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