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 static inline void remove_entry(int remove)
  11 {
  12         if (remove >= 0)
  13                 remove_cache_entry_at(remove);
  14 }
  15
  16 /* Unlink the last component and attempt to remove leading
  17  * directories, in case this unlink is the removal of the
  18  * last entry in the directory -- empty directories are removed.
  19  */
  20 static void unlink_entry(char *name, char *last_symlink)
  21 {
  22         char *cp, *prev;
  23
  24         if (has_symlink_leading_path(name, last_symlink))
  25                 return;
  26         if (unlink(name))
  27                 return;
  28         prev = NULL;
  29         while (1) {
  30                 int status;
  31                 cp = strrchr(name, '/');
  32                 if (prev)
  33                         *prev = '/';
  34                 if (!cp)
  35                         break;
  36
  37                 *cp = 0;
  38                 status = rmdir(name);
  39                 if (status) {
  40                         *cp = '/';
  41                         break;
  42                 }
  43                 prev = cp;
  44         }
  45 }
  46
  47 static struct checkout state;
  48 static void check_updates(struct unpack_trees_options *o)
  49 {
  50         unsigned cnt = 0, total = 0;
  51         struct progress *progress = NULL;
  52         char last_symlink[PATH_MAX];
  53         int i;
  54
  55         if (o->update && o->verbose_update) {
  56                 for (total = cnt = 0; cnt < active_nr; cnt++) {
  57                         struct cache_entry *ce = active_cache[cnt];
  58                         if (ce->ce_flags & (CE_UPDATE | CE_REMOVE))
  59                                 total++;
  60                 }
  61
  62                 progress = start_progress_delay("Checking out files",
  63                                                 total, 50, 1);
  64                 cnt = 0;
  65         }
  66
  67         *last_symlink = '\0';
  68         for (i = 0; i < active_nr; i++) {
  69                 struct cache_entry *ce = active_cache[i];
  70
  71                 if (ce->ce_flags & (CE_UPDATE | CE_REMOVE))
  72                         display_progress(progress, ++cnt);
  73                 if (ce->ce_flags & CE_REMOVE) {
  74                         if (o->update)
  75                                 unlink_entry(ce->name, last_symlink);
  76                         remove_cache_entry_at(i);
  77                         i--;
  78                         continue;
  79                 }
  80                 if (ce->ce_flags & CE_UPDATE) {
  81                         ce->ce_flags &= ~CE_UPDATE;
  82                         if (o->update) {
  83                                 checkout_entry(ce, &state, NULL);
  84                                 *last_symlink = '\0';
  85                         }
  86                 }
  87         }
  88         stop_progress(&progress);
  89 }
  90
  91 static inline int call_unpack_fn(struct cache_entry **src, struct unpack_trees_options *o, int remove)
  92 {
  93         int ret = o->fn(src, o, remove);
  94         if (ret > 0) {
  95                 o->pos += ret;
  96                 ret = 0;
  97         }
  98         return ret;
  99 }
 100
 101 static int unpack_index_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 102 {
 103         struct cache_entry *src[5] = { ce, };
 104         if (ce_stage(ce)) {
 105                 if (o->skip_unmerged) {
 106                         o->pos++;
 107                 } else {
 108                         remove_entry(o->pos);
 109                 }
 110                 return 0;
 111         }
 112         return call_unpack_fn(src, o, o->pos);
 113 }
 114
 115 int traverse_trees_recursive(int n, unsigned long dirmask, unsigned long df_conflicts, struct name_entry *names, struct traverse_info *info)
 116 {
 117         int i;
 118         struct tree_desc t[3];
 119         struct traverse_info newinfo;
 120         struct name_entry *p;
 121
 122         p = names;
 123         while (!p->mode)
 124                 p++;
 125
 126         newinfo = *info;
 127         newinfo.prev = info;
 128         newinfo.name = *p;
 129         newinfo.pathlen += tree_entry_len(p->path, p->sha1) + 1;
 130         newinfo.conflicts |= df_conflicts;
 131
 132         for (i = 0; i < n; i++, dirmask >>= 1) {
 133                 const unsigned char *sha1 = NULL;
 134                 if (dirmask & 1)
 135                         sha1 = names[i].sha1;
 136                 fill_tree_descriptor(t+i, sha1);
 137         }
 138         traverse_trees(n, t, &newinfo);
 139         return 0;
 140 }
 141
 142 /*
 143  * Compare the traverse-path to the cache entry without actually
 144  * having to generate the textual representation of the traverse
 145  * path.
