Andrew's git / gitweb.git / commit.c
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commit.con commit Merge branch 'jn/web' into next (811476d)
   1#include "cache.h"
   2#include "tag.h"
   3#include "commit.h"
   4
   5int save_commit_buffer = 1;
   6
   7struct sort_node
   8{
   9        /*
  10         * the number of children of the associated commit
  11         * that also occur in the list being sorted.
  12         */
  13        unsigned int indegree;
  14
  15        /*
  16         * reference to original list item that we will re-use
  17         * on output.
  18         */
  19        struct commit_list * list_item;
  20
  21};
  22
  23const char *commit_type = "commit";
  24
  25struct cmt_fmt_map {
  26        const char *n;
  27        size_t cmp_len;
  28        enum cmit_fmt v;
  29} cmt_fmts[] = {
  30        { "raw",        1,      CMIT_FMT_RAW },
  31        { "medium",     1,      CMIT_FMT_MEDIUM },
  32        { "short",      1,      CMIT_FMT_SHORT },
  33        { "email",      1,      CMIT_FMT_EMAIL },
  34        { "full",       5,      CMIT_FMT_FULL },
  35        { "fuller",     5,      CMIT_FMT_FULLER },
  36        { "oneline",    1,      CMIT_FMT_ONELINE },
  37};
  38
  39enum cmit_fmt get_commit_format(const char *arg)
  40{
  41        int i;
  42
  43        if (!arg || !*arg)
  44                return CMIT_FMT_DEFAULT;
  45        if (*arg == '=')
  46                arg++;
  47        for (i = 0; i < ARRAY_SIZE(cmt_fmts); i++) {
  48                if (!strncmp(arg, cmt_fmts[i].n, cmt_fmts[i].cmp_len))
  49                        return cmt_fmts[i].v;
  50        }
  51
  52        die("invalid --pretty format: %s", arg);
  53}
  54
  55static struct commit *check_commit(struct object *obj,
  56                                   const unsigned char *sha1,
  57                                   int quiet)
  58{
  59        if (obj->type != TYPE_COMMIT) {
  60                if (!quiet)
  61                        error("Object %s is a %s, not a commit",
  62                              sha1_to_hex(sha1), typename(obj->type));
  63                return NULL;
  64        }
  65        return (struct commit *) obj;
  66}
  67
  68struct commit *lookup_commit_reference_gently(const unsigned char *sha1,
  69                                              int quiet)
  70{
  71        struct object *obj = deref_tag(parse_object(sha1), NULL, 0);
  72
  73        if (!obj)
  74                return NULL;
  75        return check_commit(obj, sha1, quiet);
  76}
  77
  78struct commit *lookup_commit_reference(const unsigned char *sha1)
  79{
  80        return lookup_commit_reference_gently(sha1, 0);
  81}
  82
  83struct commit *lookup_commit(const unsigned char *sha1)
  84{
  85        struct object *obj = lookup_object(sha1);
  86        if (!obj) {
  87                struct commit *ret = alloc_commit_node();
  88                created_object(sha1, &ret->object);
  89                ret->object.type = TYPE_COMMIT;
  90                return ret;
  91        }
  92        if (!obj->type)
  93                obj->type = TYPE_COMMIT;
  94        return check_commit(obj, sha1, 0);
  95}
  96
  97static unsigned long parse_commit_date(const char *buf)
  98{
  99        unsigned long date;
 100
 101        if (memcmp(buf, "author", 6))
 102                return 0;
 103        while (*buf++ != '\n')
 104                /* nada */;
 105        if (memcmp(buf, "committer", 9))
 106                return 0;
 107        while (*buf++ != '>')
 108                /* nada */;
 109        date = strtoul(buf, NULL, 10);
 110        if (date == ULONG_MAX)
 111                date = 0;
 112        return date;
 113}
 114
 115static struct commit_graft **commit_graft;
 116static int commit_graft_alloc, commit_graft_nr;
 117
 118static int commit_graft_pos(const unsigned char *sha1)
 119{
 120        int lo, hi;
 121        lo = 0;
 122        hi = commit_graft_nr;
 123        while (lo < hi) {
 124                int mi = (lo + hi) / 2;
 125                struct commit_graft *graft = commit_graft[mi];
 126                int cmp = memcmp(sha1, graft->sha1, 20);
 127                if (!cmp)
 128                        return mi;
 129                if (cmp < 0)
