git.oblomov.eu Git - git/blob - revision.c

   1 #include "cache.h"
   2 #include "tag.h"
   3 #include "blob.h"
   4 #include "tree.h"
   5 #include "commit.h"
   6 #include "diff.h"
   7 #include "refs.h"
   8 #include "revision.h"
   9
  10 static char *path_name(struct name_path *path, const char *name)
  11 {
  12         struct name_path *p;
  13         char *n, *m;
  14         int nlen = strlen(name);
  15         int len = nlen + 1;
  16
  17         for (p = path; p; p = p->up) {
  18                 if (p->elem_len)
  19                         len += p->elem_len + 1;
  20         }
  21         n = xmalloc(len);
  22         m = n + len - (nlen + 1);
  23         strcpy(m, name);
  24         for (p = path; p; p = p->up) {
  25                 if (p->elem_len) {
  26                         m -= p->elem_len + 1;
  27                         memcpy(m, p->elem, p->elem_len);
  28                         m[p->elem_len] = '/';
  29                 }
  30         }
  31         return n;
  32 }
  33
  34 struct object_list **add_object(struct object *obj,
  35                                        struct object_list **p,
  36                                        struct name_path *path,
  37                                        const char *name)
  38 {
  39         struct object_list *entry = xmalloc(sizeof(*entry));
  40         entry->item = obj;
  41         entry->next = *p;
  42         entry->name = path_name(path, name);
  43         *p = entry;
  44         return &entry->next;
  45 }
  46
  47 static void mark_blob_uninteresting(struct blob *blob)
  48 {
  49         if (blob->object.flags & UNINTERESTING)
  50                 return;
  51         blob->object.flags |= UNINTERESTING;
  52 }
  53
  54 void mark_tree_uninteresting(struct tree *tree)
  55 {
  56         struct object *obj = &tree->object;
  57         struct tree_entry_list *entry;
  58
  59         if (obj->flags & UNINTERESTING)
  60                 return;
  61         obj->flags |= UNINTERESTING;
  62         if (!has_sha1_file(obj->sha1))
  63                 return;
  64         if (parse_tree(tree) < 0)
  65                 die("bad tree %s", sha1_to_hex(obj->sha1));
  66         entry = tree->entries;
  67         tree->entries = NULL;
  68         while (entry) {
  69                 struct tree_entry_list *next = entry->next;
  70                 if (entry->directory)
  71                         mark_tree_uninteresting(entry->item.tree);
  72                 else
  73                         mark_blob_uninteresting(entry->item.blob);
  74                 free(entry);
  75                 entry = next;
  76         }
  77 }
  78
  79 void mark_parents_uninteresting(struct commit *commit)
  80 {
  81         struct commit_list *parents = commit->parents;
  82
  83         while (parents) {
  84                 struct commit *commit = parents->item;
  85                 if (!(commit->object.flags & UNINTERESTING)) {
  86                         commit->object.flags |= UNINTERESTING;
  87
  88                         /*
  89                          * Normally we haven't parsed the parent
  90                          * yet, so we won't have a parent of a parent
  91                          * here. However, it may turn out that we've
  92                          * reached this commit some other way (where it
  93                          * wasn't uninteresting), in which case we need
  94                          * to mark its parents recursively too..
  95                          */
  96                         if (commit->parents)
  97                                 mark_parents_uninteresting(commit);
  98                 }
  99
 100                 /*
 101                  * A missing commit is ok iff its parent is marked
 102                  * uninteresting.
 103                  *
 104                  * We just mark such a thing parsed, so that when
 105                  * it is popped next time around, we won't be trying
 106                  * to parse it and get an error.
 107                  */
 108                 if (!has_sha1_file(commit->object.sha1))
 109                         commit->object.parsed = 1;
 110                 parents = parents->next;
 111         }
 112 }
 113
 114 static void add_pending_object(struct rev_info *revs, struct object *obj, const char *name)
 115 {
 116         add_object(obj, &revs->pending_objects, NULL, name);
 117 }
 118
 119 static struct commit *get_commit_reference(struct rev_info *revs, const char *name, const unsigned char *sha1, unsigned int flags)
 120 {
 121         struct object *object;
 122
 123         object = parse_object(sha1);
 124         if (!object)
 125                 die("bad object %s", name);
 126
 127         /*
 128          * Tag object? Look what it points to..