 146  *
 147  * NOTE! This *only* compares up to the size of the traverse path
 148  * itself - the caller needs to do the final check for the cache
 149  * entry having more data at the end!
 150  */
 151 static int do_compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
 152 {
 153         int len, pathlen, ce_len;
 154         const char *ce_name;
 155
 156         if (info->prev) {
 157                 int cmp = do_compare_entry(ce, info->prev, &info->name);
 158                 if (cmp)
 159                         return cmp;
 160         }
 161         pathlen = info->pathlen;
 162         ce_len = ce_namelen(ce);
 163
 164         /* If ce_len < pathlen then we must have previously hit "name == directory" entry */
 165         if (ce_len < pathlen)
 166                 return -1;
 167
 168         ce_len -= pathlen;
 169         ce_name = ce->name + pathlen;
 170
 171         len = tree_entry_len(n->path, n->sha1);
 172         return df_name_compare(ce_name, ce_len, S_IFREG, n->path, len, n->mode);
 173 }
 174
 175 static int compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
 176 {
 177         int cmp = do_compare_entry(ce, info, n);
 178         if (cmp)
 179                 return cmp;
 180
 181         /*
 182          * Even if the beginning compared identically, the ce should
 183          * compare as bigger than a directory leading up to it!
 184          */
 185         return ce_namelen(ce) > traverse_path_len(info, n);
 186 }
 187
 188 static struct cache_entry *create_ce_entry(const struct traverse_info *info, const struct name_entry *n, int stage)
 189 {
 190         int len = traverse_path_len(info, n);
 191         struct cache_entry *ce = xcalloc(1, cache_entry_size(len));
 192
 193         ce->ce_mode = create_ce_mode(n->mode);
 194         ce->ce_flags = create_ce_flags(len, stage);
 195         hashcpy(ce->sha1, n->sha1);
 196         make_traverse_path(ce->name, info, n);
 197
 198         return ce;
 199 }
 200
 201 static int unpack_nondirectories(int n, unsigned long mask, unsigned long dirmask, struct cache_entry *src[5],
 202         const struct name_entry *names, const struct traverse_info *info, int remove)
 203 {
 204         int i;
 205         struct unpack_trees_options *o = info->data;
 206         unsigned long conflicts;
 207
 208         /* Do we have *only* directories? Nothing to do */
 209         if (mask == dirmask && !src[0])
 210                 return 0;
 211
 212         conflicts = info->conflicts;
 213         if (o->merge)
 214                 conflicts >>= 1;
 215         conflicts |= dirmask;
 216
 217         /*
 218          * Ok, we've filled in up to any potential index entry in src[0],
 219          * now do the rest.
 220          */
 221         for (i = 0; i < n; i++) {
 222                 int stage;
 223                 unsigned int bit = 1ul << i;
 224                 if (conflicts & bit) {
 225                         src[i + o->merge] = o->df_conflict_entry;
 226                         continue;
 227                 }
 228                 if (!(mask & bit))
 229                         continue;
 230                 if (!o->merge)
 231                         stage = 0;
 232                 else if (i + 1 < o->head_idx)
 233                         stage = 1;
 234                 else if (i + 1 > o->head_idx)
 235                         stage = 3;
 236                 else
 237                         stage = 2;
 238                 src[i + o->merge] = create_ce_entry(info, names + i, stage);
 239         }
 240
 241         if (o->merge)
 242                 return call_unpack_fn(src, o, remove);
 243
 244         n += o->merge;
 245         remove_entry(remove);
 246         for (i = 0; i < n; i++)
 247                 add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
 248         return 0;
 249 }
 250
 251 static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *names, struct traverse_info *info)
 252 {
 253         struct cache_entry *src[5] = { NULL, };
 254         struct unpack_trees_options *o = info->data;
 255         int remove = -1;
 256         const struct name_entry *p = names;
 257
 258         /* Find first entry with a real name (we could use "mask" too) */
 259         while (!p->mode)
 260                 p++;
 261
 262         /* Are we supposed to look at the index too? */
 263         if (o->merge) {
 264                 while (o->pos < active_nr) {
 265                         struct cache_entry *ce = active_cache[o->pos];
 266                         int cmp = compare_entry(ce, info, p);
 267                         if (cmp < 0) {
 268                                 if (unpack_index_entry(ce, o) < 0)
 269                                         return -1;
 270                                 continue;
 271                         }
 272                         if (!cmp) {
 273                                 if (ce_stage(ce)) {
 274                                         /*
 275                                          * If we skip unmerged index entries, we'll skip this
 276                                          * entry *and* the tree entries associated with it!
