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                         printf("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                         printf("%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                                 printf("%s:\n", first);
 213                                 for (i = 0; i < src_size; i++) {
 214                                         printf(" %d ", i);
 215                                         if (src[i])
 216                                                 printf("%s\n", sha1_to_hex(src[i]->sha1));
 217                                         else
 218                                                 printf("\n");
 219                                 }
 220 #endif
 221                                 ret = o->fn(src, o, remove);
 222                                 if (ret < 0)
 223                                         return ret;
 224
 225 #if DBRT_DEBUG > 1
 226                                 printf("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 cache_entry **src, int nr,
 292                         struct unpack_trees_options *o)
 293 {
 294         unsigned cnt = 0, total = 0;
 295         struct progress *progress = NULL;
 296         char last_symlink[PATH_MAX];
 297
 298         if (o->update && o->verbose_update) {
 299                 for (total = cnt = 0; cnt < nr; cnt++) {
 300                         struct cache_entry *ce = src[cnt];
 301                         if (ce->ce_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         while (nr--) {
 312                 struct cache_entry *ce = *src++;
 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                         continue;
 320                 }
 321                 if (ce->ce_flags & CE_UPDATE) {
 322                         ce->ce_flags &= ~CE_UPDATE;
 323                         if (o->update) {
 324                                 checkout_entry(ce, &state, NULL);
 325                                 *last_symlink = '\0';
 326                         }
 327                 }
 328         }
 329         stop_progress(&progress);
 330 }
 331
 332 int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
 333 {
 334         struct tree_entry_list **posns;
 335         int i;
 336         struct tree_entry_list df_conflict_list;
 337         static struct cache_entry *dfc;
 338
 339         memset(&df_conflict_list, 0, sizeof(df_conflict_list));
 340         df_conflict_list.next = &df_conflict_list;
 341         memset(&state, 0, sizeof(state));
 342         state.base_dir = "";
 343         state.force = 1;
 344         state.quiet = 1;
 345         state.refresh_cache = 1;
 346
 347         o->merge_size = len;
 348
 349         if (!dfc)
 350                 dfc = xcalloc(1, sizeof(struct cache_entry) + 1);
 351         o->df_conflict_entry = dfc;
 352
 353         if (len) {
 354                 posns = xmalloc(len * sizeof(struct tree_entry_list *));
 355                 for (i = 0; i < len; i++)
 356                         posns[i] = create_tree_entry_list(t+i);
 357
 358                 if (unpack_trees_rec(posns, len, o->prefix ? o->prefix : "",
 359                                      o, &df_conflict_list))
 360                         return -1;
 361         }
 362
 363         if (o->trivial_merges_only && o->nontrivial_merge)
 364                 return error("Merge requires file-level merging");
 365
 366         check_updates(active_cache, active_nr, o);
 367         return 0;
 368 }
 369
 370 /* Here come the merge functions */
 371
 372 static int reject_merge(struct cache_entry *ce)
 373 {
 374         return error("Entry '%s' would be overwritten by merge. Cannot merge.",
 375                      ce->name);
 376 }
 377
 378 static int same(struct cache_entry *a, struct cache_entry *b)
 379 {
 380         if (!!a != !!b)
 381                 return 0;
 382         if (!a && !b)
 383                 return 1;
 384         return a->ce_mode == b->ce_mode &&
 385                !hashcmp(a->sha1, b->sha1);
 386 }
 387
 388
 389 /*
 390  * When a CE gets turned into an unmerged entry, we
 391  * want it to be up-to-date
 392  */
 393 static int verify_uptodate(struct cache_entry *ce,
 394                 struct unpack_trees_options *o)
 395 {
 396         struct stat st;
 397
 398         if (o->index_only || o->reset)
 399                 return 0;
 400
 401         if (!lstat(ce->name, &st)) {
 402                 unsigned changed = ce_match_stat(ce, &st, CE_MATCH_IGNORE_VALID);
 403                 if (!changed)
 404                         return 0;
 405                 /*
 406                  * NEEDSWORK: the current default policy is to allow
 407                  * submodule to be out of sync wrt the supermodule
 408                  * index.  This needs to be tightened later for
 409                  * submodules that are marked to be automatically
 410                  * checked out.
