unpack-trees.c

   1 #include "cache.h"
   2 #include "dir.h"
   3 #include "tree.h"
   4 #include "tree-walk.h"
   5 #include "cache-tree.h"
   6 #include "unpack-trees.h"
   7 #include "progress.h"
   8 #include "refs.h"
   9
  10 #define DBRT_DEBUG 1
  11
  12 struct tree_entry_list {
  13         struct tree_entry_list *next;
  14         unsigned directory : 1;
  15         unsigned executable : 1;
  16         unsigned symlink : 1;
  17         unsigned int mode;
  18         const char *name;
  19         const unsigned char *sha1;
  20 };
  21
  22 static struct tree_entry_list *create_tree_entry_list(struct tree *tree)
  23 {
  24         struct tree_desc desc;
  25         struct name_entry one;
  26         struct tree_entry_list *ret = NULL;
  27         struct tree_entry_list **list_p = &ret;
  28
  29         if (!tree->object.parsed)
  30                 parse_tree(tree);
  31
  32         init_tree_desc(&desc, tree->buffer, tree->size);
  33
  34         while (tree_entry(&desc, &one)) {
  35                 struct tree_entry_list *entry;
  36
  37                 entry = xmalloc(sizeof(struct tree_entry_list));
  38                 entry->name = one.path;
  39                 entry->sha1 = one.sha1;
  40                 entry->mode = one.mode;
  41                 entry->directory = S_ISDIR(one.mode) != 0;
  42                 entry->executable = (one.mode & S_IXUSR) != 0;
  43                 entry->symlink = S_ISLNK(one.mode) != 0;
  44                 entry->next = NULL;
  45
  46                 *list_p = entry;
  47                 list_p = &entry->next;
  48         }
  49         return ret;
  50 }
  51
  52 static int entcmp(const char *name1, int dir1, const char *name2, int dir2)
  53 {
  54         int len1 = strlen(name1);
  55         int len2 = strlen(name2);
  56         int len = len1 < len2 ? len1 : len2;
  57         int ret = memcmp(name1, name2, len);
  58         unsigned char c1, c2;
  59         if (ret)
  60                 return ret;
  61         c1 = name1[len];
  62         c2 = name2[len];
  63         if (!c1 && dir1)
  64                 c1 = '/';
  65         if (!c2 && dir2)
  66                 c2 = '/';
  67         ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
  68         if (c1 && c2 && !ret)
  69                 ret = len1 - len2;
  70         return ret;
  71 }
  72
  73 static int unpack_trees_rec(struct tree_entry_list **posns, int len,
  74                             const char *base, struct unpack_trees_options *o,
  75                             struct tree_entry_list *df_conflict_list)
  76 {
  77         int baselen = strlen(base);
  78         int src_size = len + 1;
  79         int i_stk = i_stk;
  80         int retval = 0;
  81
  82         if (o->dir)
  83                 i_stk = push_exclude_per_directory(o->dir, base, strlen(base));
  84
  85         do {
  86                 int i;
  87                 const char *first;
  88                 int firstdir = 0;
  89                 int pathlen;
  90                 unsigned ce_size;
  91                 struct tree_entry_list **subposns;
  92                 struct cache_entry **src;
  93                 int any_files = 0;
  94                 int any_dirs = 0;
  95                 char *cache_name;
  96                 int ce_stage;
  97
  98                 /* Find the first name in the input. */
  99
 100                 first = NULL;
 101                 cache_name = NULL;
 102
 103                 /* Check the cache */
 104                 if (o->merge && o->pos < active_nr) {
 105                         /* This is a bit tricky: */
 106                         /* If the index has a subdirectory (with
 107                          * contents) as the first name, it'll get a
 108                          * filename like "foo/bar". But that's after
 109                          * "foo", so the entry in trees will get
 110                          * handled first, at which point we'll go into
 111                          * "foo", and deal with "bar" from the index,
 112                          * because the base will be "foo/". The only
 113                          * way we can actually have "foo/bar" first of
 114                          * all the things is if the trees don't
 115                          * contain "foo" at all, in which case we'll
 116                          * handle "foo/bar" without going into the
 117                          * directory, but that's fine (and will return
 118                          * an error anyway, with the added unknown
 119                          * file case.
