Andrew's git / gitweb.git / commit.c
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commit.con commit dir.c: use ALLOC_GROW() in create_simplify() (9af49f8)
   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#include "gpg-interface.h"
  10#include "mergesort.h"
  11#include "commit-slab.h"
  12#include "prio-queue.h"
  13
  14static struct commit_extra_header *read_commit_extra_header_lines(const char *buf, size_t len, const char **);
  15
  16int save_commit_buffer = 1;
  17
  18const char *commit_type = "commit";
  19static int commit_count;
  20
  21static struct commit *check_commit(struct object *obj,
  22                                   const unsigned char *sha1,
  23                                   int quiet)
  24{
  25        if (obj->type != OBJ_COMMIT) {
  26                if (!quiet)
  27                        error("Object %s is a %s, not a commit",
  28                              sha1_to_hex(sha1), typename(obj->type));
  29                return NULL;
  30        }
  31        return (struct commit *) obj;
  32}
  33
  34struct commit *lookup_commit_reference_gently(const unsigned char *sha1,
  35                                              int quiet)
  36{
  37        struct object *obj = deref_tag(parse_object(sha1), NULL, 0);
  38
  39        if (!obj)
  40                return NULL;
  41        return check_commit(obj, sha1, quiet);
  42}
  43
  44struct commit *lookup_commit_reference(const unsigned char *sha1)
  45{
  46        return lookup_commit_reference_gently(sha1, 0);
  47}
  48
  49struct commit *lookup_commit_or_die(const unsigned char *sha1, const char *ref_name)
  50{
  51        struct commit *c = lookup_commit_reference(sha1);
  52        if (!c)
  53                die(_("could not parse %s"), ref_name);
  54        if (hashcmp(sha1, c->object.sha1)) {
  55                warning(_("%s %s is not a commit!"),
  56                        ref_name, sha1_to_hex(sha1));
  57        }
  58        return c;
  59}
  60
  61struct commit *lookup_commit(const unsigned char *sha1)
  62{
  63        struct object *obj = lookup_object(sha1);
  64        if (!obj) {
  65                struct commit *c = alloc_commit_node();
  66                c->index = commit_count++;
  67                return create_object(sha1, OBJ_COMMIT, c);
  68        }
  69        if (!obj->type)
  70                obj->type = OBJ_COMMIT;
  71        return check_commit(obj, sha1, 0);
  72}
  73
  74struct commit *lookup_commit_reference_by_name(const char *name)
  75{
  76        unsigned char sha1[20];
  77        struct commit *commit;
  78
  79        if (get_sha1_committish(name, sha1))
  80                return NULL;
  81        commit = lookup_commit_reference(sha1);
  82        if (parse_commit(commit))
  83                return NULL;
  84        return commit;
  85}
  86
  87static unsigned long parse_commit_date(const char *buf, const char *tail)
  88{
  89        const char *dateptr;
  90
  91        if (buf + 6 >= tail)
  92                return 0;
  93        if (memcmp(buf, "author", 6))
  94                return 0;
  95        while (buf < tail && *buf++ != '\n')
  96                /* nada */;
  97        if (buf + 9 >= tail)
  98                return 0;
  99        if (memcmp(buf, "committer", 9))
 100                return 0;
 101        while (buf < tail && *buf++ != '>')
 102                /* nada */;
 103        if (buf >= tail)
 104                return 0;
 105        dateptr = buf;
 106        while (buf < tail && *buf++ != '\n')
 107                /* nada */;
 108        if (buf >= tail)
 109                return 0;
 110        /* dateptr < buf && buf[-1] == '\n', so strtoul will stop at buf-1 */
 111        return strtoul(dateptr, NULL, 10);
 112}
 113
 114static struct commit_graft **commit_graft;
 115static int commit_graft_alloc, commit_graft_nr;
 116
 117static int commit_graft_pos(const unsigned char *sha1)
 118{
 119        int lo, hi;
 120        lo = 0;
 121        hi = commit_graft_nr;
 122        while (lo < hi) {
 123                int mi = (lo + hi) / 2;
 124                struct commit_graft *graft = commit_graft[mi];
 125                int cmp = hashcmp(sha1, graft->sha1);
 126                if (!cmp)
 127                        return mi;
 128                if (cmp < 0)
 129                        hi = mi;
 130                else
 131                        lo = mi + 1;
 132        }
 133        return -lo - 1;
 134}
 135
 136int register_commit_graft(struct commit_graft *graft, int ignore_dups)
 137{
 138        int pos = commit_graft_pos(graft->sha1);
 139
 140        if (0 <= pos) {
 141                if (ignore_dups)
 142                        free(graft);
 143                else {
 144                        free(commit_graft[pos]);
 145                        commit_graft[pos] = graft;
 146                }
 147                return 1;
 148        }
 149        pos = -pos - 1;
 150        ALLOC_GROW(commit_graft, commit_graft_nr + 1, commit_graft_alloc);
 151        commit_graft_nr++;
 152        if (pos < commit_graft_nr)
 153                memmove(commit_graft + pos + 1,
 154                        commit_graft + pos,
 155                        (commit_graft_nr - pos - 1) *
 156                        sizeof(*commit_graft));
 157        commit_graft[pos] = graft;
 158        return 0;
 159}
 160
 161struct commit_graft *read_graft_line(char *buf, int len)
 162{
 163        /* The format is just "Commit Parent1 Parent2 ...\n" */
 164        int i;
 165        struct commit_graft *graft = NULL;
 166
 167        while (len && isspace(buf[len-1]))
 168                buf[--len] = '\0';
 169        if (buf[0] == '#' || buf[0] == '\0')
 170                return NULL;
 171        if ((len + 1) % 41)
 172                goto bad_graft_data;
 173        i = (len + 1) / 41 - 1;
 174        graft = xmalloc(sizeof(*graft) + 20 * i);
 175        graft->nr_parent = i;
 176        if (get_sha1_hex(buf, graft->sha1))
 177                goto bad_graft_data;
 178        for (i = 40; i < len; i += 41) {
 179                if (buf[i] != ' ')
 180                        goto bad_graft_data;
 181                if (get_sha1_hex(buf + i + 1, graft->parent[i/41]))
 182                        goto bad_graft_data;
 183        }
 184        return graft;
 185
 186bad_graft_data:
 187        error("bad graft data: %s", buf);
 188        free(graft);
 189        return NULL;
 190}
 191
 192static int read_graft_file(const char *graft_file)
 193{
 194        FILE *fp = fopen(graft_file, "r");
 195        struct strbuf buf = STRBUF_INIT;
 196        if (!fp)
 197                return -1;
 198        while (!strbuf_getwholeline(&buf, fp, '\n')) {
