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 void add_entry(struct unpack_trees_options *o, struct cache_entry *ce,
  12         unsigned int set, unsigned int clear)
  13 {
  14         unsigned int size = ce_size(ce);
  15         struct cache_entry *new = xmalloc(size);
  16
  17         clear |= CE_HASHED | CE_UNHASHED;
  18
  19         memcpy(new, ce, size);
  20         new->next = NULL;
  21         new->ce_flags = (new->ce_flags & ~clear) | set;
  22         add_index_entry(&o->result, new, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE|ADD_CACHE_SKIP_DFCHECK);
  23 }
  24
  25 /* Unlink the last component and attempt to remove leading
  26  * directories, in case this unlink is the removal of the
  27  * last entry in the directory -- empty directories are removed.
  28  */
  29 static void unlink_entry(char *name, char *last_symlink)
  30 {
  31         char *cp, *prev;
  32
  33         if (has_symlink_leading_path(name, last_symlink))
  34                 return;
  35         if (unlink(name))
  36                 return;
  37         prev = NULL;
  38         while (1) {
  39                 int status;
  40                 cp = strrchr(name, '/');
  41                 if (prev)
  42                         *prev = '/';
  43                 if (!cp)
  44                         break;
  45
  46                 *cp = 0;
  47                 status = rmdir(name);
  48                 if (status) {
  49                         *cp = '/';
  50                         break;
  51                 }
  52                 prev = cp;
  53         }
  54 }
  55
  56 static struct checkout state;
  57 static void check_updates(struct unpack_trees_options *o)
  58 {
  59         unsigned cnt = 0, total = 0;
  60         struct progress *progress = NULL;
  61         char last_symlink[PATH_MAX];
  62         struct index_state *index = &o->result;
  63         int i;
  64
  65         if (o->update && o->verbose_update) {
  66                 for (total = cnt = 0; cnt < index->cache_nr; cnt++) {
  67                         struct cache_entry *ce = index->cache[cnt];
  68                         if (ce->ce_flags & (CE_UPDATE | CE_REMOVE))
  69                                 total++;
  70                 }
  71
  72                 progress = start_progress_delay("Checking out files",
  73                                                 total, 50, 1);
  74                 cnt = 0;
  75         }
  76
  77         *last_symlink = '\0';
  78         for (i = 0; i < index->cache_nr; i++) {
  79                 struct cache_entry *ce = index->cache[i];
  80
  81                 if (ce->ce_flags & (CE_UPDATE | CE_REMOVE))
  82                         display_progress(progress, ++cnt);
  83                 if (ce->ce_flags & CE_REMOVE) {
  84                         if (o->update)
  85                                 unlink_entry(ce->name, last_symlink);
  86                         remove_index_entry_at(&o->result, i);
  87                         i--;
  88                         continue;
  89                 }
  90                 if (ce->ce_flags & CE_UPDATE) {
  91                         ce->ce_flags &= ~CE_UPDATE;
  92                         if (o->update) {
  93                                 checkout_entry(ce, &state, NULL);
  94                                 *last_symlink = '\0';
  95                         }
  96                 }
  97         }
  98         stop_progress(&progress);
  99 }
 100
 101 static inline int call_unpack_fn(struct cache_entry **src, struct unpack_trees_options *o)
 102 {
 103         int ret = o->fn(src, o);
 104         if (ret > 0)
 105                 ret = 0;
 106         return ret;
 107 }
 108
 109 static int unpack_index_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 110 {
 111         struct cache_entry *src[5] = { ce, };
 112
 113         o->pos++;
 114         if (ce_stage(ce)) {
 115                 if (o->skip_unmerged) {
 116                         add_entry(o, ce, 0, 0);
 117                         return 0;
 118                 }
 119         }
 120         return call_unpack_fn(src, o);
 121 }
 122
 123 int traverse_trees_recursive(int n, unsigned long dirmask, unsigned long df_conflicts, struct name_entry *names, struct traverse_info *info)
 124 {
 125         int i;
 126         struct tree_desc t[3];
 127         struct traverse_info newinfo;
 128         struct name_entry *p;
 129
 130         p = names;
 131         while (!p->mode)
 132                 p++;
 133
 134         newinfo = *info;
 135         newinfo.prev = info;
 136         newinfo.name = *p;
 137         newinfo.pathlen += tree_entry_len(p->path, p->sha1) + 1;
 138         newinfo.conflicts |= df_conflicts;
 139
 140         for (i = 0; i < n; i++, dirmask >>= 1) {
 141                 const unsigned char *sha1 = NULL;
 142                 if (dirmask & 1)
 143                         sha1 = names[i].sha1;
 144                 fill_tree_descriptor(t+i, sha1);
 145         }
 146         return traverse_trees(n, t, &newinfo);
 147 }
 148
 149 /*
 150  * Compare the traverse-path to the cache entry without actually
 151  * having to generate the textual representation of the traverse
 152  * path.
