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 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                         if (o->gently) {
 361                                 discard_cache();
 362                                 read_cache();
 363                         }
 364                         return -1;
 365                 }
 366         }
 367
 368         if (o->trivial_merges_only && o->nontrivial_merge) {
 369                 if (o->gently) {
 370                         discard_cache();
 371                         read_cache();
 372                 }
 373                 return o->gently ? -1 :
 374                         error("Merge requires file-level merging");
 375         }
 376
 377         check_updates(active_cache, active_nr, o);
 378         return 0;
 379 }
 380
 381 /* Here come the merge functions */
 382
 383 static int reject_merge(struct cache_entry *ce)
 384 {
 385         return error("Entry '%s' would be overwritten by merge. Cannot merge.",
 386                      ce->name);
 387 }
 388
 389 static int same(struct cache_entry *a, struct cache_entry *b)
 390 {
 391         if (!!a != !!b)
 392                 return 0;
 393         if (!a && !b)
 394                 return 1;
 395         return a->ce_mode == b->ce_mode &&
 396                !hashcmp(a->sha1, b->sha1);
 397 }
 398
 399
 400 /*
 401  * When a CE gets turned into an unmerged entry, we
 402  * want it to be up-to-date
 403  */
 404 static int verify_uptodate(struct cache_entry *ce,
 405                 struct unpack_trees_options *o)
 406 {
 407         struct stat st;
 408
 409         if (o->index_only || o->reset)
 410                 return 0;
 411
 412         if (!lstat(ce->name, &st)) {
 413                 unsigned changed = ce_match_stat(ce, &st, CE_MATCH_IGNORE_VALID);
 414                 if (!changed)
 415                         return 0;
 416                 /*
 417                  * NEEDSWORK: the current default policy is to allow
 418                  * submodule to be out of sync wrt the supermodule
 419                  * index.  This needs to be tightened later for
 420                  * submodules that are marked to be automatically
 421                  * checked out.
 422                  */
 423                 if (S_ISGITLINK(ce->ce_mode))
 424                         return 0;
 425                 errno = 0;
 426         }
 427         if (errno == ENOENT)
 428                 return 0;
 429         return o->gently ? -1 :
 430                 error("Entry '%s' not uptodate. Cannot merge.", ce->name);
 431 }
 432
 433 static void invalidate_ce_path(struct cache_entry *ce)
 434 {
 435         if (ce)
 436                 cache_tree_invalidate_path(active_cache_tree, ce->name);
 437 }
 438
 439 /*
 440  * Check that checking out ce->sha1 in subdir ce->name is not
 441  * going to overwrite any working files.
 442  *
 443  * Currently, git does not checkout subprojects during a superproject
 444  * checkout, so it is not going to overwrite anything.
 445  */
 446 static int verify_clean_submodule(struct cache_entry *ce, const char *action,
 447                                       struct unpack_trees_options *o)
 448 {
 449         return 0;
 450 }
 451
 452 static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
 453                                       struct unpack_trees_options *o)
 454 {
 455         /*
 456          * we are about to extract "ce->name"; we would not want to lose
 457          * anything in the existing directory there.
 458          */
 459         int namelen;
 460         int pos, i;
 461         struct dir_struct d;
 462         char *pathbuf;
 463         int cnt = 0;
 464         unsigned char sha1[20];
 465
 466         if (S_ISGITLINK(ce->ce_mode) &&
 467             resolve_gitlink_ref(ce->name, "HEAD", sha1) == 0) {
 468                 /* If we are not going to update the submodule, then
 469                  * we don't care.
 470                  */
 471                 if (!hashcmp(sha1, ce->sha1))
 472                         return 0;
 473                 return verify_clean_submodule(ce, action, o);
 474         }
 475
 476         /*
 477          * First let's make sure we do not have a local modification
 478          * in that directory.