 199                /* The format is just "Commit Parent1 Parent2 ...\n" */
 200                struct commit_graft *graft = read_graft_line(buf.buf, buf.len);
 201                if (!graft)
 202                        continue;
 203                if (register_commit_graft(graft, 1))
 204                        error("duplicate graft data: %s", buf.buf);
 205        }
 206        fclose(fp);
 207        strbuf_release(&buf);
 208        return 0;
 209}
 210
 211static void prepare_commit_graft(void)
 212{
 213        static int commit_graft_prepared;
 214        char *graft_file;
 215
 216        if (commit_graft_prepared)
 217                return;
 218        graft_file = get_graft_file();
 219        read_graft_file(graft_file);
 220        /* make sure shallows are read */
 221        is_repository_shallow();
 222        commit_graft_prepared = 1;
 223}
 224
 225struct commit_graft *lookup_commit_graft(const unsigned char *sha1)
 226{
 227        int pos;
 228        prepare_commit_graft();
 229        pos = commit_graft_pos(sha1);
 230        if (pos < 0)
 231                return NULL;
 232        return commit_graft[pos];
 233}
 234
 235int for_each_commit_graft(each_commit_graft_fn fn, void *cb_data)
 236{
 237        int i, ret;
 238        for (i = ret = 0; i < commit_graft_nr && !ret; i++)
 239                ret = fn(commit_graft[i], cb_data);
 240        return ret;
 241}
 242
 243int 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
 256int 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
 311int 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
 340void parse_commit_or_die(struct commit *item)
 341{
 342        if (parse_commit(item))
 343                die("unable to parse commit %s",
 344                    item ? sha1_to_hex(item->object.sha1) : "(null)");
 345}
 346
 347int find_commit_subject(const char *commit_buffer, const char **subject)
 348{
 349        const char *eol;
 350        const char *p = commit_buffer;
 351
 352        while (*p && (*p != '\n' || p[1] != '\n'))
 353                p++;
 354        if (*p) {
 355                p += 2;
 356                for (eol = p; *eol && *eol != '\n'; eol++)
 357                        ; /* do nothing */
 358        } else
 359                eol = p;
 360
 361        *subject = p;
 362
 363        return eol - p;
 364}
 365
 366struct commit_list *commit_list_insert(struct commit *item, struct commit_list **list_p)
 367{
 368        struct commit_list *new_list = xmalloc(sizeof(struct commit_list));
 369        new_list->item = item;
 370        new_list->next = *list_p;
 371        *list_p = new_list;
 372        return new_list;
 373}
 374
 375unsigned commit_list_count(const struct commit_list *l)
 376{
 377        unsigned c = 0;
 378        for (; l; l = l->next )
 379                c++;
 380        return c;
 381}
 382
 383struct commit_list *copy_commit_list(struct commit_list *list)
 384{
 385        struct commit_list *head = NULL;
 386        struct commit_list **pp = &head;
 387        while (list) {
 388                struct commit_list *new;
 389                new = xmalloc(sizeof(struct commit_list));
 390                new->item = list->item;
 391                new->next = NULL;
 392                *pp = new;
 393                pp = &new->next;
 394                list = list->next;
 395        }
 396        return head;
 397}
 398
 399void free_commit_list(struct commit_list *list)
 400{
 401        while (list) {
 402                struct commit_list *temp = list;
 403                list = temp->next;
 404                free(temp);
 405        }
 406}
 407
 408struct commit_list * commit_list_insert_by_date(struct commit *item, struct commit_list **list)
 409{
 410        struct commit_list **pp = list;
 411        struct commit_list *p;
 412        while ((p = *pp) != NULL) {
 413                if (p->item->date < item->date) {
 414                        break;
 415                }
 416                pp = &p->next;
 417        }
 418        return commit_list_insert(item, pp);
 419}
 420
 421static int commit_list_compare_by_date(const void *a, const void *b)
 422{
 423        unsigned long a_date = ((const struct commit_list *)a)->item->date;
 424        unsigned long b_date = ((const struct commit_list *)b)->item->date;
 425        if (a_date < b_date)
 426                return 1;
 427        if (a_date > b_date)
 428                return -1;
 429        return 0;
 430}
 431
 432static void *commit_list_get_next(const void *a)
 433{
 434        return ((const struct commit_list *)a)->next;
 435}
 436
 437static void commit_list_set_next(void *a, void *next)
 438{
 439        ((struct commit_list *)a)->next = next;
 440}
 441
 442void commit_list_sort_by_date(struct commit_list **list)
 443{
 444        *list = llist_mergesort(*list, commit_list_get_next, commit_list_set_next,
 445                                commit_list_compare_by_date);
 446}
 447
 448struct commit *pop_most_recent_commit(struct commit_list **list,
 449                                      unsigned int mark)
 450{
 451        struct commit *ret = (*list)->item;
 452        struct commit_list *parents = ret->parents;
 453        struct commit_list *old = *list;
 454
 455        *list = (*list)->next;
 456        free(old);
 457
 458        while (parents) {
 459                struct commit *commit = parents->item;
 460                if (!parse_commit(commit) && !(commit->object.flags & mark)) {
 461                        commit->object.flags |= mark;
 462                        commit_list_insert_by_date(commit, list);
 463                }
 464                parents = parents->next;
 465        }
 466        return ret;
 467}
 468
 469static void clear_commit_marks_1(struct commit_list **plist,
 470                                 struct commit *commit, unsigned int mark)
 471{
 472        while (commit) {
 473                struct commit_list *parents;
 474
 475                if (!(mark & commit->object.flags))
 476                        return;
 477
 478                commit->object.flags &= ~mark;
 479
 480                parents = commit->parents;
 481                if (!parents)
 482                        return;
 483
 484                while ((parents = parents->next))
 485                        commit_list_insert(parents->item, plist);
 486
 487                commit = commit->parents->item;
 488        }
 489}
 490
 491void clear_commit_marks_many(int nr, struct commit **commit, unsigned int mark)
 492{
 493        struct commit_list *list = NULL;
 494
 495        while (nr--) {
 496                commit_list_insert(*commit, &list);
 497                commit++;
 498        }
 499        while (list)
