unpack-trees.c

   1 #define NO_THE_INDEX_COMPATIBILITY_MACROS
   2 #include "cache.h"
   3 #include "dir.h"
   4 #include "tree.h"
   5 #include "tree-walk.h"
   6 #include "cache-tree.h"
   7 #include "unpack-trees.h"
   8 #include "progress.h"
   9 #include "refs.h"
  10
  11 static inline void remove_entry(int remove, struct unpack_trees_options *o)
  12 {
  13         if (remove >= 0)
  14                 remove_index_entry_at(o->index, remove);
  15 }
  16
  17 /* Unlink the last component and attempt to remove leading
  18  * directories, in case this unlink is the removal of the
  19  * last entry in the directory -- empty directories are removed.
  20  */
  21 static void unlink_entry(char *name, char *last_symlink)
  22 {
  23         char *cp, *prev;
  24
  25         if (has_symlink_leading_path(name, last_symlink))
  26                 return;
  27         if (unlink(name))
  28                 return;
  29         prev = NULL;
  30         while (1) {
  31                 int status;
  32                 cp = strrchr(name, '/');
  33                 if (prev)
  34                         *prev = '/';
  35                 if (!cp)
  36                         break;
  37
  38                 *cp = 0;
  39                 status = rmdir(name);
  40                 if (status) {
  41                         *cp = '/';
  42                         break;
  43                 }
  44                 prev = cp;
  45         }
  46 }
  47
  48 static struct checkout state;
  49 static void check_updates(struct unpack_trees_options *o)
  50 {
  51         unsigned cnt = 0, total = 0;
  52         struct progress *progress = NULL;
  53         char last_symlink[PATH_MAX];
  54         int i;
  55
  56         if (o->update && o->verbose_update) {
  57                 for (total = cnt = 0; cnt < o->index->cache_nr; cnt++) {
  58                         struct cache_entry *ce = o->index->cache[cnt];
  59                         if (ce->ce_flags & (CE_UPDATE | CE_REMOVE))
  60                                 total++;
  61                 }
  62
  63                 progress = start_progress_delay("Checking out files",
  64                                                 total, 50, 1);
  65                 cnt = 0;
  66         }
  67
  68         *last_symlink = '\0';
  69         for (i = 0; i < o->index->cache_nr; i++) {
  70                 struct cache_entry *ce = o->index->cache[i];
  71
  72                 if (ce->ce_flags & (CE_UPDATE | CE_REMOVE))
  73                         display_progress(progress, ++cnt);
  74                 if (ce->ce_flags & CE_REMOVE) {
  75                         if (o->update)
  76                                 unlink_entry(ce->name, last_symlink);
  77                         remove_index_entry_at(o->index, i);
  78                         i--;
  79                         continue;
  80                 }
  81                 if (ce->ce_flags & CE_UPDATE) {
  82                         ce->ce_flags &= ~CE_UPDATE;
  83                         if (o->update) {
  84                                 checkout_entry(ce, &state, NULL);
  85                                 *last_symlink = '\0';
  86                         }
  87                 }
  88         }
  89         stop_progress(&progress);
  90 }
  91
  92 static inline int call_unpack_fn(struct cache_entry **src, struct unpack_trees_options *o, int remove)
  93 {
  94         int ret = o->fn(src, o, remove);
  95         if (ret > 0) {
  96                 o->pos += ret;
  97                 ret = 0;
  98         }
  99         return ret;
 100 }
 101
 102 static int unpack_index_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 103 {
 104         struct cache_entry *src[5] = { ce, };
 105         if (ce_stage(ce)) {
 106                 if (o->skip_unmerged) {
 107                         o->pos++;
 108                 } else {
 109                         remove_entry(o->pos, o);
 110                 }
 111                 return 0;
 112         }
 113         return call_unpack_fn(src, o, o->pos);
 114 }
 115
 116 int traverse_trees_recursive(int n, unsigned long dirmask, unsigned long df_conflicts, struct name_entry *names, struct traverse_info *info)
 117 {
 118         int i;
 119         struct tree_desc t[3];
 120         struct traverse_info newinfo;
 121         struct name_entry *p;
 122
 123         p = names;
 124         while (!p->mode)
 125                 p++;
 126
 127         newinfo = *info;
 128         newinfo.prev = info;
 129         newinfo.name = *p;
 130         newinfo.pathlen += tree_entry_len(p->path, p->sha1) + 1;
 131         newinfo.conflicts |= df_conflicts;
 132
 133         for (i = 0; i < n; i++, dirmask >>= 1) {
 134                 const unsigned char *sha1 = NULL;
 135                 if (dirmask & 1)
 136                         sha1 = names[i].sha1;
 137                 fill_tree_descriptor(t+i, sha1);
 138         }
 139         traverse_trees(n, t, &newinfo);
 140         return 0;
 141 }
 142
 143 /*
 144  * Compare the traverse-path to the cache entry without actually
 145  * having to generate the textual representation of the traverse
 146  * path.