 130                        hi = mi;
 131                else
 132                        lo = mi + 1;
 133        }
 134        return -lo - 1;
 135}
 136
 137int register_commit_graft(struct commit_graft *graft, int ignore_dups)
 138{
 139        int pos = commit_graft_pos(graft->sha1);
 140        
 141        if (0 <= pos) {
 142                if (ignore_dups)
 143                        free(graft);
 144                else {
 145                        free(commit_graft[pos]);
 146                        commit_graft[pos] = graft;
 147                }
 148                return 1;
 149        }
 150        pos = -pos - 1;
 151        if (commit_graft_alloc <= ++commit_graft_nr) {
 152                commit_graft_alloc = alloc_nr(commit_graft_alloc);
 153                commit_graft = xrealloc(commit_graft,
 154                                        sizeof(*commit_graft) *
 155                                        commit_graft_alloc);
 156        }
 157        if (pos < commit_graft_nr)
 158                memmove(commit_graft + pos + 1,
 159                        commit_graft + pos,
 160                        (commit_graft_nr - pos - 1) *
 161                        sizeof(*commit_graft));
 162        commit_graft[pos] = graft;
 163        return 0;
 164}
 165
 166struct commit_graft *read_graft_line(char *buf, int len)
 167{
 168        /* The format is just "Commit Parent1 Parent2 ...\n" */
 169        int i;
 170        struct commit_graft *graft = NULL;
 171
 172        if (buf[len-1] == '\n')
 173                buf[--len] = 0;
 174        if (buf[0] == '#' || buf[0] == '\0')
 175                return NULL;
 176        if ((len + 1) % 41) {
 177        bad_graft_data:
 178                error("bad graft data: %s", buf);
 179                free(graft);
 180                return NULL;
 181        }
 182        i = (len + 1) / 41 - 1;
 183        graft = xmalloc(sizeof(*graft) + 20 * i);
 184        graft->nr_parent = i;
 185        if (get_sha1_hex(buf, graft->sha1))
 186                goto bad_graft_data;
 187        for (i = 40; i < len; i += 41) {
 188                if (buf[i] != ' ')
 189                        goto bad_graft_data;
 190                if (get_sha1_hex(buf + i + 1, graft->parent[i/41]))
 191                        goto bad_graft_data;
 192        }
 193        return graft;
 194}
 195
 196int read_graft_file(const char *graft_file)
 197{
 198        FILE *fp = fopen(graft_file, "r");
 199        char buf[1024];
 200        if (!fp)
 201                return -1;
 202        while (fgets(buf, sizeof(buf), fp)) {
 203                /* The format is just "Commit Parent1 Parent2 ...\n" */
 204                int len = strlen(buf);
 205                struct commit_graft *graft = read_graft_line(buf, len);
 206                if (!graft)
 207                        continue;
 208                if (register_commit_graft(graft, 1))
 209                        error("duplicate graft data: %s", buf);
 210        }
 211        fclose(fp);
 212        return 0;
 213}
 214
 215static void prepare_commit_graft(void)
 216{
 217        static int commit_graft_prepared;
 218        char *graft_file;
 219
 220        if (commit_graft_prepared)
 221                return;
 222        graft_file = get_graft_file();
 223        read_graft_file(graft_file);
 224        commit_graft_prepared = 1;
 225}
 226
 227static struct commit_graft *lookup_commit_graft(const unsigned char *sha1)
 228{
 229        int pos;
 230        prepare_commit_graft();
 231        pos = commit_graft_pos(sha1);
 232        if (pos < 0)
 233                return NULL;
 234        return commit_graft[pos];
 235}
 236
 237int parse_commit_buffer(struct commit *item, void *buffer, unsigned long size)
 238{
 239        char *bufptr = buffer;
 240        unsigned char parent[20];
 241        struct commit_list **pptr;
 242        struct commit_graft *graft;
 243        unsigned n_refs = 0;
 244
 245        if (item->object.parsed)
 246                return 0;
 247        item->object.parsed = 1;
 248        if (memcmp(bufptr, "tree ", 5))
 249                return error("bogus commit object %s", sha1_to_hex(item->object.sha1));
 250        if (get_sha1_hex(bufptr + 5, parent) < 0)
 251                return error("bad tree pointer in commit %s",