 277                                          */
 278                                         if (o->skip_unmerged)
 279                                                 return mask;
 280                                         remove_entry(o->pos);
 281                                         continue;
 282                                 }
 283                                 src[0] = ce;
 284                                 remove = o->pos;
 285                         }
 286                         break;
 287                 }
 288         }
 289
 290         if (unpack_nondirectories(n, mask, dirmask, src, names, info, remove) < 0)
 291                 return -1;
 292
 293         /* Now handle any directories.. */
 294         if (dirmask) {
 295                 unsigned long conflicts = mask & ~dirmask;
 296                 if (o->merge) {
 297                         conflicts <<= 1;
 298                         if (src[0])
 299                                 conflicts |= 1;
 300                 }
 301                 traverse_trees_recursive(n, dirmask, conflicts, names, info);
 302                 return mask;
 303         }
 304
 305         return mask;
 306 }
 307
 308 static int unpack_failed(struct unpack_trees_options *o, const char *message)
 309 {
 310         if (!o->gently) {
 311                 if (message)
 312                         return error(message);
 313                 return -1;
 314         }
 315         discard_cache();
 316         read_cache();
 317         return -1;
 318 }
 319
 320 int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
 321 {
 322         static struct cache_entry *dfc;
 323
 324         if (len > 4)
 325                 die("unpack_trees takes at most four trees");
 326         memset(&state, 0, sizeof(state));
 327         state.base_dir = "";
 328         state.force = 1;
 329         state.quiet = 1;
 330         state.refresh_cache = 1;
 331
 332         o->merge_size = len;
 333
 334         if (!dfc)
 335                 dfc = xcalloc(1, sizeof(struct cache_entry) + 1);
 336         o->df_conflict_entry = dfc;
 337
 338         if (len) {
 339                 const char *prefix = o->prefix ? o->prefix : "";
 340                 struct traverse_info info;
 341
 342                 setup_traverse_info(&info, prefix);
 343                 info.fn = unpack_callback;
 344                 info.data = o;
 345
 346                 if (traverse_trees(len, t, &info) < 0)
 347                         return unpack_failed(o, NULL);
 348         }
 349
 350         /* Any left-over entries in the index? */
 351         if (o->merge) {
 352                 while (o->pos < active_nr) {
 353                         struct cache_entry *ce = active_cache[o->pos];
 354                         if (unpack_index_entry(ce, o) < 0)
 355                                 return unpack_failed(o, NULL);
 356                 }
 357         }
 358
 359         if (o->trivial_merges_only && o->nontrivial_merge)
 360                 return unpack_failed(o, "Merge requires file-level merging");
 361
 362         check_updates(o);
 363         return 0;
 364 }
 365
 366 /* Here come the merge functions */
 367
 368 static int reject_merge(struct cache_entry *ce)
 369 {
 370         return error("Entry '%s' would be overwritten by merge. Cannot merge.",
 371                      ce->name);
 372 }
 373
 374 static int same(struct cache_entry *a, struct cache_entry *b)
 375 {
 376         if (!!a != !!b)
 377                 return 0;
 378         if (!a && !b)
 379                 return 1;
 380         return a->ce_mode == b->ce_mode &&
 381                !hashcmp(a->sha1, b->sha1);
 382 }
 383
 384
 385 /*
 386  * When a CE gets turned into an unmerged entry, we
 387  * want it to be up-to-date
 388  */
 389 static int verify_uptodate(struct cache_entry *ce,
 390                 struct unpack_trees_options *o)
 391 {
 392         struct stat st;
 393
 394         if (o->index_only || o->reset)
 395                 return 0;
 396
 397         if (!lstat(ce->name, &st)) {
 398                 unsigned changed = ce_match_stat(ce, &st, CE_MATCH_IGNORE_VALID);
 399                 if (!changed)
 400                         return 0;
 401                 /*
 402                  * NEEDSWORK: the current default policy is to allow
 403                  * submodule to be out of sync wrt the supermodule
 404                  * index.  This needs to be tightened later for
 405                  * submodules that are marked to be automatically
 406                  * checked out.
