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(struct cache_entry *ce)
  30 {
  31         char *cp, *prev;
  32         char *name = ce->name;
  33
  34         if (has_symlink_leading_path(ce_namelen(ce), ce->name))
  35                 return;
  36         if (unlink(name))
  37                 return;
  38         prev = NULL;
  39         while (1) {
  40                 int status;
  41                 cp = strrchr(name, '/');
  42                 if (prev)
  43                         *prev = '/';
  44                 if (!cp)
  45                         break;
  46
  47                 *cp = 0;
  48                 status = rmdir(name);
  49                 if (status) {
  50                         *cp = '/';
  51                         break;
  52                 }
  53                 prev = cp;
  54         }
  55 }
  56
  57 static struct checkout state;
  58 static int check_updates(struct unpack_trees_options *o)
  59 {
  60         unsigned cnt = 0, total = 0;
  61         struct progress *progress = NULL;
  62         struct index_state *index = &o->result;
  63         int i;
  64         int errs = 0;
  65
  66         if (o->update && o->verbose_update) {
  67                 for (total = cnt = 0; cnt < index->cache_nr; cnt++) {
  68                         struct cache_entry *ce = index->cache[cnt];
  69                         if (ce->ce_flags & (CE_UPDATE | CE_REMOVE))
  70                                 total++;
  71                 }
  72
  73                 progress = start_progress_delay("Checking out files",
  74                                                 total, 50, 1);
  75                 cnt = 0;
  76         }
  77
  78         for (i = 0; i < index->cache_nr; i++) {
  79                 struct cache_entry *ce = index->cache[i];
  80
  81                 if (ce->ce_flags & CE_REMOVE) {
  82                         display_progress(progress, ++cnt);
  83                         if (o->update)
  84                                 unlink_entry(ce);
  85                         remove_index_entry_at(&o->result, i);
  86                         i--;
  87                         continue;
  88                 }
  89         }
  90
  91         for (i = 0; i < index->cache_nr; i++) {
  92                 struct cache_entry *ce = index->cache[i];
  93
  94                 if (ce->ce_flags & CE_UPDATE) {
  95                         display_progress(progress, ++cnt);
  96                         ce->ce_flags &= ~CE_UPDATE;
  97                         if (o->update) {
  98                                 errs |= checkout_entry(ce, &state, NULL);
  99                         }
 100                 }
 101         }
 102         stop_progress(&progress);
 103         return errs != 0;
 104 }
 105
 106 static inline int call_unpack_fn(struct cache_entry **src, struct unpack_trees_options *o)
 107 {
 108         int ret = o->fn(src, o);
 109         if (ret > 0)
 110                 ret = 0;
 111         return ret;
 112 }
 113
 114 static int unpack_index_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 115 {
 116         struct cache_entry *src[5] = { ce, };
 117
 118         o->pos++;
 119         if (ce_stage(ce)) {
 120                 if (o->skip_unmerged) {
 121                         add_entry(o, ce, 0, 0);
 122                         return 0;
 123                 }
 124         }
 125         return call_unpack_fn(src, o);
 126 }
 127
 128 int traverse_trees_recursive(int n, unsigned long dirmask, unsigned long df_conflicts, struct name_entry *names, struct traverse_info *info)
 129 {
 130         int i;
 131         struct tree_desc t[MAX_UNPACK_TREES];
 132         struct traverse_info newinfo;
 133         struct name_entry *p;
 134
 135         p = names;
 136         while (!p->mode)
 137                 p++;
 138
 139         newinfo = *info;
 140         newinfo.prev = info;
 141         newinfo.name = *p;
 142         newinfo.pathlen += tree_entry_len(p->path, p->sha1) + 1;
 143         newinfo.conflicts |= df_conflicts;
 144
 145         for (i = 0; i < n; i++, dirmask >>= 1) {
 146                 const unsigned char *sha1 = NULL;
 147                 if (dirmask & 1)
 148                         sha1 = names[i].sha1;
 149                 fill_tree_descriptor(t+i, sha1);
 150         }
 151         return traverse_trees(n, t, &newinfo);
 152 }
 153
 154 /*
 155  * Compare the traverse-path to the cache entry without actually
 156  * having to generate the textual representation of the traverse
 157  * path.
