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