commit.c

   1 #include "cache.h"
   2 #include "tag.h"
   3 #include "commit.h"
   4
   5 int save_commit_buffer = 1;
   6
   7 struct 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
  23 const char *commit_type = "commit";
  24
  25 struct 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
  39 enum 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
  55 static 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
  68 struct 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
  78 struct commit *lookup_commit_reference(const unsigned char *sha1)
  79 {
  80         return lookup_commit_reference_gently(sha1, 0);
  81 }
  82
  83 struct 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
  97 static 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
 115 static struct commit_graft **commit_graft;
 116 static int commit_graft_alloc, commit_graft_nr;
 117
 118 static 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
 137 int 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
 166 struct 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
 196 int 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
 215 static 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
 227 static 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
 237 int parse_commit_buffer(struct commit *item, void *buffer, unsigned long size)
 238 {
 239         char *tail = buffer;
 240         char *bufptr = buffer;
 241         unsigned char parent[20];
 242         struct commit_list **pptr;
 243         struct commit_graft *graft;
 244         unsigned n_refs = 0;
 245
 246         if (item->object.parsed)
 247                 return 0;
 248         item->object.parsed = 1;
 249         tail += size;
 250         if (tail <= bufptr + 5 || memcmp(bufptr, "tree ", 5))
 251                 return error("bogus commit object %s", sha1_to_hex(item->object.sha1));
 252         if (tail <= bufptr + 45 || get_sha1_hex(bufptr + 5, parent) < 0)
 253                 return error("bad tree pointer in commit %s",
 254                              sha1_to_hex(item->object.sha1));
 255         item->tree = lookup_tree(parent);
 256         if (item->tree)
 257                 n_refs++;
 258         bufptr += 46; /* "tree " + "hex sha1" + "\n" */
 259         pptr = &item->parents;
 260
 261         graft = lookup_commit_graft(item->object.sha1);
 262         while (bufptr + 48 < tail && !memcmp(bufptr, "parent ", 7)) {
 263                 struct commit *new_parent;
 264
 265                 if (tail <= bufptr + 48 ||
 266                     get_sha1_hex(bufptr + 7, parent) ||
 267                     bufptr[47] != '\n')
 268                         return error("bad parents in commit %s", sha1_to_hex(item->object.sha1));
 269                 bufptr += 48;
 270                 if (graft)
 271                         continue;
 272                 new_parent = lookup_commit(parent);
 273                 if (new_parent) {
 274                         pptr = &commit_list_insert(new_parent, pptr)->next;
 275                         n_refs++;
 276                 }
 277         }
 278         if (graft) {
 279                 int i;
 280                 struct commit *new_parent;
 281                 for (i = 0; i < graft->nr_parent; i++) {
 282                         new_parent = lookup_commit(graft->parent[i]);
 283                         if (!new_parent)
 284                                 continue;
 285                         pptr = &commit_list_insert(new_parent, pptr)->next;
 286                         n_refs++;
 287                 }
 288         }
 289         item->date = parse_commit_date(bufptr);
 290
 291         if (track_object_refs) {
 292                 unsigned i = 0;
 293                 struct commit_list *p;
 294                 struct object_refs *refs = alloc_object_refs(n_refs);
 295                 if (item->tree)
 296                         refs->ref[i++] = &item->tree->object;
 297                 for (p = item->parents; p; p = p->next)
 298                         refs->ref[i++] = &p->item->object;
 299                 set_object_refs(&item->object, refs);
 300         }
 301
 302         return 0;
 303 }
 304
 305 int parse_commit(struct commit *item)
 306 {
 307         char type[20];
 308         void *buffer;
 309         unsigned long size;
 310         int ret;
 311
 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 (strcmp(type, commit_type)) {
 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