 153  *
 154  * NOTE! This *only* compares up to the size of the traverse path
 155  * itself - the caller needs to do the final check for the cache
 156  * entry having more data at the end!
 157  */
 158 static int do_compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
 159 {
 160         int len, pathlen, ce_len;
 161         const char *ce_name;
 162
 163         if (info->prev) {
 164                 int cmp = do_compare_entry(ce, info->prev, &info->name);
 165                 if (cmp)
 166                         return cmp;
 167         }
 168         pathlen = info->pathlen;
 169         ce_len = ce_namelen(ce);
 170
 171         /* If ce_len < pathlen then we must have previously hit "name == directory" entry */
 172         if (ce_len < pathlen)
 173                 return -1;
 174
 175         ce_len -= pathlen;
 176         ce_name = ce->name + pathlen;
 177
 178         len = tree_entry_len(n->path, n->sha1);
 179         return df_name_compare(ce_name, ce_len, S_IFREG, n->path, len, n->mode);
 180 }
 181
 182 static int compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
 183 {
 184         int cmp = do_compare_entry(ce, info, n);
 185         if (cmp)
 186                 return cmp;
 187
 188         /*
 189          * Even if the beginning compared identically, the ce should
 190          * compare as bigger than a directory leading up to it!
 191          */
 192         return ce_namelen(ce) > traverse_path_len(info, n);
 193 }
 194
 195 static struct cache_entry *create_ce_entry(const struct traverse_info *info, const struct name_entry *n, int stage)
 196 {
 197         int len = traverse_path_len(info, n);
 198         struct cache_entry *ce = xcalloc(1, cache_entry_size(len));
 199
 200         ce->ce_mode = create_ce_mode(n->mode);
 201         ce->ce_flags = create_ce_flags(len, stage);
 202         hashcpy(ce->sha1, n->sha1);
 203         make_traverse_path(ce->name, info, n);
 204
 205         return ce;
 206 }
 207
 208 static int unpack_nondirectories(int n, unsigned long mask, unsigned long dirmask, struct cache_entry *src[5],
 209         const struct name_entry *names, const struct traverse_info *info)
 210 {
 211         int i;
 212         struct unpack_trees_options *o = info->data;
 213         unsigned long conflicts;
 214
 215         /* Do we have *only* directories? Nothing to do */
 216         if (mask == dirmask && !src[0])
 217                 return 0;
 218
 219         conflicts = info->conflicts;
 220         if (o->merge)
 221                 conflicts >>= 1;
 222         conflicts |= dirmask;
 223
 224         /*
 225          * Ok, we've filled in up to any potential index entry in src[0],
 226          * now do the rest.
 227          */
 228         for (i = 0; i < n; i++) {
 229                 int stage;
 230                 unsigned int bit = 1ul << i;
 231                 if (conflicts & bit) {
 232                         src[i + o->merge] = o->df_conflict_entry;
 233                         continue;
 234                 }
 235                 if (!(mask & bit))
 236                         continue;
 237                 if (!o->merge)
 238                         stage = 0;
 239                 else if (i + 1 < o->head_idx)
 240                         stage = 1;
 241                 else if (i + 1 > o->head_idx)
 242                         stage = 3;
 243                 else
 244                         stage = 2;
 245                 src[i + o->merge] = create_ce_entry(info, names + i, stage);
 246         }
 247
 248         if (o->merge)
 249                 return call_unpack_fn(src, o);
 250
 251         n += o->merge;
 252         for (i = 0; i < n; i++)
 253                 add_entry(o, src[i], 0, 0);
 254         return 0;
 255 }
 256
 257 static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *names, struct traverse_info *info)
 258 {
 259         struct cache_entry *src[5] = { NULL, };
 260         struct unpack_trees_options *o = info->data;
 261         const struct name_entry *p = names;
 262
 263         /* Find first entry with a real name (we could use "mask" too) */
 264         while (!p->mode)
 265                 p++;
 266
 267         /* Are we supposed to look at the index too? */
 268         if (o->merge) {
 269                 while (o->pos < o->src_index->cache_nr) {
 270                         struct cache_entry *ce = o->src_index->cache[o->pos];
 271                         int cmp = compare_entry(ce, info, p);
 272                         if (cmp < 0) {
 273                                 if (unpack_index_entry(ce, o) < 0)
 274                                         return -1;
 275                                 continue;
 276                         }
 277                         if (!cmp) {
 278                                 o->pos++;
 279                                 if (ce_stage(ce)) {
 280                                         /*
 281                                          * If we skip unmerged index entries, we'll skip this
 282                                          * entry *and* the tree entries associated with it!
