf buffer;
 853
 854        assert_sha1_type(tree, OBJ_TREE);
 855
 856        /* Not having i18n.commitencoding is the same as having utf-8 */
 857        encoding_is_utf8 = is_encoding_utf8(git_commit_encoding);
 858
 859        strbuf_init(&buffer, 8192); /* should avoid reallocs for the headers */
 860        strbuf_addf(&buffer, "tree %s\n", sha1_to_hex(tree));
 861
 862        /*
 863         * NOTE! This ordering means that the same exact tree merged with a
 864         * different order of parents will be a _different_ changeset even
 865         * if everything else stays the same.
 866         */
 867        while (parents) {
 868                struct commit_list *next = parents->next;
 869                strbuf_addf(&buffer, "parent %s\n",
 870                        sha1_to_hex(parents->item->object.sha1));
 871                free(parents);
 872                parents = next;
 873        }
 874
 875        /* Person/date information */
 876        if (!author)
 877                author = git_author_info(IDENT_ERROR_ON_NO_NAME);
 878        strbuf_addf(&buffer, "author %s\n", author);
 879        strbuf_addf(&buffer, "committer %s\n", git_committer_info(IDENT_ERROR_ON_NO_NAME));
 880        if (!encoding_is_utf8)
 881                strbuf_addf(&buffer, "encoding %s\n", git_commit_encoding);
 882        strbuf_addch(&buffer, '\n');
 883
 884        /* And add the comment */
 885        strbuf_addstr(&buffer, msg);
 886
 887        /* And check the encoding */
 888        if (encoding_is_utf8 && !is_utf8(buffer.buf))
 889                fprintf(stderr, commit_utf8_warn);
 890
 891        result = write_sha1_file(buffer.buf, buffer.len, commit_type, ret);
 892        strbuf_release(&buffer);
 893        return result;
 894}