unpack-trees.c

   1 #include "cache.h"
   2 #include "dir.h"
   3 #include "tree.h"
   4 #include "tree-walk.h"
   5 #include "cache-tree.h"
   6 #include "unpack-trees.h"
   7 #include "progress.h"
   8 #include "refs.h"
   9
  10 #define DBRT_DEBUG 1
  11
  12 struct tree_entry_list {
  13         struct tree_entry_list *next;
  14         unsigned int mode;
  15         const char *name;
  16         const unsigned char *sha1;
  17 };
  18
  19 static struct tree_entry_list *create_tree_entry_list(struct tree_desc *desc)
  20 {
  21         struct name_entry one;
  22         struct tree_entry_list *ret = NULL;
  23         struct tree_entry_list **list_p = &ret;
  24
  25         while (tree_entry(desc, &one)) {
  26                 struct tree_entry_list *entry;
  27
  28                 entry = xmalloc(sizeof(struct tree_entry_list));
  29                 entry->name = one.path;
  30                 entry->sha1 = one.sha1;
  31                 entry->mode = one.mode;
  32                 entry->next = NULL;
  33
  34                 *list_p = entry;
  35                 list_p = &entry->next;
  36         }
  37         return ret;
  38 }
  39
  40 static int entcmp(const char *name1, int dir1, const char *name2, int dir2)
  41 {
  42         int len1 = strlen(name1);
  43         int len2 = strlen(name2);
  44         int len = len1 < len2 ? len1 : len2;
  45         int ret = memcmp(name1, name2, len);
  46         unsigned char c1, c2;
  47         if (ret)
  48                 return ret;
  49         c1 = name1[len];
  50         c2 = name2[len];
  51         if (!c1 && dir1)
  52                 c1 = '/';
  53         if (!c2 && dir2)
  54                 c2 = '/';
  55         ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
  56         if (c1 && c2 && !ret)
  57                 ret = len1 - len2;
  58         return ret;
  59 }
  60
  61 static inline void remove_entry(int remove)
  62 {
  63         if (remove >= 0)
  64                 remove_cache_entry_at(remove);
  65 }
  66
  67 static int unpack_trees_rec(struct tree_entry_list **posns, int len,
  68                             const char *base, struct unpack_trees_options *o,
  69                             struct tree_entry_list *df_conflict_list)
  70 {
  71         int remove;
  72         int baselen = strlen(base);
  73         int src_size = len + 1;
  74         int retval = 0;
  75
  76         do {
  77                 int i;
  78                 const char *first;
  79                 int firstdir = 0;
  80                 int pathlen;
  81                 unsigned ce_size;
  82                 struct tree_entry_list **subposns;
  83                 struct cache_entry **src;
  84                 int any_files = 0;
  85                 int any_dirs = 0;
  86                 char *cache_name;
  87                 int ce_stage;
  88
  89                 /* Find the first name in the input. */
  90
  91                 first = NULL;
  92                 cache_name = NULL;
  93
  94                 /* Check the cache */
  95                 if (o->merge && o->pos < active_nr) {
  96                         /* This is a bit tricky: */
  97                         /* If the index has a subdirectory (with
  98                          * contents) as the first name, it'll get a
  99                          * filename like "foo/bar". But that's after
 100                          * "foo", so the entry in trees will get
 101                          * handled first, at which point we'll go into
 102                          * "foo", and deal with "bar" from the index,
 103                          * because the base will be "foo/". The only
 104                          * way we can actually have "foo/bar" first of
 105                          * all the things is if the trees don't
 106                          * contain "foo" at all, in which case we'll
 107                          * handle "foo/bar" without going into the
 108                          * directory, but that's fine (and will return
 109                          * an error anyway, with the added unknown
 110                          * file case.