 479          */
 480         namelen = strlen(ce->name);
 481         pos = cache_name_pos(ce->name, namelen);
 482         if (0 <= pos)
 483                 return cnt; /* we have it as nondirectory */
 484         pos = -pos - 1;
 485         for (i = pos; i < active_nr; i++) {
 486                 struct cache_entry *ce = active_cache[i];
 487                 int len = ce_namelen(ce);
 488                 if (len < namelen ||
 489                     strncmp(ce->name, ce->name, namelen) ||
 490                     ce->name[namelen] != '/')
 491                         break;
 492                 /*
 493                  * ce->name is an entry in the subdirectory.
 494                  */
 495                 if (!ce_stage(ce)) {
 496                         if (verify_uptodate(ce, o))
 497                                 return -1;
 498                         ce->ce_flags |= CE_REMOVE;
 499                 }
 500                 cnt++;
 501         }
 502
 503         /*
 504          * Then we need to make sure that we do not lose a locally
 505          * present file that is not ignored.
 506          */
 507         pathbuf = xmalloc(namelen + 2);
 508         memcpy(pathbuf, ce->name, namelen);
 509         strcpy(pathbuf+namelen, "/");
 510
 511         memset(&d, 0, sizeof(d));
 512         if (o->dir)
 513                 d.exclude_per_dir = o->dir->exclude_per_dir;
 514         i = read_directory(&d, ce->name, pathbuf, namelen+1, NULL);
 515         if (i)
 516                 return o->gently ? -1 :
 517                         error("Updating '%s' would lose untracked files in it",
 518                               ce->name);
 519         free(pathbuf);
 520         return cnt;
 521 }
 522
 523 /*
 524  * We do not want to remove or overwrite a working tree file that
 525  * is not tracked, unless it is ignored.
 526  */
 527 static int verify_absent(struct cache_entry *ce, const char *action,
 528                          struct unpack_trees_options *o)
 529 {
 530         struct stat st;
 531
 532         if (o->index_only || o->reset || !o->update)
 533                 return 0;
 534
 535         if (has_symlink_leading_path(ce->name, NULL))
 536                 return 0;
 537
 538         if (!lstat(ce->name, &st)) {
 539                 int cnt;
 540
 541                 if (o->dir && excluded(o->dir, ce->name))
 542                         /*
 543                          * ce->name is explicitly excluded, so it is Ok to
 544                          * overwrite it.
 545                          */
 546                         return 0;
 547                 if (S_ISDIR(st.st_mode)) {
 548                         /*
 549                          * We are checking out path "foo" and
 550                          * found "foo/." in the working tree.
 551                          * This is tricky -- if we have modified
 552                          * files that are in "foo/" we would lose
 553                          * it.
 554                          */
 555                         cnt = verify_clean_subdirectory(ce, action, o);
 556
 557                         /*
 558                          * If this removed entries from the index,
 559                          * what that means is:
 560                          *
 561                          * (1) the caller unpack_trees_rec() saw path/foo
 562                          * in the index, and it has not removed it because
 563                          * it thinks it is handling 'path' as blob with
 564                          * D/F conflict;
 565                          * (2) we will return "ok, we placed a merged entry
 566                          * in the index" which would cause o->pos to be
 567                          * incremented by one;
 568                          * (3) however, original o->pos now has 'path/foo'
 569                          * marked with "to be removed".
 570                          *
 571                          * We need to increment it by the number of
 572                          * deleted entries here.
 573                          */
 574                         o->pos += cnt;
 575                         return 0;
 576                 }
 577
 578                 /*
 579                  * The previous round may already have decided to
 580                  * delete this path, which is in a subdirectory that
 581                  * is being replaced with a blob.
 582                  */
 583                 cnt = cache_name_pos(ce->name, strlen(ce->name));
 584                 if (0 <= cnt) {
 585                         struct cache_entry *ce = active_cache[cnt];
 586                         if (ce->ce_flags & CE_REMOVE)
 587                                 return 0;
 588                 }
 589
 590                 return o->gently ? -1 :
 591                         error("Untracked working tree file '%s' "
 592                               "would be %s by merge.", ce->name, action);
 593         }
 594         return 0;
 595 }
 596
 597 static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
 598                 struct unpack_trees_options *o)
 599 {
 600         merge->ce_flags |= CE_UPDATE;
 601         if (old) {
 602                 /*
 603                  * See if we can re-use the old CE directly?