 411                  */
 412                 if (S_ISGITLINK(ce->ce_mode))
 413                         return 0;
 414                 errno = 0;
 415         }
 416         if (errno == ENOENT)
 417                 return 0;
 418         return error("Entry '%s' not uptodate. Cannot merge.", ce->name);
 419 }
 420
 421 static void invalidate_ce_path(struct cache_entry *ce)
 422 {
 423         if (ce)
 424                 cache_tree_invalidate_path(active_cache_tree, ce->name);
 425 }
 426
 427 /*
 428  * Check that checking out ce->sha1 in subdir ce->name is not
 429  * going to overwrite any working files.
 430  *
 431  * Currently, git does not checkout subprojects during a superproject
 432  * checkout, so it is not going to overwrite anything.
 433  */
 434 static int verify_clean_submodule(struct cache_entry *ce, const char *action,
 435                                       struct unpack_trees_options *o)
 436 {
 437         return 0;
 438 }
 439
 440 static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
 441                                       struct unpack_trees_options *o)
 442 {
 443         /*
 444          * we are about to extract "ce->name"; we would not want to lose
 445          * anything in the existing directory there.
 446          */
 447         int namelen;
 448         int pos, i;
 449         struct dir_struct d;
 450         char *pathbuf;
 451         int cnt = 0;
 452         unsigned char sha1[20];
 453
 454         if (S_ISGITLINK(ce->ce_mode) &&
 455             resolve_gitlink_ref(ce->name, "HEAD", sha1) == 0) {
 456                 /* If we are not going to update the submodule, then
 457                  * we don't care.
 458                  */
 459                 if (!hashcmp(sha1, ce->sha1))
 460                         return 0;
 461                 return verify_clean_submodule(ce, action, o);
 462         }
 463
 464         /*
 465          * First let's make sure we do not have a local modification
 466          * in that directory.
 467          */
 468         namelen = strlen(ce->name);
 469         pos = cache_name_pos(ce->name, namelen);
 470         if (0 <= pos)
 471                 return cnt; /* we have it as nondirectory */
 472         pos = -pos - 1;
 473         for (i = pos; i < active_nr; i++) {
 474                 struct cache_entry *ce = active_cache[i];
 475                 int len = ce_namelen(ce);
 476                 if (len < namelen ||
 477                     strncmp(ce->name, ce->name, namelen) ||
 478                     ce->name[namelen] != '/')
 479                         break;
 480                 /*
 481                  * ce->name is an entry in the subdirectory.
 482                  */
 483                 if (!ce_stage(ce)) {
 484                         if (verify_uptodate(ce, o))
 485                                 return -1;
 486                         ce->ce_flags |= CE_REMOVE;
 487                 }
 488                 cnt++;
 489         }
 490
 491         /*
 492          * Then we need to make sure that we do not lose a locally
 493          * present file that is not ignored.
 494          */
 495         pathbuf = xmalloc(namelen + 2);
 496         memcpy(pathbuf, ce->name, namelen);
 497         strcpy(pathbuf+namelen, "/");
 498
 499         memset(&d, 0, sizeof(d));
 500         if (o->dir)
 501                 d.exclude_per_dir = o->dir->exclude_per_dir;
 502         i = read_directory(&d, ce->name, pathbuf, namelen+1, NULL);
 503         if (i)
 504                 return error("Updating '%s' would lose untracked files in it",
 505                              ce->name);
 506         free(pathbuf);
 507         return cnt;
 508 }
 509
 510 /*
 511  * We do not want to remove or overwrite a working tree file that
 512  * is not tracked, unless it is ignored.
 513  */
 514 static int verify_absent(struct cache_entry *ce, const char *action,
 515                          struct unpack_trees_options *o)
 516 {
 517         struct stat st;
 518
 519         if (o->index_only || o->reset || !o->update)
 520                 return 0;
 521
 522         if (has_symlink_leading_path(ce->name, NULL))
 523                 return 0;
 524
 525         if (!lstat(ce->name, &st)) {
 526                 int cnt;
 527
 528                 if (o->dir && excluded(o->dir, ce->name))
 529                         /*
 530                          * ce->name is explicitly excluded, so it is Ok to
 531                          * overwrite it.
 532                          */
 533                         return 0;
 534                 if (S_ISDIR(st.st_mode)) {
 535                         /*
 536                          * We are checking out path "foo" and
 537                          * found "foo/." in the working tree.
 538                          * This is tricky -- if we have modified
 539                          * files that are in "foo/" we would lose
 540                          * it.