 252                             sha1_to_hex(item->object.sha1));
 253        item->tree = lookup_tree(parent);
 254        if (item->tree)
 255                n_refs++;
 256        bufptr += 46; /* "tree " + "hex sha1" + "\n" */
 257        pptr = &item->parents;
 258
 259        graft = lookup_commit_graft(item->object.sha1);
 260        while (!memcmp(bufptr, "parent ", 7)) {
 261                struct commit *new_parent;
 262
 263                if (get_sha1_hex(bufptr + 7, parent) || bufptr[47] != '\n')
 264                        return error("bad parents in commit %s", sha1_to_hex(item->object.sha1));
 265                bufptr += 48;
 266                if (graft)
 267                        continue;
 268                new_parent = lookup_commit(parent);
 269                if (new_parent) {
 270                        pptr = &commit_list_insert(new_parent, pptr)->next;
 271                        n_refs++;
 272                }
 273        }
 274        if (graft) {
 275                int i;
 276                struct commit *new_parent;
 277                for (i = 0; i < graft->nr_parent; i++) {
 278                        new_parent = lookup_commit(graft->parent[i]);
 279                        if (!new_parent)
 280                                continue;
 281                        pptr = &commit_list_insert(new_parent, pptr)->next;
 282                        n_refs++;
 283                }
 284        }
 285        item->date = parse_commit_date(bufptr);
 286
 287        if (track_object_refs) {
 288                unsigned i = 0;
 289                struct commit_list *p;
 290                struct object_refs *refs = alloc_object_refs(n_refs);
 291                if (item->tree)
 292                        refs->ref[i++] = &item->tree->object;
 293                for (p = item->parents; p; p = p->next)
 294                        refs->ref[i++] = &p->item->object;
 295                set_object_refs(&item->object, refs);
 296        }
 297
 298        return 0;
 299}
 300
 301int parse_commit(struct commit *item)
 302{
 303        char type[20];
 304        void *buffer;
 305        unsigned long size;
 306        int ret;
 307
 308        if (item->object.parsed)
 309                return 0;
 310        buffer = read_sha1_file(item->object.sha1, type, &size);
 311        if (!buffer)
 312                return error("Could not read %s",
 313                             sha1_to_hex(item->object.sha1));
 314        if (strcmp(type, commit_type)) {
 315                free(buffer);
 316                return error("Object %s not a commit",
 317                             sha1_to_hex(item->object.sha1));
 318        }
 319        ret = parse_commit_buffer(item, buffer, size);
 320        if (save_commit_buffer && !ret) {
 321                item->buffer = buffer;
 322                return 0;
 323        }
 324        free(buffer);
 325        return ret;
 326}
 327
 328struct commit_list *commit_list_insert(struct commit *item, struct commit_list **list_p)
 329{
 330        struct commit_list *new_list = xmalloc(sizeof(struct commit_list));
 331        new_list->item = item;
 332        new_list->next = *list_p;
 333        *list_p = new_list;
 334        return new_list;
 335}
 336
 337void free_commit_list(struct commit_list *list)
 338{
 339        while (list) {
 340                struct commit_list *temp = list;
 341                list = temp->next;
 342                free(temp);
 343        }
 344}
 345
 346struct commit_list * insert_by_date(struct commit *item, struct commit_list **list)
 347{
 348        struct commit_list **pp = list;
 349        struct commit_list *p;
 350        while ((p = *pp) != NULL) {
 351                if (p->item->date < item->date) {
 352                        break;
 353                }
 354                pp = &p->next;
 355        }
 356        return commit_list_insert(item, pp);
 357}
 358
 359        
 360void sort_by_date(struct commit_list **list)
 361{
 362        struct commit_list *ret = NULL;
 363        while (*list) {
 364                insert_by_date((*list)->item, &ret);
 365                *list = (*list)->next;
 366        }
 367        *list = ret;
 368}
 369