 407                  */
 408                 if (S_ISGITLINK(ce->ce_mode))
 409                         return 0;
 410                 errno = 0;
 411         }
 412         if (errno == ENOENT)
 413                 return 0;
 414         return o->gently ? -1 :
 415                 error("Entry '%s' not uptodate. Cannot merge.", ce->name);
 416 }
 417
 418 static void invalidate_ce_path(struct cache_entry *ce)
 419 {
 420         if (ce)
 421                 cache_tree_invalidate_path(active_cache_tree, ce->name);
 422 }
 423
 424 /*
 425  * Check that checking out ce->sha1 in subdir ce->name is not
 426  * going to overwrite any working files.
 427  *
 428  * Currently, git does not checkout subprojects during a superproject
 429  * checkout, so it is not going to overwrite anything.
 430  */
 431 static int verify_clean_submodule(struct cache_entry *ce, const char *action,
 432                                       struct unpack_trees_options *o)
 433 {
 434         return 0;
 435 }
 436
 437 static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
 438                                       struct unpack_trees_options *o)
 439 {
 440         /*
 441          * we are about to extract "ce->name"; we would not want to lose
 442          * anything in the existing directory there.
 443          */
 444         int namelen;
 445         int pos, i;
 446         struct dir_struct d;
 447         char *pathbuf;
 448         int cnt = 0;
 449         unsigned char sha1[20];
 450
 451         if (S_ISGITLINK(ce->ce_mode) &&
 452             resolve_gitlink_ref(ce->name, "HEAD", sha1) == 0) {
 453                 /* If we are not going to update the submodule, then
 454                  * we don't care.
 455                  */
 456                 if (!hashcmp(sha1, ce->sha1))
 457                         return 0;
 458                 return verify_clean_submodule(ce, action, o);
 459         }
 460
 461         /*
 462          * First let's make sure we do not have a local modification
 463          * in that directory.
 464          */
 465         namelen = strlen(ce->name);
 466         pos = cache_name_pos(ce->name, namelen);
 467         if (0 <= pos)
 468                 return cnt; /* we have it as nondirectory */
 469         pos = -pos - 1;
 470         for (i = pos; i < active_nr; i++) {
 471                 struct cache_entry *ce = active_cache[i];
 472                 int len = ce_namelen(ce);
 473                 if (len < namelen ||
 474                     strncmp(ce->name, ce->name, namelen) ||
 475                     ce->name[namelen] != '/')
 476                         break;
 477                 /*
 478                  * ce->name is an entry in the subdirectory.
 479                  */
 480                 if (!ce_stage(ce)) {
 481                         if (verify_uptodate(ce, o))
 482                                 return -1;
 483                         ce->ce_flags |= CE_REMOVE;
 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                 return o->gently ? -1 :
 502                         error("Updating '%s' would lose untracked files in it",
 503                               ce->name);
 504         free(pathbuf);
 505         return cnt;
 506 }
 507
 508 /*
 509  * We do not want to remove or overwrite a working tree file that
 510  * is not tracked, unless it is ignored.
 511  */
 512 static int verify_absent(struct cache_entry *ce, const char *action,
 513                          struct unpack_trees_options *o)
 514 {
 515         struct stat st;
 516
 517         if (o->index_only || o->reset || !o->update)
 518                 return 0;
 519
 520         if (has_symlink_leading_path(ce->name, NULL))
 521                 return 0;
 522
 523         if (!lstat(ce->name, &st)) {
 524                 int cnt;
 525                 int dtype = ce_to_dtype(ce);
 526
 527                 if (o->dir && excluded(o->dir, ce->name, &dtype))
 528                         /*
 529                          * ce->name is explicitly excluded, so it is Ok to
 530                          * overwrite it.
 531                          */
 532                         return 0;
 533                 if (S_ISDIR(st.st_mode)) {
 534                         /*
 535                          * We are checking out path "foo" and
 536                          * found "foo/." in the working tree.
 537                          * This is tricky -- if we have modified
 538                          * files that are in "foo/" we would lose
 539                          * it.