 541                          */
 542                         cnt = verify_clean_subdirectory(ce, action, o);
 543
 544                         /*
 545                          * If this removed entries from the index,
 546                          * what that means is:
 547                          *
 548                          * (1) the caller unpack_trees_rec() saw path/foo
 549                          * in the index, and it has not removed it because
 550                          * it thinks it is handling 'path' as blob with
 551                          * D/F conflict;
 552                          * (2) we will return "ok, we placed a merged entry
 553                          * in the index" which would cause o->pos to be
 554                          * incremented by one;
 555                          * (3) however, original o->pos now has 'path/foo'
 556                          * marked with "to be removed".
 557                          *
 558                          * We need to increment it by the number of
 559                          * deleted entries here.
 560                          */
 561                         o->pos += cnt;
 562                         return 0;
 563                 }
 564
 565                 /*
 566                  * The previous round may already have decided to
 567                  * delete this path, which is in a subdirectory that
 568                  * is being replaced with a blob.
 569                  */
 570                 cnt = cache_name_pos(ce->name, strlen(ce->name));
 571                 if (0 <= cnt) {
 572                         struct cache_entry *ce = active_cache[cnt];
 573                         if (ce->ce_flags & CE_REMOVE)
 574                                 return 0;
 575                 }
 576
 577                 return error("Untracked working tree file '%s' "
 578                              "would be %s by merge.", ce->name, action);
 579         }
 580         return 0;
 581 }
 582
 583 static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
 584                 struct unpack_trees_options *o)
 585 {
 586         merge->ce_flags |= CE_UPDATE;
 587         if (old) {
 588                 /*
 589                  * See if we can re-use the old CE directly?
 590                  * That way we get the uptodate stat info.
 591                  *
 592                  * This also removes the UPDATE flag on
 593                  * a match.
 594                  */
 595                 if (same(old, merge)) {
 596                         memcpy(merge, old, offsetof(struct cache_entry, name));
 597                 } else {
 598                         if (verify_uptodate(old, o))
 599                                 return -1;
 600                         invalidate_ce_path(old);
 601                 }
 602         }
 603         else {
 604                 if (verify_absent(merge, "overwritten", o))
 605                         return -1;
 606                 invalidate_ce_path(merge);
 607         }
 608
 609         merge->ce_flags &= ~CE_STAGEMASK;
 610         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 611         return 1;
 612 }
 613
 614 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
 615                 struct unpack_trees_options *o)
 616 {
 617         if (old) {
 618                 if (verify_uptodate(old, o))
 619                         return -1;
 620         } else
 621                 if (verify_absent(ce, "removed", o))
 622                         return -1;
 623         ce->ce_flags |= CE_REMOVE;
 624         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 625         invalidate_ce_path(ce);
 626         return 1;
 627 }
 628
 629 static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 630 {
 631         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 632         return 1;
 633 }
 634
 635 #if DBRT_DEBUG
 636 static void show_stage_entry(FILE *o,
 637                              const char *label, const struct cache_entry *ce)
 638 {
 639         if (!ce)
 640                 fprintf(o, "%s (missing)\n", label);
 641         else
 642                 fprintf(o, "%s%06o %s %d\t%s\n",
 643                         label,
 644                         ce->ce_mode,
 645                         sha1_to_hex(ce->sha1),
 646                         ce_stage(ce),
 647                         ce->name);
 648 }
 649 #endif
 650
 651 int threeway_merge(struct cache_entry **stages,
 652                 struct unpack_trees_options *o,
 653                 int remove)
 654 {
 655         struct cache_entry *index;
 656         struct cache_entry *head;
 657         struct cache_entry *remote = stages[o->head_idx + 1];
 658         int count;
 659         int head_match = 0;
 660         int remote_match = 0;
 661
 662         int df_conflict_head = 0;
 663         int df_conflict_remote = 0;
 664
 665         int any_anc_missing = 0;
 666         int no_anc_exists = 1;
 667         int i;
 668
 669         for (i = 1; i < o->head_idx; i++) {
 670                 if (!stages[i] || stages[i] == o->df_conflict_entry)
 671                         any_anc_missing = 1;
 672                 else
 673                         no_anc_exists = 0;
 674         }
 675
 676         index = stages[0];
 677         head = stages[o->head_idx];
 678
 679         if (head == o->df_conflict_entry) {
 680                 df_conflict_head = 1;
 681                 head = NULL;
 682         }
 683
 684         if (remote == o->df_conflict_entry) {
 685                 df_conflict_remote = 1;
 686                 remote = NULL;
 687         }
 688
 689         /* First, if there's a #16 situation, note that to prevent #13
 690          * and #14.