 604                  * That way we get the uptodate stat info.
 605                  *
 606                  * This also removes the UPDATE flag on
 607                  * a match.
 608                  */
 609                 if (same(old, merge)) {
 610                         memcpy(merge, old, offsetof(struct cache_entry, name));
 611                 } else {
 612                         if (verify_uptodate(old, o))
 613                                 return -1;
 614                         invalidate_ce_path(old);
 615                 }
 616         }
 617         else {
 618                 if (verify_absent(merge, "overwritten", o))
 619                         return -1;
 620                 invalidate_ce_path(merge);
 621         }
 622
 623         merge->ce_flags &= ~CE_STAGEMASK;
 624         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 625         return 1;
 626 }
 627
 628 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
 629                 struct unpack_trees_options *o)
 630 {
 631         if (old) {
 632                 if (verify_uptodate(old, o))
 633                         return -1;
 634         } else
 635                 if (verify_absent(ce, "removed", o))
 636                         return -1;
 637         ce->ce_flags |= CE_REMOVE;
 638         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 639         invalidate_ce_path(ce);
 640         return 1;
 641 }
 642
 643 static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 644 {
 645         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 646         return 1;
 647 }
 648
 649 #if DBRT_DEBUG
 650 static void show_stage_entry(FILE *o,
 651                              const char *label, const struct cache_entry *ce)
 652 {
 653         if (!ce)
 654                 fprintf(o, "%s (missing)\n", label);
 655         else
 656                 fprintf(o, "%s%06o %s %d\t%s\n",
 657                         label,
 658                         ce->ce_mode,
 659                         sha1_to_hex(ce->sha1),
 660                         ce_stage(ce),
 661                         ce->name);
 662 }
 663 #endif
 664
 665 int threeway_merge(struct cache_entry **stages,
 666                 struct unpack_trees_options *o,
 667                 int remove)
 668 {
 669         struct cache_entry *index;
 670         struct cache_entry *head;
 671         struct cache_entry *remote = stages[o->head_idx + 1];
 672         int count;
 673         int head_match = 0;
 674         int remote_match = 0;
 675
 676         int df_conflict_head = 0;
 677         int df_conflict_remote = 0;
 678
 679         int any_anc_missing = 0;
 680         int no_anc_exists = 1;
 681         int i;
 682
 683         for (i = 1; i < o->head_idx; i++) {
 684                 if (!stages[i] || stages[i] == o->df_conflict_entry)
 685                         any_anc_missing = 1;
 686                 else
 687                         no_anc_exists = 0;
 688         }
 689
 690         index = stages[0];
 691         head = stages[o->head_idx];
 692
 693         if (head == o->df_conflict_entry) {
 694                 df_conflict_head = 1;
 695                 head = NULL;
 696         }
 697
 698         if (remote == o->df_conflict_entry) {
 699                 df_conflict_remote = 1;
 700                 remote = NULL;
 701         }
 702
 703         /* First, if there's a #16 situation, note that to prevent #13
 704          * and #14.
 705          */
 706         if (!same(remote, head)) {
 707                 for (i = 1; i < o->head_idx; i++) {
 708                         if (same(stages[i], head)) {
 709                                 head_match = i;
 710                         }
 711                         if (same(stages[i], remote)) {
 712                                 remote_match = i;
 713                         }
 714                 }
 715         }
 716
 717         /* We start with cases where the index is allowed to match
 718          * something other than the head: #14(ALT) and #2ALT, where it
 719          * is permitted to match the result instead.
 720          */
 721         /* #14, #14ALT, #2ALT */
 722         if (remote && !df_conflict_head && head_match && !remote_match) {
 723                 if (index && !same(index, remote) && !same(index, head))
 724                         return o->gently ? -1 : reject_merge(index);
 725                 return merged_entry(remote, index, o);
 726         }
 727         /*
 728          * If we have an entry in the index cache, then we want to
 729          * make sure that it matches head.