 370struct commit *pop_most_recent_commit(struct commit_list **list,
 371                                      unsigned int mark)
 372{
 373        struct commit *ret = (*list)->item;
 374        struct commit_list *parents = ret->parents;
 375        struct commit_list *old = *list;
 376
 377        *list = (*list)->next;
 378        free(old);
 379
 380        while (parents) {
 381                struct commit *commit = parents->item;
 382                parse_commit(commit);
 383                if (!(commit->object.flags & mark)) {
 384                        commit->object.flags |= mark;
 385                        insert_by_date(commit, list);
 386                }
 387                parents = parents->next;
 388        }
 389        return ret;
 390}
 391
 392void clear_commit_marks(struct commit *commit, unsigned int mark)
 393{
 394        struct commit_list *parents;
 395
 396        parents = commit->parents;
 397        commit->object.flags &= ~mark;
 398        while (parents) {
 399                struct commit *parent = parents->item;
 400                if (parent && parent->object.parsed &&
 401                    (parent->object.flags & mark))
 402                        clear_commit_marks(parent, mark);
 403                parents = parents->next;
 404        }
 405}
 406
 407/*
 408 * Generic support for pretty-printing the header
 409 */
 410static int get_one_line(const char *msg, unsigned long len)
 411{
 412        int ret = 0;
 413
 414        while (len--) {
 415                char c = *msg++;
 416                if (!c)
 417                        break;
 418                ret++;
 419                if (c == '\n')
 420                        break;
 421        }
 422        return ret;
 423}
 424
 425static int is_rfc2047_special(char ch)
 426{
 427        return ((ch & 0x80) || (ch == '=') || (ch == '?') || (ch == '_'));
 428}
 429
 430static int add_rfc2047(char *buf, const char *line, int len)
 431{
 432        char *bp = buf;
 433        int i, needquote;
 434        static const char q_utf8[] = "=?utf-8?q?";
 435
 436        for (i = needquote = 0; !needquote && i < len; i++) {
 437                unsigned ch = line[i];
 438                if (ch & 0x80)
 439                        needquote++;
 440                if ((i + 1 < len) &&
 441                    (ch == '=' && line[i+1] == '?'))
 442                        needquote++;
 443        }
 444        if (!needquote)
 445                return sprintf(buf, "%.*s", len, line);
 446
 447        memcpy(bp, q_utf8, sizeof(q_utf8)-1);
 448        bp += sizeof(q_utf8)-1;
 449        for (i = 0; i < len; i++) {
 450                unsigned ch = line[i] & 0xFF;
 451                if (is_rfc2047_special(ch)) {
 452                        sprintf(bp, "=%02X", ch);
 453                        bp += 3;
 454                }
 455                else if (ch == ' ')
 456                        *bp++ = '_';
 457                else
 458                        *bp++ = ch;
 459        }
 460        memcpy(bp, "?=", 2);
 461        bp += 2;
 462        return bp - buf;
 463}
 464
 465static int add_user_info(const char *what, enum cmit_fmt fmt, char *buf, const char *line)
 466{
 467        char *date;
 468        int namelen;
 469        unsigned long time;
 470        int tz, ret;
 471        const char *filler = "    ";
 472
 473        if (fmt == CMIT_FMT_ONELINE)
 474                return 0;
 475        date = strchr(line, '>');
 476        if (!date)
 477                return 0;
 478        namelen = ++date - line;
 479        time = strtoul(date, &date, 10);
 480        tz = strtol(date, NULL, 10);
 481
 482        if (fmt == CMIT_FMT_EMAIL) {
 483                char *name_tail = strchr(line, '<');
 484                int display_name_length;
 485                if (!name_tail)
 486                        return 0;
 487                while (line < name_tail && isspace(name_tail[-1]))
 488                        name_tail--;
 489                display_name_length = name_tail - line;
 490                filler = "";
 491                strcpy(buf, "From: ");
 492                ret = strlen(buf);
 493                ret += add_rfc2047(buf + ret, line, display_name_length);
 494                memcpy(buf + ret, name_tail, namelen - display_name_length);