 158  *
 159  * NOTE! This *only* compares up to the size of the traverse path
 160  * itself - the caller needs to do the final check for the cache
 161  * entry having more data at the end!
 162  */
 163 static int do_compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
 164 {
 165         int len, pathlen, ce_len;
 166         const char *ce_name;
 167
 168         if (info->prev) {
 169                 int cmp = do_compare_entry(ce, info->prev, &info->name);
 170                 if (cmp)
 171                         return cmp;
 172         }
 173         pathlen = info->pathlen;
 174         ce_len = ce_namelen(ce);
 175
 176         /* If ce_len < pathlen then we must have previously hit "name == directory" entry */
 177         if (ce_len < pathlen)
 178                 return -1;
 179
 180         ce_len -= pathlen;
 181         ce_name = ce->name + pathlen;
 182
 183         len = tree_entry_len(n->path, n->sha1);
 184         return df_name_compare(ce_name, ce_len, S_IFREG, n->path, len, n->mode);
 185 }
 186
 187 static int compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
 188 {
 189         int cmp = do_compare_entry(ce, info, n);
 190         if (cmp)
 191                 return cmp;
 192
 193         /*
 194          * Even if the beginning compared identically, the ce should
 195          * compare as bigger than a directory leading up to it!
 196          */
 197         return ce_namelen(ce) > traverse_path_len(info, n);
 198 }
 199
 200 static struct cache_entry *create_ce_entry(const struct traverse_info *info, const struct name_entry *n, int stage)
 201 {
 202         int len = traverse_path_len(info, n);
 203         struct cache_entry *ce = xcalloc(1, cache_entry_size(len));
 204
 205         ce->ce_mode = create_ce_mode(n->mode);
 206         ce->ce_flags = create_ce_flags(len, stage);
 207         hashcpy(ce->sha1, n->sha1);
 208         make_traverse_path(ce->name, info, n);
 209
 210         return ce;
 211 }
 212
 213 static int unpack_nondirectories(int n, unsigned long mask, unsigned long dirmask, struct cache_entry *src[5],
 214         const struct name_entry *names, const struct traverse_info *info)
 215 {
 216         int i;
 217         struct unpack_trees_options *o = info->data;
 218         unsigned long conflicts;
 219
 220         /* Do we have *only* directories? Nothing to do */
 221         if (mask == dirmask && !src[0])
 222                 return 0;
 223
 224         conflicts = info->conflicts;
 225         if (o->merge)
 226                 conflicts >>= 1;
 227         conflicts |= dirmask;
 228
 229         /*
 230          * Ok, we've filled in up to any potential index entry in src[0],
 231          * now do the rest.
 232          */
 233         for (i = 0; i < n; i++) {
 234                 int stage;
 235                 unsigned int bit = 1ul << i;
 236                 if (conflicts & bit) {
 237                         src[i + o->merge] = o->df_conflict_entry;
 238                         continue;
 239                 }
 240                 if (!(mask & bit))
 241                         continue;
 242                 if (!o->merge)
 243                         stage = 0;
 244                 else if (i + 1 < o->head_idx)
 245                         stage = 1;
 246                 else if (i + 1 > o->head_idx)
 247                         stage = 3;
 248                 else
 249                         stage = 2;
 250                 src[i + o->merge] = create_ce_entry(info, names + i, stage);
 251         }
 252
 253         if (o->merge)
 254                 return call_unpack_fn(src, o);
 255
 256         n += o->merge;
 257         for (i = 0; i < n; i++)
 258                 add_entry(o, src[i], 0, 0);
 259         return 0;
 260 }
 261
 262 static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *names, struct traverse_info *info)
 263 {
 264         struct cache_entry *src[5] = { NULL, };
 265         struct unpack_trees_options *o = info->data;
 266         const struct name_entry *p = names;
 267
 268         /* Find first entry with a real name (we could use "mask" too) */
 269         while (!p->mode)
 270                 p++;
 271
 272         /* Are we supposed to look at the index too? */
 273         if (o->merge) {
 274                 while (o->pos < o->src_index->cache_nr) {
 275                         struct cache_entry *ce = o->src_index->cache[o->pos];
 276                         int cmp = compare_entry(ce, info, p);
 277                         if (cmp < 0) {
 278                                 if (unpack_index_entry(ce, o) < 0)
 279                                         return -1;
 280                                 continue;
 281                         }
 282                         if (!cmp) {
 283                                 o->pos++;
 284                                 if (ce_stage(ce)) {
 285                                         /*
 286                                          * If we skip unmerged index entries, we'll skip this
 287                                          * entry *and* the tree entries associated with it!
