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