 111                          */
 112
 113                         cache_name = active_cache[o->pos]->name;
 114                         if (strlen(cache_name) > baselen &&
 115                             !memcmp(cache_name, base, baselen)) {
 116                                 cache_name += baselen;
 117                                 first = cache_name;
 118                         } else {
 119                                 cache_name = NULL;
 120                         }
 121                 }
 122
 123 #if DBRT_DEBUG > 1
 124                 if (first)
 125                         fprintf(stderr, "index %s\n", first);
 126 #endif
 127                 for (i = 0; i < len; i++) {
 128                         if (!posns[i] || posns[i] == df_conflict_list)
 129                                 continue;
 130 #if DBRT_DEBUG > 1
 131                         fprintf(stderr, "%d %s\n", i + 1, posns[i]->name);
 132 #endif
 133                         if (!first || entcmp(first, firstdir,
 134                                              posns[i]->name,
 135                                              S_ISDIR(posns[i]->mode)) > 0) {
 136                                 first = posns[i]->name;
 137                                 firstdir = S_ISDIR(posns[i]->mode);
 138                         }
 139                 }
 140                 /* No name means we're done */
 141                 if (!first)
 142                         goto leave_directory;
 143
 144                 pathlen = strlen(first);
 145                 ce_size = cache_entry_size(baselen + pathlen);
 146
 147                 src = xcalloc(src_size, sizeof(struct cache_entry *));
 148
 149                 subposns = xcalloc(len, sizeof(struct tree_list_entry *));
 150
 151                 remove = -1;
 152                 if (cache_name && !strcmp(cache_name, first)) {
 153                         any_files = 1;
 154                         src[0] = active_cache[o->pos];
 155                         remove = o->pos;
 156                 }
 157
 158                 for (i = 0; i < len; i++) {
 159                         struct cache_entry *ce;
 160
 161                         if (!posns[i] ||
 162                             (posns[i] != df_conflict_list &&
 163                              strcmp(first, posns[i]->name))) {
 164                                 continue;
 165                         }
 166
 167                         if (posns[i] == df_conflict_list) {
 168                                 src[i + o->merge] = o->df_conflict_entry;
 169                                 continue;
 170                         }
 171
 172                         if (S_ISDIR(posns[i]->mode)) {
 173                                 struct tree *tree = lookup_tree(posns[i]->sha1);
 174                                 struct tree_desc t;
 175                                 any_dirs = 1;
 176                                 parse_tree(tree);
 177                                 init_tree_desc(&t, tree->buffer, tree->size);
 178                                 subposns[i] = create_tree_entry_list(&t);
 179                                 posns[i] = posns[i]->next;
 180                                 src[i + o->merge] = o->df_conflict_entry;
 181                                 continue;
 182                         }
 183
 184                         if (!o->merge)
 185                                 ce_stage = 0;
 186                         else if (i + 1 < o->head_idx)
 187                                 ce_stage = 1;
 188                         else if (i + 1 > o->head_idx)
 189                                 ce_stage = 3;
 190                         else
 191                                 ce_stage = 2;
 192
 193                         ce = xcalloc(1, ce_size);
 194                         ce->ce_mode = create_ce_mode(posns[i]->mode);
 195                         ce->ce_flags = create_ce_flags(baselen + pathlen,
 196                                                        ce_stage);
 197                         memcpy(ce->name, base, baselen);
 198                         memcpy(ce->name + baselen, first, pathlen + 1);
 199
 200                         any_files = 1;
 201
 202                         hashcpy(ce->sha1, posns[i]->sha1);
 203                         src[i + o->merge] = ce;
 204                         subposns[i] = df_conflict_list;
 205                         posns[i] = posns[i]->next;
 206                 }
 207                 if (any_files) {
 208                         if (o->merge) {
 209                                 int ret;
 210
 211 #if DBRT_DEBUG > 1
 212                                 fprintf(stderr, "%s:\n", first);
 213                                 for (i = 0; i < src_size; i++) {
 214                                         fprintf(stderr, " %d ", i);
 215                                         if (src[i])