 288                                          */
 289                                         if (o->skip_unmerged) {
 290                                                 add_entry(o, ce, 0, 0);
 291                                                 return mask;
 292                                         }
 293                                 }
 294                                 src[0] = ce;
 295                         }
 296                         break;
 297                 }
 298         }
 299
 300         if (unpack_nondirectories(n, mask, dirmask, src, names, info) < 0)
 301                 return -1;
 302
 303         /* Now handle any directories.. */
 304         if (dirmask) {
 305                 unsigned long conflicts = mask & ~dirmask;
 306                 if (o->merge) {
 307                         conflicts <<= 1;
 308                         if (src[0])
 309                                 conflicts |= 1;
 310                 }
 311                 if (traverse_trees_recursive(n, dirmask, conflicts,
 312                                              names, info) < 0)
 313                         return -1;
 314                 return mask;
 315         }
 316
 317         return mask;
 318 }
 319
 320 static int unpack_failed(struct unpack_trees_options *o, const char *message)
 321 {
 322         discard_index(&o->result);
 323         if (!o->gently) {
 324                 if (message)
 325                         return error(message);
 326                 return -1;
 327         }
 328         return -1;
 329 }
 330
 331 int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
 332 {
 333         static struct cache_entry *dfc;
 334
 335         if (len > MAX_UNPACK_TREES)
 336                 die("unpack_trees takes at most %d trees", MAX_UNPACK_TREES);
 337         memset(&state, 0, sizeof(state));
 338         state.base_dir = "";
 339         state.force = 1;
 340         state.quiet = 1;
 341         state.refresh_cache = 1;
 342
 343         memset(&o->result, 0, sizeof(o->result));
 344         if (o->src_index)
 345                 o->result.timestamp = o->src_index->timestamp;
 346         o->merge_size = len;
 347
 348         if (!dfc)
 349                 dfc = xcalloc(1, sizeof(struct cache_entry) + 1);
 350         o->df_conflict_entry = dfc;
 351
 352         if (len) {
 353                 const char *prefix = o->prefix ? o->prefix : "";
 354                 struct traverse_info info;
 355
 356                 setup_traverse_info(&info, prefix);
 357                 info.fn = unpack_callback;
 358                 info.data = o;
 359
 360                 if (traverse_trees(len, t, &info) < 0)
 361                         return unpack_failed(o, NULL);
 362         }
 363
 364         /* Any left-over entries in the index? */
 365         if (o->merge) {
 366                 while (o->pos < o->src_index->cache_nr) {
 367                         struct cache_entry *ce = o->src_index->cache[o->pos];
 368                         if (unpack_index_entry(ce, o) < 0)
 369                                 return unpack_failed(o, NULL);
 370                 }
 371         }
 372
 373         if (o->trivial_merges_only && o->nontrivial_merge)
 374                 return unpack_failed(o, "Merge requires file-level merging");
 375
 376         o->src_index = NULL;
 377         if (check_updates(o))
 378                 return -1;
 379         if (o->dst_index)
 380                 *o->dst_index = o->result;
 381         return 0;
 382 }
 383
 384 /* Here come the merge functions */
 385
 386 static int reject_merge(struct cache_entry *ce)
 387 {
 388         return error("Entry '%s' would be overwritten by merge. Cannot merge.",
 389                      ce->name);
 390 }
 391
 392 static int same(struct cache_entry *a, struct cache_entry *b)
 393 {
 394         if (!!a != !!b)
 395                 return 0;
 396         if (!a && !b)
 397                 return 1;
 398         return a->ce_mode == b->ce_mode &&
 399                !hashcmp(a->sha1, b->sha1);
 400 }
 401
 402
 403 /*
 404  * When a CE gets turned into an unmerged entry, we
 405  * want it to be up-to-date
 406  */
 407 static int verify_uptodate(struct cache_entry *ce,
 408                 struct unpack_trees_options *o)
 409 {
 410         struct stat st;
 411
 412         if (o->index_only || o->reset)
 413                 return 0;
 414
 415         if (!lstat(ce->name, &st)) {
 416                 unsigned changed = ie_match_stat(o->src_index, ce, &st, CE_MATCH_IGNORE_VALID);
 417                 if (!changed)
 418                         return 0;
 419                 /*
 420                  * NEEDSWORK: the current default policy is to allow
 421                  * submodule to be out of sync wrt the supermodule
 422                  * index.  This needs to be tightened later for
 423                  * submodules that are marked to be automatically
 424                  * checked out.