 332 struct commit_list *commit_list_insert(struct commit *item, struct commit_list **list_p)
 333 {
 334         struct commit_list *new_list = xmalloc(sizeof(struct commit_list));
 335         new_list->item = item;
 336         new_list->next = *list_p;
 337         *list_p = new_list;
 338         return new_list;
 339 }
 340
 341 void free_commit_list(struct commit_list *list)
 342 {
 343         while (list) {
 344                 struct commit_list *temp = list;
 345                 list = temp->next;
 346                 free(temp);
 347         }
 348 }
 349
 350 struct commit_list * insert_by_date(struct commit *item, struct commit_list **list)
 351 {
 352         struct commit_list **pp = list;
 353         struct commit_list *p;
 354         while ((p = *pp) != NULL) {
 355                 if (p->item->date < item->date) {
 356                         break;
 357                 }
 358                 pp = &p->next;
 359         }
 360         return commit_list_insert(item, pp);
 361 }
 362
 363
 364 void sort_by_date(struct commit_list **list)
 365 {
 366         struct commit_list *ret = NULL;
 367         while (*list) {
 368                 insert_by_date((*list)->item, &ret);
 369                 *list = (*list)->next;
 370         }
 371         *list = ret;
 372 }
 373
 374 struct commit *pop_most_recent_commit(struct commit_list **list,
 375                                       unsigned int mark)
 376 {
 377         struct commit *ret = (*list)->item;
 378         struct commit_list *parents = ret->parents;
 379         struct commit_list *old = *list;
 380
 381         *list = (*list)->next;
 382         free(old);
 383
 384         while (parents) {
 385                 struct commit *commit = parents->item;
 386                 parse_commit(commit);
 387                 if (!(commit->object.flags & mark)) {
 388                         commit->object.flags |= mark;
 389                         insert_by_date(commit, list);
 390                 }
 391                 parents = parents->next;
 392         }
 393         return ret;
 394 }
 395
 396 void clear_commit_marks(struct commit *commit, unsigned int mark)
 397 {
 398         struct commit_list *parents;
 399
 400         if (!commit)
 401                 return;
 402         parents = commit->parents;
 403         commit->object.flags &= ~mark;
 404         while (parents) {
 405                 clear_commit_marks(parents->item, mark);
 406                 parents = parents->next;
 407         }
 408 }
 409
 410 /*
 411  * Generic support for pretty-printing the header
 412  */
 413 static int get_one_line(const char *msg, unsigned long len)
 414 {
 415         int ret = 0;
 416
 417         while (len--) {
 418                 char c = *msg++;
 419                 if (!c)
 420                         break;
 421                 ret++;
 422                 if (c == '\n')
 423                         break;
 424         }
 425         return ret;
 426 }
 427
 428 static int is_rfc2047_special(char ch)
 429 {
 430         return ((ch & 0x80) || (ch == '=') || (ch == '?') || (ch == '_'));
 431 }
 432
 433 static int add_rfc2047(char *buf, const char *line, int len)
 434 {
 435         char *bp = buf;
 436         int i, needquote;
 437         static const char q_utf8[] = "=?utf-8?q?";
 438
 439         for (i = needquote = 0; !needquote && i < len; i++) {
 440                 unsigned ch = line[i];
 441                 if (ch & 0x80)
 442                         needquote++;
 443                 if ((i + 1 < len) &&
 444                     (ch == '=' && line[i+1] == '?'))
 445                         needquote++;
 446         }
 447         if (!needquote)
 448                 return sprintf(buf, "%.*s", len, line);
 449
 450         memcpy(bp, q_utf8, sizeof(q_utf8)-1);
 451         bp += sizeof(q_utf8)-1;
 452         for (i = 0; i < len; i++) {
 453                 unsigned ch = line[i] & 0xFF;
 454                 if (is_rfc2047_special(ch)) {
 455                         sprintf(bp, "=%02X", ch);
 456                         bp += 3;
 457                 }
 458                 else if (ch == ' ')
 459                         *bp++ = '_';
 460                 else
 461                         *bp++ = ch;
 462         }
 463         memcpy(bp, "?=", 2);
 464         bp += 2;
 465         return bp - buf;
 466 }
 467
 468 static int add_user_info(const char *what, enum cmit_fmt fmt, char *buf, const char *line)
 469 {
 470         char *date;