 540                          */
 541                         cnt = verify_clean_subdirectory(ce, action, o);
 542
 543                         /*
 544                          * If this removed entries from the index,
 545                          * what that means is:
 546                          *
 547                          * (1) the caller unpack_trees_rec() saw path/foo
 548                          * in the index, and it has not removed it because
 549                          * it thinks it is handling 'path' as blob with
 550                          * D/F conflict;
 551                          * (2) we will return "ok, we placed a merged entry
 552                          * in the index" which would cause o->pos to be
 553                          * incremented by one;
 554                          * (3) however, original o->pos now has 'path/foo'
 555                          * marked with "to be removed".
 556                          *
 557                          * We need to increment it by the number of
 558                          * deleted entries here.
 559                          */
 560                         o->pos += cnt;
 561                         return 0;
 562                 }
 563
 564                 /*
 565                  * The previous round may already have decided to
 566                  * delete this path, which is in a subdirectory that
 567                  * is being replaced with a blob.
 568                  */
 569                 cnt = cache_name_pos(ce->name, strlen(ce->name));
 570                 if (0 <= cnt) {
 571                         struct cache_entry *ce = active_cache[cnt];
 572                         if (ce->ce_flags & CE_REMOVE)
 573                                 return 0;
 574                 }
 575
 576                 return o->gently ? -1 :
 577                         error("Untracked working tree file '%s' "
 578                               "would be %s by merge.", ce->name, action);
 579         }
 580         return 0;
 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 |= 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                         copy_cache_entry(merge, old);
 597                 } else {
 598                         if (verify_uptodate(old, o))
 599                                 return -1;
 600                         invalidate_ce_path(old);
 601                 }
 602         }
 603         else {
 604                 if (verify_absent(merge, "overwritten", o))
 605                         return -1;
 606                 invalidate_ce_path(merge);
 607         }
 608
 609         merge->ce_flags &= ~CE_STAGEMASK;
 610         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 611         return 1;
 612 }
 613
 614 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
 615                 struct unpack_trees_options *o)
 616 {
 617         if (old) {
 618                 if (verify_uptodate(old, o))
 619                         return -1;
 620         } else
 621                 if (verify_absent(ce, "removed", o))
 622                         return -1;
 623         ce->ce_flags |= CE_REMOVE;
 624         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 625         invalidate_ce_path(ce);
 626         return 1;
 627 }
 628
 629 static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 630 {
 631         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 632         return 1;
 633 }
 634
 635 #if DBRT_DEBUG
 636 static void show_stage_entry(FILE *o,
 637                              const char *label, const struct cache_entry *ce)
 638 {
 639         if (!ce)
 640                 fprintf(o, "%s (missing)\n", label);
 641         else
 642                 fprintf(o, "%s%06o %s %d\t%s\n",
 643                         label,
 644                         ce->ce_mode,
 645                         sha1_to_hex(ce->sha1),
 646                         ce_stage(ce),
 647                         ce->name);
 648 }
 649 #endif
 650
 651 int threeway_merge(struct cache_entry **stages,
 652                 struct unpack_trees_options *o,
 653                 int remove)
 654 {
 655         struct cache_entry *index;
 656         struct cache_entry *head;
 657         struct cache_entry *remote = stages[o->head_idx + 1];
 658         int count;
 659         int head_match = 0;
 660         int remote_match = 0;
 661
 662         int df_conflict_head = 0;
 663         int df_conflict_remote = 0;
 664
 665         int any_anc_missing = 0;
 666         int no_anc_exists = 1;
 667         int i;
 668
 669         for (i = 1; i < o->head_idx; i++) {
 670                 if (!stages[i] || stages[i] == o->df_conflict_entry)
 671                         any_anc_missing = 1;
 672                 else
 673                         no_anc_exists = 0;
 674         }
 675
 676         index = stages[0];
 677         head = stages[o->head_idx];
 678
 679         if (head == o->df_conflict_entry) {
 680                 df_conflict_head = 1;
 681                 head = NULL;
 682         }
 683
 684         if (remote == o->df_conflict_entry) {
 685                 df_conflict_remote = 1;
 686                 remote = NULL;
 687         }
 688
 689         /* First, if there's a #16 situation, note that to prevent #13
 690          * and #14.