 216                                                 fprintf(stderr, "%06x %s\n", src[i]->ce_mode, sha1_to_hex(src[i]->sha1));
 217                                         else
 218                                                 fprintf(stderr, "\n");
 219                                 }
 220 #endif
 221                                 ret = o->fn(src, o, remove);
 222                                 if (ret < 0)
 223                                         return ret;
 224
 225 #if DBRT_DEBUG > 1
 226                                 fprintf(stderr, "Added %d entries\n", ret);
 227 #endif
 228                                 o->pos += ret;
 229                         } else {
 230                                 remove_entry(remove);
 231                                 for (i = 0; i < src_size; i++) {
 232                                         if (src[i]) {
 233                                                 add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
 234                                         }
 235                                 }
 236                         }
 237                 }
 238                 if (any_dirs) {
 239                         char *newbase = xmalloc(baselen + 2 + pathlen);
 240                         memcpy(newbase, base, baselen);
 241                         memcpy(newbase + baselen, first, pathlen);
 242                         newbase[baselen + pathlen] = '/';
 243                         newbase[baselen + pathlen + 1] = '\0';
 244                         if (unpack_trees_rec(subposns, len, newbase, o,
 245                                              df_conflict_list)) {
 246                                 retval = -1;
 247                                 goto leave_directory;
 248                         }
 249                         free(newbase);
 250                 }
 251                 free(subposns);
 252                 free(src);
 253         } while (1);
 254
 255  leave_directory:
 256         return retval;
 257 }
 258
 259 /* Unlink the last component and attempt to remove leading
 260  * directories, in case this unlink is the removal of the
 261  * last entry in the directory -- empty directories are removed.
 262  */
 263 static void unlink_entry(char *name, char *last_symlink)
 264 {
 265         char *cp, *prev;
 266
 267         if (has_symlink_leading_path(name, last_symlink))
 268                 return;
 269         if (unlink(name))
 270                 return;
 271         prev = NULL;
 272         while (1) {
 273                 int status;
 274                 cp = strrchr(name, '/');
 275                 if (prev)
 276                         *prev = '/';
 277                 if (!cp)
 278                         break;
 279
 280                 *cp = 0;
 281                 status = rmdir(name);
 282                 if (status) {
 283                         *cp = '/';
 284                         break;
 285                 }
 286                 prev = cp;
 287         }
 288 }
 289
 290 static struct checkout state;
 291 static void check_updates(struct unpack_trees_options *o)
 292 {
 293         unsigned cnt = 0, total = 0;
 294         struct progress *progress = NULL;
 295         char last_symlink[PATH_MAX];
 296         int i;
 297
 298         if (o->update && o->verbose_update) {
 299                 for (total = cnt = 0; cnt < active_nr; cnt++) {
 300                         struct cache_entry *ce = active_cache[cnt];
 301                         if (ce->ce_flags & (CE_UPDATE | CE_REMOVE))
 302                                 total++;
 303                 }
 304
 305                 progress = start_progress_delay("Checking out files",
 306                                                 total, 50, 2);
 307                 cnt = 0;
 308         }
 309
 310         *last_symlink = '\0';
 311         for (i = 0; i < active_nr; i++) {
 312                 struct cache_entry *ce = active_cache[i];
 313
 314                 if (ce->ce_flags & (CE_UPDATE | CE_REMOVE))
 315                         display_progress(progress, ++cnt);
 316                 if (ce->ce_flags & CE_REMOVE) {
 317                         if (o->update)
 318                                 unlink_entry(ce->name, last_symlink);
 319                         remove_cache_entry_at(i);
 320                         i--;
 321                         continue;
 322                 }
 323                 if (ce->ce_flags & CE_UPDATE) {
 324                         ce->ce_flags &= ~CE_UPDATE;
 325                         if (o->update) {
 326                                 checkout_entry(ce, &state, NULL);
 327                                 *last_symlink = '\0';
 328                         }
 329                 }
 330         }
 331         stop_progress(&progress);
 332 }
 333
 334 int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