 471         int namelen;
 472         unsigned long time;
 473         int tz, ret;
 474         const char *filler = "    ";
 475
 476         if (fmt == CMIT_FMT_ONELINE)
 477                 return 0;
 478         date = strchr(line, '>');
 479         if (!date)
 480                 return 0;
 481         namelen = ++date - line;
 482         time = strtoul(date, &date, 10);
 483         tz = strtol(date, NULL, 10);
 484
 485         if (fmt == CMIT_FMT_EMAIL) {
 486                 char *name_tail = strchr(line, '<');
 487                 int display_name_length;
 488                 if (!name_tail)
 489                         return 0;
 490                 while (line < name_tail && isspace(name_tail[-1]))
 491                         name_tail--;
 492                 display_name_length = name_tail - line;
 493                 filler = "";
 494                 strcpy(buf, "From: ");
 495                 ret = strlen(buf);
 496                 ret += add_rfc2047(buf + ret, line, display_name_length);
 497                 memcpy(buf + ret, name_tail, namelen - display_name_length);
 498                 ret += namelen - display_name_length;
 499                 buf[ret++] = '\n';
 500         }
 501         else {
 502                 ret = sprintf(buf, "%s: %.*s%.*s\n", what,
 503                               (fmt == CMIT_FMT_FULLER) ? 4 : 0,
 504                               filler, namelen, line);
 505         }
 506         switch (fmt) {
 507         case CMIT_FMT_MEDIUM:
 508                 ret += sprintf(buf + ret, "Date:   %s\n", show_date(time, tz));
 509                 break;
 510         case CMIT_FMT_EMAIL:
 511                 ret += sprintf(buf + ret, "Date: %s\n",
 512                                show_rfc2822_date(time, tz));
 513                 break;
 514         case CMIT_FMT_FULLER:
 515                 ret += sprintf(buf + ret, "%sDate: %s\n", what, show_date(time, tz));
 516                 break;
 517         default:
 518                 /* notin' */
 519                 break;
 520         }
 521         return ret;
 522 }
 523
 524 static int is_empty_line(const char *line, int *len_p)
 525 {
 526         int len = *len_p;
 527         while (len && isspace(line[len-1]))
 528                 len--;
 529         *len_p = len;
 530         return !len;
 531 }
 532
 533 static int add_merge_info(enum cmit_fmt fmt, char *buf, const struct commit *commit, int abbrev)
 534 {
 535         struct commit_list *parent = commit->parents;
 536         int offset;
 537
 538         if ((fmt == CMIT_FMT_ONELINE) || (fmt == CMIT_FMT_EMAIL) ||
 539             !parent || !parent->next)
 540                 return 0;
 541
 542         offset = sprintf(buf, "Merge:");
 543
 544         while (parent) {
 545                 struct commit *p = parent->item;
 546                 const char *hex = abbrev
 547                         ? find_unique_abbrev(p->object.sha1, abbrev)
 548                         : sha1_to_hex(p->object.sha1);
 549                 const char *dots = (abbrev && strlen(hex) != 40) ? "..." : "";
 550                 parent = parent->next;
 551
 552                 offset += sprintf(buf + offset, " %s%s", hex, dots);
 553         }
 554         buf[offset++] = '\n';
 555         return offset;
 556 }
 557
 558 unsigned 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)
 559 {
 560         int hdr = 1, body = 0;
 561         unsigned long offset = 0;
 562         int indent = 4;
 563         int parents_shown = 0;
 564         const char *msg = commit->buffer;
 565         int plain_non_ascii = 0;
 566
 567         if (fmt == CMIT_FMT_ONELINE || fmt == CMIT_FMT_EMAIL)
 568                 indent = 0;
 569
 570         /* After-subject is used to pass in Content-Type: multipart
 571          * MIME header; in that case we do not have to do the
 572          * plaintext content type even if the commit message has
 573          * non 7-bit ASCII character.  Otherwise, check if we need
 574          * to say this is not a 7-bit ASCII.
 575          */
 576         if (fmt == CMIT_FMT_EMAIL && !after_subject) {
 577                 int i, ch, in_body;
 578
 579                 for (in_body = i = 0; (ch = msg[i]) && i < len; i++) {
 580                         if (!in_body) {
 581                                 /* author could be non 7-bit ASCII but
 582                                  * the log may so; skip over the
 583                                  * header part first.