 129          */
 130         while (object->type == tag_type) {
 131                 struct tag *tag = (struct tag *) object;
 132                 object->flags |= flags;
 133                 if (revs->tag_objects && !(object->flags & UNINTERESTING))
 134                         add_pending_object(revs, object, tag->tag);
 135                 object = parse_object(tag->tagged->sha1);
 136                 if (!object)
 137                         die("bad object %s", sha1_to_hex(tag->tagged->sha1));
 138         }
 139
 140         /*
 141          * Commit object? Just return it, we'll do all the complex
 142          * reachability crud.
 143          */
 144         if (object->type == commit_type) {
 145                 struct commit *commit = (struct commit *)object;
 146                 object->flags |= flags;
 147                 if (parse_commit(commit) < 0)
 148                         die("unable to parse commit %s", name);
 149                 if (flags & UNINTERESTING) {
 150                         mark_parents_uninteresting(commit);
 151                         revs->limited = 1;
 152                 }
 153                 return commit;
 154         }
 155
 156         /*
 157          * Tree object? Either mark it uniniteresting, or add it
 158          * to the list of objects to look at later..
 159          */
 160         if (object->type == tree_type) {
 161                 struct tree *tree = (struct tree *)object;
 162                 if (!revs->tree_objects)
 163                         return NULL;
 164                 if (flags & UNINTERESTING) {
 165                         mark_tree_uninteresting(tree);
 166                         return NULL;
 167                 }
 168                 add_pending_object(revs, object, "");
 169                 return NULL;
 170         }
 171
 172         /*
 173          * Blob object? You know the drill by now..
 174          */
 175         if (object->type == blob_type) {
 176                 struct blob *blob = (struct blob *)object;
 177                 if (!revs->blob_objects)
 178                         return NULL;
 179                 if (flags & UNINTERESTING) {
 180                         mark_blob_uninteresting(blob);
 181                         return NULL;
 182                 }
 183                 add_pending_object(revs, object, "");
 184                 return NULL;
 185         }
 186         die("%s is unknown object", name);
 187 }
 188
 189 static int everybody_uninteresting(struct commit_list *orig)
 190 {
 191         struct commit_list *list = orig;
 192         while (list) {
 193                 struct commit *commit = list->item;
 194                 list = list->next;
 195                 if (commit->object.flags & UNINTERESTING)
 196                         continue;
 197                 return 0;
 198         }
 199         return 1;
 200 }
 201
 202 static int tree_difference = REV_TREE_SAME;
 203
 204 static void file_add_remove(struct diff_options *options,
 205                     int addremove, unsigned mode,
 206                     const unsigned char *sha1,
 207                     const char *base, const char *path)
 208 {
 209         int diff = REV_TREE_DIFFERENT;
 210
 211         /*
 212          * Is it an add of a new file? It means that the old tree
 213          * didn't have it at all, so we will turn "REV_TREE_SAME" ->
 214          * "REV_TREE_NEW", but leave any "REV_TREE_DIFFERENT" alone
 215          * (and if it already was "REV_TREE_NEW", we'll keep it
 216          * "REV_TREE_NEW" of course).
 217          */
 218         if (addremove == '+') {
 219                 diff = tree_difference;
 220                 if (diff != REV_TREE_SAME)
 221                         return;
 222                 diff = REV_TREE_NEW;
 223         }
 224         tree_difference = diff;
 225 }
 226
 227 static void file_change(struct diff_options *options,
 228                  unsigned old_mode, unsigned new_mode,
 229                  const unsigned char *old_sha1,
 230                  const unsigned char *new_sha1,
 231                  const char *base, const char *path)
 232 {
 233         tree_difference = REV_TREE_DIFFERENT;
 234 }
 235
 236 static struct diff_options diff_opt = {
 237         .recursive = 1,
 238         .add_remove = file_add_remove,
 239         .change = file_change,
 240 };
 241
 242 int rev_compare_tree(struct tree *t1, struct tree *t2)
 243 {
 244         if (!t1)
 245                 return REV_TREE_NEW;
 246         if (!t2)
 247                 return REV_TREE_DIFFERENT;
 248         tree_difference = REV_TREE_SAME;
 249         if (diff_tree_sha1(t1->object.sha1, t2->object.sha1, "", &diff_opt) < 0)
 250                 return REV_TREE_DIFFERENT;
 251         return tree_difference;
 252 }
 253
 254 int rev_same_tree_as_empty(struct tree *t1)
 255 {
 256         int retval;
 257         void *tree;
 258         struct tree_desc empty, real;