 500                clear_commit_marks_1(&list, pop_commit(&list), mark);
 501}
 502
 503void clear_commit_marks(struct commit *commit, unsigned int mark)
 504{
 505        clear_commit_marks_many(1, &commit, mark);
 506}
 507
 508void clear_commit_marks_for_object_array(struct object_array *a, unsigned mark)
 509{
 510        struct object *object;
 511        struct commit *commit;
 512        unsigned int i;
 513
 514        for (i = 0; i < a->nr; i++) {
 515                object = a->objects[i].item;
 516                commit = lookup_commit_reference_gently(object->sha1, 1);
 517                if (commit)
 518                        clear_commit_marks(commit, mark);
 519        }
 520}
 521
 522struct commit *pop_commit(struct commit_list **stack)
 523{
 524        struct commit_list *top = *stack;
 525        struct commit *item = top ? top->item : NULL;
 526
 527        if (top) {
 528                *stack = top->next;
 529                free(top);
 530        }
 531        return item;
 532}
 533
 534/*
 535 * Topological sort support
 536 */
 537
 538/* count number of children that have not been emitted */
 539define_commit_slab(indegree_slab, int);
 540
 541/* record author-date for each commit object */
 542define_commit_slab(author_date_slab, unsigned long);
 543
 544static void record_author_date(struct author_date_slab *author_date,
 545                               struct commit *commit)
 546{
 547        const char *buf, *line_end;
 548        char *buffer = NULL;
 549        struct ident_split ident;
 550        char *date_end;
 551        unsigned long date;
 552
 553        if (!commit->buffer) {
 554                unsigned long size;
 555                enum object_type type;
 556                buffer = read_sha1_file(commit->object.sha1, &type, &size);
 557                if (!buffer)
 558                        return;
 559        }
 560
 561        for (buf = commit->buffer ? commit->buffer : buffer;
 562             buf;
 563             buf = line_end + 1) {
 564                line_end = strchrnul(buf, '\n');
 565                if (!starts_with(buf, "author ")) {
 566                        if (!line_end[0] || line_end[1] == '\n')
 567                                return; /* end of header */
 568                        continue;
 569                }
 570                if (split_ident_line(&ident,
 571                                     buf + strlen("author "),
 572                                     line_end - (buf + strlen("author "))) ||
 573                    !ident.date_begin || !ident.date_end)
 574                        goto fail_exit; /* malformed "author" line */
 575                break;
 576        }
 577
 578        date = strtoul(ident.date_begin, &date_end, 10);
 579        if (date_end != ident.date_end)
 580                goto fail_exit; /* malformed date */
 581        *(author_date_slab_at(author_date, commit)) = date;
 582
 583fail_exit:
 584        free(buffer);
 585}
 586
 587static int compare_commits_by_author_date(const void *a_, const void *b_,
 588                                          void *cb_data)
 589{
 590        const struct commit *a = a_, *b = b_;
 591        struct author_date_slab *author_date = cb_data;
 592        unsigned long a_date = *(author_date_slab_at(author_date, a));
 593        unsigned long b_date = *(author_date_slab_at(author_date, b));
 594
 595        /* newer commits with larger date first */
 596        if (a_date < b_date)
 597                return 1;
 598        else if (a_date > b_date)
 599                return -1;
 600        return 0;
 601}
 602
 603int compare_commits_by_commit_date(const void *a_, const void *b_, void *unused)
 604{
 605        const struct commit *a = a_, *b = b_;
 606        /* newer commits with larger date first */
 607        if (a->date < b->date)
 608                return 1;
 609        else if (a->date > b->date)
 610                return -1;
 611        return 0;
 612}
 613
 614/*
 615 * Performs an in-place topological sort on the list supplied.
 616 */
 617void sort_in_topological_order(struct commit_list **list, enum rev_sort_order sort_order)
 618{
 619        struct commit_list *next, *orig = *list;
 620        struct commit_list **pptr;
 621        struct indegree_slab indegree;
 622        struct prio_queue queue;
 623        struct commit *commit;
 624        struct author_date_slab author_date;
 625
 626        if (!orig)
 627                return;
 628        *list = NULL;
 629
 630        init_indegree_slab(&indegree);
 631        memset(&queue, '\0', sizeof(queue));
 632
 633        switch (sort_order) {
 634        default: /* REV_SORT_IN_GRAPH_ORDER */
 635                queue.compare = NULL;
 636                break;
 637        case REV_SORT_BY_COMMIT_DATE:
 638                queue.compare = compare_commits_by_commit_date;
 639                break;
 640        case REV_SORT_BY_AUTHOR_DATE:
 641                init_author_date_slab(&author_date);
 642                queue.compare = compare_commits_by_author_date;
 643                queue.cb_data = &author_date;
 644                break;
 645        }
 646
 647        /* Mark them and clear the indegree */
 648        for (next = orig; next; next = next->next) {
 649                struct commit *commit = next->item;
 650                *(indegree_slab_at(&indegree, commit)) = 1;
 651                /* also record the author dates, if needed */
 652                if (sort_order == REV_SORT_BY_AUTHOR_DATE)
 653                        record_author_date(&author_date, commit);
 654        }
 655
 656        /* update the indegree */
 657        for (next = orig; next; next = next->next) {
 658                struct commit_list *parents = next->item->parents;
 659                while (parents) {
 660                        struct commit *parent = parents->item;
 661                        int *pi = indegree_slab_at(&indegree, parent);
 662
 663                        if (*pi)
 664                                (*pi)++;
 665                        parents = parents->next;
 666                }
 667        }
 668
 669        /*
 670         * find the tips
 671         *
 672         * tips are nodes not reachable from any other node in the list
 673         *
 674         * the tips serve as a starting set for the work queue.
 675         */
 676        for (next = orig; next; next = next->next) {
 677                struct commit *commit = next->item;
 678
 679                if (*(indegree_slab_at(&indegree, commit)) == 1)
 680                        prio_queue_put(&queue, commit);
 681        }
 682
 683        /*
 684         * This is unfortunate; the initial tips need to be shown
 685         * in the order given from the revision traversal machinery.