 283                                          */
 284                                         if (o->skip_unmerged) {
 285                                                 add_entry(o, ce, 0, 0);
 286                                                 return mask;
 287                                         }
 288                                 }
 289                                 src[0] = ce;
 290                         }
 291                         break;
 292                 }
 293         }
 294
 295         if (unpack_nondirectories(n, mask, dirmask, src, names, info) < 0)
 296                 return -1;
 297
 298         /* Now handle any directories.. */
 299         if (dirmask) {
 300                 unsigned long conflicts = mask & ~dirmask;
 301                 if (o->merge) {
 302                         conflicts <<= 1;
 303                         if (src[0])
 304                                 conflicts |= 1;
 305                 }
 306                 if (traverse_trees_recursive(n, dirmask, conflicts,
 307                                              names, info) < 0)
 308                         return -1;
 309                 return mask;
 310         }
 311
 312         return mask;
 313 }
 314
 315 static int unpack_failed(struct unpack_trees_options *o, const char *message)
 316 {
 317         discard_index(&o->result);
 318         if (!o->gently) {
 319                 if (message)
 320                         return error(message);
 321                 return -1;
 322         }
 323         return -1;
 324 }
 325
 326 int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
 327 {
 328         static struct cache_entry *dfc;
 329
 330         if (len > 4)
 331                 die("unpack_trees takes at most four trees");
 332         memset(&state, 0, sizeof(state));
 333         state.base_dir = "";
 334         state.force = 1;
 335         state.quiet = 1;
 336         state.refresh_cache = 1;
 337
 338         memset(&o->result, 0, sizeof(o->result));
 339         o->merge_size = len;
 340
 341         if (!dfc)
 342                 dfc = xcalloc(1, sizeof(struct cache_entry) + 1);
 343         o->df_conflict_entry = dfc;
 344
 345         if (len) {
 346                 const char *prefix = o->prefix ? o->prefix : "";
 347                 struct traverse_info info;
 348
 349                 setup_traverse_info(&info, prefix);
 350                 info.fn = unpack_callback;
 351                 info.data = o;
 352
 353                 if (traverse_trees(len, t, &info) < 0)
 354                         return unpack_failed(o, NULL);
 355         }
 356
 357         /* Any left-over entries in the index? */
 358         if (o->merge) {
 359                 while (o->pos < o->src_index->cache_nr) {
 360                         struct cache_entry *ce = o->src_index->cache[o->pos];
 361                         if (unpack_index_entry(ce, o) < 0)
 362                                 return unpack_failed(o, NULL);
 363                 }
 364         }
 365
 366         if (o->trivial_merges_only && o->nontrivial_merge)
 367                 return unpack_failed(o, "Merge requires file-level merging");
 368
 369         o->src_index = NULL;
 370         check_updates(o);
 371         if (o->dst_index)
 372                 *o->dst_index = o->result;
 373         return 0;
 374 }
 375
 376 /* Here come the merge functions */
 377
 378 static int reject_merge(struct cache_entry *ce)
 379 {
 380         return error("Entry '%s' would be overwritten by merge. Cannot merge.",
 381                      ce->name);
 382 }
 383
 384 static int same(struct cache_entry *a, struct cache_entry *b)
 385 {
 386         if (!!a != !!b)
 387                 return 0;
 388         if (!a && !b)
 389                 return 1;
 390         return a->ce_mode == b->ce_mode &&
 391                !hashcmp(a->sha1, b->sha1);
 392 }
 393
 394
 395 /*
 396  * When a CE gets turned into an unmerged entry, we
 397  * want it to be up-to-date
 398  */
 399 static int verify_uptodate(struct cache_entry *ce,
 400                 struct unpack_trees_options *o)
 401 {
 402         struct stat st;
 403
 404         if (o->index_only || o->reset)
 405                 return 0;
 406
 407         if (!lstat(ce->name, &st)) {
 408                 unsigned changed = ie_match_stat(o->src_index, ce, &st, CE_MATCH_IGNORE_VALID);
 409                 if (!changed)
 410                         return 0;
 411                 /*
 412                  * NEEDSWORK: the current default policy is to allow
 413                  * submodule to be out of sync wrt the supermodule
 414                  * index.  This needs to be tightened later for
 415                  * submodules that are marked to be automatically
 416                  * checked out.