 147  *
 148  * NOTE! This *only* compares up to the size of the traverse path
 149  * itself - the caller needs to do the final check for the cache
 150  * entry having more data at the end!
 151  */
 152 static int do_compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
 153 {
 154         int len, pathlen, ce_len;
 155         const char *ce_name;
 156
 157         if (info->prev) {
 158                 int cmp = do_compare_entry(ce, info->prev, &info->name);
 159                 if (cmp)
 160                         return cmp;
 161         }
 162         pathlen = info->pathlen;
 163         ce_len = ce_namelen(ce);
 164
 165         /* If ce_len < pathlen then we must have previously hit "name == directory" entry */
 166         if (ce_len < pathlen)
 167                 return -1;
 168
 169         ce_len -= pathlen;
 170         ce_name = ce->name + pathlen;
 171
 172         len = tree_entry_len(n->path, n->sha1);
 173         return df_name_compare(ce_name, ce_len, S_IFREG, n->path, len, n->mode);
 174 }
 175
 176 static int compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
 177 {
 178         int cmp = do_compare_entry(ce, info, n);
 179         if (cmp)
 180                 return cmp;
 181
 182         /*
 183          * Even if the beginning compared identically, the ce should
 184          * compare as bigger than a directory leading up to it!
 185          */
 186         return ce_namelen(ce) > traverse_path_len(info, n);
 187 }
 188
 189 static struct cache_entry *create_ce_entry(const struct traverse_info *info, const struct name_entry *n, int stage)
 190 {
 191         int len = traverse_path_len(info, n);
 192         struct cache_entry *ce = xcalloc(1, cache_entry_size(len));
 193
 194         ce->ce_mode = create_ce_mode(n->mode);
 195         ce->ce_flags = create_ce_flags(len, stage);
 196         hashcpy(ce->sha1, n->sha1);
 197         make_traverse_path(ce->name, info, n);
 198
 199         return ce;
 200 }
 201
 202 static int unpack_nondirectories(int n, unsigned long mask, unsigned long dirmask, struct cache_entry *src[5],
 203         const struct name_entry *names, const struct traverse_info *info, int remove)
 204 {
 205         int i;
 206         struct unpack_trees_options *o = info->data;
 207         unsigned long conflicts;
 208
 209         /* Do we have *only* directories? Nothing to do */
 210         if (mask == dirmask && !src[0])
 211                 return 0;
 212
 213         conflicts = info->conflicts;
 214         if (o->merge)
 215                 conflicts >>= 1;
 216         conflicts |= dirmask;
 217
 218         /*
 219          * Ok, we've filled in up to any potential index entry in src[0],
 220          * now do the rest.
 221          */
 222         for (i = 0; i < n; i++) {
 223                 int stage;
 224                 unsigned int bit = 1ul << i;
 225                 if (conflicts & bit) {
 226                         src[i + o->merge] = o->df_conflict_entry;
 227                         continue;
 228                 }
 229                 if (!(mask & bit))
 230                         continue;
 231                 if (!o->merge)
 232                         stage = 0;
 233                 else if (i + 1 < o->head_idx)
 234                         stage = 1;
 235                 else if (i + 1 > o->head_idx)
 236                         stage = 3;
 237                 else
 238                         stage = 2;
 239                 src[i + o->merge] = create_ce_entry(info, names + i, stage);
 240         }
 241
 242         if (o->merge)
 243                 return call_unpack_fn(src, o, remove);
 244
 245         n += o->merge;
 246         remove_entry(remove, o);
 247         for (i = 0; i < n; i++)
 248                 add_index_entry(o->index, src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
 249         return 0;
 250 }
 251
 252 static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *names, struct traverse_info *info)
 253 {
 254         struct cache_entry *src[5] = { NULL, };
 255         struct unpack_trees_options *o = info->data;
 256         int remove = -1;
 257         const struct name_entry *p = names;
 258
 259         /* Find first entry with a real name (we could use "mask" too) */
 260         while (!p->mode)
 261                 p++;
 262
 263         /* Are we supposed to look at the index too? */
 264         if (o->merge) {
 265                 while (o->pos < o->index->cache_nr) {
 266                         struct cache_entry *ce = o->index->cache[o->pos];
 267                         int cmp = compare_entry(ce, info, p);
 268                         if (cmp < 0) {
 269                                 if (unpack_index_entry(ce, o) < 0)
 270                                         return -1;
 271                                 continue;
 272                         }
 273                         if (!cmp) {
 274                                 if (ce_stage(ce)) {
 275                                         /*
 276                                          * If we skip unmerged index entries, we'll skip this
 277                                          * entry *and* the tree entries associated with it!