 120                          */
 121
 122                         cache_name = active_cache[o->pos]->name;
 123                         if (strlen(cache_name) > baselen &&
 124                             !memcmp(cache_name, base, baselen)) {
 125                                 cache_name += baselen;
 126                                 first = cache_name;
 127                         } else {
 128                                 cache_name = NULL;
 129                         }
 130                 }
 131
 132 #if DBRT_DEBUG > 1
 133                 if (first)
 134                         printf("index %s\n", first);
 135 #endif
 136                 for (i = 0; i < len; i++) {
 137                         if (!posns[i] || posns[i] == df_conflict_list)
 138                                 continue;
 139 #if DBRT_DEBUG > 1
 140                         printf("%d %s\n", i + 1, posns[i]->name);
 141 #endif
 142                         if (!first || entcmp(first, firstdir,
 143                                              posns[i]->name,
 144                                              posns[i]->directory) > 0) {
 145                                 first = posns[i]->name;
 146                                 firstdir = posns[i]->directory;
 147                         }
 148                 }
 149                 /* No name means we're done */
 150                 if (!first)
 151                         goto leave_directory;
 152
 153                 pathlen = strlen(first);
 154                 ce_size = cache_entry_size(baselen + pathlen);
 155
 156                 src = xcalloc(src_size, sizeof(struct cache_entry *));
 157
 158                 subposns = xcalloc(len, sizeof(struct tree_list_entry *));
 159
 160                 if (cache_name && !strcmp(cache_name, first)) {
 161                         any_files = 1;
 162                         src[0] = active_cache[o->pos];
 163                         remove_cache_entry_at(o->pos);
 164                 }
 165
 166                 for (i = 0; i < len; i++) {
 167                         struct cache_entry *ce;
 168
 169                         if (!posns[i] ||
 170                             (posns[i] != df_conflict_list &&
 171                              strcmp(first, posns[i]->name))) {
 172                                 continue;
 173                         }
 174
 175                         if (posns[i] == df_conflict_list) {
 176                                 src[i + o->merge] = o->df_conflict_entry;
 177                                 continue;
 178                         }
 179
 180                         if (posns[i]->directory) {
 181                                 struct tree *tree = lookup_tree(posns[i]->sha1);
 182                                 any_dirs = 1;
 183                                 parse_tree(tree);
 184                                 subposns[i] = create_tree_entry_list(tree);
 185                                 posns[i] = posns[i]->next;
 186                                 src[i + o->merge] = o->df_conflict_entry;
 187                                 continue;
 188                         }
 189
 190                         if (!o->merge)
 191                                 ce_stage = 0;
 192                         else if (i + 1 < o->head_idx)
 193                                 ce_stage = 1;
 194                         else if (i + 1 > o->head_idx)
 195                                 ce_stage = 3;
 196                         else
 197                                 ce_stage = 2;
 198
 199                         ce = xcalloc(1, ce_size);
 200                         ce->ce_mode = create_ce_mode(posns[i]->mode);
 201                         ce->ce_flags = create_ce_flags(baselen + pathlen,
 202                                                        ce_stage);
 203                         memcpy(ce->name, base, baselen);
 204                         memcpy(ce->name + baselen, first, pathlen + 1);
 205
 206                         any_files = 1;
 207
 208                         hashcpy(ce->sha1, posns[i]->sha1);
 209                         src[i + o->merge] = ce;
 210                         subposns[i] = df_conflict_list;
 211                         posns[i] = posns[i]->next;
 212                 }
 213                 if (any_files) {
 214                         if (o->merge) {