 425                  */
 426                 if (S_ISGITLINK(ce->ce_mode))
 427                         return 0;
 428                 errno = 0;
 429         }
 430         if (errno == ENOENT)
 431                 return 0;
 432         return o->gently ? -1 :
 433                 error("Entry '%s' not uptodate. Cannot merge.", ce->name);
 434 }
 435
 436 static void invalidate_ce_path(struct cache_entry *ce, struct unpack_trees_options *o)
 437 {
 438         if (ce)
 439                 cache_tree_invalidate_path(o->src_index->cache_tree, ce->name);
 440 }
 441
 442 /*
 443  * Check that checking out ce->sha1 in subdir ce->name is not
 444  * going to overwrite any working files.
 445  *
 446  * Currently, git does not checkout subprojects during a superproject
 447  * checkout, so it is not going to overwrite anything.
 448  */
 449 static int verify_clean_submodule(struct cache_entry *ce, const char *action,
 450                                       struct unpack_trees_options *o)
 451 {
 452         return 0;
 453 }
 454
 455 static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
 456                                       struct unpack_trees_options *o)
 457 {
 458         /*
 459          * we are about to extract "ce->name"; we would not want to lose
 460          * anything in the existing directory there.
 461          */
 462         int namelen;
 463         int pos, i;
 464         struct dir_struct d;
 465         char *pathbuf;
 466         int cnt = 0;
 467         unsigned char sha1[20];
 468
 469         if (S_ISGITLINK(ce->ce_mode) &&
 470             resolve_gitlink_ref(ce->name, "HEAD", sha1) == 0) {
 471                 /* If we are not going to update the submodule, then
 472                  * we don't care.
 473                  */
 474                 if (!hashcmp(sha1, ce->sha1))
 475                         return 0;
 476                 return verify_clean_submodule(ce, action, o);
 477         }
 478
 479         /*
 480          * First let's make sure we do not have a local modification
 481          * in that directory.
 482          */
 483         namelen = strlen(ce->name);
 484         pos = index_name_pos(o->src_index, ce->name, namelen);
 485         if (0 <= pos)
 486                 return cnt; /* we have it as nondirectory */
 487         pos = -pos - 1;
 488         for (i = pos; i < o->src_index->cache_nr; i++) {
 489                 struct cache_entry *ce = o->src_index->cache[i];
 490                 int len = ce_namelen(ce);
 491                 if (len < namelen ||
 492                     strncmp(ce->name, ce->name, namelen) ||
 493                     ce->name[namelen] != '/')
 494                         break;
 495                 /*
 496                  * ce->name is an entry in the subdirectory.
 497                  */
 498                 if (!ce_stage(ce)) {
 499                         if (verify_uptodate(ce, o))
 500                                 return -1;
 501                         add_entry(o, ce, CE_REMOVE, 0);
 502                 }
 503                 cnt++;
 504         }
 505
 506         /*
 507          * Then we need to make sure that we do not lose a locally
 508          * present file that is not ignored.