 278                                          */
 279                                         if (o->skip_unmerged)
 280                                                 return mask;
 281                                         remove_entry(o->pos, o);
 282                                         continue;
 283                                 }
 284                                 src[0] = ce;
 285                                 remove = o->pos;
 286                         }
 287                         break;
 288                 }
 289         }
 290
 291         if (unpack_nondirectories(n, mask, dirmask, src, names, info, remove) < 0)
 292                 return -1;
 293
 294         /* Now handle any directories.. */
 295         if (dirmask) {
 296                 unsigned long conflicts = mask & ~dirmask;
 297                 if (o->merge) {
 298                         conflicts <<= 1;
 299                         if (src[0])
 300                                 conflicts |= 1;
 301                 }
 302                 traverse_trees_recursive(n, dirmask, conflicts, names, info);
 303                 return mask;
 304         }
 305
 306         return mask;
 307 }
 308
 309 static int unpack_failed(struct unpack_trees_options *o, const char *message)
 310 {
 311         if (!o->gently) {
 312                 if (message)
 313                         return error(message);
 314                 return -1;
 315         }
 316         discard_index(o->index);
 317         read_index(o->index);
 318         return -1;
 319 }
 320
 321 int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
 322 {
 323         static struct cache_entry *dfc;
 324
 325         if (len > 4)
 326                 die("unpack_trees takes at most four trees");
 327         memset(&state, 0, sizeof(state));
 328         state.base_dir = "";
 329         state.force = 1;
 330         state.quiet = 1;
 331         state.refresh_cache = 1;
 332
 333         o->merge_size = len;
 334
 335         if (!dfc)
 336                 dfc = xcalloc(1, sizeof(struct cache_entry) + 1);
 337         o->df_conflict_entry = dfc;
 338
 339         if (len) {
 340                 const char *prefix = o->prefix ? o->prefix : "";
 341                 struct traverse_info info;
 342
 343                 setup_traverse_info(&info, prefix);
 344                 info.fn = unpack_callback;
 345                 info.data = o;
 346
 347                 if (traverse_trees(len, t, &info) < 0)
 348                         return unpack_failed(o, NULL);
 349         }
 350
 351         /* Any left-over entries in the index? */
 352         if (o->merge) {
 353                 while (o->pos < o->index->cache_nr) {
 354                         struct cache_entry *ce = o->index->cache[o->pos];
 355                         if (unpack_index_entry(ce, o) < 0)
 356                                 return unpack_failed(o, NULL);
 357                 }
 358         }
 359
 360         if (o->trivial_merges_only && o->nontrivial_merge)
 361                 return unpack_failed(o, "Merge requires file-level merging");
 362
 363         check_updates(o);
 364         return 0;
 365 }
 366
 367 /* Here come the merge functions */
 368
 369 static int reject_merge(struct cache_entry *ce)
 370 {
 371         return error("Entry '%s' would be overwritten by merge. Cannot merge.",
 372                      ce->name);
 373 }
 374
 375 static int same(struct cache_entry *a, struct cache_entry *b)
 376 {
 377         if (!!a != !!b)
 378                 return 0;
 379         if (!a && !b)
 380                 return 1;
 381         return a->ce_mode == b->ce_mode &&
 382                !hashcmp(a->sha1, b->sha1);
 383 }
 384
 385
 386 /*
 387  * When a CE gets turned into an unmerged entry, we
 388  * want it to be up-to-date
 389  */
 390 static int verify_uptodate(struct cache_entry *ce,
 391                 struct unpack_trees_options *o)
 392 {
 393         struct stat st;
 394
 395         if (o->index_only || o->reset)
 396                 return 0;
 397
 398         if (!lstat(ce->name, &st)) {
 399                 unsigned changed = ie_match_stat(o->index, ce, &st, CE_MATCH_IGNORE_VALID);
 400                 if (!changed)
 401                         return 0;
 402                 /*
 403                  * NEEDSWORK: the current default policy is to allow
 404                  * submodule to be out of sync wrt the supermodule
 405                  * index.  This needs to be tightened later for
 406                  * submodules that are marked to be automatically
 407                  * checked out.