 686         */
 687        if (sort_order == REV_SORT_IN_GRAPH_ORDER)
 688                prio_queue_reverse(&queue);
 689
 690        /* We no longer need the commit list */
 691        free_commit_list(orig);
 692
 693        pptr = list;
 694        *list = NULL;
 695        while ((commit = prio_queue_get(&queue)) != NULL) {
 696                struct commit_list *parents;
 697
 698                for (parents = commit->parents; parents ; parents = parents->next) {
 699                        struct commit *parent = parents->item;
 700                        int *pi = indegree_slab_at(&indegree, parent);
 701
 702                        if (!*pi)
 703                                continue;
 704
 705                        /*
 706                         * parents are only enqueued for emission
 707                         * when all their children have been emitted thereby
 708                         * guaranteeing topological order.
 709                         */
 710                        if (--(*pi) == 1)
 711                                prio_queue_put(&queue, parent);
 712                }
 713                /*
 714                 * all children of commit have already been
 715                 * emitted. we can emit it now.
 716                 */
 717                *(indegree_slab_at(&indegree, commit)) = 0;
 718
 719                pptr = &commit_list_insert(commit, pptr)->next;
 720        }
 721
 722        clear_indegree_slab(&indegree);
 723        clear_prio_queue(&queue);
 724        if (sort_order == REV_SORT_BY_AUTHOR_DATE)
 725                clear_author_date_slab(&author_date);
 726}
 727
 728/* merge-base stuff */
 729
 730/* bits #0..15 in revision.h */
 731#define PARENT1         (1u<<16)
 732#define PARENT2         (1u<<17)
 733#define STALE           (1u<<18)
 734#define RESULT          (1u<<19)
 735
 736static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);
 737
 738static struct commit *interesting(struct commit_list *list)
 739{
 740        while (list) {
 741                struct commit *commit = list->item;
 742                list = list->next;
 743                if (commit->object.flags & STALE)
 744                        continue;
 745                return commit;
 746        }
 747        return NULL;
 748}
 749
 750/* all input commits in one and twos[] must have been parsed! */
 751static struct commit_list *paint_down_to_common(struct commit *one, int n, struct commit **twos)
 752{
 753        struct commit_list *list = NULL;
 754        struct commit_list *result = NULL;
 755        int i;
 756
 757        one->object.flags |= PARENT1;
 758        commit_list_insert_by_date(one, &list);
 759        if (!n)
 760                return list;
 761        for (i = 0; i < n; i++) {
 762                twos[i]->object.flags |= PARENT2;
 763                commit_list_insert_by_date(twos[i], &list);
 764        }
 765
 766        while (interesting(list)) {
 767                struct commit *commit;
 768                struct commit_list *parents;
 769                struct commit_list *next;
 770                int flags;
 771
 772                commit = list->item;
 773                next = list->next;
 774                free(list);
 775                list = next;
 776
 777                flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
 778                if (flags == (PARENT1 | PARENT2)) {
 779                        if (!(commit->object.flags & RESULT)) {
 780                                commit->object.flags |= RESULT;
 781                                commit_list_insert_by_date(commit, &result);
 782                        }
 783                        /* Mark parents of a found merge stale */
 784                        flags |= STALE;
 785                }
 786                parents = commit->parents;
 787                while (parents) {
 788                        struct commit *p = parents->item;
 789                        parents = parents->next;
 790                        if ((p->object.flags & flags) == flags)
 791                                continue;
 792                        if (parse_commit(p))
 793                                return NULL;
 794                        p->object.flags |= flags;
 795                        commit_list_insert_by_date(p, &list);
 796                }
 797        }
 798
 799        free_commit_list(list);
 800        return result;
 801}
 802
 803static struct commit_list *merge_bases_many(struct commit *one, int n, struct commit **twos)
 804{
 805        struct commit_list *list = NULL;
 806        struct commit_list *result = NULL;
 807        int i;
 808
 809        for (i = 0; i < n; i++) {
 810                if (one == twos[i])
 811                        /*
 812                         * We do not mark this even with RESULT so we do not
 813                         * have to clean it up.
 814                         */
 815                        return commit_list_insert(one, &result);
 816        }
 817
 818        if (parse_commit(one))
 819                return NULL;
 820        for (i = 0; i < n; i++) {
 821                if (parse_commit(twos[i]))
 822                        return NULL;
 823        }
 824
 825        list = paint_down_to_common(one, n, twos);
 826
 827        while (list) {
 828                struct commit_list *next = list->next;
 829                if (!(list->item->object.flags & STALE))
 830                        commit_list_insert_by_date(list->item, &result);
 831                free(list);
 832                list = next;
 833        }
 834        return result;
 835}
 836
 837struct commit_list *get_octopus_merge_bases(struct commit_list *in)
 838{
 839        struct commit_list *i, *j, *k, *ret = NULL;
 840
 841        if (!in)
 842                return ret;
 843
 844        commit_list_insert(in->item, &ret);
 845
 846        for (i = in->next; i; i = i->next) {
 847                struct commit_list *new = NULL, *end = NULL;
 848
 849                for (j = ret; j; j = j->next) {
 850                        struct commit_list *bases;
 851                        bases = get_merge_bases(i->item, j->item, 1);
 852                        if (!new)
 853                                new = bases;
 854                        else
 855                                end->next = bases;
 856                        for (k = bases; k; k = k->next)
 857                                end = k;
 858                }
 859                ret = new;
 860        }
 861        return ret;
 862}
 863
 864static int remove_redundant(struct commit **array, int cnt)
 865{
 866        /*
 867         * Some commit in the array may be an ancestor of
 868         * another commit.  Move such commit to the end of
 869         * the array, and return the number of commits that
 870         * are independent from each other.