 335 {
 336         struct tree_entry_list **posns;
 337         int i;
 338         struct tree_entry_list df_conflict_list;
 339         static struct cache_entry *dfc;
 340
 341         memset(&df_conflict_list, 0, sizeof(df_conflict_list));
 342         df_conflict_list.next = &df_conflict_list;
 343         memset(&state, 0, sizeof(state));
 344         state.base_dir = "";
 345         state.force = 1;
 346         state.quiet = 1;
 347         state.refresh_cache = 1;
 348
 349         o->merge_size = len;
 350
 351         if (!dfc)
 352                 dfc = xcalloc(1, sizeof(struct cache_entry) + 1);
 353         o->df_conflict_entry = dfc;
 354
 355         if (len) {
 356                 posns = xmalloc(len * sizeof(struct tree_entry_list *));
 357                 for (i = 0; i < len; i++)
 358                         posns[i] = create_tree_entry_list(t+i);
 359
 360                 if (unpack_trees_rec(posns, len, o->prefix ? o->prefix : "",
 361                                      o, &df_conflict_list)) {
 362                         if (o->gently) {
 363                                 discard_cache();
 364                                 read_cache();
 365                         }
 366                         return -1;
 367                 }
 368         }
 369
 370         if (o->trivial_merges_only && o->nontrivial_merge) {
 371                 if (o->gently) {
 372                         discard_cache();
 373                         read_cache();
 374                 }
 375                 return o->gently ? -1 :
 376                         error("Merge requires file-level merging");
 377         }
 378
 379         check_updates(o);
 380         return 0;
 381 }
 382
 383 /* Here come the merge functions */
 384
 385 static int reject_merge(struct cache_entry *ce)
 386 {
 387         return error("Entry '%s' would be overwritten by merge. Cannot merge.",
 388                      ce->name);
 389 }
 390
 391 static int same(struct cache_entry *a, struct cache_entry *b)
 392 {
 393         if (!!a != !!b)
 394                 return 0;
 395         if (!a && !b)
 396                 return 1;
 397         return a->ce_mode == b->ce_mode &&
 398                !hashcmp(a->sha1, b->sha1);
 399 }
 400
 401
 402 /*
 403  * When a CE gets turned into an unmerged entry, we
 404  * want it to be up-to-date
 405  */
 406 static int verify_uptodate(struct cache_entry *ce,
 407                 struct unpack_trees_options *o)
 408 {
 409         struct stat st;
 410
 411         if (o->index_only || o->reset)
 412                 return 0;
 413
 414         if (!lstat(ce->name, &st)) {
 415                 unsigned changed = ce_match_stat(ce, &st, CE_MATCH_IGNORE_VALID);
 416                 if (!changed)
 417                         return 0;
 418                 /*
 419                  * NEEDSWORK: the current default policy is to allow
 420                  * submodule to be out of sync wrt the supermodule
 421                  * index.  This needs to be tightened later for
 422                  * submodules that are marked to be automatically
 423                  * checked out.
 424                  */
 425                 if (S_ISGITLINK(ce->ce_mode))
 426                         return 0;
 427                 errno = 0;
 428         }
 429         if (errno == ENOENT)
 430                 return 0;
 431         return o->gently ? -1 :
 432                 error("Entry '%s' not uptodate. Cannot merge.", ce->name);
 433 }
 434
 435 static void invalidate_ce_path(struct cache_entry *ce)
 436 {
 437         if (ce)
 438                 cache_tree_invalidate_path(active_cache_tree, ce->name);
 439 }
 440
 441 /*
 442  * Check that checking out ce->sha1 in subdir ce->name is not
 443  * going to overwrite any working files.
 444  *
 445  * Currently, git does not checkout subprojects during a superproject
 446  * checkout, so it is not going to overwrite anything.
 447  */
 448 static int verify_clean_submodule(struct cache_entry *ce, const char *action,
 449                                       struct unpack_trees_options *o)
 450 {
 451         return 0;
 452 }
 453
 454 static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
 455                                       struct unpack_trees_options *o)
 456 {
 457         /*
 458          * we are about to extract "ce->name"; we would not want to lose
 459          * anything in the existing directory there.
 460          */
 461         int namelen;
 462         int pos, i;
 463         struct dir_struct d;
 464         char *pathbuf;
 465         int cnt = 0;
 466         unsigned char sha1[20];
 467
 468         if (S_ISGITLINK(ce->ce_mode) &&
 469             resolve_gitlink_ref(ce->name, "HEAD", sha1) == 0) {
 470                 /* If we are not going to update the submodule, then
 471                  * we don't care.