 215                                 int ret;
 216
 217 #if DBRT_DEBUG > 1
 218                                 printf("%s:\n", first);
 219                                 for (i = 0; i < src_size; i++) {
 220                                         printf(" %d ", i);
 221                                         if (src[i])
 222                                                 printf("%s\n", sha1_to_hex(src[i]->sha1));
 223                                         else
 224                                                 printf("\n");
 225                                 }
 226 #endif
 227                                 ret = o->fn(src, o);
 228
 229 #if DBRT_DEBUG > 1
 230                                 printf("Added %d entries\n", ret);
 231 #endif
 232                                 o->pos += ret;
 233                         } else {
 234                                 for (i = 0; i < src_size; i++) {
 235                                         if (src[i]) {
 236                                                 add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
 237                                         }
 238                                 }
 239                         }
 240                 }
 241                 if (any_dirs) {
 242                         char *newbase = xmalloc(baselen + 2 + pathlen);
 243                         memcpy(newbase, base, baselen);
 244                         memcpy(newbase + baselen, first, pathlen);
 245                         newbase[baselen + pathlen] = '/';
 246                         newbase[baselen + pathlen + 1] = '\0';
 247                         if (unpack_trees_rec(subposns, len, newbase, o,
 248                                              df_conflict_list)) {
 249                                 retval = -1;
 250                                 goto leave_directory;
 251                         }
 252                         free(newbase);
 253                 }
 254                 free(subposns);
 255                 free(src);
 256         } while (1);
 257
 258  leave_directory:
 259         if (o->dir)
 260                 pop_exclude_per_directory(o->dir, i_stk);
 261         return retval;
 262 }
 263
 264 /* Unlink the last component and attempt to remove leading
 265  * directories, in case this unlink is the removal of the
 266  * last entry in the directory -- empty directories are removed.
 267  */
 268 static void unlink_entry(char *name, char *last_symlink)
 269 {
 270         char *cp, *prev;
 271
 272         if (has_symlink_leading_path(name, last_symlink))
 273                 return;
 274         if (unlink(name))
 275                 return;
 276         prev = NULL;
 277         while (1) {
 278                 int status;
 279                 cp = strrchr(name, '/');
 280                 if (prev)
 281                         *prev = '/';
 282                 if (!cp)
 283                         break;
 284
 285                 *cp = 0;
 286                 status = rmdir(name);
 287                 if (status) {
 288                         *cp = '/';
 289                         break;
 290                 }
 291                 prev = cp;
 292         }
 293 }
 294
 295 static struct checkout state;
 296 static void check_updates(struct cache_entry **src, int nr,
 297                         struct unpack_trees_options *o)
 298 {
 299         unsigned short mask = htons(CE_UPDATE);
 300         unsigned cnt = 0, total = 0;
 301         struct progress progress;
 302         char last_symlink[PATH_MAX];
 303
 304         if (o->update && o->verbose_update) {
 305                 for (total = cnt = 0; cnt < nr; cnt++) {
 306                         struct cache_entry *ce = src[cnt];
 307                         if (!ce->ce_mode || ce->ce_flags & mask)
 308                                 total++;
 309                 }
 310
 311                 start_progress_delay(&progress, "Checking %u files out...",
 312                                      "", total, 50, 2);
 313                 cnt = 0;
 314         }
 315
 316         *last_symlink = '\0';
 317         while (nr--) {
 318                 struct cache_entry *ce = *src++;
 319
 320                 if (total)
 321                         if (!ce->ce_mode || ce->ce_flags & mask)
 322                                 display_progress(&progress, ++cnt);
 323                 if (!ce->ce_mode) {