 584                                  */
 585                                 if (ch == '\n' &&
 586                                     i + 1 < len && msg[i+1] == '\n')
 587                                         in_body = 1;
 588                         }
 589                         else if (ch & 0x80) {
 590                                 plain_non_ascii = 1;
 591                                 break;
 592                         }
 593                 }
 594         }
 595
 596         for (;;) {
 597                 const char *line = msg;
 598                 int linelen = get_one_line(msg, len);
 599
 600                 if (!linelen)
 601                         break;
 602
 603                 /*
 604                  * We want some slop for indentation and a possible
 605                  * final "...". Thus the "+ 20".
 606                  */
 607                 if (offset + linelen + 20 > space) {
 608                         memcpy(buf + offset, "    ...\n", 8);
 609                         offset += 8;
 610                         break;
 611                 }
 612
 613                 msg += linelen;
 614                 len -= linelen;
 615                 if (hdr) {
 616                         if (linelen == 1) {
 617                                 hdr = 0;
 618                                 if ((fmt != CMIT_FMT_ONELINE) && !subject)
 619                                         buf[offset++] = '\n';
 620                                 continue;
 621                         }
 622                         if (fmt == CMIT_FMT_RAW) {
 623                                 memcpy(buf + offset, line, linelen);
 624                                 offset += linelen;
 625                                 continue;
 626                         }
 627                         if (!memcmp(line, "parent ", 7)) {
 628                                 if (linelen != 48)
 629                                         die("bad parent line in commit");
 630                                 continue;
 631                         }
 632
 633                         if (!parents_shown) {
 634                                 offset += add_merge_info(fmt, buf + offset,
 635                                                          commit, abbrev);
 636                                 parents_shown = 1;
 637                                 continue;
 638                         }
 639                         /*
 640                          * MEDIUM == DEFAULT shows only author with dates.
 641                          * FULL shows both authors but not dates.
 642                          * FULLER shows both authors and dates.
 643                          */
 644                         if (!memcmp(line, "author ", 7))
 645                                 offset += add_user_info("Author", fmt,
 646                                                         buf + offset,
 647                                                         line + 7);
 648                         if (!memcmp(line, "committer ", 10) &&
 649                             (fmt == CMIT_FMT_FULL || fmt == CMIT_FMT_FULLER))
 650                                 offset += add_user_info("Commit", fmt,
 651                                                         buf + offset,
 652                                                         line + 10);
 653                         continue;
 654                 }
 655
 656                 if (is_empty_line(line, &linelen)) {
 657                         if (!body)
 658                                 continue;
 659                         if (subject)
 660                                 continue;
 661                         if (fmt == CMIT_FMT_SHORT)
 662                                 break;
 663                 } else {
 664                         body = 1;
 665                 }
 666
 667                 if (subject) {
 668                         int slen = strlen(subject);
 669                         memcpy(buf + offset, subject, slen);
 670                         offset += slen;
 671                         offset += add_rfc2047(buf + offset, line, linelen);
 672                 }
 673                 else {
 674                         memset(buf + offset, ' ', indent);
 675                         memcpy(buf + offset + indent, line, linelen);
 676                         offset += linelen + indent;
 677                 }
 678                 buf[offset++] = '\n';
 679                 if (fmt == CMIT_FMT_ONELINE)
 680                         break;
 681                 if (subject && plain_non_ascii) {
 682                         static const char header[] =
 683                                 "Content-Type: text/plain; charset=UTF-8\n"
 684                                 "Content-Transfer-Encoding: 8bit\n";
 685                         memcpy(buf + offset, header, sizeof(header)-1);
 686                         offset += sizeof(header)-1;
 687                 }
 688                 if (after_subject) {
 689                         int slen = strlen(after_subject);
 690                         if (slen > space - offset - 1)
 691                                 slen = space - offset - 1;
 692                         memcpy(buf + offset, after_subject, slen);
 693                         offset += slen;
 694                         after_subject = NULL;
 695                 }
 696                 subject = NULL;
 697         }
 698         while (offset && isspace(buf[offset-1]))
 699                 offset--;
 700         /* Make sure there is an EOLN for the non-oneline case */
 701         if (fmt != CMIT_FMT_ONELINE)
 702                 buf[offset++] = '\n';
 703         buf[offset] = '\0';
 704         return offset;
 705 }
 706
 707 struct commit *pop_commit(struct commit_list **stack)
 708 {
 709         struct commit_list *top = *stack;
 710         struct commit *item = top ? top->item : NULL;
 711
 712         if (top) {
 713                 *stack = top->next;
 714                 free(top);
 715         }
 716         return item;
 717 }
 718
 719 int count_parents(struct commit * commit)
 720 {
 721         int count = 0;
 722         struct commit_list * parents = commit->parents;
 723         for (count=0;parents; parents=parents->next,count++)
 724           ;
 725         return count;
 726 }
 727
 728 void topo_sort_default_setter(struct commit *c, void *data)
 729 {
 730         c->util = data;
 731 }
 732
 733 void *topo_sort_default_getter(struct commit *c)
 734 {
 735         return c->util;
 736 }
 737
 738 /*
 739  * Performs an in-place topological sort on the list supplied.