 871         */
 872        struct commit **work;
 873        unsigned char *redundant;
 874        int *filled_index;
 875        int i, j, filled;
 876
 877        work = xcalloc(cnt, sizeof(*work));
 878        redundant = xcalloc(cnt, 1);
 879        filled_index = xmalloc(sizeof(*filled_index) * (cnt - 1));
 880
 881        for (i = 0; i < cnt; i++)
 882                parse_commit(array[i]);
 883        for (i = 0; i < cnt; i++) {
 884                struct commit_list *common;
 885
 886                if (redundant[i])
 887                        continue;
 888                for (j = filled = 0; j < cnt; j++) {
 889                        if (i == j || redundant[j])
 890                                continue;
 891                        filled_index[filled] = j;
 892                        work[filled++] = array[j];
 893                }
 894                common = paint_down_to_common(array[i], filled, work);
 895                if (array[i]->object.flags & PARENT2)
 896                        redundant[i] = 1;
 897                for (j = 0; j < filled; j++)
 898                        if (work[j]->object.flags & PARENT1)
 899                                redundant[filled_index[j]] = 1;
 900                clear_commit_marks(array[i], all_flags);
 901                for (j = 0; j < filled; j++)
 902                        clear_commit_marks(work[j], all_flags);
 903                free_commit_list(common);
 904        }
 905
 906        /* Now collect the result */
 907        memcpy(work, array, sizeof(*array) * cnt);
 908        for (i = filled = 0; i < cnt; i++)
 909                if (!redundant[i])
 910                        array[filled++] = work[i];
 911        for (j = filled, i = 0; i < cnt; i++)
 912                if (redundant[i])
 913                        array[j++] = work[i];
 914        free(work);
 915        free(redundant);
 916        free(filled_index);
 917        return filled;
 918}
 919
 920struct commit_list *get_merge_bases_many(struct commit *one,
 921                                         int n,
 922                                         struct commit **twos,
 923                                         int cleanup)
 924{
 925        struct commit_list *list;
 926        struct commit **rslt;
 927        struct commit_list *result;
 928        int cnt, i;
 929
 930        result = merge_bases_many(one, n, twos);
 931        for (i = 0; i < n; i++) {
 932                if (one == twos[i])
 933                        return result;
 934        }
 935        if (!result || !result->next) {
 936                if (cleanup) {
 937                        clear_commit_marks(one, all_flags);
 938                        clear_commit_marks_many(n, twos, all_flags);
 939                }
 940                return result;
 941        }
 942
 943        /* There are more than one */
 944        cnt = 0;
 945        list = result;
 946        while (list) {
 947                list = list->next;
 948                cnt++;
 949        }
 950        rslt = xcalloc(cnt, sizeof(*rslt));
 951        for (list = result, i = 0; list; list = list->next)
 952                rslt[i++] = list->item;
 953        free_commit_list(result);
 954
 955        clear_commit_marks(one, all_flags);
 956        clear_commit_marks_many(n, twos, all_flags);
 957
 958        cnt = remove_redundant(rslt, cnt);
 959        result = NULL;
 960        for (i = 0; i < cnt; i++)
 961                commit_list_insert_by_date(rslt[i], &result);
 962        free(rslt);
 963        return result;
 964}
 965
 966struct commit_list *get_merge_bases(struct commit *one, struct commit *two,
 967                                    int cleanup)
 968{
 969        return get_merge_bases_many(one, 1, &two, cleanup);
 970}
 971
 972/*
 973 * Is "commit" a descendant of one of the elements on the "with_commit" list?
 974 */
 975int is_descendant_of(struct commit *commit, struct commit_list *with_commit)
 976{
 977        if (!with_commit)
 978                return 1;
 979        while (with_commit) {
 980                struct commit *other;
 981
 982                other = with_commit->item;
 983                with_commit = with_commit->next;
 984                if (in_merge_bases(other, commit))
 985                        return 1;
 986        }
 987        return 0;
 988}
 989
 990/*
 991 * Is "commit" an ancestor of one of the "references"?
 992 */
 993int in_merge_bases_many(struct commit *commit, int nr_reference, struct commit **reference)
 994{
 995        struct commit_list *bases;
 996        int ret = 0, i;
 997
 998        if (parse_commit(commit))
 999                return ret;
1000        for (i = 0; i < nr_reference; i++)
1001                if (parse_commit(reference[i]))
1002                        return ret;
1003
1004        bases = paint_down_to_common(commit, nr_reference, reference);
1005        if (commit->object.flags & PARENT2)
1006                ret = 1;
1007        clear_commit_marks(commit, all_flags);
1008        clear_commit_marks_many(nr_reference, reference, all_flags);
1009        free_commit_list(bases);
1010        return ret;
1011}
1012
1013/*
1014 * Is "commit" an ancestor of (i.e. reachable from) the "reference"?
1015 */
1016int in_merge_bases(struct commit *commit, struct commit *reference)
1017{
1018        return in_merge_bases_many(commit, 1, &reference);
1019}
1020
1021struct commit_list *reduce_heads(struct commit_list *heads)
1022{
1023        struct commit_list *p;
1024        struct commit_list *result = NULL, **tail = &result;
1025        struct commit **array;
1026        int num_head, i;
1027
1028        if (!heads)
1029                return NULL;
1030
1031        /* Uniquify */
1032        for (p = heads; p; p = p->next)
1033                p->item->object.flags &= ~STALE;
1034        for (p = heads, num_head = 0; p; p = p->next) {
1035                if (p->item->object.flags & STALE)
1036                        continue;
1037                p->item->object.flags |= STALE;
1038                num_head++;
1039        }
1040        array = xcalloc(sizeof(*array), num_head);
1041        for (p = heads, i = 0; p; p = p->next) {
1042                if (p->item->object.flags & STALE) {
1043                        array[i++] = p->item;
1044                        p->item->object.flags &= ~STALE;
1045                }
1046        }
1047        num_head = remove_redundant(array, num_head);
1048        for (i = 0; i < num_head; i++)
1049                tail = &commit_list_insert(array[i], tail)->next;
1050        return result;
1051}
1052
1053static const char gpg_sig_header[] = "gpgsig";
1054static const int gpg_sig_header_len = sizeof(gpg_sig_header) - 1;
1055
1056static int do_sign_commit(struct strbuf *buf, const char *keyid)
1057{