 324                         if (o->update)
 325                                 unlink_entry(ce->name, last_symlink);
 326                         continue;
 327                 }
 328                 if (ce->ce_flags & mask) {
 329                         ce->ce_flags &= ~mask;
 330                         if (o->update) {
 331                                 checkout_entry(ce, &state, NULL);
 332                                 *last_symlink = '\0';
 333                         }
 334                 }
 335         }
 336         if (total)
 337                 stop_progress(&progress);;
 338 }
 339
 340 int unpack_trees(struct object_list *trees, struct unpack_trees_options *o)
 341 {
 342         unsigned len = object_list_length(trees);
 343         struct tree_entry_list **posns;
 344         int i;
 345         struct object_list *posn = trees;
 346         struct tree_entry_list df_conflict_list;
 347         static struct cache_entry *dfc;
 348
 349         memset(&df_conflict_list, 0, sizeof(df_conflict_list));
 350         df_conflict_list.next = &df_conflict_list;
 351         memset(&state, 0, sizeof(state));
 352         state.base_dir = "";
 353         state.force = 1;
 354         state.quiet = 1;
 355         state.refresh_cache = 1;
 356
 357         o->merge_size = len;
 358
 359         if (!dfc)
 360                 dfc = xcalloc(1, sizeof(struct cache_entry) + 1);
 361         o->df_conflict_entry = dfc;
 362
 363         if (len) {
 364                 posns = xmalloc(len * sizeof(struct tree_entry_list *));
 365                 for (i = 0; i < len; i++) {
 366                         posns[i] = create_tree_entry_list((struct tree *) posn->item);
 367                         posn = posn->next;
 368                 }
 369                 if (unpack_trees_rec(posns, len, o->prefix ? o->prefix : "",
 370                                      o, &df_conflict_list))
 371                         return -1;
 372         }
 373
 374         if (o->trivial_merges_only && o->nontrivial_merge)
 375                 die("Merge requires file-level merging");
 376
 377         check_updates(active_cache, active_nr, o);
 378         return 0;
 379 }
 380
 381 /* Here come the merge functions */
 382
 383 static void reject_merge(struct cache_entry *ce)
 384 {
 385         die("Entry '%s' would be overwritten by merge. Cannot merge.",
 386             ce->name);
 387 }
 388
 389 static int same(struct cache_entry *a, struct cache_entry *b)
 390 {
 391         if (!!a != !!b)
 392                 return 0;
 393         if (!a && !b)
 394                 return 1;
 395         return a->ce_mode == b->ce_mode &&
 396                !hashcmp(a->sha1, b->sha1);
 397 }
 398
 399
 400 /*
 401  * When a CE gets turned into an unmerged entry, we
 402  * want it to be up-to-date
 403  */
 404 static void verify_uptodate(struct cache_entry *ce,
 405                 struct unpack_trees_options *o)
 406 {
 407         struct stat st;
 408
 409         if (o->index_only || o->reset)
 410                 return;
 411
 412         if (!lstat(ce->name, &st)) {
 413                 unsigned changed = ce_match_stat(ce, &st, 1);
 414                 if (!changed)
 415                         return;
 416                 errno = 0;
 417         }
 418         if (errno == ENOENT)
 419                 return;
 420         die("Entry '%s' not uptodate. Cannot merge.", ce->name);
 421 }
 422
 423 static void invalidate_ce_path(struct cache_entry *ce)
 424 {
 425         if (ce)
 426                 cache_tree_invalidate_path(active_cache_tree, ce->name);
 427 }
 428
 429 /*
 430  * Check that checking out ce->sha1 in subdir ce->name is not
 431  * going to overwrite any working files.
 432  *
 433  * Currently, git does not checkout subprojects during a superproject
 434  * checkout, so it is not going to overwrite anything.
 435  */
 436 static int verify_clean_submodule(struct cache_entry *ce, const char *action,
 437                                       struct unpack_trees_options *o)
 438 {
 439         return 0;
 440 }
 441
 442 static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
 443                                       struct unpack_trees_options *o)
 444 {
 445         /*
 446          * we are about to extract "ce->name"; we would not want to lose
 447          * anything in the existing directory there.