 408                  */
 409                 if (S_ISGITLINK(ce->ce_mode))
 410                         return 0;
 411                 errno = 0;
 412         }
 413         if (errno == ENOENT)
 414                 return 0;
 415         return o->gently ? -1 :
 416                 error("Entry '%s' not uptodate. Cannot merge.", ce->name);
 417 }
 418
 419 static void invalidate_ce_path(struct cache_entry *ce, struct unpack_trees_options *o)
 420 {
 421         if (ce)
 422                 cache_tree_invalidate_path(o->index->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(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 = index_name_pos(o->index, ce->name, namelen);
 468         if (0 <= pos)
 469                 return cnt; /* we have it as nondirectory */
 470         pos = -pos - 1;
 471         for (i = pos; i < o->index->cache_nr; i++) {
 472                 struct cache_entry *ce = o->index->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                         if (verify_uptodate(ce, o))
 483                                 return -1;
 484                         ce->ce_flags |= CE_REMOVE;
 485                 }
 486                 cnt++;
 487         }
 488
 489         /*
 490          * Then we need to make sure that we do not lose a locally
 491          * present file that is not ignored.
 492          */
 493         pathbuf = xmalloc(namelen + 2);
 494         memcpy(pathbuf, ce->name, namelen);
 495         strcpy(pathbuf+namelen, "/");
 496
 497         memset(&d, 0, sizeof(d));
 498         if (o->dir)
 499                 d.exclude_per_dir = o->dir->exclude_per_dir;
 500         i = read_directory(&d, ce->name, pathbuf, namelen+1, NULL);
 501         if (i)
 502                 return o->gently ? -1 :
 503                         error("Updating '%s' would lose untracked files in it",
 504                               ce->name);
 505         free(pathbuf);
 506         return cnt;
 507 }
 508
 509 /*
 510  * We do not want to remove or overwrite a working tree file that
 511  * is not tracked, unless it is ignored.
 512  */
 513 static int verify_absent(struct cache_entry *ce, const char *action,
 514                          struct unpack_trees_options *o)
 515 {
 516         struct stat st;
 517
 518         if (o->index_only || o->reset || !o->update)
 519                 return 0;
 520
 521         if (has_symlink_leading_path(ce->name, NULL))
 522                 return 0;
 523
 524         if (!lstat(ce->name, &st)) {
 525                 int cnt;
 526                 int dtype = ce_to_dtype(ce);
 527
 528                 if (o->dir && excluded(o->dir, ce->name, &dtype))
 529                         /*
 530                          * ce->name is explicitly excluded, so it is Ok to
 531                          * overwrite it.
 532                          */
 533                         return 0;
 534                 if (S_ISDIR(st.st_mode)) {
 535                         /*
 536                          * We are checking out path "foo" and
 537                          * found "foo/." in the working tree.
 538                          * This is tricky -- if we have modified
 539                          * files that are in "foo/" we would lose
 540                          * it.
 541                          */
 542                         cnt = verify_clean_subdirectory(ce, action, o);
 543
 544                         /*
 545                          * If this removed entries from the index,
 546                          * what that means is:
 547                          *
 548                          * (1) the caller unpack_trees_rec() saw path/foo
 549                          * in the index, and it has not removed it because
 550                          * it thinks it is handling 'path' as blob with
 551                          * D/F conflict;
 552                          * (2) we will return "ok, we placed a merged entry
 553                          * in the index" which would cause o->pos to be
 554                          * incremented by one;
 555                          * (3) however, original o->pos now has 'path/foo'
 556                          * marked with "to be removed".