 472                  */
 473                 if (!hashcmp(sha1, ce->sha1))
 474                         return 0;
 475                 return verify_clean_submodule(ce, action, o);
 476         }
 477
 478         /*
 479          * First let's make sure we do not have a local modification
 480          * in that directory.
 481          */
 482         namelen = strlen(ce->name);
 483         pos = cache_name_pos(ce->name, namelen);
 484         if (0 <= pos)
 485                 return cnt; /* we have it as nondirectory */
 486         pos = -pos - 1;
 487         for (i = pos; i < active_nr; i++) {
 488                 struct cache_entry *ce = active_cache[i];
 489                 int len = ce_namelen(ce);
 490                 if (len < namelen ||
 491                     strncmp(ce->name, ce->name, namelen) ||
 492                     ce->name[namelen] != '/')
 493                         break;
 494                 /*
 495                  * ce->name is an entry in the subdirectory.
 496                  */
 497                 if (!ce_stage(ce)) {
 498                         if (verify_uptodate(ce, o))
 499                                 return -1;
 500                         ce->ce_flags |= CE_REMOVE;
 501                 }
 502                 cnt++;
 503         }
 504
 505         /*
 506          * Then we need to make sure that we do not lose a locally
 507          * present file that is not ignored.
 508          */
 509         pathbuf = xmalloc(namelen + 2);
 510         memcpy(pathbuf, ce->name, namelen);
 511         strcpy(pathbuf+namelen, "/");
 512
 513         memset(&d, 0, sizeof(d));
 514         if (o->dir)
 515                 d.exclude_per_dir = o->dir->exclude_per_dir;
 516         i = read_directory(&d, ce->name, pathbuf, namelen+1, NULL);
 517         if (i)
 518                 return o->gently ? -1 :
 519                         error("Updating '%s' would lose untracked files in it",
 520                               ce->name);
 521         free(pathbuf);
 522         return cnt;
 523 }
 524
 525 /*
 526  * We do not want to remove or overwrite a working tree file that
 527  * is not tracked, unless it is ignored.
 528  */
 529 static int verify_absent(struct cache_entry *ce, const char *action,
 530                          struct unpack_trees_options *o)
 531 {
 532         struct stat st;
 533
 534         if (o->index_only || o->reset || !o->update)
 535                 return 0;
 536
 537         if (has_symlink_leading_path(ce->name, NULL))
 538                 return 0;
 539
 540         if (!lstat(ce->name, &st)) {
 541                 int cnt;
 542
 543                 if (o->dir && excluded(o->dir, ce->name))
 544                         /*
 545                          * ce->name is explicitly excluded, so it is Ok to
 546                          * overwrite it.
 547                          */
 548                         return 0;
 549                 if (S_ISDIR(st.st_mode)) {
 550                         /*
 551                          * We are checking out path "foo" and
 552                          * found "foo/." in the working tree.
 553                          * This is tricky -- if we have modified
 554                          * files that are in "foo/" we would lose
 555                          * it.
 556                          */
 557                         cnt = verify_clean_subdirectory(ce, action, o);
 558
 559                         /*
 560                          * If this removed entries from the index,
 561                          * what that means is:
 562                          *
 563                          * (1) the caller unpack_trees_rec() saw path/foo
 564                          * in the index, and it has not removed it because
 565                          * it thinks it is handling 'path' as blob with
 566                          * D/F conflict;
 567                          * (2) we will return "ok, we placed a merged entry
 568                          * in the index" which would cause o->pos to be
 569                          * incremented by one;
 570                          * (3) however, original o->pos now has 'path/foo'
 571                          * marked with "to be removed".
 572                          *
 573                          * We need to increment it by the number of
 574                          * deleted entries here.
 575                          */
 576                         o->pos += cnt;
 577                         return 0;
 578                 }
 579
 580                 /*
 581                  * The previous round may already have decided to
 582                  * delete this path, which is in a subdirectory that
 583                  * is being replaced with a blob.