 417                  */
 418                 if (S_ISGITLINK(ce->ce_mode))
 419                         return 0;
 420                 errno = 0;
 421         }
 422         if (errno == ENOENT)
 423                 return 0;
 424         return o->gently ? -1 :
 425                 error("Entry '%s' not uptodate. Cannot merge.", ce->name);
 426 }
 427
 428 static void invalidate_ce_path(struct cache_entry *ce, struct unpack_trees_options *o)
 429 {
 430         if (ce)
 431                 cache_tree_invalidate_path(o->src_index->cache_tree, ce->name);
 432 }
 433
 434 /*
 435  * Check that checking out ce->sha1 in subdir ce->name is not
 436  * going to overwrite any working files.
 437  *
 438  * Currently, git does not checkout subprojects during a superproject
 439  * checkout, so it is not going to overwrite anything.
 440  */
 441 static int verify_clean_submodule(struct cache_entry *ce, const char *action,
 442                                       struct unpack_trees_options *o)
 443 {
 444         return 0;
 445 }
 446
 447 static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
 448                                       struct unpack_trees_options *o)
 449 {
 450         /*
 451          * we are about to extract "ce->name"; we would not want to lose
 452          * anything in the existing directory there.
 453          */
 454         int namelen;
 455         int pos, i;
 456         struct dir_struct d;
 457         char *pathbuf;
 458         int cnt = 0;
 459         unsigned char sha1[20];
 460
 461         if (S_ISGITLINK(ce->ce_mode) &&
 462             resolve_gitlink_ref(ce->name, "HEAD", sha1) == 0) {
 463                 /* If we are not going to update the submodule, then
 464                  * we don't care.
 465                  */
 466                 if (!hashcmp(sha1, ce->sha1))
 467                         return 0;
 468                 return verify_clean_submodule(ce, action, o);
 469         }
 470
 471         /*
 472          * First let's make sure we do not have a local modification
 473          * in that directory.
 474          */
 475         namelen = strlen(ce->name);
 476         pos = index_name_pos(o->src_index, ce->name, namelen);
 477         if (0 <= pos)
 478                 return cnt; /* we have it as nondirectory */
 479         pos = -pos - 1;
 480         for (i = pos; i < o->src_index->cache_nr; i++) {
 481                 struct cache_entry *ce = o->src_index->cache[i];
 482                 int len = ce_namelen(ce);
 483                 if (len < namelen ||
 484                     strncmp(ce->name, ce->name, namelen) ||
 485                     ce->name[namelen] != '/')
 486                         break;
 487                 /*
 488                  * ce->name is an entry in the subdirectory.
 489                  */
 490                 if (!ce_stage(ce)) {
 491                         if (verify_uptodate(ce, o))
 492                                 return -1;
 493                         add_entry(o, ce, CE_REMOVE, 0);
 494                 }
 495                 cnt++;
 496         }
 497
 498         /*
 499          * Then we need to make sure that we do not lose a locally
 500          * present file that is not ignored.
 501          */
 502         pathbuf = xmalloc(namelen + 2);
 503         memcpy(pathbuf, ce->name, namelen);
 504         strcpy(pathbuf+namelen, "/");
 505
 506         memset(&d, 0, sizeof(d));
 507         if (o->dir)
 508                 d.exclude_per_dir = o->dir->exclude_per_dir;
 509         i = read_directory(&d, ce->name, pathbuf, namelen+1, NULL);
 510         if (i)
 511                 return o->gently ? -1 :
 512                         error("Updating '%s' would lose untracked files in it",
 513                               ce->name);
 514         free(pathbuf);
 515         return cnt;
 516 }
 517
 518 /*
 519  * We do not want to remove or overwrite a working tree file that
 520  * is not tracked, unless it is ignored.