 259
 260         if (!t1)
 261                 return 0;
 262
 263         tree = read_object_with_reference(t1->object.sha1, "tree", &real.size, NULL);
 264         if (!tree)
 265                 return 0;
 266         real.buf = tree;
 267
 268         empty.buf = "";
 269         empty.size = 0;
 270
 271         tree_difference = 0;
 272         retval = diff_tree(&empty, &real, "", &diff_opt);
 273         free(tree);
 274
 275         return retval >= 0 && !tree_difference;
 276 }
 277
 278 static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
 279 {
 280         struct commit_list **pp, *parent;
 281         int tree_changed = 0;
 282
 283         if (!commit->tree)
 284                 return;
 285
 286         if (!commit->parents) {
 287                 if (!rev_same_tree_as_empty(commit->tree))
 288                         commit->object.flags |= TREECHANGE;
 289                 return;
 290         }
 291
 292         pp = &commit->parents;
 293         while ((parent = *pp) != NULL) {
 294                 struct commit *p = parent->item;
 295
 296                 parse_commit(p);
 297                 switch (rev_compare_tree(p->tree, commit->tree)) {
 298                 case REV_TREE_SAME:
 299                         if (p->object.flags & UNINTERESTING) {
 300                                 /* Even if a merge with an uninteresting
 301                                  * side branch brought the entire change
 302                                  * we are interested in, we do not want
 303                                  * to lose the other branches of this
 304                                  * merge, so we just keep going.
 305                                  */
 306                                 pp = &parent->next;
 307                                 continue;
 308                         }
 309                         parent->next = NULL;
 310                         commit->parents = parent;
 311                         return;
 312
 313                 case REV_TREE_NEW:
 314                         if (revs->remove_empty_trees &&
 315                             rev_same_tree_as_empty(p->tree)) {
 316                                 /* We are adding all the specified
 317                                  * paths from this parent, so the
 318                                  * history beyond this parent is not
 319                                  * interesting.  Remove its parents
 320                                  * (they are grandparents for us).
 321                                  * IOW, we pretend this parent is a
 322                                  * "root" commit.
 323                                  */
 324                                 parse_commit(p);
 325                                 p->parents = NULL;
 326                         }
 327                 /* fallthrough */
 328                 case REV_TREE_DIFFERENT:
 329                         tree_changed = 1;
 330                         pp = &parent->next;
 331                         continue;
 332                 }
 333                 die("bad tree compare for commit %s", sha1_to_hex(commit->object.sha1));
 334         }
 335         if (tree_changed)
 336                 commit->object.flags |= TREECHANGE;
 337 }
 338
 339 static void add_parents_to_list(struct rev_info *revs, struct commit *commit, struct commit_list **list)
 340 {
 341         struct commit_list *parent = commit->parents;
 342
 343         /*
 344          * If the commit is uninteresting, don't try to
 345          * prune parents - we want the maximal uninteresting
 346          * set.
 347          *
 348          * Normally we haven't parsed the parent
 349          * yet, so we won't have a parent of a parent
 350          * here. However, it may turn out that we've
 351          * reached this commit some other way (where it
 352          * wasn't uninteresting), in which case we need
 353          * to mark its parents recursively too..
 354          */
 355         if (commit->object.flags & UNINTERESTING) {
 356                 while (parent) {
 357                         struct commit *p = parent->item;
 358                         parent = parent->next;
 359                         parse_commit(p);
 360                         p->object.flags |= UNINTERESTING;
 361                         if (p->parents)
 362                                 mark_parents_uninteresting(p);
 363                         if (p->object.flags & SEEN)
 364                                 continue;
 365                         p->object.flags |= SEEN;
 366                         insert_by_date(p, list);
 367                 }
 368                 return;
 369         }
 370
 371         /*
 372          * Ok, the commit wasn't uninteresting. Try to
 373          * simplify the commit history and find the parent
 374          * that has no differences in the path set if one exists.