 448          */
 449         int namelen;
 450         int pos, i;
 451         struct dir_struct d;
 452         char *pathbuf;
 453         int cnt = 0;
 454         unsigned char sha1[20];
 455
 456         if (S_ISGITLINK(ntohl(ce->ce_mode)) &&
 457             resolve_gitlink_ref(ce->name, "HEAD", sha1) == 0) {
 458                 /* If we are not going to update the submodule, then
 459                  * we don't care.
 460                  */
 461                 if (!hashcmp(sha1, ce->sha1))
 462                         return 0;
 463                 return verify_clean_submodule(ce, action, o);
 464         }
 465
 466         /*
 467          * First let's make sure we do not have a local modification
 468          * in that directory.
 469          */
 470         namelen = strlen(ce->name);
 471         pos = cache_name_pos(ce->name, namelen);
 472         if (0 <= pos)
 473                 return cnt; /* we have it as nondirectory */
 474         pos = -pos - 1;
 475         for (i = pos; i < active_nr; i++) {
 476                 struct cache_entry *ce = active_cache[i];
 477                 int len = ce_namelen(ce);
 478                 if (len < namelen ||
 479                     strncmp(ce->name, ce->name, namelen) ||
 480                     ce->name[namelen] != '/')
 481                         break;
 482                 /*
 483                  * ce->name is an entry in the subdirectory.
 484                  */
 485                 if (!ce_stage(ce)) {
 486                         verify_uptodate(ce, o);
 487                         ce->ce_mode = 0;
 488                 }
 489                 cnt++;
 490         }
 491
 492         /*
 493          * Then we need to make sure that we do not lose a locally
 494          * present file that is not ignored.
 495          */
 496         pathbuf = xmalloc(namelen + 2);
 497         memcpy(pathbuf, ce->name, namelen);
 498         strcpy(pathbuf+namelen, "/");
 499
 500         memset(&d, 0, sizeof(d));
 501         if (o->dir)
 502                 d.exclude_per_dir = o->dir->exclude_per_dir;
 503         i = read_directory(&d, ce->name, pathbuf, namelen+1, NULL);
 504         if (i)
 505                 die("Updating '%s' would lose untracked files in it",
 506                     ce->name);
 507         free(pathbuf);
 508         return cnt;
 509 }
 510
 511 /*
 512  * We do not want to remove or overwrite a working tree file that
 513  * is not tracked, unless it is ignored.
 514  */
 515 static void verify_absent(struct cache_entry *ce, const char *action,
 516                 struct unpack_trees_options *o)
 517 {
 518         struct stat st;
 519
 520         if (o->index_only || o->reset || !o->update)
 521                 return;
 522
 523         if (has_symlink_leading_path(ce->name, NULL))
 524                 return;
 525
 526         if (!lstat(ce->name, &st)) {
 527                 int cnt;
 528
 529                 if (o->dir && excluded(o->dir, ce->name))
 530                         /*
 531                          * ce->name is explicitly excluded, so it is Ok to
 532                          * overwrite it.
 533                          */
 534                         return;
 535                 if (S_ISDIR(st.st_mode)) {
 536                         /*
 537                          * We are checking out path "foo" and
 538                          * found "foo/." in the working tree.
 539                          * This is tricky -- if we have modified
 540                          * files that are in "foo/" we would lose
 541                          * it.
 542                          */
 543                         cnt = verify_clean_subdirectory(ce, action, o);
 544
 545                         /*
 546                          * If this removed entries from the index,
 547                          * what that means is:
 548                          *
 549                          * (1) the caller unpack_trees_rec() saw path/foo
 550                          * in the index, and it has not removed it because
 551                          * it thinks it is handling 'path' as blob with
 552                          * D/F conflict;
 553                          * (2) we will return "ok, we placed a merged entry
 554                          * in the index" which would cause o->pos to be
 555                          * incremented by one;
 556                          * (3) however, original o->pos now has 'path/foo'
 557                          * marked with "to be removed".
 558                          *
 559                          * We need to increment it by the number of
 560                          * deleted entries here.