 521  */
 522 static int verify_absent(struct cache_entry *ce, const char *action,
 523                          struct unpack_trees_options *o)
 524 {
 525         struct stat st;
 526
 527         if (o->index_only || o->reset || !o->update)
 528                 return 0;
 529
 530         if (has_symlink_leading_path(ce->name, NULL))
 531                 return 0;
 532
 533         if (!lstat(ce->name, &st)) {
 534                 int cnt;
 535                 int dtype = ce_to_dtype(ce);
 536
 537                 if (o->dir && excluded(o->dir, ce->name, &dtype))
 538                         /*
 539                          * ce->name is explicitly excluded, so it is Ok to
 540                          * overwrite it.
 541                          */
 542                         return 0;
 543                 if (S_ISDIR(st.st_mode)) {
 544                         /*
 545                          * We are checking out path "foo" and
 546                          * found "foo/." in the working tree.
 547                          * This is tricky -- if we have modified
 548                          * files that are in "foo/" we would lose
 549                          * it.
 550                          */
 551                         cnt = verify_clean_subdirectory(ce, action, o);
 552
 553                         /*
 554                          * If this removed entries from the index,
 555                          * what that means is:
 556                          *
 557                          * (1) the caller unpack_trees_rec() saw path/foo
 558                          * in the index, and it has not removed it because
 559                          * it thinks it is handling 'path' as blob with
 560                          * D/F conflict;
 561                          * (2) we will return "ok, we placed a merged entry
 562                          * in the index" which would cause o->pos to be
 563                          * incremented by one;
 564                          * (3) however, original o->pos now has 'path/foo'
 565                          * marked with "to be removed".
 566                          *
 567                          * We need to increment it by the number of
 568                          * deleted entries here.
 569                          */
 570                         o->pos += cnt;
 571                         return 0;
 572                 }
 573
 574                 /*
 575                  * The previous round may already have decided to
 576                  * delete this path, which is in a subdirectory that
 577                  * is being replaced with a blob.
 578                  */
 579                 cnt = index_name_pos(&o->result, ce->name, strlen(ce->name));
 580                 if (0 <= cnt) {
 581                         struct cache_entry *ce = o->result.cache[cnt];
 582                         if (ce->ce_flags & CE_REMOVE)
 583                                 return 0;
 584                 }
 585
 586                 return o->gently ? -1 :
 587                         error("Untracked working tree file '%s' "
 588                               "would be %s by merge.", ce->name, action);
 589         }
 590         return 0;
 591 }
 592
 593 static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
 594                 struct unpack_trees_options *o)
 595 {
 596         if (old) {
 597                 /*
 598                  * See if we can re-use the old CE directly?
 599                  * That way we get the uptodate stat info.
 600                  *
 601                  * This also removes the UPDATE flag on
 602                  * a match.