 509          */
 510         pathbuf = xmalloc(namelen + 2);
 511         memcpy(pathbuf, ce->name, namelen);
 512         strcpy(pathbuf+namelen, "/");
 513
 514         memset(&d, 0, sizeof(d));
 515         if (o->dir)
 516                 d.exclude_per_dir = o->dir->exclude_per_dir;
 517         i = read_directory(&d, ce->name, pathbuf, namelen+1, NULL);
 518         if (i)
 519                 return o->gently ? -1 :
 520                         error("Updating '%s' would lose untracked files in it",
 521                               ce->name);
 522         free(pathbuf);
 523         return cnt;
 524 }
 525
 526 /*
 527  * This gets called when there was no index entry for the tree entry 'dst',
 528  * but we found a file in the working tree that 'lstat()' said was fine,
 529  * and we're on a case-insensitive filesystem.
 530  *
 531  * See if we can find a case-insensitive match in the index that also
 532  * matches the stat information, and assume it's that other file!
 533  */
 534 static int icase_exists(struct unpack_trees_options *o, struct cache_entry *dst, struct stat *st)
 535 {
 536         struct cache_entry *src;
 537
 538         src = index_name_exists(o->src_index, dst->name, ce_namelen(dst), 1);
 539         return src && !ie_match_stat(o->src_index, src, st, CE_MATCH_IGNORE_VALID);
 540 }
 541
 542 /*
 543  * We do not want to remove or overwrite a working tree file that
 544  * is not tracked, unless it is ignored.
 545  */
 546 static int verify_absent(struct cache_entry *ce, const char *action,
 547                          struct unpack_trees_options *o)
 548 {
 549         struct stat st;
 550
 551         if (o->index_only || o->reset || !o->update)
 552                 return 0;
 553
 554         if (has_symlink_leading_path(ce_namelen(ce), ce->name))
 555                 return 0;
 556
 557         if (!lstat(ce->name, &st)) {
 558                 int cnt;
 559                 int dtype = ce_to_dtype(ce);
 560                 struct cache_entry *result;
 561
 562                 /*
 563                  * It may be that the 'lstat()' succeeded even though
 564                  * target 'ce' was absent, because there is an old
 565                  * entry that is different only in case..
 566                  *
 567                  * Ignore that lstat() if it matches.
 568                  */
 569                 if (ignore_case && icase_exists(o, ce, &st))
 570                         return 0;
 571
 572                 if (o->dir && excluded(o->dir, ce->name, &dtype))
 573                         /*
 574                          * ce->name is explicitly excluded, so it is Ok to
 575                          * overwrite it.
 576                          */
 577                         return 0;
 578                 if (S_ISDIR(st.st_mode)) {
 579                         /*
 580                          * We are checking out path "foo" and
 581                          * found "foo/." in the working tree.
 582                          * This is tricky -- if we have modified
 583                          * files that are in "foo/" we would lose
 584                          * it.
 585                          */
 586                         cnt = verify_clean_subdirectory(ce, action, o);
 587
 588                         /*
 589                          * If this removed entries from the index,
 590                          * what that means is:
 591                          *
 592                          * (1) the caller unpack_trees_rec() saw path/foo
 593                          * in the index, and it has not removed it because
 594                          * it thinks it is handling 'path' as blob with
 595                          * D/F conflict;
 596                          * (2) we will return "ok, we placed a merged entry
 597                          * in the index" which would cause o->pos to be
 598                          * incremented by one;
 599                          * (3) however, original o->pos now has 'path/foo'
 600                          * marked with "to be removed".
 601                          *
 602                          * We need to increment it by the number of
 603                          * deleted entries here.
 604                          */
 605                         o->pos += cnt;
 606                         return 0;
 607                 }
 608
 609                 /*
 610                  * The previous round may already have decided to
 611                  * delete this path, which is in a subdirectory that
 612                  * is being replaced with a blob.