 584                  */
 585                 cnt = cache_name_pos(ce->name, strlen(ce->name));
 586                 if (0 <= cnt) {
 587                         struct cache_entry *ce = active_cache[cnt];
 588                         if (ce->ce_flags & CE_REMOVE)
 589                                 return 0;
 590                 }
 591
 592                 return o->gently ? -1 :
 593                         error("Untracked working tree file '%s' "
 594                               "would be %s by merge.", ce->name, action);
 595         }
 596         return 0;
 597 }
 598
 599 static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
 600                 struct unpack_trees_options *o)
 601 {
 602         merge->ce_flags |= CE_UPDATE;
 603         if (old) {
 604                 /*
 605                  * See if we can re-use the old CE directly?
 606                  * That way we get the uptodate stat info.
 607                  *
 608                  * This also removes the UPDATE flag on
 609                  * a match.
 610                  */
 611                 if (same(old, merge)) {
 612                         memcpy(merge, old, offsetof(struct cache_entry, name));
 613                 } else {
 614                         if (verify_uptodate(old, o))
 615                                 return -1;
 616                         invalidate_ce_path(old);
 617                 }
 618         }
 619         else {
 620                 if (verify_absent(merge, "overwritten", o))
 621                         return -1;
 622                 invalidate_ce_path(merge);
 623         }
 624
 625         merge->ce_flags &= ~CE_STAGEMASK;
 626         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 627         return 1;
 628 }
 629
 630 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
 631                 struct unpack_trees_options *o)
 632 {
 633         if (old) {
 634                 if (verify_uptodate(old, o))
 635                         return -1;
 636         } else
 637                 if (verify_absent(ce, "removed", o))
 638                         return -1;
 639         ce->ce_flags |= CE_REMOVE;
 640         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 641         invalidate_ce_path(ce);
 642         return 1;
 643 }
 644
 645 static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 646 {
 647         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 648         return 1;
 649 }
 650
 651 #if DBRT_DEBUG
 652 static void show_stage_entry(FILE *o,
 653                              const char *label, const struct cache_entry *ce)
 654 {
 655         if (!ce)
 656                 fprintf(o, "%s (missing)\n", label);
 657         else
 658                 fprintf(o, "%s%06o %s %d\t%s\n",
 659                         label,
 660                         ce->ce_mode,
 661                         sha1_to_hex(ce->sha1),
 662                         ce_stage(ce),
 663                         ce->name);
 664 }
 665 #endif
 666
 667 int threeway_merge(struct cache_entry **stages,
 668                 struct unpack_trees_options *o,
 669                 int remove)
 670 {
 671         struct cache_entry *index;
 672         struct cache_entry *head;
 673         struct cache_entry *remote = stages[o->head_idx + 1];
 674         int count;
 675         int head_match = 0;
 676         int remote_match = 0;
 677
 678         int df_conflict_head = 0;
 679         int df_conflict_remote = 0;
 680
 681         int any_anc_missing = 0;
 682         int no_anc_exists = 1;
 683         int i;
 684
 685         for (i = 1; i < o->head_idx; i++) {
 686                 if (!stages[i] || stages[i] == o->df_conflict_entry)
 687                         any_anc_missing = 1;
 688                 else
 689                         no_anc_exists = 0;
 690         }
 691
 692         index = stages[0];
 693         head = stages[o->head_idx];
 694
 695         if (head == o->df_conflict_entry) {
 696                 df_conflict_head = 1;
 697                 head = NULL;
 698         }
 699
 700         if (remote == o->df_conflict_entry) {
 701                 df_conflict_remote = 1;
 702                 remote = NULL;
 703         }
 704
 705         /* First, if there's a #16 situation, note that to prevent #13
 706          * and #14.
 707          */
 708         if (!same(remote, head)) {
 709                 for (i = 1; i < o->head_idx; i++) {
 710                         if (same(stages[i], head)) {
 711                                 head_match = i;
 712                         }
 713                         if (same(stages[i], remote)) {
 714                                 remote_match = i;
 715                         }
 716                 }
 717         }
 718
 719         /* We start with cases where the index is allowed to match
 720          * something other than the head: #14(ALT) and #2ALT, where it
 721          * is permitted to match the result instead.