 603                  */
 604                 if (same(old, merge)) {
 605                         copy_cache_entry(merge, old);
 606                 } else {
 607                         if (verify_uptodate(old, o))
 608                                 return -1;
 609                         invalidate_ce_path(old, o);
 610                 }
 611         }
 612         else {
 613                 if (verify_absent(merge, "overwritten", o))
 614                         return -1;
 615                 invalidate_ce_path(merge, o);
 616         }
 617
 618         add_entry(o, merge, CE_UPDATE, CE_STAGEMASK);
 619         return 1;
 620 }
 621
 622 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
 623                 struct unpack_trees_options *o)
 624 {
 625         /* Did it exist in the index? */
 626         if (!old) {
 627                 if (verify_absent(ce, "removed", o))
 628                         return -1;
 629                 return 0;
 630         }
 631         if (verify_uptodate(old, o))
 632                 return -1;
 633         add_entry(o, ce, CE_REMOVE, 0);
 634         invalidate_ce_path(ce, o);
 635         return 1;
 636 }
 637
 638 static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 639 {
 640         add_entry(o, ce, 0, 0);
 641         return 1;
 642 }
 643
 644 #if DBRT_DEBUG
 645 static void show_stage_entry(FILE *o,
 646                              const char *label, const struct cache_entry *ce)
 647 {
 648         if (!ce)
 649                 fprintf(o, "%s (missing)\n", label);
 650         else
 651                 fprintf(o, "%s%06o %s %d\t%s\n",
 652                         label,
 653                         ce->ce_mode,
 654                         sha1_to_hex(ce->sha1),
 655                         ce_stage(ce),
 656                         ce->name);
 657 }
 658 #endif
 659
 660 int threeway_merge(struct cache_entry **stages, struct unpack_trees_options *o)
 661 {
 662         struct cache_entry *index;
 663         struct cache_entry *head;
 664         struct cache_entry *remote = stages[o->head_idx + 1];
 665         int count;
 666         int head_match = 0;
 667         int remote_match = 0;
 668
 669         int df_conflict_head = 0;
 670         int df_conflict_remote = 0;
 671
 672         int any_anc_missing = 0;
 673         int no_anc_exists = 1;
 674         int i;
 675
 676         for (i = 1; i < o->head_idx; i++) {
 677                 if (!stages[i] || stages[i] == o->df_conflict_entry)
 678                         any_anc_missing = 1;
 679                 else
 680                         no_anc_exists = 0;
 681         }
 682
 683         index = stages[0];
 684         head = stages[o->head_idx];
 685
 686         if (head == o->df_conflict_entry) {
 687                 df_conflict_head = 1;
 688                 head = NULL;
 689         }
 690
 691         if (remote == o->df_conflict_entry) {
 692                 df_conflict_remote = 1;
 693                 remote = NULL;
 694         }
 695
 696         /* First, if there's a #16 situation, note that to prevent #13
 697          * and #14.
 698          */
 699         if (!same(remote, head)) {
 700                 for (i = 1; i < o->head_idx; i++) {
 701                         if (same(stages[i], head)) {
 702                                 head_match = i;
 703                         }
 704                         if (same(stages[i], remote)) {
 705                                 remote_match = i;
 706                         }
 707                 }
 708         }
 709
 710         /* We start with cases where the index is allowed to match
 711          * something other than the head: #14(ALT) and #2ALT, where it
 712          * is permitted to match the result instead.
 713          */
 714         /* #14, #14ALT, #2ALT */
 715         if (remote && !df_conflict_head && head_match && !remote_match) {
 716                 if (index && !same(index, remote) && !same(index, head))
 717                         return o->gently ? -1 : reject_merge(index);
 718                 return merged_entry(remote, index, o);
 719         }
 720         /*
 721          * If we have an entry in the index cache, then we want to
 722          * make sure that it matches head.
 723          */
 724         if (index && !same(index, head))
 725                 return o->gently ? -1 : reject_merge(index);
 726
 727         if (head) {
 728                 /* #5ALT, #15 */
 729                 if (same(head, remote))
 730                         return merged_entry(head, index, o);
 731                 /* #13, #3ALT */
 732                 if (!df_conflict_remote && remote_match && !head_match)
 733                         return merged_entry(head, index, o);
 734         }
 735
 736         /* #1 */
 737         if (!head && !remote && any_anc_missing)
 738                 return 0;
 739
 740         /* Under the new "aggressive" rule, we resolve mostly trivial
 741          * cases that we historically had git-merge-one-file resolve.
 742          */
 743         if (o->aggressive) {
 744                 int head_deleted = !head && !df_conflict_head;
 745                 int remote_deleted = !remote && !df_conflict_remote;
 746                 struct cache_entry *ce = NULL;
 747
 748                 if (index)
 749                         ce = index;
 750                 else if (head)
 751                         ce = head;
 752                 else if (remote)
 753                         ce = remote;
 754                 else {
 755                         for (i = 1; i < o->head_idx; i++) {
 756                                 if (stages[i] && stages[i] != o->df_conflict_entry) {
 757                                         ce = stages[i];
 758                                         break;
 759                                 }
 760                         }
 761                 }
 762
 763                 /*
 764                  * Deleted in both.
 765                  * Deleted in one and unchanged in the other.
 766                  */
 767                 if ((head_deleted && remote_deleted) ||
 768                     (head_deleted && remote && remote_match) ||
 769                     (remote_deleted && head && head_match)) {
 770                         if (index)
 771                                 return deleted_entry(index, index, o);
 772                         if (ce && !head_deleted) {
 773                                 if (verify_absent(ce, "removed", o))
 774                                         return -1;
 775                         }
 776                         return 0;
 777                 }
 778                 /*
 779                  * Added in both, identically.