 691          */
 692         if (!same(remote, head)) {
 693                 for (i = 1; i < o->head_idx; i++) {
 694                         if (same(stages[i], head)) {
 695                                 head_match = i;
 696                         }
 697                         if (same(stages[i], remote)) {
 698                                 remote_match = i;
 699                         }
 700                 }
 701         }
 702
 703         /* We start with cases where the index is allowed to match
 704          * something other than the head: #14(ALT) and #2ALT, where it
 705          * is permitted to match the result instead.
 706          */
 707         /* #14, #14ALT, #2ALT */
 708         if (remote && !df_conflict_head && head_match && !remote_match) {
 709                 if (index && !same(index, remote) && !same(index, head))
 710                         return reject_merge(index);
 711                 return merged_entry(remote, index, o);
 712         }
 713         /*
 714          * If we have an entry in the index cache, then we want to
 715          * make sure that it matches head.
 716          */
 717         if (index && !same(index, head)) {
 718                 return reject_merge(index);
 719         }
 720
 721         if (head) {
 722                 /* #5ALT, #15 */
 723                 if (same(head, remote))
 724                         return merged_entry(head, index, o);
 725                 /* #13, #3ALT */
 726                 if (!df_conflict_remote && remote_match && !head_match)
 727                         return merged_entry(head, index, o);
 728         }
 729
 730         /* #1 */
 731         if (!head && !remote && any_anc_missing) {
 732                 remove_entry(remove);
 733                 return 0;
 734         }
 735
 736         /* Under the new "aggressive" rule, we resolve mostly trivial
 737          * cases that we historically had git-merge-one-file resolve.
 738          */
 739         if (o->aggressive) {
 740                 int head_deleted = !head && !df_conflict_head;
 741                 int remote_deleted = !remote && !df_conflict_remote;
 742                 struct cache_entry *ce = NULL;
 743
 744                 if (index)
 745                         ce = index;
 746                 else if (head)
 747                         ce = head;
 748                 else if (remote)
 749                         ce = remote;
 750                 else {
 751                         for (i = 1; i < o->head_idx; i++) {
 752                                 if (stages[i] && stages[i] != o->df_conflict_entry) {
 753                                         ce = stages[i];
 754                                         break;
 755                                 }
 756                         }
 757                 }
 758
 759                 /*
 760                  * Deleted in both.
 761                  * Deleted in one and unchanged in the other.
 762                  */
 763                 if ((head_deleted && remote_deleted) ||
 764                     (head_deleted && remote && remote_match) ||
 765                     (remote_deleted && head && head_match)) {
 766                         remove_entry(remove);
 767                         if (index)
 768                                 return deleted_entry(index, index, o);
 769                         else if (ce && !head_deleted) {
 770                                 if (verify_absent(ce, "removed", o))
 771                                         return -1;
 772                         }
 773                         return 0;
 774                 }
 775                 /*
 776                  * Added in both, identically.
 777                  */
 778                 if (no_anc_exists && head && remote && same(head, remote))
 779                         return merged_entry(head, index, o);
 780
 781         }
 782
 783         /* Below are "no merge" cases, which require that the index be
 784          * up-to-date to avoid the files getting overwritten with
 785          * conflict resolution files.
 786          */
 787         if (index) {
 788                 if (verify_uptodate(index, o))
 789                         return -1;
 790         }
 791
 792         remove_entry(remove);
 793         o->nontrivial_merge = 1;
 794
 795         /* #2, #3, #4, #6, #7, #9, #10, #11. */
 796         count = 0;
 797         if (!head_match || !remote_match) {
 798                 for (i = 1; i < o->head_idx; i++) {
 799                         if (stages[i] && stages[i] != o->df_conflict_entry) {
 800                                 keep_entry(stages[i], o);
 801                                 count++;
 802                                 break;
 803                         }
 804                 }
 805         }
 806 #if DBRT_DEBUG
 807         else {
 808                 fprintf(stderr, "read-tree: warning #16 detected\n");
 809                 show_stage_entry(stderr, "head   ", stages[head_match]);
 810                 show_stage_entry(stderr, "remote ", stages[remote_match]);
 811         }
 812 #endif
 813         if (head) { count += keep_entry(head, o); }
 814         if (remote) { count += keep_entry(remote, o); }
 815         return count;
 816 }
 817
 818 /*
 819  * Two-way merge.