 740  */
 741 void sort_in_topological_order(struct commit_list ** list, int lifo)
 742 {
 743         sort_in_topological_order_fn(list, lifo, topo_sort_default_setter,
 744                                      topo_sort_default_getter);
 745 }
 746
 747 void sort_in_topological_order_fn(struct commit_list ** list, int lifo,
 748                                   topo_sort_set_fn_t setter,
 749                                   topo_sort_get_fn_t getter)
 750 {
 751         struct commit_list * next = *list;
 752         struct commit_list * work = NULL, **insert;
 753         struct commit_list ** pptr = list;
 754         struct sort_node * nodes;
 755         struct sort_node * next_nodes;
 756         int count = 0;
 757
 758         /* determine the size of the list */
 759         while (next) {
 760                 next = next->next;
 761                 count++;
 762         }
 763
 764         if (!count)
 765                 return;
 766         /* allocate an array to help sort the list */
 767         nodes = xcalloc(count, sizeof(*nodes));
 768         /* link the list to the array */
 769         next_nodes = nodes;
 770         next=*list;
 771         while (next) {
 772                 next_nodes->list_item = next;
 773                 setter(next->item, next_nodes);
 774                 next_nodes++;
 775                 next = next->next;
 776         }
 777         /* update the indegree */
 778         next=*list;
 779         while (next) {
 780                 struct commit_list * parents = next->item->parents;
 781                 while (parents) {
 782                         struct commit * parent=parents->item;
 783                         struct sort_node * pn = (struct sort_node *) getter(parent);
 784
 785                         if (pn)
 786                                 pn->indegree++;
 787                         parents=parents->next;
 788                 }
 789                 next=next->next;
 790         }
 791         /*
 792          * find the tips
 793          *
 794          * tips are nodes not reachable from any other node in the list
 795          *
 796          * the tips serve as a starting set for the work queue.
 797          */
 798         next=*list;
 799         insert = &work;
 800         while (next) {
 801                 struct sort_node * node = (struct sort_node *) getter(next->item);
 802
 803                 if (node->indegree == 0) {
 804                         insert = &commit_list_insert(next->item, insert)->next;
 805                 }
 806                 next=next->next;
 807         }
 808
 809         /* process the list in topological order */
 810         if (!lifo)
 811                 sort_by_date(&work);
 812         while (work) {
 813                 struct commit * work_item = pop_commit(&work);
 814                 struct sort_node * work_node = (struct sort_node *) getter(work_item);
 815                 struct commit_list * parents = work_item->parents;
 816
 817                 while (parents) {
 818                         struct commit * parent=parents->item;
 819                         struct sort_node * pn = (struct sort_node *) getter(parent);
 820
 821                         if (pn) {
 822                                 /*
 823                                  * parents are only enqueued for emission
 824                                  * when all their children have been emitted thereby
 825                                  * guaranteeing topological order.
 826                                  */
 827                                 pn->indegree--;
 828                                 if (!pn->indegree) {
 829                                         if (!lifo)
 830                                                 insert_by_date(parent, &work);
 831                                         else
 832                                                 commit_list_insert(parent, &work);
 833                                 }
 834                         }
 835                         parents=parents->next;
 836                 }
 837                 /*
 838                  * work_item is a commit all of whose children
 839                  * have already been emitted. we can emit it now.