 730          */
 731         if (index && !same(index, head)) {
 732                 return o->gently ? -1 : reject_merge(index);
 733         }
 734
 735         if (head) {
 736                 /* #5ALT, #15 */
 737                 if (same(head, remote))
 738                         return merged_entry(head, index, o);
 739                 /* #13, #3ALT */
 740                 if (!df_conflict_remote && remote_match && !head_match)
 741                         return merged_entry(head, index, o);
 742         }
 743
 744         /* #1 */
 745         if (!head && !remote && any_anc_missing) {
 746                 remove_entry(remove);
 747                 return 0;
 748         }
 749
 750         /* Under the new "aggressive" rule, we resolve mostly trivial
 751          * cases that we historically had git-merge-one-file resolve.
 752          */
 753         if (o->aggressive) {
 754                 int head_deleted = !head && !df_conflict_head;
 755                 int remote_deleted = !remote && !df_conflict_remote;
 756                 struct cache_entry *ce = NULL;
 757
 758                 if (index)
 759                         ce = index;
 760                 else if (head)
 761                         ce = head;
 762                 else if (remote)
 763                         ce = remote;
 764                 else {
 765                         for (i = 1; i < o->head_idx; i++) {
 766                                 if (stages[i] && stages[i] != o->df_conflict_entry) {
 767                                         ce = stages[i];
 768                                         break;
 769                                 }
 770                         }
 771                 }
 772
 773                 /*
 774                  * Deleted in both.
 775                  * Deleted in one and unchanged in the other.
 776                  */
 777                 if ((head_deleted && remote_deleted) ||
 778                     (head_deleted && remote && remote_match) ||
 779                     (remote_deleted && head && head_match)) {
 780                         remove_entry(remove);
 781                         if (index)
 782                                 return deleted_entry(index, index, o);
 783                         else if (ce && !head_deleted) {
 784                                 if (verify_absent(ce, "removed", o))
 785                                         return -1;
 786                         }
 787                         return 0;
 788                 }
 789                 /*
 790                  * Added in both, identically.
 791                  */
 792                 if (no_anc_exists && head && remote && same(head, remote))
 793                         return merged_entry(head, index, o);
 794
 795         }
 796
 797         /* Below are "no merge" cases, which require that the index be
 798          * up-to-date to avoid the files getting overwritten with
 799          * conflict resolution files.
 800          */
 801         if (index) {
 802                 if (verify_uptodate(index, o))
 803                         return -1;
 804         }
 805
 806         remove_entry(remove);
 807         o->nontrivial_merge = 1;
 808
 809         /* #2, #3, #4, #6, #7, #9, #10, #11. */
 810         count = 0;
 811         if (!head_match || !remote_match) {
 812                 for (i = 1; i < o->head_idx; i++) {
 813                         if (stages[i] && stages[i] != o->df_conflict_entry) {
 814                                 keep_entry(stages[i], o);
 815                                 count++;
 816                                 break;
 817                         }
 818                 }
 819         }
 820 #if DBRT_DEBUG
 821         else {
 822                 fprintf(stderr, "read-tree: warning #16 detected\n");
 823                 show_stage_entry(stderr, "head   ", stages[head_match]);
 824                 show_stage_entry(stderr, "remote ", stages[remote_match]);
 825         }
 826 #endif
 827         if (head) { count += keep_entry(head, o); }
 828         if (remote) { count += keep_entry(remote, o); }
 829         return count;
 830 }
 831
 832 /*
 833  * Two-way merge.