 691          */
 692         if (!same(remote, head)) {
 693                 for (i = 1; i < o->head_idx; i++) {
 694                         if (same(stages[i], head)) {
 695                                 head_match = i;
 696                         }
 697                         if (same(stages[i], remote)) {
 698                                 remote_match = i;
 699                         }
 700                 }
 701         }
 702
 703         /* We start with cases where the index is allowed to match
 704          * something other than the head: #14(ALT) and #2ALT, where it
 705          * is permitted to match the result instead.
 706          */
 707         /* #14, #14ALT, #2ALT */
 708         if (remote && !df_conflict_head && head_match && !remote_match) {
 709                 if (index && !same(index, remote) && !same(index, head))
 710                         return o->gently ? -1 : reject_merge(index);
 711                 return merged_entry(remote, index, o);
 712         }
 713         /*
 714          * If we have an entry in the index cache, then we want to
 715          * make sure that it matches head.
 716          */
 717         if (index && !same(index, head))
 718                 return o->gently ? -1 : reject_merge(index);
 719
 720         if (head) {
 721                 /* #5ALT, #15 */
 722                 if (same(head, remote))
 723                         return merged_entry(head, index, o);
 724                 /* #13, #3ALT */
 725                 if (!df_conflict_remote && remote_match && !head_match)
 726                         return merged_entry(head, index, o);
 727         }
 728
 729         /* #1 */
 730         if (!head && !remote && any_anc_missing) {
 731                 remove_entry(remove);
 732                 return 0;
 733         }
 734
 735         /* Under the new "aggressive" rule, we resolve mostly trivial
 736          * cases that we historically had git-merge-one-file resolve.
 737          */
 738         if (o->aggressive) {
 739                 int head_deleted = !head && !df_conflict_head;
 740                 int remote_deleted = !remote && !df_conflict_remote;
 741                 struct cache_entry *ce = NULL;
 742
 743                 if (index)
 744                         ce = index;
 745                 else if (head)
 746                         ce = head;
 747                 else if (remote)
 748                         ce = remote;
 749                 else {
 750                         for (i = 1; i < o->head_idx; i++) {
 751                                 if (stages[i] && stages[i] != o->df_conflict_entry) {
 752                                         ce = stages[i];
 753                                         break;
 754                                 }
 755                         }
 756                 }
 757
 758                 /*
 759                  * Deleted in both.
 760                  * Deleted in one and unchanged in the other.
 761                  */
 762                 if ((head_deleted && remote_deleted) ||
 763                     (head_deleted && remote && remote_match) ||
 764                     (remote_deleted && head && head_match)) {
 765                         remove_entry(remove);
 766                         if (index)
 767                                 return deleted_entry(index, index, o);
 768                         else if (ce && !head_deleted) {
 769                                 if (verify_absent(ce, "removed", o))
 770                                         return -1;
 771                         }
 772                         return 0;
 773                 }
 774                 /*
 775                  * Added in both, identically.
 776                  */
 777                 if (no_anc_exists && head && remote && same(head, remote))
 778                         return merged_entry(head, index, o);
 779
 780         }
 781
 782         /* Below are "no merge" cases, which require that the index be
 783          * up-to-date to avoid the files getting overwritten with
 784          * conflict resolution files.
 785          */
 786         if (index) {
 787                 if (verify_uptodate(index, o))
 788                         return -1;
 789         }
 790
 791         remove_entry(remove);
 792         o->nontrivial_merge = 1;
 793
 794         /* #2, #3, #4, #6, #7, #9, #10, #11. */
 795         count = 0;
 796         if (!head_match || !remote_match) {
 797                 for (i = 1; i < o->head_idx; i++) {
 798                         if (stages[i] && stages[i] != o->df_conflict_entry) {
 799                                 keep_entry(stages[i], o);
 800                                 count++;
 801                                 break;
 802                         }
 803                 }
 804         }
 805 #if DBRT_DEBUG
 806         else {
 807                 fprintf(stderr, "read-tree: warning #16 detected\n");
 808                 show_stage_entry(stderr, "head   ", stages[head_match]);
 809                 show_stage_entry(stderr, "remote ", stages[remote_match]);
 810         }
 811 #endif
 812         if (head) { count += keep_entry(head, o); }
 813         if (remote) { count += keep_entry(remote, o); }
 814         return count;
 815 }
 816
 817 /*
 818  * Two-way merge.