 722          */
 723         /* #14, #14ALT, #2ALT */
 724         if (remote && !df_conflict_head && head_match && !remote_match) {
 725                 if (index && !same(index, remote) && !same(index, head))
 726                         return o->gently ? -1 : reject_merge(index);
 727                 return merged_entry(remote, index, o);
 728         }
 729         /*
 730          * If we have an entry in the index cache, then we want to
 731          * make sure that it matches head.
 732          */
 733         if (index && !same(index, head)) {
 734                 return o->gently ? -1 : reject_merge(index);
 735         }
 736
 737         if (head) {
 738                 /* #5ALT, #15 */
 739                 if (same(head, remote))
 740                         return merged_entry(head, index, o);
 741                 /* #13, #3ALT */
 742                 if (!df_conflict_remote && remote_match && !head_match)
 743                         return merged_entry(head, index, o);
 744         }
 745
 746         /* #1 */
 747         if (!head && !remote && any_anc_missing) {
 748                 remove_entry(remove);
 749                 return 0;
 750         }
 751
 752         /* Under the new "aggressive" rule, we resolve mostly trivial
 753          * cases that we historically had git-merge-one-file resolve.
 754          */
 755         if (o->aggressive) {
 756                 int head_deleted = !head && !df_conflict_head;
 757                 int remote_deleted = !remote && !df_conflict_remote;
 758                 struct cache_entry *ce = NULL;
 759
 760                 if (index)
 761                         ce = index;
 762                 else if (head)
 763                         ce = head;
 764                 else if (remote)
 765                         ce = remote;
 766                 else {
 767                         for (i = 1; i < o->head_idx; i++) {
 768                                 if (stages[i] && stages[i] != o->df_conflict_entry) {
 769                                         ce = stages[i];
 770                                         break;
 771                                 }
 772                         }
 773                 }
 774
 775                 /*
 776                  * Deleted in both.
 777                  * Deleted in one and unchanged in the other.
 778                  */
 779                 if ((head_deleted && remote_deleted) ||
 780                     (head_deleted && remote && remote_match) ||
 781                     (remote_deleted && head && head_match)) {
 782                         remove_entry(remove);
 783                         if (index)
 784                                 return deleted_entry(index, index, o);
 785                         else if (ce && !head_deleted) {
 786                                 if (verify_absent(ce, "removed", o))
 787                                         return -1;
 788                         }
 789                         return 0;
 790                 }
 791                 /*
 792                  * Added in both, identically.
 793                  */
 794                 if (no_anc_exists && head && remote && same(head, remote))
 795                         return merged_entry(head, index, o);
 796
 797         }
 798
 799         /* Below are "no merge" cases, which require that the index be
 800          * up-to-date to avoid the files getting overwritten with
 801          * conflict resolution files.
 802          */
 803         if (index) {
 804                 if (verify_uptodate(index, o))
 805                         return -1;
 806         }
 807
 808         remove_entry(remove);
 809         o->nontrivial_merge = 1;
 810
 811         /* #2, #3, #4, #6, #7, #9, #10, #11. */
 812         count = 0;
 813         if (!head_match || !remote_match) {
 814                 for (i = 1; i < o->head_idx; i++) {
 815                         if (stages[i] && stages[i] != o->df_conflict_entry) {
 816                                 keep_entry(stages[i], o);
 817                                 count++;
 818                                 break;
 819                         }
 820                 }
 821         }
 822 #if DBRT_DEBUG
 823         else {
 824                 fprintf(stderr, "read-tree: warning #16 detected\n");
 825                 show_stage_entry(stderr, "head   ", stages[head_match]);
 826                 show_stage_entry(stderr, "remote ", stages[remote_match]);
 827         }
 828 #endif
 829         if (head) { count += keep_entry(head, o); }
 830         if (remote) { count += keep_entry(remote, o); }
 831         return count;
 832 }
 833
 834 /*
 835  * Two-way merge.