 495                ret += namelen - display_name_length;
 496                buf[ret++] = '\n';
 497        }
 498        else {
 499                ret = sprintf(buf, "%s: %.*s%.*s\n", what,
 500                              (fmt == CMIT_FMT_FULLER) ? 4 : 0,
 501                              filler, namelen, line);
 502        }
 503        switch (fmt) {
 504        case CMIT_FMT_MEDIUM:
 505                ret += sprintf(buf + ret, "Date:   %s\n", show_date(time, tz));
 506                break;
 507        case CMIT_FMT_EMAIL:
 508                ret += sprintf(buf + ret, "Date: %s\n",
 509                               show_rfc2822_date(time, tz));
 510                break;
 511        case CMIT_FMT_FULLER:
 512                ret += sprintf(buf + ret, "%sDate: %s\n", what, show_date(time, tz));
 513                break;
 514        default:
 515                /* notin' */
 516                break;
 517        }
 518        return ret;
 519}
 520
 521static int is_empty_line(const char *line, int *len_p)
 522{
 523        int len = *len_p;
 524        while (len && isspace(line[len-1]))
 525                len--;
 526        *len_p = len;
 527        return !len;
 528}
 529
 530static int add_merge_info(enum cmit_fmt fmt, char *buf, const struct commit *commit, int abbrev)
 531{
 532        struct commit_list *parent = commit->parents;
 533        int offset;
 534
 535        if ((fmt == CMIT_FMT_ONELINE) || (fmt == CMIT_FMT_EMAIL) ||
 536            !parent || !parent->next)
 537                return 0;
 538
 539        offset = sprintf(buf, "Merge:");
 540
 541        while (parent) {
 542                struct commit *p = parent->item;
 543                const char *hex = abbrev
 544                        ? find_unique_abbrev(p->object.sha1, abbrev)
 545                        : sha1_to_hex(p->object.sha1);
 546                char *dots = (abbrev && strlen(hex) != 40) ? "..." : "";
 547                parent = parent->next;
 548
 549                offset += sprintf(buf + offset, " %s%s", hex, dots);
 550        }
 551        buf[offset++] = '\n';
 552        return offset;
 553}
 554
 555unsigned long pretty_print_commit(enum cmit_fmt fmt, const struct commit *commit, unsigned long len, char *buf, unsigned long space, int abbrev, const char *subject, const char *after_subject)
 556{
 557        int hdr = 1, body = 0;
 558        unsigned long offset = 0;
 559        int indent = 4;
 560        int parents_shown = 0;
 561        const char *msg = commit->buffer;
 562        int plain_non_ascii = 0;
 563
 564        if (fmt == CMIT_FMT_ONELINE || fmt == CMIT_FMT_EMAIL)
 565                indent = 0;
 566
 567        /* After-subject is used to pass in Content-Type: multipart
 568         * MIME header; in that case we do not have to do the
 569         * plaintext content type even if the commit message has
 570         * non 7-bit ASCII character.  Otherwise, check if we need
 571         * to say this is not a 7-bit ASCII.
 572         */
 573        if (fmt == CMIT_FMT_EMAIL && !after_subject) {
 574                int i, ch, in_body;
 575
 576                for (in_body = i = 0; (ch = msg[i]) && i < len; i++) {
 577                        if (!in_body) {
 578                                /* author could be non 7-bit ASCII but
 579                                 * the log may so; skip over the
 580                                 * header part first.
 581                                 */
 582                                if (ch == '\n' &&
 583                                    i + 1 < len && msg[i+1] == '\n')
 584                                        in_body = 1;
 585                        }
 586                        else if (ch & 0x80) {
 587                                plain_non_ascii = 1;
 588                                break;
 589                        }
 590                }
 591        }
 592
 593        for (;;) {
 594                const char *line = msg;
 595                int linelen = get_one_line(msg, len);
 596
 597                if (!linelen)
 598                        break;
 599
 600                /*
 601                 * We want some slop for indentation and a possible
 602                 * final "...". Thus the "+ 20".