 840                  */
 841                 *pptr = work_node->list_item;
 842                 pptr = &(*pptr)->next;
 843                 *pptr = NULL;
 844                 setter(work_item, NULL);
 845         }
 846         free(nodes);
 847 }
 848
 849 /* merge-rebase stuff */
 850
 851 /* bits #0..7 in revision.h */
 852 #define PARENT1         (1u<< 8)
 853 #define PARENT2         (1u<< 9)
 854 #define STALE           (1u<<10)
 855
 856 static struct commit *interesting(struct commit_list *list)
 857 {
 858         while (list) {
 859                 struct commit *commit = list->item;
 860                 list = list->next;
 861                 if (commit->object.flags & STALE)
 862                         continue;
 863                 return commit;
 864         }
 865         return NULL;
 866 }
 867
 868 /*
 869  * A pathological example of how this thing works.
 870  *
 871  * Suppose we had this commit graph, where chronologically
 872  * the timestamp on the commit are A <= B <= C <= D <= E <= F
 873  * and we are trying to figure out the merge base for E and F
 874  * commits.
 875  *
 876  *                  F
 877  *                 / \
 878  *            E   A   D
 879  *             \ /   /
 880  *              B   /
 881  *               \ /
 882  *                C
 883  *
 884  * First we push E and F to list to be processed.  E gets bit 1
 885  * and F gets bit 2.  The list becomes:
 886  *
 887  *     list=F(2) E(1), result=empty
 888  *
 889  * Then we pop F, the newest commit, from the list.  Its flag is 2.
 890  * We scan its parents, mark them reachable from the side that F is
 891  * reachable from, and push them to the list:
 892  *
 893  *     list=E(1) D(2) A(2), result=empty
 894  *
 895  * Next pop E and do the same.
 896  *
 897  *     list=D(2) B(1) A(2), result=empty
 898  *
 899  * Next pop D and do the same.
 900  *
 901  *     list=C(2) B(1) A(2), result=empty
 902  *
 903  * Next pop C and do the same.
 904  *
 905  *     list=B(1) A(2), result=empty
 906  *
 907  * Now it is B's turn.  We mark its parent, C, reachable from B's side,
 908  * and push it to the list:
 909  *
 910  *     list=C(3) A(2), result=empty
 911  *
 912  * Now pop C and notice it has flags==3.  It is placed on the result list,
 913  * and the list now contains:
 914  *
 915  *     list=A(2), result=C(3)
 916  *
 917  * We pop A and do the same.
 918  *
 919  *     list=B(3), result=C(3)
 920  *
 921  * Next, we pop B and something very interesting happens.  It has flags==3
 922  * so it is also placed on the result list, and its parents are marked
 923  * stale, retroactively, and placed back on the list:
 924  *
 925  *    list=C(7), result=C(7) B(3)
 926  *
 927  * Now, list does not have any interesting commit.  So we find the newest
 928  * commit from the result list that is not marked stale.  Which is
 929  * commit B.
 930  *
 931  *
 932  * Another pathological example how this thing used to fail to mark an
 933  * ancestor of a merge base as STALE before we introduced the
 934  * postprocessing phase (mark_reachable_commits).
 935  *
 936  *                2
 937  *                H
 938  *          1    / \
 939  *          G   A   \
 940  *          |\ /     \
 941  *          | B       \
 942  *          |  \       \
 943  *           \  C       F
 944  *            \  \     /
 945  *             \  D   /
 946  *              \ |  /
 947  *               \| /
 948  *                E
 949  *
 950  *       list                   A B C D E F G H
 951  *       G1 H2                  - - - - - - 1 2
 952  *       H2 E1 B1               - 1 - - 1 - 1 2
 953  *       F2 E1 B1 A2            2 1 - - 1 2 1 2
 954  *       E3 B1 A2               2 1 - - 3 2 1 2
 955  *       B1 A2                  2 1 - - 3 2 1 2
 956  *       C1 A2                  2 1 1 - 3 2 1 2
 957  *       D1 A2                  2 1 1 1 3 2 1 2
 958  *       A2                     2 1 1 1 3 2 1 2
 959  *       B3                     2 3 1 1 3 2 1 2
 960  *       C7                     2 3 7 1 3 2 1 2
 961  *
 962  * At this point, unfortunately, everybody in the list is
 963  * stale, so we fail to complete the following two
 964  * steps to fully marking stale commits.