 557                          *
 558                          * We need to increment it by the number of
 559                          * deleted entries here.
 560                          */
 561                         o->pos += cnt;
 562                         return 0;
 563                 }
 564
 565                 /*
 566                  * The previous round may already have decided to
 567                  * delete this path, which is in a subdirectory that
 568                  * is being replaced with a blob.
 569                  */
 570                 cnt = index_name_pos(o->index, ce->name, strlen(ce->name));
 571                 if (0 <= cnt) {
 572                         struct cache_entry *ce = o->index->cache[cnt];
 573                         if (ce->ce_flags & CE_REMOVE)
 574                                 return 0;
 575                 }
 576
 577                 return o->gently ? -1 :
 578                         error("Untracked working tree file '%s' "
 579                               "would be %s by merge.", ce->name, action);
 580         }
 581         return 0;
 582 }
 583
 584 static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
 585                 struct unpack_trees_options *o)
 586 {
 587         merge->ce_flags |= CE_UPDATE;
 588         if (old) {
 589                 /*
 590                  * See if we can re-use the old CE directly?
 591                  * That way we get the uptodate stat info.
 592                  *
 593                  * This also removes the UPDATE flag on
 594                  * a match.
 595                  */
 596                 if (same(old, merge)) {
 597                         copy_cache_entry(merge, old);
 598                 } else {
 599                         if (verify_uptodate(old, o))
 600                                 return -1;
 601                         invalidate_ce_path(old, o);
 602                 }
 603         }
 604         else {
 605                 if (verify_absent(merge, "overwritten", o))
 606                         return -1;
 607                 invalidate_ce_path(merge, o);
 608         }
 609
 610         merge->ce_flags &= ~CE_STAGEMASK;
 611         add_index_entry(o->index, merge, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 612         return 1;
 613 }
 614
 615 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
 616                 struct unpack_trees_options *o)
 617 {
 618         if (old) {
 619                 if (verify_uptodate(old, o))
 620                         return -1;
 621         } else
 622                 if (verify_absent(ce, "removed", o))
 623                         return -1;
 624         ce->ce_flags |= CE_REMOVE;
 625         add_index_entry(o->index, ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 626         invalidate_ce_path(ce, o);
 627         return 1;
 628 }
 629
 630 static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 631 {
 632         add_index_entry(o->index, ce, ADD_CACHE_OK_TO_ADD);
 633         return 1;
 634 }
 635
 636 #if DBRT_DEBUG
 637 static void show_stage_entry(FILE *o,
 638                              const char *label, const struct cache_entry *ce)
 639 {
 640         if (!ce)
 641                 fprintf(o, "%s (missing)\n", label);
 642         else
 643                 fprintf(o, "%s%06o %s %d\t%s\n",
 644                         label,
 645                         ce->ce_mode,
 646                         sha1_to_hex(ce->sha1),
 647                         ce_stage(ce),
 648                         ce->name);
 649 }
 650 #endif
 651
 652 int threeway_merge(struct cache_entry **stages,
 653                 struct unpack_trees_options *o,
 654                 int remove)
 655 {
 656         struct cache_entry *index;
 657         struct cache_entry *head;
 658         struct cache_entry *remote = stages[o->head_idx + 1];
 659         int count;
 660         int head_match = 0;
 661         int remote_match = 0;
 662
 663         int df_conflict_head = 0;
 664         int df_conflict_remote = 0;
 665
 666         int any_anc_missing = 0;
 667         int no_anc_exists = 1;
 668         int i;
 669
 670         for (i = 1; i < o->head_idx; i++) {
 671                 if (!stages[i] || stages[i] == o->df_conflict_entry)
 672                         any_anc_missing = 1;
 673                 else
 674                         no_anc_exists = 0;
 675         }
 676
 677         index = stages[0];
 678         head = stages[o->head_idx];
 679
 680         if (head == o->df_conflict_entry) {
 681                 df_conflict_head = 1;
 682                 head = NULL;
 683         }
 684
 685         if (remote == o->df_conflict_entry) {
 686                 df_conflict_remote = 1;
 687                 remote = NULL;
 688         }
 689
 690         /* First, if there's a #16 situation, note that to prevent #13
 691          * and #14.