 603                 */
 604                if (offset + linelen + 20 > space) {
 605                        memcpy(buf + offset, "    ...\n", 8);
 606                        offset += 8;
 607                        break;
 608                }
 609
 610                msg += linelen;
 611                len -= linelen;
 612                if (hdr) {
 613                        if (linelen == 1) {
 614                                hdr = 0;
 615                                if ((fmt != CMIT_FMT_ONELINE) && !subject)
 616                                        buf[offset++] = '\n';
 617                                continue;
 618                        }
 619                        if (fmt == CMIT_FMT_RAW) {
 620                                memcpy(buf + offset, line, linelen);
 621                                offset += linelen;
 622                                continue;
 623                        }
 624                        if (!memcmp(line, "parent ", 7)) {
 625                                if (linelen != 48)
 626                                        die("bad parent line in commit");
 627                                continue;
 628                        }
 629
 630                        if (!parents_shown) {
 631                                offset += add_merge_info(fmt, buf + offset,
 632                                                         commit, abbrev);
 633                                parents_shown = 1;
 634                                continue;
 635                        }
 636                        /*
 637                         * MEDIUM == DEFAULT shows only author with dates.
 638                         * FULL shows both authors but not dates.
 639                         * FULLER shows both authors and dates.
 640                         */
 641                        if (!memcmp(line, "author ", 7))
 642                                offset += add_user_info("Author", fmt,
 643                                                        buf + offset,
 644                                                        line + 7);
 645                        if (!memcmp(line, "committer ", 10) &&
 646                            (fmt == CMIT_FMT_FULL || fmt == CMIT_FMT_FULLER))
 647                                offset += add_user_info("Commit", fmt,
 648                                                        buf + offset,
 649                                                        line + 10);
 650                        continue;
 651                }
 652
 653                if (is_empty_line(line, &linelen)) {
 654                        if (!body)
 655                                continue;
 656                        if (subject)
 657                                continue;
 658                        if (fmt == CMIT_FMT_SHORT)
 659                                break;
 660                } else {
 661                        body = 1;
 662                }
 663
 664                if (subject) {
 665                        int slen = strlen(subject);
 666                        memcpy(buf + offset, subject, slen);
 667                        offset += slen;
 668                        offset += add_rfc2047(buf + offset, line, linelen);
 669                }
 670                else {
 671                        memset(buf + offset, ' ', indent);
 672                        memcpy(buf + offset + indent, line, linelen);
 673                        offset += linelen + indent;
 674                }
 675                buf[offset++] = '\n';
 676                if (fmt == CMIT_FMT_ONELINE)
 677                        break;
 678                if (subject && plain_non_ascii) {
 679                        static const char header[] =
 680                                "Content-Type: text/plain; charset=UTF-8\n"
 681                                "Content-Transfer-Encoding: 8bit\n";
 682                        memcpy(buf + offset, header, sizeof(header)-1);
 683                        offset += sizeof(header)-1;
 684                }
 685                if (after_subject) {
 686                        int slen = strlen(after_subject);
 687                        if (slen > space - offset - 1)
 688                                slen = space - offset - 1;
 689                        memcpy(buf + offset, after_subject, slen);
 690                        offset += slen;
 691                        after_subject = NULL;
 692                }
 693                subject = NULL;
 694        }
 695        while (offset && isspace(buf[offset-1]))
 696                offset--;
 697        /* Make sure there is an EOLN for the non-oneline case */
 698        if (fmt != CMIT_FMT_ONELINE)
 699                buf[offset++] = '\n';
 700        buf[offset] = '\0';
 701        return offset;
 702}
 703
 704struct commit *pop_commit(struct commit_list **stack)
 705{
 706        struct commit_list *top = *stack;
 707        struct commit *item = top ? top->item : NULL;
 708
 709        if (top) {
 710                *stack = top->next;
 711                free(top);
 712        }
 713        return item;
 714}
 715
 716int count_parents(struct commit * commit)
 717{
 718        int count = 0;
 719        struct commit_list * parents = commit->parents;
 720        for (count=0;parents; parents=parents->next,count++)
 721          ;
 722        return count;
 723}
 724
 725void topo_sort_default_setter(struct commit *c, void *data)
 726{
 727        c->util = data;
 728}
 729
 730void *topo_sort_default_getter(struct commit *c)
 731{
 732        return c->util;
 733}
 734
 735/*
 736 * Performs an in-place topological sort on the list supplied.