 613                  */
 614                 result = index_name_exists(&o->result, ce->name, ce_namelen(ce), 0);
 615                 if (result) {
 616                         if (result->ce_flags & CE_REMOVE)
 617                                 return 0;
 618                 }
 619
 620                 return o->gently ? -1 :
 621                         error("Untracked working tree file '%s' "
 622                               "would be %s by merge.", ce->name, action);
 623         }
 624         return 0;
 625 }
 626
 627 static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
 628                 struct unpack_trees_options *o)
 629 {
 630         int update = CE_UPDATE;
 631
 632         if (old) {
 633                 /*
 634                  * See if we can re-use the old CE directly?
 635                  * That way we get the uptodate stat info.
 636                  *
 637                  * This also removes the UPDATE flag on a match; otherwise
 638                  * we will end up overwriting local changes in the work tree.
 639                  */
 640                 if (same(old, merge)) {
 641                         copy_cache_entry(merge, old);
 642                         update = 0;
 643                 } else {
 644                         if (verify_uptodate(old, o))
 645                                 return -1;
 646                         invalidate_ce_path(old, o);
 647                 }
 648         }
 649         else {
 650                 if (verify_absent(merge, "overwritten", o))
 651                         return -1;
 652                 invalidate_ce_path(merge, o);
 653         }
 654
 655         add_entry(o, merge, update, CE_STAGEMASK);
 656         return 1;
 657 }
 658
 659 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
 660                 struct unpack_trees_options *o)
 661 {
 662         /* Did it exist in the index? */
 663         if (!old) {
 664                 if (verify_absent(ce, "removed", o))
 665                         return -1;
 666                 return 0;
 667         }
 668         if (verify_uptodate(old, o))
 669                 return -1;
 670         add_entry(o, ce, CE_REMOVE, 0);
 671         invalidate_ce_path(ce, o);
 672         return 1;
 673 }
 674
 675 static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 676 {
 677         add_entry(o, ce, 0, 0);
 678         return 1;
 679 }
 680
 681 #if DBRT_DEBUG
 682 static void show_stage_entry(FILE *o,
 683                              const char *label, const struct cache_entry *ce)
 684 {
 685         if (!ce)
 686                 fprintf(o, "%s (missing)\n", label);
 687         else
 688                 fprintf(o, "%s%06o %s %d\t%s\n",
 689                         label,
 690                         ce->ce_mode,
 691                         sha1_to_hex(ce->sha1),
 692                         ce_stage(ce),
 693                         ce->name);
 694 }
 695 #endif
 696
 697 int threeway_merge(struct cache_entry **stages, struct unpack_trees_options *o)
 698 {
 699         struct cache_entry *index;
 700         struct cache_entry *head;
 701         struct cache_entry *remote = stages[o->head_idx + 1];
 702         int count;
 703         int head_match = 0;
 704         int remote_match = 0;
 705
 706         int df_conflict_head = 0;
 707         int df_conflict_remote = 0;
 708
 709         int any_anc_missing = 0;
 710         int no_anc_exists = 1;
 711         int i;
 712
 713         for (i = 1; i < o->head_idx; i++) {
 714                 if (!stages[i] || stages[i] == o->df_conflict_entry)
 715                         any_anc_missing = 1;
 716                 else
 717                         no_anc_exists = 0;
 718         }
 719
 720         index = stages[0];
 721         head = stages[o->head_idx];
 722
 723         if (head == o->df_conflict_entry) {
 724                 df_conflict_head = 1;
 725                 head = NULL;
 726         }
 727
 728         if (remote == o->df_conflict_entry) {
 729                 df_conflict_remote = 1;
 730                 remote = NULL;
 731         }
 732
 733         /* First, if there's a #16 situation, note that to prevent #13
 734          * and #14.
 735          */
 736         if (!same(remote, head)) {
 737                 for (i = 1; i < o->head_idx; i++) {
 738                         if (same(stages[i], head)) {
 739                                 head_match = i;
 740                         }
 741                         if (same(stages[i], remote)) {
 742                                 remote_match = i;
 743                         }
 744                 }
 745         }
 746
 747         /* We start with cases where the index is allowed to match
 748          * something other than the head: #14(ALT) and #2ALT, where it
 749          * is permitted to match the result instead.