 692          */
 693         if (!same(remote, head)) {
 694                 for (i = 1; i < o->head_idx; i++) {
 695                         if (same(stages[i], head)) {
 696                                 head_match = i;
 697                         }
 698                         if (same(stages[i], remote)) {
 699                                 remote_match = i;
 700                         }
 701                 }
 702         }
 703
 704         /* We start with cases where the index is allowed to match
 705          * something other than the head: #14(ALT) and #2ALT, where it
 706          * is permitted to match the result instead.
 707          */
 708         /* #14, #14ALT, #2ALT */
 709         if (remote && !df_conflict_head && head_match && !remote_match) {
 710                 if (index && !same(index, remote) && !same(index, head))
 711                         return o->gently ? -1 : reject_merge(index);
 712                 return merged_entry(remote, index, o);
 713         }
 714         /*
 715          * If we have an entry in the index cache, then we want to
 716          * make sure that it matches head.
 717          */
 718         if (index && !same(index, head))
 719                 return o->gently ? -1 : reject_merge(index);
 720
 721         if (head) {
 722                 /* #5ALT, #15 */
 723                 if (same(head, remote))
 724                         return merged_entry(head, index, o);
 725                 /* #13, #3ALT */
 726                 if (!df_conflict_remote && remote_match && !head_match)
 727                         return merged_entry(head, index, o);
 728         }
 729
 730         /* #1 */
 731         if (!head && !remote && any_anc_missing) {
 732                 remove_entry(remove, o);
 733                 return 0;
 734         }
 735
 736         /* Under the new "aggressive" rule, we resolve mostly trivial
 737          * cases that we historically had git-merge-one-file resolve.
 738          */
 739         if (o->aggressive) {
 740                 int head_deleted = !head && !df_conflict_head;
 741                 int remote_deleted = !remote && !df_conflict_remote;
 742                 struct cache_entry *ce = NULL;
 743
 744                 if (index)
 745                         ce = index;
 746                 else if (head)
 747                         ce = head;
 748                 else if (remote)
 749                         ce = remote;
 750                 else {
 751                         for (i = 1; i < o->head_idx; i++) {
 752                                 if (stages[i] && stages[i] != o->df_conflict_entry) {
 753                                         ce = stages[i];
 754                                         break;
 755                                 }
 756                         }
 757                 }
 758
 759                 /*
 760                  * Deleted in both.
 761                  * Deleted in one and unchanged in the other.
 762                  */
 763                 if ((head_deleted && remote_deleted) ||
 764                     (head_deleted && remote && remote_match) ||
 765                     (remote_deleted && head && head_match)) {
 766                         remove_entry(remove, o);
 767                         if (index)
 768                                 return deleted_entry(index, index, o);
 769                         else if (ce && !head_deleted) {
 770                                 if (verify_absent(ce, "removed", o))
 771                                         return -1;
 772                         }
 773                         return 0;
 774                 }
 775                 /*
 776                  * Added in both, identically.
 777                  */
 778                 if (no_anc_exists && head && remote && same(head, remote))
 779                         return merged_entry(head, index, o);
 780
 781         }
 782
 783         /* Below are "no merge" cases, which require that the index be
 784          * up-to-date to avoid the files getting overwritten with
 785          * conflict resolution files.
 786          */
 787         if (index) {
 788                 if (verify_uptodate(index, o))
 789                         return -1;
 790         }
 791
 792         remove_entry(remove, o);
 793         o->nontrivial_merge = 1;
 794
 795         /* #2, #3, #4, #6, #7, #9, #10, #11. */
 796         count = 0;
 797         if (!head_match || !remote_match) {
 798                 for (i = 1; i < o->head_idx; i++) {
 799                         if (stages[i] && stages[i] != o->df_conflict_entry) {
 800                                 keep_entry(stages[i], o);
 801                                 count++;
 802                                 break;
 803                         }
 804                 }
 805         }
 806 #if DBRT_DEBUG
 807         else {
 808                 fprintf(stderr, "read-tree: warning #16 detected\n");
 809                 show_stage_entry(stderr, "head   ", stages[head_match]);
 810                 show_stage_entry(stderr, "remote ", stages[remote_match]);
 811         }
 812 #endif
 813         if (head) { count += keep_entry(head, o); }
 814         if (remote) { count += keep_entry(remote, o); }
 815         return count;
 816 }
 817
 818 /*
 819  * Two-way merge.