 737 */
 738void sort_in_topological_order(struct commit_list ** list, int lifo)
 739{
 740        sort_in_topological_order_fn(list, lifo, topo_sort_default_setter,
 741                                     topo_sort_default_getter);
 742}
 743
 744void sort_in_topological_order_fn(struct commit_list ** list, int lifo,
 745                                  topo_sort_set_fn_t setter,
 746                                  topo_sort_get_fn_t getter)
 747{
 748        struct commit_list * next = *list;
 749        struct commit_list * work = NULL, **insert;
 750        struct commit_list ** pptr = list;
 751        struct sort_node * nodes;
 752        struct sort_node * next_nodes;
 753        int count = 0;
 754
 755        /* determine the size of the list */
 756        while (next) {
 757                next = next->next;
 758                count++;
 759        }
 760        
 761        if (!count)
 762                return;
 763        /* allocate an array to help sort the list */
 764        nodes = xcalloc(count, sizeof(*nodes));
 765        /* link the list to the array */
 766        next_nodes = nodes;
 767        next=*list;
 768        while (next) {
 769                next_nodes->list_item = next;
 770                setter(next->item, next_nodes);
 771                next_nodes++;
 772                next = next->next;
 773        }
 774        /* update the indegree */
 775        next=*list;
 776        while (next) {
 777                struct commit_list * parents = next->item->parents;
 778                while (parents) {
 779                        struct commit * parent=parents->item;
 780                        struct sort_node * pn = (struct sort_node *) getter(parent);
 781
 782                        if (pn)
 783                                pn->indegree++;
 784                        parents=parents->next;
 785                }
 786                next=next->next;
 787        }
 788        /* 
 789         * find the tips
 790         *
 791         * tips are nodes not reachable from any other node in the list 
 792         * 
 793         * the tips serve as a starting set for the work queue.
 794         */
 795        next=*list;
 796        insert = &work;
 797        while (next) {
 798                struct sort_node * node = (struct sort_node *) getter(next->item);
 799
 800                if (node->indegree == 0) {
 801                        insert = &commit_list_insert(next->item, insert)->next;
 802                }
 803                next=next->next;
 804        }
 805
 806        /* process the list in topological order */
 807        if (!lifo)
 808                sort_by_date(&work);
 809        while (work) {
 810                struct commit * work_item = pop_commit(&work);
 811                struct sort_node * work_node = (struct sort_node *) getter(work_item);
 812                struct commit_list * parents = work_item->parents;
 813
 814                while (parents) {
 815                        struct commit * parent=parents->item;
 816                        struct sort_node * pn = (struct sort_node *) getter(parent);
 817
 818                        if (pn) {
 819                                /*
 820                                 * parents are only enqueued for emission 
 821                                 * when all their children have been emitted thereby
 822                                 * guaranteeing topological order.
 823                                 */
 824                                pn->indegree--;
 825                                if (!pn->indegree) {
 826                                        if (!lifo)
 827                                                insert_by_date(parent, &work);
 828                                        else
 829                                                commit_list_insert(parent, &work);
 830                                }
 831                        }
 832                        parents=parents->next;
 833                }
 834                /*
 835                 * work_item is a commit all of whose children
 836                 * have already been emitted. we can emit it now.
 837                 */
 838                *pptr = work_node->list_item;
 839                pptr = &(*pptr)->next;
 840                *pptr = NULL;
 841                setter(work_item, NULL);
 842        }
 843        free(nodes);
 844}