 561                          */
 562                         o->pos += cnt;
 563                         return;
 564                 }
 565
 566                 /*
 567                  * The previous round may already have decided to
 568                  * delete this path, which is in a subdirectory that
 569                  * is being replaced with a blob.
 570                  */
 571                 cnt = cache_name_pos(ce->name, strlen(ce->name));
 572                 if (0 <= cnt) {
 573                         struct cache_entry *ce = active_cache[cnt];
 574                         if (!ce_stage(ce) && !ce->ce_mode)
 575                                 return;
 576                 }
 577
 578                 die("Untracked working tree file '%s' "
 579                     "would be %s by merge.", ce->name, action);
 580         }
 581 }
 582
 583 static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
 584                 struct unpack_trees_options *o)
 585 {
 586         merge->ce_flags |= htons(CE_UPDATE);
 587         if (old) {
 588                 /*
 589                  * See if we can re-use the old CE directly?
 590                  * That way we get the uptodate stat info.
 591                  *
 592                  * This also removes the UPDATE flag on
 593                  * a match.
 594                  */
 595                 if (same(old, merge)) {
 596                         *merge = *old;
 597                 } else {
 598                         verify_uptodate(old, o);
 599                         invalidate_ce_path(old);
 600                 }
 601         }
 602         else {
 603                 verify_absent(merge, "overwritten", o);
 604                 invalidate_ce_path(merge);
 605         }
 606
 607         merge->ce_flags &= ~htons(CE_STAGEMASK);
 608         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 609         return 1;
 610 }
 611
 612 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
 613                 struct unpack_trees_options *o)
 614 {
 615         if (old)
 616                 verify_uptodate(old, o);
 617         else
 618                 verify_absent(ce, "removed", o);
 619         ce->ce_mode = 0;
 620         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 621         invalidate_ce_path(ce);
 622         return 1;
 623 }
 624
 625 static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 626 {
 627         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 628         return 1;
 629 }
 630
 631 #if DBRT_DEBUG
 632 static void show_stage_entry(FILE *o,
 633                              const char *label, const struct cache_entry *ce)
 634 {
 635         if (!ce)
 636                 fprintf(o, "%s (missing)\n", label);
 637         else
 638                 fprintf(o, "%s%06o %s %d\t%s\n",
 639                         label,
 640                         ntohl(ce->ce_mode),
 641                         sha1_to_hex(ce->sha1),
 642                         ce_stage(ce),
 643                         ce->name);
 644 }
 645 #endif
 646
 647 int threeway_merge(struct cache_entry **stages,
 648                 struct unpack_trees_options *o)
 649 {
 650         struct cache_entry *index;
 651         struct cache_entry *head;
 652         struct cache_entry *remote = stages[o->head_idx + 1];
 653         int count;
 654         int head_match = 0;
 655         int remote_match = 0;
 656
 657         int df_conflict_head = 0;
 658         int df_conflict_remote = 0;
 659
 660         int any_anc_missing = 0;
 661         int no_anc_exists = 1;
 662         int i;
 663
 664         for (i = 1; i < o->head_idx; i++) {
 665                 if (!stages[i] || stages[i] == o->df_conflict_entry)
 666                         any_anc_missing = 1;
 667                 else
 668                         no_anc_exists = 0;
 669         }
 670
 671         index = stages[0];
 672         head = stages[o->head_idx];
 673
 674         if (head == o->df_conflict_entry) {
 675                 df_conflict_head = 1;
 676                 head = NULL;
 677         }
 678
 679         if (remote == o->df_conflict_entry) {
 680                 df_conflict_remote = 1;
 681                 remote = NULL;
 682         }
 683
 684         /* First, if there's a #16 situation, note that to prevent #13
 685          * and #14.