 820  *
 821  * The rule is to "carry forward" what is in the index without losing
 822  * information across a "fast forward", favoring a successful merge
 823  * over a merge failure when it makes sense.  For details of the
 824  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 825  *
 826  */
 827 int twoway_merge(struct cache_entry **src,
 828                 struct unpack_trees_options *o,
 829                 int remove)
 830 {
 831         struct cache_entry *current = src[0];
 832         struct cache_entry *oldtree = src[1];
 833         struct cache_entry *newtree = src[2];
 834
 835         if (o->merge_size != 2)
 836                 return error("Cannot do a twoway merge of %d trees",
 837                              o->merge_size);
 838
 839         if (oldtree == o->df_conflict_entry)
 840                 oldtree = NULL;
 841         if (newtree == o->df_conflict_entry)
 842                 newtree = NULL;
 843
 844         if (current) {
 845                 if ((!oldtree && !newtree) || /* 4 and 5 */
 846                     (!oldtree && newtree &&
 847                      same(current, newtree)) || /* 6 and 7 */
 848                     (oldtree && newtree &&
 849                      same(oldtree, newtree)) || /* 14 and 15 */
 850                     (oldtree && newtree &&
 851                      !same(oldtree, newtree) && /* 18 and 19 */
 852                      same(current, newtree))) {
 853                         return keep_entry(current, o);
 854                 }
 855                 else if (oldtree && !newtree && same(current, oldtree)) {
 856                         /* 10 or 11 */
 857                         remove_entry(remove, o);
 858                         return deleted_entry(oldtree, current, o);
 859                 }
 860                 else if (oldtree && newtree &&
 861                          same(current, oldtree) && !same(current, newtree)) {
 862                         /* 20 or 21 */
 863                         return merged_entry(newtree, current, o);
 864                 }
 865                 else {
 866                         /* all other failures */
 867                         remove_entry(remove, o);
 868                         if (oldtree)
 869                                 return o->gently ? -1 : reject_merge(oldtree);
 870                         if (current)
 871                                 return o->gently ? -1 : reject_merge(current);
 872                         if (newtree)
 873                                 return o->gently ? -1 : reject_merge(newtree);
 874                         return -1;
 875                 }
 876         }
 877         else if (newtree)
 878                 return merged_entry(newtree, current, o);
 879         remove_entry(remove, o);
 880         return deleted_entry(oldtree, current, o);
 881 }
 882
 883 /*
 884  * Bind merge.
 885  *
 886  * Keep the index entries at stage0, collapse stage1 but make sure
 887  * stage0 does not have anything there.
 888  */
 889 int bind_merge(struct cache_entry **src,
 890                 struct unpack_trees_options *o,
 891                 int remove)
 892 {
 893         struct cache_entry *old = src[0];
 894         struct cache_entry *a = src[1];
 895
 896         if (o->merge_size != 1)
 897                 return error("Cannot do a bind merge of %d trees\n",
 898                              o->merge_size);
 899         if (a && old)
 900                 return o->gently ? -1 :
 901                         error("Entry '%s' overlaps.  Cannot bind.", a->name);
 902         if (!a)
 903                 return keep_entry(old, o);
 904         else
 905                 return merged_entry(a, NULL, o);
 906 }
 907
 908 /*
 909  * One-way merge.
 910  *
 911  * The rule is:
 912  * - take the stat information from stage0, take the data from stage1
 913  */
 914 int oneway_merge(struct cache_entry **src,
 915                 struct unpack_trees_options *o,
 916                 int remove)
 917 {
 918         struct cache_entry *old = src[0];
 919         struct cache_entry *a = src[1];
 920
 921         if (o->merge_size != 1)
 922                 return error("Cannot do a oneway merge of %d trees",
 923                              o->merge_size);
 924
 925         if (!a) {
 926                 remove_entry(remove, o);
 927                 return deleted_entry(old, old, o);
 928         }
 929         if (old && same(old, a)) {
 930                 if (o->reset) {
 931                         struct stat st;
 932                         if (lstat(old->name, &st) ||
 933                             ie_match_stat(o->index, old, &st, CE_MATCH_IGNORE_VALID))
 934                                 old->ce_flags |= CE_UPDATE;
 935                 }
 936                 return keep_entry(old, o);
 937         }
 938         return merged_entry(a, old, o);
 939 }