 780                  */
 781                 if (no_anc_exists && head && remote && same(head, remote))
 782                         return merged_entry(head, index, o);
 783
 784         }
 785
 786         /* Below are "no merge" cases, which require that the index be
 787          * up-to-date to avoid the files getting overwritten with
 788          * conflict resolution files.
 789          */
 790         if (index) {
 791                 if (verify_uptodate(index, o))
 792                         return -1;
 793         }
 794
 795         o->nontrivial_merge = 1;
 796
 797         /* #2, #3, #4, #6, #7, #9, #10, #11. */
 798         count = 0;
 799         if (!head_match || !remote_match) {
 800                 for (i = 1; i < o->head_idx; i++) {
 801                         if (stages[i] && stages[i] != o->df_conflict_entry) {
 802                                 keep_entry(stages[i], o);
 803                                 count++;
 804                                 break;
 805                         }
 806                 }
 807         }
 808 #if DBRT_DEBUG
 809         else {
 810                 fprintf(stderr, "read-tree: warning #16 detected\n");
 811                 show_stage_entry(stderr, "head   ", stages[head_match]);
 812                 show_stage_entry(stderr, "remote ", stages[remote_match]);
 813         }
 814 #endif
 815         if (head) { count += keep_entry(head, o); }
 816         if (remote) { count += keep_entry(remote, o); }
 817         return count;
 818 }
 819
 820 /*
 821  * Two-way merge.
 822  *
 823  * The rule is to "carry forward" what is in the index without losing
 824  * information across a "fast forward", favoring a successful merge
 825  * over a merge failure when it makes sense.  For details of the
 826  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 827  *
 828  */
 829 int twoway_merge(struct cache_entry **src, struct unpack_trees_options *o)
 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                         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                         if (oldtree)
 867                                 return o->gently ? -1 : reject_merge(oldtree);
 868                         if (current)
 869                                 return o->gently ? -1 : reject_merge(current);
 870                         if (newtree)
 871                                 return o->gently ? -1 : reject_merge(newtree);
 872                         return -1;
 873                 }
 874         }
 875         else if (newtree)
 876                 return merged_entry(newtree, current, o);
 877         return deleted_entry(oldtree, current, o);
 878 }
 879
 880 /*
 881  * Bind merge.
 882  *
 883  * Keep the index entries at stage0, collapse stage1 but make sure
 884  * stage0 does not have anything there.
 885  */
 886 int bind_merge(struct cache_entry **src,
 887                 struct unpack_trees_options *o)
 888 {
 889         struct cache_entry *old = src[0];
 890         struct cache_entry *a = src[1];
 891
 892         if (o->merge_size != 1)
 893                 return error("Cannot do a bind merge of %d trees\n",
 894                              o->merge_size);
 895         if (a && old)
 896                 return o->gently ? -1 :
 897                         error("Entry '%s' overlaps with '%s'.  Cannot bind.", a->name, old->name);
 898         if (!a)
 899                 return keep_entry(old, o);
 900         else
 901                 return merged_entry(a, NULL, o);
 902 }
 903
 904 /*
 905  * One-way merge.
 906  *
 907  * The rule is:
 908  * - take the stat information from stage0, take the data from stage1
 909  */
 910 int oneway_merge(struct cache_entry **src, struct unpack_trees_options *o)
 911 {
 912         struct cache_entry *old = src[0];
 913         struct cache_entry *a = src[1];
 914
 915         if (o->merge_size != 1)
 916                 return error("Cannot do a oneway merge of %d trees",
 917                              o->merge_size);
 918
 919         if (!a)
 920                 return deleted_entry(old, old, o);
 921
 922         if (old && same(old, a)) {
 923                 int update = 0;
 924                 if (o->reset) {
 925                         struct stat st;
 926                         if (lstat(old->name, &st) ||
 927                             ie_match_stat(o->src_index, old, &st, CE_MATCH_IGNORE_VALID))
 928                                 update |= CE_UPDATE;
 929                 }
 930                 add_entry(o, old, update, 0);
 931                 return 0;
 932         }
 933         return merged_entry(a, old, o);
 934 }