 836  *
 837  * The rule is to "carry forward" what is in the index without losing
 838  * information across a "fast forward", favoring a successful merge
 839  * over a merge failure when it makes sense.  For details of the
 840  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 841  *
 842  */
 843 int twoway_merge(struct cache_entry **src,
 844                 struct unpack_trees_options *o,
 845                 int remove)
 846 {
 847         struct cache_entry *current = src[0];
 848         struct cache_entry *oldtree = src[1];
 849         struct cache_entry *newtree = src[2];
 850
 851         if (o->merge_size != 2)
 852                 return error("Cannot do a twoway merge of %d trees",
 853                              o->merge_size);
 854
 855         if (oldtree == o->df_conflict_entry)
 856                 oldtree = NULL;
 857         if (newtree == o->df_conflict_entry)
 858                 newtree = NULL;
 859
 860         if (current) {
 861                 if ((!oldtree && !newtree) || /* 4 and 5 */
 862                     (!oldtree && newtree &&
 863                      same(current, newtree)) || /* 6 and 7 */
 864                     (oldtree && newtree &&
 865                      same(oldtree, newtree)) || /* 14 and 15 */
 866                     (oldtree && newtree &&
 867                      !same(oldtree, newtree) && /* 18 and 19 */
 868                      same(current, newtree))) {
 869                         return keep_entry(current, o);
 870                 }
 871                 else if (oldtree && !newtree && same(current, oldtree)) {
 872                         /* 10 or 11 */
 873                         remove_entry(remove);
 874                         return deleted_entry(oldtree, current, o);
 875                 }
 876                 else if (oldtree && newtree &&
 877                          same(current, oldtree) && !same(current, newtree)) {
 878                         /* 20 or 21 */
 879                         return merged_entry(newtree, current, o);
 880                 }
 881                 else {
 882                         /* all other failures */
 883                         remove_entry(remove);
 884                         if (oldtree)
 885                                 return o->gently ? -1 : reject_merge(oldtree);
 886                         if (current)
 887                                 return o->gently ? -1 : reject_merge(current);
 888                         if (newtree)
 889                                 return o->gently ? -1 : reject_merge(newtree);
 890                         return -1;
 891                 }
 892         }
 893         else if (newtree)
 894                 return merged_entry(newtree, current, o);
 895         remove_entry(remove);
 896         return deleted_entry(oldtree, current, o);
 897 }
 898
 899 /*
 900  * Bind merge.
 901  *
 902  * Keep the index entries at stage0, collapse stage1 but make sure
 903  * stage0 does not have anything there.
 904  */
 905 int bind_merge(struct cache_entry **src,
 906                 struct unpack_trees_options *o,
 907                 int remove)
 908 {
 909         struct cache_entry *old = src[0];
 910         struct cache_entry *a = src[1];
 911
 912         if (o->merge_size != 1)
 913                 return error("Cannot do a bind merge of %d trees\n",
 914                              o->merge_size);
 915         if (a && old)
 916                 return o->gently ? -1 :
 917                         error("Entry '%s' overlaps.  Cannot bind.", a->name);
 918         if (!a)
 919                 return keep_entry(old, o);
 920         else
 921                 return merged_entry(a, NULL, o);
 922 }
 923
 924 /*
 925  * One-way merge.
 926  *
 927  * The rule is:
 928  * - take the stat information from stage0, take the data from stage1
 929  */
 930 int oneway_merge(struct cache_entry **src,
 931                 struct unpack_trees_options *o,
 932                 int remove)
 933 {
 934         struct cache_entry *old = src[0];
 935         struct cache_entry *a = src[1];
 936
 937         if (o->merge_size != 1)
 938                 return error("Cannot do a oneway merge of %d trees",
 939                              o->merge_size);
 940
 941         if (!a) {
 942                 remove_entry(remove);
 943                 return deleted_entry(old, old, o);
 944         }
 945         if (old && same(old, a)) {
 946                 if (o->reset) {
 947                         struct stat st;
 948                         if (lstat(old->name, &st) ||
 949                             ce_match_stat(old, &st, CE_MATCH_IGNORE_VALID))
 950                                 old->ce_flags |= CE_UPDATE;
 951                 }
 952                 return keep_entry(old, o);
 953         }
 954         return merged_entry(a, old, o);
 955 }