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