1058        struct strbuf sig = STRBUF_INIT;
1059        int inspos, copypos;
1060
1061        /* find the end of the header */
1062        inspos = strstr(buf->buf, "\n\n") - buf->buf + 1;
1063
1064        if (!keyid || !*keyid)
1065                keyid = get_signing_key();
1066        if (sign_buffer(buf, &sig, keyid)) {
1067                strbuf_release(&sig);
1068                return -1;
1069        }
1070
1071        for (copypos = 0; sig.buf[copypos]; ) {
1072                const char *bol = sig.buf + copypos;
1073                const char *eol = strchrnul(bol, '\n');
1074                int len = (eol - bol) + !!*eol;
1075
1076                if (!copypos) {
1077                        strbuf_insert(buf, inspos, gpg_sig_header, gpg_sig_header_len);
1078                        inspos += gpg_sig_header_len;
1079                }
1080                strbuf_insert(buf, inspos++, " ", 1);
1081                strbuf_insert(buf, inspos, bol, len);
1082                inspos += len;
1083                copypos += len;
1084        }
1085        strbuf_release(&sig);
1086        return 0;
1087}
1088
1089int parse_signed_commit(const unsigned char *sha1,
1090                        struct strbuf *payload, struct strbuf *signature)
1091{
1092        unsigned long size;
1093        enum object_type type;
1094        char *buffer = read_sha1_file(sha1, &type, &size);
1095        int in_signature, saw_signature = -1;
1096        char *line, *tail;
1097
1098        if (!buffer || type != OBJ_COMMIT)
1099                goto cleanup;
1100
1101        line = buffer;
1102        tail = buffer + size;
1103        in_signature = 0;
1104        saw_signature = 0;
1105        while (line < tail) {
1106                const char *sig = NULL;
1107                char *next = memchr(line, '\n', tail - line);
1108
1109                next = next ? next + 1 : tail;
1110                if (in_signature && line[0] == ' ')
1111                        sig = line + 1;
1112                else if (starts_with(line, gpg_sig_header) &&
1113                         line[gpg_sig_header_len] == ' ')
1114                        sig = line + gpg_sig_header_len + 1;
1115                if (sig) {
1116                        strbuf_add(signature, sig, next - sig);
1117                        saw_signature = 1;
1118                        in_signature = 1;
1119                } else {
1120                        if (*line == '\n')
1121                                /* dump the whole remainder of the buffer */
1122                                next = tail;
1123                        strbuf_add(payload, line, next - line);
1124                        in_signature = 0;
1125                }
1126                line = next;
1127        }
1128 cleanup:
1129        free(buffer);
1130        return saw_signature;
1131}
1132
1133static void handle_signed_tag(struct commit *parent, struct commit_extra_header ***tail)
1134{
1135        struct merge_remote_desc *desc;
1136        struct commit_extra_header *mergetag;
1137        char *buf;
1138        unsigned long size, len;
1139        enum object_type type;
1140
1141        desc = merge_remote_util(parent);
1142        if (!desc || !desc->obj)
1143                return;
1144        buf = read_sha1_file(desc->obj->sha1, &type, &size);
1145        if (!buf || type != OBJ_TAG)
1146                goto free_return;
1147        len = parse_signature(buf, size);
1148        if (size == len)
1149                goto free_return;
1150        /*
1151         * We could verify this signature and either omit the tag when
1152         * it does not validate, but the integrator may not have the
1153         * public key of the signer of the tag he is merging, while a
1154         * later auditor may have it while auditing, so let's not run
1155         * verify-signed-buffer here for now...
1156         *
1157         * if (verify_signed_buffer(buf, len, buf + len, size - len, ...))
1158         *      warn("warning: signed tag unverified.");
1159         */
1160        mergetag = xcalloc(1, sizeof(*mergetag));
1161        mergetag->key = xstrdup("mergetag");
1162        mergetag->value = buf;
1163        mergetag->len = size;
1164
1165        **tail = mergetag;
1166        *tail = &mergetag->next;
1167        return;
1168
1169free_return:
1170        free(buf);
1171}
1172
1173static struct {
1174        char result;
1175        const char *check;
1176} sigcheck_gpg_status[] = {
1177        { 'G', "\n[GNUPG:] GOODSIG " },
1178        { 'B', "\n[GNUPG:] BADSIG " },
1179        { 'U', "\n[GNUPG:] TRUST_NEVER" },
1180        { 'U', "\n[GNUPG:] TRUST_UNDEFINED" },
1181};
1182
1183static void parse_gpg_output(struct signature_check *sigc)
1184{
1185        const char *buf = sigc->gpg_status;
1186        int i;
1187
1188        /* Iterate over all search strings */
1189        for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
1190                const char *found, *next;
1191
1192                if (starts_with(buf, sigcheck_gpg_status[i].check + 1)) {
1193                        /* At the very beginning of the buffer */
1194                        found = buf + strlen(sigcheck_gpg_status[i].check + 1);
1195                } else {
1196                        found = strstr(buf, sigcheck_gpg_status[i].check);
1197                        if (!found)
1198                                continue;
1199                        found += strlen(sigcheck_gpg_status[i].check);
1200                }
1201                sigc->result = sigcheck_gpg_status[i].result;
1202                /* The trust messages are not followed by key/signer information */
1203                if (sigc->result != 'U') {
1204                        sigc->key = xmemdupz(found, 16);
1205                        found += 17;
1206                        next = strchrnul(found, '\n');
1207                        sigc->signer = xmemdupz(found, next - found);
1208                }
1209        }
1210}
1211
1212void check_commit_signature(const struct commit* commit, struct signature_check *sigc)
1213{
1214        struct strbuf payload = STRBUF_INIT;
1215        struct strbuf signature = STRBUF_INIT;
1216        struct strbuf gpg_output = STRBUF_INIT;
1217        struct strbuf gpg_status = STRBUF_INIT;
1218        int status;
1219
1220        sigc->result = 'N';
1221
1222        if (parse_signed_commit(commit->object.sha1,
1223                                &payload, &signature) <= 0)
1224                goto out;
1225        status = verify_signed_buffer(payload.buf, payload.len,
1226                                      signature.buf, signature.len,
1227                                      &gpg_output, &gpg_status);
1228        if (status && !gpg_output.len)
1229                goto out;
1230        sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