 375          */
 376         if (revs->prune_fn)
 377                 revs->prune_fn(revs, commit);
 378
 379         parent = commit->parents;
 380         while (parent) {
 381                 struct commit *p = parent->item;
 382
 383                 parent = parent->next;
 384
 385                 parse_commit(p);
 386                 if (p->object.flags & SEEN)
 387                         continue;
 388                 p->object.flags |= SEEN;
 389                 insert_by_date(p, list);
 390         }
 391 }
 392
 393 static void limit_list(struct rev_info *revs)
 394 {
 395         struct commit_list *list = revs->commits;
 396         struct commit_list *newlist = NULL;
 397         struct commit_list **p = &newlist;
 398
 399         while (list) {
 400                 struct commit_list *entry = list;
 401                 struct commit *commit = list->item;
 402                 struct object *obj = &commit->object;
 403
 404                 list = list->next;
 405                 free(entry);
 406
 407                 if (revs->max_age != -1 && (commit->date < revs->max_age))
 408                         obj->flags |= UNINTERESTING;
 409                 if (revs->unpacked && has_sha1_pack(obj->sha1))
 410                         obj->flags |= UNINTERESTING;
 411                 add_parents_to_list(revs, commit, &list);
 412                 if (obj->flags & UNINTERESTING) {
 413                         mark_parents_uninteresting(commit);
 414                         if (everybody_uninteresting(list))
 415                                 break;
 416                         continue;
 417                 }
 418                 if (revs->min_age != -1 && (commit->date > revs->min_age))
 419                         continue;
 420                 p = &commit_list_insert(commit, p)->next;
 421         }
 422         revs->commits = newlist;
 423 }
 424
 425 static void add_one_commit(struct commit *commit, struct rev_info *revs)
 426 {
 427         if (!commit || (commit->object.flags & SEEN))
 428                 return;
 429         commit->object.flags |= SEEN;
 430         commit_list_insert(commit, &revs->commits);
 431 }
 432
 433 static int all_flags;
 434 static struct rev_info *all_revs;
 435
 436 static int handle_one_ref(const char *path, const unsigned char *sha1)
 437 {
 438         struct commit *commit = get_commit_reference(all_revs, path, sha1, all_flags);
 439         add_one_commit(commit, all_revs);
 440         return 0;
 441 }
 442
 443 static void handle_all(struct rev_info *revs, unsigned flags)
 444 {
 445         all_revs = revs;
 446         all_flags = flags;
 447         for_each_ref(handle_one_ref);
 448 }
 449
 450 void init_revisions(struct rev_info *revs)
 451 {
 452         memset(revs, 0, sizeof(*revs));
 453         revs->lifo = 1;
 454         revs->dense = 1;
 455         revs->prefix = setup_git_directory();
 456         revs->max_age = -1;
 457         revs->min_age = -1;
 458         revs->max_count = -1;
 459
 460         revs->prune_fn = NULL;
 461         revs->prune_data = NULL;
 462
 463         revs->topo_setter = topo_sort_default_setter;
 464         revs->topo_getter = topo_sort_default_getter;
 465 }
 466
 467 /*
 468  * Parse revision information, filling in the "rev_info" structure,
 469  * and removing the used arguments from the argument list.
 470  *
 471  * Returns the number of arguments left that weren't recognized
 472  * (which are also moved to the head of the argument list)
 473  */
 474 int setup_revisions(int argc, const char **argv, struct rev_info *revs, const char *def)
 475 {
 476         int i, flags, seen_dashdash;
 477         const char **unrecognized = argv + 1;
 478         int left = 1;
 479
 480         init_revisions(revs);
 481
 482         /* First, search for "--" */
 483         seen_dashdash = 0;
 484         for (i = 1; i < argc; i++) {
 485                 const char *arg = argv[i];
 486                 if (strcmp(arg, "--"))
 487                         continue;
 488                 argv[i] = NULL;
 489                 argc = i;
 490                 revs->prune_data = get_pathspec(revs->prefix, argv + i + 1);
 491                 seen_dashdash = 1;
 492                 break;
 493         }
 494
 495         flags = 0;
 496         for (i = 1; i < argc; i++) {
 497                 struct commit *commit;
 498                 const char *arg = argv[i];
 499                 unsigned char sha1[20];
 500                 char *dotdot;
 501                 int local_flags;
 502
 503                 if (*arg == '-') {
 504                         if (!strncmp(arg, "--max-count=", 12)) {
 505                                 revs->max_count = atoi(arg + 12);
 506                                 continue;
 507                         }
 508                         /* accept -<digit>, like traditilnal "head" */
 509                         if ((*arg == '-') && isdigit(arg[1])) {
 510                                 revs->max_count = atoi(arg + 1);
 511                                 continue;
 512                         }
 513                         if (!strcmp(arg, "-n")) {
 514                                 if (argc <= i + 1)
 515                                         die("-n requires an argument");
 516                                 revs->max_count = atoi(argv[++i]);
 517                                 continue;
 518                         }