 686          */
 687         if (!same(remote, head)) {
 688                 for (i = 1; i < o->head_idx; i++) {
 689                         if (same(stages[i], head)) {
 690                                 head_match = i;
 691                         }
 692                         if (same(stages[i], remote)) {
 693                                 remote_match = i;
 694                         }
 695                 }
 696         }
 697
 698         /* We start with cases where the index is allowed to match
 699          * something other than the head: #14(ALT) and #2ALT, where it
 700          * is permitted to match the result instead.
 701          */
 702         /* #14, #14ALT, #2ALT */
 703         if (remote && !df_conflict_head && head_match && !remote_match) {
 704                 if (index && !same(index, remote) && !same(index, head))
 705                         reject_merge(index);
 706                 return merged_entry(remote, index, o);
 707         }
 708         /*
 709          * If we have an entry in the index cache, then we want to
 710          * make sure that it matches head.
 711          */
 712         if (index && !same(index, head)) {
 713                 reject_merge(index);
 714         }
 715
 716         if (head) {
 717                 /* #5ALT, #15 */
 718                 if (same(head, remote))
 719                         return merged_entry(head, index, o);
 720                 /* #13, #3ALT */
 721                 if (!df_conflict_remote && remote_match && !head_match)
 722                         return merged_entry(head, index, o);
 723         }
 724
 725         /* #1 */
 726         if (!head && !remote && any_anc_missing)
 727                 return 0;
 728
 729         /* Under the new "aggressive" rule, we resolve mostly trivial
 730          * cases that we historically had git-merge-one-file resolve.
 731          */
 732         if (o->aggressive) {
 733                 int head_deleted = !head && !df_conflict_head;
 734                 int remote_deleted = !remote && !df_conflict_remote;
 735                 struct cache_entry *ce = NULL;
 736
 737                 if (index)
 738                         ce = index;
 739                 else if (head)
 740                         ce = head;
 741                 else if (remote)
 742                         ce = remote;
 743                 else {
 744                         for (i = 1; i < o->head_idx; i++) {
 745                                 if (stages[i] && stages[i] != o->df_conflict_entry) {
 746                                         ce = stages[i];
 747                                         break;
 748                                 }
 749                         }
 750                 }
 751
 752                 /*
 753                  * Deleted in both.
 754                  * Deleted in one and unchanged in the other.
 755                  */
 756                 if ((head_deleted && remote_deleted) ||
 757                     (head_deleted && remote && remote_match) ||
 758                     (remote_deleted && head && head_match)) {
 759                         if (index)
 760                                 return deleted_entry(index, index, o);
 761                         else if (ce && !head_deleted)
 762                                 verify_absent(ce, "removed", o);
 763                         return 0;
 764                 }
 765                 /*
 766                  * Added in both, identically.
 767                  */
 768                 if (no_anc_exists && head && remote && same(head, remote))
 769                         return merged_entry(head, index, o);
 770
 771         }
 772
 773         /* Below are "no merge" cases, which require that the index be
 774          * up-to-date to avoid the files getting overwritten with
 775          * conflict resolution files.
 776          */
 777         if (index) {
 778                 verify_uptodate(index, o);
 779         }
 780
 781         o->nontrivial_merge = 1;
 782
 783         /* #2, #3, #4, #6, #7, #9, #10, #11. */
 784         count = 0;
 785         if (!head_match || !remote_match) {
 786                 for (i = 1; i < o->head_idx; i++) {
 787                         if (stages[i] && stages[i] != o->df_conflict_entry) {
 788                                 keep_entry(stages[i], o);
 789                                 count++;
 790                                 break;
 791                         }
 792                 }
 793         }
 794 #if DBRT_DEBUG
 795         else {
 796                 fprintf(stderr, "read-tree: warning #16 detected\n");
 797                 show_stage_entry(stderr, "head   ", stages[head_match]);
 798                 show_stage_entry(stderr, "remote ", stages[remote_match]);
 799         }
 800 #endif
 801         if (head) { count += keep_entry(head, o); }
 802         if (remote) { count += keep_entry(remote, o); }
 803         return count;
 804 }
 805
 806 /*
 807  * Two-way merge.
