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