 519                         if (!strncmp(arg,"-n",2)) {
 520                                 revs->max_count = atoi(arg + 2);
 521                                 continue;
 522                         }
 523                         if (!strncmp(arg, "--max-age=", 10)) {
 524                                 revs->max_age = atoi(arg + 10);
 525                                 revs->limited = 1;
 526                                 continue;
 527                         }
 528                         if (!strncmp(arg, "--min-age=", 10)) {
 529                                 revs->min_age = atoi(arg + 10);
 530                                 revs->limited = 1;
 531                                 continue;
 532                         }
 533                         if (!strncmp(arg, "--since=", 8)) {
 534                                 revs->max_age = approxidate(arg + 8);
 535                                 revs->limited = 1;
 536                                 continue;
 537                         }
 538                         if (!strncmp(arg, "--after=", 8)) {
 539                                 revs->max_age = approxidate(arg + 8);
 540                                 revs->limited = 1;
 541                                 continue;
 542                         }
 543                         if (!strncmp(arg, "--before=", 9)) {
 544                                 revs->min_age = approxidate(arg + 9);
 545                                 revs->limited = 1;
 546                                 continue;
 547                         }
 548                         if (!strncmp(arg, "--until=", 8)) {
 549                                 revs->min_age = approxidate(arg + 8);
 550                                 revs->limited = 1;
 551                                 continue;
 552                         }
 553                         if (!strcmp(arg, "--all")) {
 554                                 handle_all(revs, flags);
 555                                 continue;
 556                         }
 557                         if (!strcmp(arg, "--not")) {
 558                                 flags ^= UNINTERESTING;
 559                                 continue;
 560                         }
 561                         if (!strcmp(arg, "--default")) {
 562                                 if (++i >= argc)
 563                                         die("bad --default argument");
 564                                 def = argv[i];
 565                                 continue;
 566                         }
 567                         if (!strcmp(arg, "--topo-order")) {
 568                                 revs->topo_order = 1;
 569                                 revs->limited = 1;
 570                                 continue;
 571                         }
 572                         if (!strcmp(arg, "--date-order")) {
 573                                 revs->lifo = 0;
 574                                 revs->topo_order = 1;
 575                                 revs->limited = 1;
 576                                 continue;
 577                         }
 578                         if (!strcmp(arg, "--dense")) {
 579                                 revs->dense = 1;
 580                                 continue;
 581                         }
 582                         if (!strcmp(arg, "--sparse")) {
 583                                 revs->dense = 0;
 584                                 continue;
 585                         }
 586                         if (!strcmp(arg, "--remove-empty")) {
 587                                 revs->remove_empty_trees = 1;
 588                                 continue;
 589                         }
 590                         if (!strncmp(arg, "--no-merges", 11)) {
 591                                 revs->no_merges = 1;
 592                                 continue;
 593                         }
 594                         if (!strcmp(arg, "--objects")) {
 595                                 revs->tag_objects = 1;
 596                                 revs->tree_objects = 1;
 597                                 revs->blob_objects = 1;
 598                                 continue;
 599                         }
 600                         if (!strcmp(arg, "--objects-edge")) {
 601                                 revs->tag_objects = 1;
 602                                 revs->tree_objects = 1;
 603                                 revs->blob_objects = 1;
 604                                 revs->edge_hint = 1;
 605                                 continue;
 606                         }
 607                         if (!strcmp(arg, "--unpacked")) {
 608                                 revs->unpacked = 1;
 609                                 revs->limited = 1;
 610                                 continue;
 611                         }
 612                         *unrecognized++ = arg;
 613                         left++;
 614                         continue;
 615                 }
 616                 dotdot = strstr(arg, "..");
 617                 if (dotdot) {
 618                         unsigned char from_sha1[20];
 619                         char *next = dotdot + 2;
 620                         *dotdot = 0;
 621                         if (!*next)
 622                                 next = "HEAD";
 623                         if (!get_sha1(arg, from_sha1) && !get_sha1(next, sha1)) {