 750          */
 751         /* #14, #14ALT, #2ALT */
 752         if (remote && !df_conflict_head && head_match && !remote_match) {
 753                 if (index && !same(index, remote) && !same(index, head))
 754                         return o->gently ? -1 : reject_merge(index);
 755                 return merged_entry(remote, index, o);
 756         }
 757         /*
 758          * If we have an entry in the index cache, then we want to
 759          * make sure that it matches head.
 760          */
 761         if (index && !same(index, head))
 762                 return o->gently ? -1 : reject_merge(index);
 763
 764         if (head) {
 765                 /* #5ALT, #15 */
 766                 if (same(head, remote))
 767                         return merged_entry(head, index, o);
 768                 /* #13, #3ALT */
 769                 if (!df_conflict_remote && remote_match && !head_match)
 770                         return merged_entry(head, index, o);
 771         }
 772
 773         /* #1 */
 774         if (!head && !remote && any_anc_missing)
 775                 return 0;
 776
 777         /* Under the new "aggressive" rule, we resolve mostly trivial
 778          * cases that we historically had git-merge-one-file resolve.
 779          */
 780         if (o->aggressive) {
 781                 int head_deleted = !head && !df_conflict_head;
 782                 int remote_deleted = !remote && !df_conflict_remote;
 783                 struct cache_entry *ce = NULL;
 784
 785                 if (index)
 786                         ce = index;
 787                 else if (head)
 788                         ce = head;
 789                 else if (remote)
 790                         ce = remote;
 791                 else {
 792                         for (i = 1; i < o->head_idx; i++) {
 793                                 if (stages[i] && stages[i] != o->df_conflict_entry) {
 794                                         ce = stages[i];
 795                                         break;
 796                                 }
 797                         }
 798                 }
 799
 800                 /*
 801                  * Deleted in both.
 802                  * Deleted in one and unchanged in the other.
 803                  */
 804                 if ((head_deleted && remote_deleted) ||
 805                     (head_deleted && remote && remote_match) ||
 806                     (remote_deleted && head && head_match)) {
 807                         if (index)
 808                                 return deleted_entry(index, index, o);
 809                         if (ce && !head_deleted) {
 810                                 if (verify_absent(ce, "removed", o))
 811                                         return -1;
 812                         }
 813                         return 0;
 814                 }
 815                 /*
 816                  * Added in both, identically.
 817                  */
 818                 if (no_anc_exists && head && remote && same(head, remote))
 819                         return merged_entry(head, index, o);
 820
 821         }
 822
 823         /* Below are "no merge" cases, which require that the index be
 824          * up-to-date to avoid the files getting overwritten with
 825          * conflict resolution files.
 826          */
 827         if (index) {
 828                 if (verify_uptodate(index, o))
 829                         return -1;
 830         }
 831
 832         o->nontrivial_merge = 1;
 833
 834         /* #2, #3, #4, #6, #7, #9, #10, #11. */
 835         count = 0;
 836         if (!head_match || !remote_match) {
 837                 for (i = 1; i < o->head_idx; i++) {
 838                         if (stages[i] && stages[i] != o->df_conflict_entry) {
 839                                 keep_entry(stages[i], o);
 840                                 count++;
 841                                 break;
 842                         }
 843                 }
 844         }
 845 #if DBRT_DEBUG
 846         else {
 847                 fprintf(stderr, "read-tree: warning #16 detected\n");
 848                 show_stage_entry(stderr, "head   ", stages[head_match]);
 849                 show_stage_entry(stderr, "remote ", stages[remote_match]);
 850         }
 851 #endif
 852         if (head) { count += keep_entry(head, o); }
 853         if (remote) { count += keep_entry(remote, o); }
 854         return count;
 855 }
 856
 857 /*
 858  * Two-way merge.