1231        sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
1232        parse_gpg_output(sigc);
1233
1234 out:
1235        strbuf_release(&gpg_status);
1236        strbuf_release(&gpg_output);
1237        strbuf_release(&payload);
1238        strbuf_release(&signature);
1239}
1240
1241
1242
1243void append_merge_tag_headers(struct commit_list *parents,
1244                              struct commit_extra_header ***tail)
1245{
1246        while (parents) {
1247                struct commit *parent = parents->item;
1248                handle_signed_tag(parent, tail);
1249                parents = parents->next;
1250        }
1251}
1252
1253static void add_extra_header(struct strbuf *buffer,
1254                             struct commit_extra_header *extra)
1255{
1256        strbuf_addstr(buffer, extra->key);
1257        if (extra->len)
1258                strbuf_add_lines(buffer, " ", extra->value, extra->len);
1259        else
1260                strbuf_addch(buffer, '\n');
1261}
1262
1263struct commit_extra_header *read_commit_extra_headers(struct commit *commit,
1264                                                      const char **exclude)
1265{
1266        struct commit_extra_header *extra = NULL;
1267        unsigned long size;
1268        enum object_type type;
1269        char *buffer = read_sha1_file(commit->object.sha1, &type, &size);
1270        if (buffer && type == OBJ_COMMIT)
1271                extra = read_commit_extra_header_lines(buffer, size, exclude);
1272        free(buffer);
1273        return extra;
1274}
1275
1276static inline int standard_header_field(const char *field, size_t len)
1277{
1278        return ((len == 4 && !memcmp(field, "tree ", 5)) ||
1279                (len == 6 && !memcmp(field, "parent ", 7)) ||
1280                (len == 6 && !memcmp(field, "author ", 7)) ||
1281                (len == 9 && !memcmp(field, "committer ", 10)) ||
1282                (len == 8 && !memcmp(field, "encoding ", 9)));
1283}
1284
1285static int excluded_header_field(const char *field, size_t len, const char **exclude)
1286{
1287        if (!exclude)
1288                return 0;
1289
1290        while (*exclude) {
1291                size_t xlen = strlen(*exclude);
1292                if (len == xlen &&
1293                    !memcmp(field, *exclude, xlen) && field[xlen] == ' ')
1294                        return 1;
1295                exclude++;
1296        }
1297        return 0;
1298}
1299
1300static struct commit_extra_header *read_commit_extra_header_lines(
1301        const char *buffer, size_t size,
1302        const char **exclude)
1303{
1304        struct commit_extra_header *extra = NULL, **tail = &extra, *it = NULL;
1305        const char *line, *next, *eof, *eob;
1306        struct strbuf buf = STRBUF_INIT;
1307
1308        for (line = buffer, eob = line + size;
1309             line < eob && *line != '\n';
1310             line = next) {
1311                next = memchr(line, '\n', eob - line);
1312                next = next ? next + 1 : eob;
1313                if (*line == ' ') {
1314                        /* continuation */
1315                        if (it)
1316                                strbuf_add(&buf, line + 1, next - (line + 1));
1317                        continue;
1318                }
1319                if (it)
1320                        it->value = strbuf_detach(&buf, &it->len);
1321                strbuf_reset(&buf);
1322                it = NULL;
1323
1324                eof = strchr(line, ' ');
1325                if (next <= eof)
1326                        eof = next;
1327
1328                if (standard_header_field(line, eof - line) ||
1329                    excluded_header_field(line, eof - line, exclude))
1330                        continue;
1331
1332                it = xcalloc(1, sizeof(*it));
1333                it->key = xmemdupz(line, eof-line);
1334                *tail = it;
1335                tail = &it->next;
1336                if (eof + 1 < next)
1337                        strbuf_add(&buf, eof + 1, next - (eof + 1));
1338        }
1339        if (it)
1340                it->value = strbuf_detach(&buf, &it->len);
1341        return extra;
1342}
1343
1344void free_commit_extra_headers(struct commit_extra_header *extra)
1345{
1346        while (extra) {
1347                struct commit_extra_header *next = extra->next;
1348                free(extra->key);
1349                free(extra->value);
1350                free(extra);
1351                extra = next;
1352        }
1353}
1354
1355int commit_tree(const struct strbuf *msg, const unsigned char *tree,
1356                struct commit_list *parents, unsigned char *ret,
1357                const char *author, const char *sign_commit)
1358{
1359        struct commit_extra_header *extra = NULL, **tail = &extra;
1360        int result;
1361
1362        append_merge_tag_headers(parents, &tail);
1363        result = commit_tree_extended(msg, tree, parents, ret,
1364                                      author, sign_commit, extra);
1365        free_commit_extra_headers(extra);
1366        return result;
1367}
1368
1369static int find_invalid_utf8(const char *buf, int len)
1370{
1371        int offset = 0;
1372        static const unsigned int max_codepoint[] = {
1373                0x7f, 0x7ff, 0xffff, 0x10ffff
1374        };
1375
1376        while (len) {
1377                unsigned char c = *buf++;
1378                int bytes, bad_offset;
1379                unsigned int codepoint;
1380                unsigned int min_val, max_val;
1381
1382                len--;
1383                offset++;
1384
1385                /* Simple US-ASCII? No worries. */
1386                if (c < 0x80)
1387                        continue;
1388
1389                bad_offset = offset-1;
1390
1391                /*
1392                 * Count how many more high bits set: that's how
1393                 * many more bytes this sequence should have.
1394                 */
1395                bytes = 0;
1396                while (c & 0x40) {
1397                        c <<= 1;
1398                        bytes++;
1399                }
1400
1401                /*
1402                 * Must be between 1 and 3 more bytes.  Longer sequences result in
1403                 * codepoints beyond U+10FFFF, which are guaranteed never to exist.
1404                 */
1405                if (bytes < 1 || 3 < bytes)
1406                        return bad_offset;
1407
1408                /* Do we *have* that many bytes? */
1409                if (len < bytes)
1410                        return bad_offset;
1411
1412                /*
1413                 * Place the encoded bits at the bottom of the value and compute the
1414                 * valid range.