 624                                 struct commit *exclude;
 625                                 struct commit *include;
 626
 627                                 exclude = get_commit_reference(revs, arg, from_sha1, flags ^ UNINTERESTING);
 628                                 include = get_commit_reference(revs, next, sha1, flags);
 629                                 if (!exclude || !include)
 630                                         die("Invalid revision range %s..%s", arg, next);
 631                                 add_one_commit(exclude, revs);
 632                                 add_one_commit(include, revs);
 633                                 continue;
 634                         }
 635                         *dotdot = '.';
 636                 }
 637                 local_flags = 0;
 638                 if (*arg == '^') {
 639                         local_flags = UNINTERESTING;
 640                         arg++;
 641                 }
 642                 if (get_sha1(arg, sha1) < 0) {
 643                         struct stat st;
 644                         int j;
 645
 646                         if (seen_dashdash || local_flags)
 647                                 die("bad revision '%s'", arg);
 648
 649                         /* If we didn't have a "--", all filenames must exist */
 650                         for (j = i; j < argc; j++) {
 651                                 if (lstat(argv[j], &st) < 0)
 652                                         die("'%s': %s", arg, strerror(errno));
 653                         }
 654                         revs->prune_data = get_pathspec(revs->prefix, argv + i);
 655                         break;
 656                 }
 657                 commit = get_commit_reference(revs, arg, sha1, flags ^ local_flags);
 658                 add_one_commit(commit, revs);
 659         }
 660         if (def && !revs->commits) {
 661                 unsigned char sha1[20];
 662                 struct commit *commit;
 663                 if (get_sha1(def, sha1) < 0)
 664                         die("bad default revision '%s'", def);
 665                 commit = get_commit_reference(revs, def, sha1, 0);
 666                 add_one_commit(commit, revs);
 667         }
 668
 669         if (revs->prune_data) {
 670                 diff_tree_setup_paths(revs->prune_data);
 671                 revs->prune_fn = try_to_simplify_commit;
 672                 revs->limited = 1;
 673         }
 674
 675         return left;
 676 }
 677
 678 void prepare_revision_walk(struct rev_info *revs)
 679 {
 680         sort_by_date(&revs->commits);
 681         if (revs->limited)
 682                 limit_list(revs);
 683         if (revs->topo_order)
 684                 sort_in_topological_order_fn(&revs->commits, revs->lifo,
 685                                              revs->topo_setter,
 686                                              revs->topo_getter);
 687 }
 688
 689 static int rewrite_one(struct commit **pp)
 690 {
 691         for (;;) {
 692                 struct commit *p = *pp;
 693                 if (p->object.flags & (TREECHANGE | UNINTERESTING))
 694                         return 0;
 695                 if (!p->parents)
 696                         return -1;
 697                 *pp = p->parents->item;
 698         }
 699 }
 700
 701 static void rewrite_parents(struct commit *commit)
 702 {
 703         struct commit_list **pp = &commit->parents;
 704         while (*pp) {
 705                 struct commit_list *parent = *pp;
 706                 if (rewrite_one(&parent->item) < 0) {
 707                         *pp = parent->next;
 708                         continue;
 709                 }
 710                 pp = &parent->next;
 711         }
 712 }
 713
 714 struct commit *get_revision(struct rev_info *revs)
 715 {
 716         struct commit_list *list = revs->commits;
 717
 718         if (!list)
 719                 return NULL;
 720
 721         /* Check the max_count ... */
 722         switch (revs->max_count) {
 723         case -1:
 724                 break;
 725         case 0:
 726                 return NULL;
 727         default:
 728                 revs->max_count--;
 729         }
 730
 731         do {
 732                 struct commit *commit = revs->commits->item;
 733
 734                 if (commit->object.flags & (UNINTERESTING|SHOWN))
 735                         goto next;
 736                 if (revs->min_age != -1 && (commit->date > revs->min_age))
 737                         goto next;
 738                 if (revs->max_age != -1 && (commit->date < revs->max_age))
 739                         return NULL;
 740                 if (revs->no_merges && commit->parents && commit->parents->next)
 741                         goto next;
 742                 if (revs->prune_fn && revs->dense) {
 743                         if (!(commit->object.flags & TREECHANGE))
 744                                 goto next;
 745                         rewrite_parents(commit);
 746                 }
 747                 /* More to go? */
 748                 if (revs->max_count)
 749                         pop_most_recent_commit(&revs->commits, SEEN);
 750                 commit->object.flags |= SHOWN;
 751                 return commit;
 752 next:
 753                 pop_most_recent_commit(&revs->commits, SEEN);
 754         } while (revs->commits);
 755         return NULL;
 756 }