 859  *
 860  * The rule is to "carry forward" what is in the index without losing
 861  * information across a "fast forward", favoring a successful merge
 862  * over a merge failure when it makes sense.  For details of the
 863  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 864  *
 865  */
 866 int twoway_merge(struct cache_entry **src, struct unpack_trees_options *o)
 867 {
 868         struct cache_entry *current = src[0];
 869         struct cache_entry *oldtree = src[1];
 870         struct cache_entry *newtree = src[2];
 871
 872         if (o->merge_size != 2)
 873                 return error("Cannot do a twoway merge of %d trees",
 874                              o->merge_size);
 875
 876         if (oldtree == o->df_conflict_entry)
 877                 oldtree = NULL;
 878         if (newtree == o->df_conflict_entry)
 879                 newtree = NULL;
 880
 881         if (current) {
 882                 if ((!oldtree && !newtree) || /* 4 and 5 */
 883                     (!oldtree && newtree &&
 884                      same(current, newtree)) || /* 6 and 7 */
 885                     (oldtree && newtree &&
 886                      same(oldtree, newtree)) || /* 14 and 15 */
 887                     (oldtree && newtree &&
 888                      !same(oldtree, newtree) && /* 18 and 19 */
 889                      same(current, newtree))) {
 890                         return keep_entry(current, o);
 891                 }
 892                 else if (oldtree && !newtree && same(current, oldtree)) {
 893                         /* 10 or 11 */
 894                         return deleted_entry(oldtree, current, o);
 895                 }
 896                 else if (oldtree && newtree &&
 897                          same(current, oldtree) && !same(current, newtree)) {
 898                         /* 20 or 21 */
 899                         return merged_entry(newtree, current, o);
 900                 }
 901                 else {
 902                         /* all other failures */
 903                         if (oldtree)
 904                                 return o->gently ? -1 : reject_merge(oldtree);
 905                         if (current)
 906                                 return o->gently ? -1 : reject_merge(current);
 907                         if (newtree)
 908                                 return o->gently ? -1 : reject_merge(newtree);
 909                         return -1;
 910                 }
 911         }
 912         else if (newtree)
 913                 return merged_entry(newtree, current, o);
 914         return deleted_entry(oldtree, current, o);
 915 }
 916
 917 /*
 918  * Bind merge.
 919  *
 920  * Keep the index entries at stage0, collapse stage1 but make sure
 921  * stage0 does not have anything there.
 922  */
 923 int bind_merge(struct cache_entry **src,
 924                 struct unpack_trees_options *o)
 925 {
 926         struct cache_entry *old = src[0];
 927         struct cache_entry *a = src[1];
 928
 929         if (o->merge_size != 1)
 930                 return error("Cannot do a bind merge of %d trees\n",
 931                              o->merge_size);
 932         if (a && old)
 933                 return o->gently ? -1 :
 934                         error("Entry '%s' overlaps with '%s'.  Cannot bind.", a->name, old->name);
 935         if (!a)
 936                 return keep_entry(old, o);
 937         else
 938                 return merged_entry(a, NULL, o);
 939 }
 940
 941 /*
 942  * One-way merge.
 943  *
 944  * The rule is:
 945  * - take the stat information from stage0, take the data from stage1
 946  */
 947 int oneway_merge(struct cache_entry **src, struct unpack_trees_options *o)
 948 {
 949         struct cache_entry *old = src[0];
 950         struct cache_entry *a = src[1];
 951
 952         if (o->merge_size != 1)
 953                 return error("Cannot do a oneway merge of %d trees",
 954                              o->merge_size);
 955
 956         if (!a)
 957                 return deleted_entry(old, old, o);
 958
 959         if (old && same(old, a)) {
 960                 int update = 0;
 961                 if (o->reset) {
 962                         struct stat st;
 963                         if (lstat(old->name, &st) ||
 964                             ie_match_stat(o->src_index, old, &st, CE_MATCH_IGNORE_VALID))
 965                                 update |= CE_UPDATE;
 966                 }
 967                 add_entry(o, old, update, 0);
 968                 return 0;
 969         }
 970         return merged_entry(a, old, o);
 971 }