 820  *
 821  * The rule is to "carry forward" what is in the index without losing
 822  * information across a "fast forward", favoring a successful merge
 823  * over a merge failure when it makes sense.  For details of the
 824  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 825  *
 826  */
 827 int twoway_merge(struct cache_entry **src,
 828                 struct unpack_trees_options *o,
 829                 int remove)
 830 {
 831         struct cache_entry *current = src[0];
 832         struct cache_entry *oldtree = src[1];
 833         struct cache_entry *newtree = src[2];
 834
 835         if (o->merge_size != 2)
 836                 return error("Cannot do a twoway merge of %d trees",
 837                              o->merge_size);
 838
 839         if (oldtree == o->df_conflict_entry)
 840                 oldtree = NULL;
 841         if (newtree == o->df_conflict_entry)
 842                 newtree = NULL;
 843
 844         if (current) {
 845                 if ((!oldtree && !newtree) || /* 4 and 5 */
 846                     (!oldtree && newtree &&
 847                      same(current, newtree)) || /* 6 and 7 */
 848                     (oldtree && newtree &&
 849                      same(oldtree, newtree)) || /* 14 and 15 */
 850                     (oldtree && newtree &&
 851                      !same(oldtree, newtree) && /* 18 and 19 */
 852                      same(current, newtree))) {
 853                         return keep_entry(current, o);
 854                 }
 855                 else if (oldtree && !newtree && same(current, oldtree)) {
 856                         /* 10 or 11 */
 857                         remove_entry(remove);
 858                         return deleted_entry(oldtree, current, o);
 859                 }
 860                 else if (oldtree && newtree &&
 861                          same(current, oldtree) && !same(current, newtree)) {
 862                         /* 20 or 21 */
 863                         return merged_entry(newtree, current, o);
 864                 }
 865                 else {
 866                         /* all other failures */
 867                         remove_entry(remove);
 868                         if (oldtree)
 869                                 return reject_merge(oldtree);
 870                         if (current)
 871                                 return reject_merge(current);
 872                         if (newtree)
 873                                 return reject_merge(newtree);
 874                         return -1;
 875                 }
 876         }
 877         else if (newtree)
 878                 return merged_entry(newtree, current, o);
 879         remove_entry(remove);
 880         return deleted_entry(oldtree, current, o);
 881 }
 882
 883 /*
 884  * Bind merge.
 885  *
 886  * Keep the index entries at stage0, collapse stage1 but make sure
 887  * stage0 does not have anything there.
 888  */
 889 int bind_merge(struct cache_entry **src,
 890                 struct unpack_trees_options *o,
 891                 int remove)
 892 {
 893         struct cache_entry *old = src[0];
 894         struct cache_entry *a = src[1];
 895
 896         if (o->merge_size != 1)
 897                 return error("Cannot do a bind merge of %d trees\n",
 898                              o->merge_size);
 899         if (a && old)
 900                 return error("Entry '%s' overlaps.  Cannot bind.", a->name);
 901         if (!a)
 902                 return keep_entry(old, o);
 903         else
 904                 return merged_entry(a, NULL, o);
 905 }
 906
 907 /*
 908  * One-way merge.
 909  *
 910  * The rule is:
 911  * - take the stat information from stage0, take the data from stage1
 912  */
 913 int oneway_merge(struct cache_entry **src,
 914                 struct unpack_trees_options *o,
 915                 int remove)
 916 {
 917         struct cache_entry *old = src[0];
 918         struct cache_entry *a = src[1];
 919
 920         if (o->merge_size != 1)
 921                 return error("Cannot do a oneway merge of %d trees",
 922                              o->merge_size);
 923
 924         if (!a) {
 925                 remove_entry(remove);
 926                 return deleted_entry(old, old, o);
 927         }
 928         if (old && same(old, a)) {
 929                 if (o->reset) {
 930                         struct stat st;
 931                         if (lstat(old->name, &st) ||
 932                             ce_match_stat(old, &st, CE_MATCH_IGNORE_VALID))
 933                                 old->ce_flags |= CE_UPDATE;
 934                 }
 935                 return keep_entry(old, o);
 936         }
 937         return merged_entry(a, old, o);
 938 }