 834  *
 835  * The rule is to "carry forward" what is in the index without losing
 836  * information across a "fast forward", favoring a successful merge
 837  * over a merge failure when it makes sense.  For details of the
 838  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 839  *
 840  */
 841 int twoway_merge(struct cache_entry **src,
 842                 struct unpack_trees_options *o,
 843                 int remove)
 844 {
 845         struct cache_entry *current = src[0];
 846         struct cache_entry *oldtree = src[1];
 847         struct cache_entry *newtree = src[2];
 848
 849         if (o->merge_size != 2)
 850                 return error("Cannot do a twoway merge of %d trees",
 851                              o->merge_size);
 852
 853         if (oldtree == o->df_conflict_entry)
 854                 oldtree = NULL;
 855         if (newtree == o->df_conflict_entry)
 856                 newtree = NULL;
 857
 858         if (current) {
 859                 if ((!oldtree && !newtree) || /* 4 and 5 */
 860                     (!oldtree && newtree &&
 861                      same(current, newtree)) || /* 6 and 7 */
 862                     (oldtree && newtree &&
 863                      same(oldtree, newtree)) || /* 14 and 15 */
 864                     (oldtree && newtree &&
 865                      !same(oldtree, newtree) && /* 18 and 19 */
 866                      same(current, newtree))) {
 867                         return keep_entry(current, o);
 868                 }
 869                 else if (oldtree && !newtree && same(current, oldtree)) {
 870                         /* 10 or 11 */
 871                         remove_entry(remove);
 872                         return deleted_entry(oldtree, current, o);
 873                 }
 874                 else if (oldtree && newtree &&
 875                          same(current, oldtree) && !same(current, newtree)) {
 876                         /* 20 or 21 */
 877                         return merged_entry(newtree, current, o);
 878                 }
 879                 else {
 880                         /* all other failures */
 881                         remove_entry(remove);
 882                         if (oldtree)
 883                                 return o->gently ? -1 : reject_merge(oldtree);
 884                         if (current)
 885                                 return o->gently ? -1 : reject_merge(current);
 886                         if (newtree)
 887                                 return o->gently ? -1 : reject_merge(newtree);
 888                         return -1;
 889                 }
 890         }
 891         else if (newtree)
 892                 return merged_entry(newtree, current, o);
 893         remove_entry(remove);
 894         return deleted_entry(oldtree, current, o);
 895 }
 896
 897 /*
 898  * Bind merge.
 899  *
 900  * Keep the index entries at stage0, collapse stage1 but make sure
 901  * stage0 does not have anything there.
 902  */
 903 int bind_merge(struct cache_entry **src,
 904                 struct unpack_trees_options *o,
 905                 int remove)
 906 {
 907         struct cache_entry *old = src[0];
 908         struct cache_entry *a = src[1];
 909
 910         if (o->merge_size != 1)
 911                 return error("Cannot do a bind merge of %d trees\n",
 912                              o->merge_size);
 913         if (a && old)
 914                 return o->gently ? -1 :
 915                         error("Entry '%s' overlaps.  Cannot bind.", a->name);
 916         if (!a)
 917                 return keep_entry(old, o);
 918         else
 919                 return merged_entry(a, NULL, o);
 920 }
 921
 922 /*
 923  * One-way merge.
 924  *
 925  * The rule is:
 926  * - take the stat information from stage0, take the data from stage1
 927  */
 928 int oneway_merge(struct cache_entry **src,
 929                 struct unpack_trees_options *o,
 930                 int remove)
 931 {
 932         struct cache_entry *old = src[0];
 933         struct cache_entry *a = src[1];
 934
 935         if (o->merge_size != 1)
 936                 return error("Cannot do a oneway merge of %d trees",
 937                              o->merge_size);
 938
 939         if (!a) {
 940                 remove_entry(remove);
 941                 return deleted_entry(old, old, o);
 942         }
 943         if (old && same(old, a)) {
 944                 if (o->reset) {
 945                         struct stat st;
 946                         if (lstat(old->name, &st) ||
 947                             ce_match_stat(old, &st, CE_MATCH_IGNORE_VALID))
 948                                 old->ce_flags |= CE_UPDATE;
 949                 }
 950                 return keep_entry(old, o);
 951         }
 952         return merged_entry(a, old, o);
 953 }