 965  *
 966  *       D7                     2 3 7 7 3 2 1 2
 967  *       E7                     2 3 7 7 7 2 1 2
 968  *
 969  * and we ended up showing E as an interesting merge base.
 970  * The postprocessing phase re-injects C and continues traversal
 971  * to contaminate D and E.
 972  */
 973
 974 static void mark_reachable_commits(struct commit_list *result,
 975                                    struct commit_list *list)
 976 {
 977         struct commit_list *tmp;
 978
 979         /*
 980          * Postprocess to fully contaminate the well.
 981          */
 982         for (tmp = result; tmp; tmp = tmp->next) {
 983                 struct commit *c = tmp->item;
 984                 /* Reinject stale ones to list,
 985                  * so we can scan their parents.
 986                  */
 987                 if (c->object.flags & STALE)
 988                         commit_list_insert(c, &list);
 989         }
 990         while (list) {
 991                 struct commit *c = list->item;
 992                 struct commit_list *parents;
 993
 994                 tmp = list;
 995                 list = list->next;
 996                 free(tmp);
 997
 998                 /* Anything taken out of the list is stale, so
 999                  * mark all its parents stale.  We do not
1000                  * parse new ones (we already parsed all the relevant
1001                  * ones).
1002                  */
1003                 parents = c->parents;
1004                 while (parents) {
1005                         struct commit *p = parents->item;
1006                         parents = parents->next;
1007                         if (!(p->object.flags & STALE)) {
1008                                 p->object.flags |= STALE;
1009                                 commit_list_insert(p, &list);
1010                         }
1011                 }
1012         }
1013 }
1014
1015 struct commit_list *get_merge_bases(struct commit *rev1, struct commit *rev2,
1016                                     int cleanup)
1017 {
1018         struct commit_list *list = NULL;
1019         struct commit_list *result = NULL;
1020         struct commit_list *tmp = NULL;
1021
1022         if (rev1 == rev2)
1023                 return commit_list_insert(rev1, &result);
1024
1025         parse_commit(rev1);
1026         parse_commit(rev2);
1027
1028         rev1->object.flags |= PARENT1;
1029         rev2->object.flags |= PARENT2;
1030         insert_by_date(rev1, &list);
1031         insert_by_date(rev2, &list);
1032
1033         while (interesting(list)) {
1034                 struct commit *commit = list->item;
1035                 struct commit_list *parents;
1036                 int flags = commit->object.flags
1037                         & (PARENT1 | PARENT2 | STALE);
1038
1039                 tmp = list;
1040                 list = list->next;
1041                 free(tmp);
1042                 if (flags == (PARENT1 | PARENT2)) {
1043                         insert_by_date(commit, &result);
1044
1045                         /* Mark parents of a found merge stale */
1046                         flags |= STALE;
1047                 }
1048                 parents = commit->parents;
1049                 while (parents) {
1050                         struct commit *p = parents->item;
1051                         parents = parents->next;
1052                         if ((p->object.flags & flags) == flags)
1053                                 continue;
1054                         parse_commit(p);
1055                         p->object.flags |= flags;
1056                         insert_by_date(p, &list);
1057                 }
1058         }
1059
1060         if (!result)
1061                 return NULL;
1062
1063         if (result->next && list)
1064                 mark_reachable_commits(result, list);
1065
1066         /* cull duplicates */
1067         for (tmp = result, list = NULL; tmp; ) {
1068                 struct commit *commit = tmp->item;
1069                 struct commit_list *next = tmp->next;
1070                 if (commit->object.flags & STALE) {
1071                         if (list != NULL)
1072                                 list->next = next;
1073                         free(tmp);
1074                 } else {
1075                         if (list == NULL)
1076                                 result = tmp;
1077                         list = tmp;
1078                         commit->object.flags |= STALE;
1079                 }
1080
1081                 tmp = next;
1082         }
1083
1084         if (cleanup) {
1085                 clear_commit_marks(rev1, PARENT1 | PARENT2 | STALE);
1086                 clear_commit_marks(rev2, PARENT1 | PARENT2 | STALE);
1087         }
1088
1089         return result;
1090 }