 808  *
 809  * The rule is to "carry forward" what is in the index without losing
 810  * information across a "fast forward", favoring a successful merge
 811  * over a merge failure when it makes sense.  For details of the
 812  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 813  *
 814  */
 815 int twoway_merge(struct cache_entry **src,
 816                 struct unpack_trees_options *o)
 817 {
 818         struct cache_entry *current = src[0];
 819         struct cache_entry *oldtree = src[1];
 820         struct cache_entry *newtree = src[2];
 821
 822         if (o->merge_size != 2)
 823                 return error("Cannot do a twoway merge of %d trees",
 824                              o->merge_size);
 825
 826         if (oldtree == o->df_conflict_entry)
 827                 oldtree = NULL;
 828         if (newtree == o->df_conflict_entry)
 829                 newtree = NULL;
 830
 831         if (current) {
 832                 if ((!oldtree && !newtree) || /* 4 and 5 */
 833                     (!oldtree && newtree &&
 834                      same(current, newtree)) || /* 6 and 7 */
 835                     (oldtree && newtree &&
 836                      same(oldtree, newtree)) || /* 14 and 15 */
 837                     (oldtree && newtree &&
 838                      !same(oldtree, newtree) && /* 18 and 19 */
 839                      same(current, newtree))) {
 840                         return keep_entry(current, o);
 841                 }
 842                 else if (oldtree && !newtree && same(current, oldtree)) {
 843                         /* 10 or 11 */
 844                         return deleted_entry(oldtree, current, o);
 845                 }
 846                 else if (oldtree && newtree &&
 847                          same(current, oldtree) && !same(current, newtree)) {
 848                         /* 20 or 21 */
 849                         return merged_entry(newtree, current, o);
 850                 }
 851                 else {
 852                         /* all other failures */
 853                         if (oldtree)
 854                                 reject_merge(oldtree);
 855                         if (current)
 856                                 reject_merge(current);
 857                         if (newtree)
 858                                 reject_merge(newtree);
 859                         return -1;
 860                 }
 861         }
 862         else if (newtree)
 863                 return merged_entry(newtree, current, o);
 864         else
 865                 return deleted_entry(oldtree, current, o);
 866 }
 867
 868 /*
 869  * Bind merge.
 870  *
 871  * Keep the index entries at stage0, collapse stage1 but make sure
 872  * stage0 does not have anything there.
 873  */
 874 int bind_merge(struct cache_entry **src,
 875                 struct unpack_trees_options *o)
 876 {
 877         struct cache_entry *old = src[0];
 878         struct cache_entry *a = src[1];
 879
 880         if (o->merge_size != 1)
 881                 return error("Cannot do a bind merge of %d trees\n",
 882                              o->merge_size);
 883         if (a && old)
 884                 die("Entry '%s' overlaps.  Cannot bind.", a->name);
 885         if (!a)
 886                 return keep_entry(old, o);
 887         else
 888                 return merged_entry(a, NULL, o);
 889 }
 890
 891 /*
 892  * One-way merge.
 893  *
 894  * The rule is:
 895  * - take the stat information from stage0, take the data from stage1
 896  */
 897 int oneway_merge(struct cache_entry **src,
 898                 struct unpack_trees_options *o)
 899 {
 900         struct cache_entry *old = src[0];
 901         struct cache_entry *a = src[1];
 902
 903         if (o->merge_size != 1)
 904                 return error("Cannot do a oneway merge of %d trees",
 905                              o->merge_size);
 906
 907         if (!a)
 908                 return deleted_entry(old, old, o);
 909         if (old && same(old, a)) {
 910                 if (o->reset) {
 911                         struct stat st;
 912                         if (lstat(old->name, &st) ||
 913                             ce_match_stat(old, &st, 1))
 914                                 old->ce_flags |= htons(CE_UPDATE);
 915                 }
 916                 return keep_entry(old, o);
 917         }
 918         return merged_entry(a, old, o);
 919 }