1415                 */
1416                codepoint = (c & 0x7f) >> bytes;
1417                min_val = max_codepoint[bytes-1] + 1;
1418                max_val = max_codepoint[bytes];
1419
1420                offset += bytes;
1421                len -= bytes;
1422
1423                /* And verify that they are good continuation bytes */
1424                do {
1425                        codepoint <<= 6;
1426                        codepoint |= *buf & 0x3f;
1427                        if ((*buf++ & 0xc0) != 0x80)
1428                                return bad_offset;
1429                } while (--bytes);
1430
1431                /* Reject codepoints that are out of range for the sequence length. */
1432                if (codepoint < min_val || codepoint > max_val)
1433                        return bad_offset;
1434                /* Surrogates are only for UTF-16 and cannot be encoded in UTF-8. */
1435                if ((codepoint & 0x1ff800) == 0xd800)
1436                        return bad_offset;
1437                /* U+xxFFFE and U+xxFFFF are guaranteed non-characters. */
1438                if ((codepoint & 0xfffe) == 0xfffe)
1439                        return bad_offset;
1440                /* So are anything in the range U+FDD0..U+FDEF. */
1441                if (codepoint >= 0xfdd0 && codepoint <= 0xfdef)
1442                        return bad_offset;
1443        }
1444        return -1;
1445}
1446
1447/*
1448 * This verifies that the buffer is in proper utf8 format.
1449 *
1450 * If it isn't, it assumes any non-utf8 characters are Latin1,
1451 * and does the conversion.
1452 */
1453static int verify_utf8(struct strbuf *buf)
1454{
1455        int ok = 1;
1456        long pos = 0;
1457
1458        for (;;) {
1459                int bad;
1460                unsigned char c;
1461                unsigned char replace[2];
1462
1463                bad = find_invalid_utf8(buf->buf + pos, buf->len - pos);
1464                if (bad < 0)
1465                        return ok;
1466                pos += bad;
1467                ok = 0;
1468                c = buf->buf[pos];
1469                strbuf_remove(buf, pos, 1);
1470
1471                /* We know 'c' must be in the range 128-255 */
1472                replace[0] = 0xc0 + (c >> 6);
1473                replace[1] = 0x80 + (c & 0x3f);
1474                strbuf_insert(buf, pos, replace, 2);
1475                pos += 2;
1476        }
1477}
1478
1479static const char commit_utf8_warn[] =
1480"Warning: commit message did not conform to UTF-8.\n"
1481"You may want to amend it after fixing the message, or set the config\n"
1482"variable i18n.commitencoding to the encoding your project uses.\n";
1483
1484int commit_tree_extended(const struct strbuf *msg, const unsigned char *tree,
1485                         struct commit_list *parents, unsigned char *ret,
1486                         const char *author, const char *sign_commit,
1487                         struct commit_extra_header *extra)
1488{
1489        int result;
1490        int encoding_is_utf8;
1491        struct strbuf buffer;
1492
1493        assert_sha1_type(tree, OBJ_TREE);
1494
1495        if (memchr(msg->buf, '\0', msg->len))
1496                return error("a NUL byte in commit log message not allowed.");
1497
1498        /* Not having i18n.commitencoding is the same as having utf-8 */
1499        encoding_is_utf8 = is_encoding_utf8(git_commit_encoding);
1500
1501        strbuf_init(&buffer, 8192); /* should avoid reallocs for the headers */
1502        strbuf_addf(&buffer, "tree %s\n", sha1_to_hex(tree));
1503
1504        /*
1505         * NOTE! This ordering means that the same exact tree merged with a
1506         * different order of parents will be a _different_ changeset even
1507         * if everything else stays the same.
1508         */
1509        while (parents) {
1510                struct commit_list *next = parents->next;
1511                struct commit *parent = parents->item;
1512
1513                strbuf_addf(&buffer, "parent %s\n",
1514                            sha1_to_hex(parent->object.sha1));
1515                free(parents);
1516                parents = next;
1517        }
1518
1519        /* Person/date information */
1520        if (!author)
1521                author = git_author_info(IDENT_STRICT);
1522        strbuf_addf(&buffer, "author %s\n", author);
1523        strbuf_addf(&buffer, "committer %s\n", git_committer_info(IDENT_STRICT));
1524        if (!encoding_is_utf8)
1525                strbuf_addf(&buffer, "encoding %s\n", git_commit_encoding);
1526
1527        while (extra) {
1528                add_extra_header(&buffer, extra);
1529                extra = extra->next;
1530        }
1531        strbuf_addch(&buffer, '\n');
1532
1533        /* And add the comment */
1534        strbuf_addbuf(&buffer, msg);
1535
1536        /* And check the encoding */
1537        if (encoding_is_utf8 && !verify_utf8(&buffer))
1538                fprintf(stderr, commit_utf8_warn);
1539
1540        if (sign_commit && do_sign_commit(&buffer, sign_commit))
1541                return -1;
1542
1543        result = write_sha1_file(buffer.buf, buffer.len, commit_type, ret);
1544        strbuf_release(&buffer);
1545        return result;
1546}
1547
1548struct commit *get_merge_parent(const char *name)
1549{
1550        struct object *obj;
1551        struct commit *commit;
1552        unsigned char sha1[20];
1553        if (get_sha1(name, sha1))
1554                return NULL;
1555        obj = parse_object(sha1);
1556        commit = (struct commit *)peel_to_type(name, 0, obj, OBJ_COMMIT);
1557        if (commit && !commit->util) {
1558                struct merge_remote_desc *desc;
1559                desc = xmalloc(sizeof(*desc));
1560                desc->obj = obj;
1561                desc->name = strdup(name);
1562                commit->util = desc;
1563        }
1564        return commit;
1565}
1566
1567/*
1568 * Append a commit to the end of the commit_list.
1569 *
1570 * next starts by pointing to the variable that holds the head of an
1571 * empty commit_list, and is updated to point to the "next" field of
1572 * the last item on the list as new commits are appended.
1573 *
1574 * Usage example:
1575 *
1576 *     struct commit_list *list;
1577 *     struct commit_list **next = &list;
1578 *
1579 *     next = commit_list_append(c1, next);
1580 *     next = commit_list_append(c2, next);
1581 *     assert(commit_list_count(list) == 2);
1582 *     return list;
1583 */
1584struct commit_list **commit_list_append(struct commit *commit,
1585                                        struct commit_list **next)
1586{
1587        struct commit_list *new = xmalloc(sizeof(struct commit_list));
1588        new->item = commit;
1589        *next = new;
1590        new->next = NULL;
1591        return &new->next;
1592}
1593
1594void print_commit_list(struct commit_list *list,
1595                       const char *format_cur,
1596                       const char *format_last)
1597{
1598        for ( ; list; list = list->next) {
1599                const char *format = list->next ? format_cur : format_last;
1600                printf(format, sha1_to_hex(list->item->object.sha1));
1601        }
1602}