 819  *
 820  * The rule is to "carry forward" what is in the index without losing
 821  * information across a "fast forward", favoring a successful merge
 822  * over a merge failure when it makes sense.  For details of the
 823  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 824  *
 825  */
 826 int twoway_merge(struct cache_entry **src,
 827                 struct unpack_trees_options *o,
 828                 int remove)
 829 {
 830         struct cache_entry *current = src[0];
 831         struct cache_entry *oldtree = src[1];
 832         struct cache_entry *newtree = src[2];
 833
 834         if (o->merge_size != 2)
 835                 return error("Cannot do a twoway merge of %d trees",
 836                              o->merge_size);
 837
 838         if (oldtree == o->df_conflict_entry)
 839                 oldtree = NULL;
 840         if (newtree == o->df_conflict_entry)
 841                 newtree = NULL;
 842
 843         if (current) {
 844                 if ((!oldtree && !newtree) || /* 4 and 5 */
 845                     (!oldtree && newtree &&
 846                      same(current, newtree)) || /* 6 and 7 */
 847                     (oldtree && newtree &&
 848                      same(oldtree, newtree)) || /* 14 and 15 */
 849                     (oldtree && newtree &&
 850                      !same(oldtree, newtree) && /* 18 and 19 */
 851                      same(current, newtree))) {
 852                         return keep_entry(current, o);
 853                 }
 854                 else if (oldtree && !newtree && same(current, oldtree)) {
 855                         /* 10 or 11 */
 856                         remove_entry(remove);
 857                         return deleted_entry(oldtree, current, o);
 858                 }
 859                 else if (oldtree && newtree &&
 860                          same(current, oldtree) && !same(current, newtree)) {
 861                         /* 20 or 21 */
 862                         return merged_entry(newtree, current, o);
 863                 }
 864                 else {
 865                         /* all other failures */
 866                         remove_entry(remove);
 867                         if (oldtree)
 868                                 return o->gently ? -1 : reject_merge(oldtree);
 869                         if (current)
 870                                 return o->gently ? -1 : reject_merge(current);
 871                         if (newtree)
 872                                 return o->gently ? -1 : reject_merge(newtree);
 873                         return -1;
 874                 }
 875         }
 876         else if (newtree)
 877                 return merged_entry(newtree, current, o);
 878         remove_entry(remove);
 879         return deleted_entry(oldtree, current, o);
 880 }
 881
 882 /*
 883  * Bind merge.
 884  *
 885  * Keep the index entries at stage0, collapse stage1 but make sure
 886  * stage0 does not have anything there.
 887  */
 888 int bind_merge(struct cache_entry **src,
 889                 struct unpack_trees_options *o,
 890                 int remove)
 891 {
 892         struct cache_entry *old = src[0];
 893         struct cache_entry *a = src[1];
 894
 895         if (o->merge_size != 1)
 896                 return error("Cannot do a bind merge of %d trees\n",
 897                              o->merge_size);
 898         if (a && old)
 899                 return o->gently ? -1 :
 900                         error("Entry '%s' overlaps.  Cannot bind.", a->name);
 901         if (!a)
 902                 return keep_entry(old, o);
 903         else
 904                 return merged_entry(a, NULL, o);
 905 }
 906
 907 /*
 908  * One-way merge.
 909  *
 910  * The rule is:
 911  * - take the stat information from stage0, take the data from stage1
 912  */
 913 int oneway_merge(struct cache_entry **src,
 914                 struct unpack_trees_options *o,
 915                 int remove)
 916 {
 917         struct cache_entry *old = src[0];
 918         struct cache_entry *a = src[1];
 919
 920         if (o->merge_size != 1)
 921                 return error("Cannot do a oneway merge of %d trees",
 922                              o->merge_size);
 923
 924         if (!a) {
 925                 remove_entry(remove);
 926                 return deleted_entry(old, old, o);
 927         }
 928         if (old && same(old, a)) {
 929                 if (o->reset) {
 930                         struct stat st;
 931                         if (lstat(old->name, &st) ||
 932                             ce_match_stat(old, &st, CE_MATCH_IGNORE_VALID))
 933                                 old->ce_flags |= CE_UPDATE;
 934                 }
 935                 return keep_entry(old, o);
 936         }
 937         return merged_entry(a, old, o);
 938 }