builtin-read-tree.c

   1 /*
   2  * GIT - The information manager from hell
   3  *
   4  * Copyright (C) Linus Torvalds, 2005
   5  */
   6 #define DBRT_DEBUG 1
   7
   8 #include "cache.h"
   9
  10 #include "object.h"
  11 #include "tree.h"
  12 #include "tree-walk.h"
  13 #include "cache-tree.h"
  14 #include <sys/time.h>
  15 #include <signal.h>
  16 #include "builtin.h"
  17
  18 static int reset = 0;
  19 static int merge = 0;
  20 static int update = 0;
  21 static int index_only = 0;
  22 static int nontrivial_merge = 0;
  23 static int trivial_merges_only = 0;
  24 static int aggressive = 0;
  25 static int verbose_update = 0;
  26 static volatile int progress_update = 0;
  27 static const char *prefix = NULL;
  28
  29 static int head_idx = -1;
  30 static int merge_size = 0;
  31
  32 static struct object_list *trees = NULL;
  33
  34 static struct cache_entry df_conflict_entry = {
  35 };
  36
  37 struct tree_entry_list {
  38         struct tree_entry_list *next;
  39         unsigned directory : 1;
  40         unsigned executable : 1;
  41         unsigned symlink : 1;
  42         unsigned int mode;
  43         const char *name;
  44         const unsigned char *sha1;
  45 };
  46
  47 static struct tree_entry_list df_conflict_list = {
  48         .name = NULL,
  49         .next = &df_conflict_list
  50 };
  51
  52 typedef int (*merge_fn_t)(struct cache_entry **src);
  53
  54 static struct tree_entry_list *create_tree_entry_list(struct tree *tree)
  55 {
  56         struct tree_desc desc;
  57         struct tree_entry_list *ret = NULL;
  58         struct tree_entry_list **list_p = &ret;
  59
  60         desc.buf = tree->buffer;
  61         desc.size = tree->size;
  62
  63         while (desc.size) {
  64                 unsigned mode;
  65                 const char *path;
  66                 const unsigned char *sha1;
  67                 struct tree_entry_list *entry;
  68
  69                 sha1 = tree_entry_extract(&desc, &path, &mode);
  70                 update_tree_entry(&desc);
  71
  72                 entry = xmalloc(sizeof(struct tree_entry_list));
  73                 entry->name = path;
  74                 entry->sha1 = sha1;
  75                 entry->mode = mode;
  76                 entry->directory = S_ISDIR(mode) != 0;
  77                 entry->executable = (mode & S_IXUSR) != 0;
  78                 entry->symlink = S_ISLNK(mode) != 0;
  79                 entry->next = NULL;
  80
  81                 *list_p = entry;
  82                 list_p = &entry->next;
  83         }
  84         return ret;
  85 }
  86
  87 static int entcmp(const char *name1, int dir1, const char *name2, int dir2)
  88 {
  89         int len1 = strlen(name1);
  90         int len2 = strlen(name2);
  91         int len = len1 < len2 ? len1 : len2;
  92         int ret = memcmp(name1, name2, len);
  93         unsigned char c1, c2;
  94         if (ret)
  95                 return ret;
  96         c1 = name1[len];
  97         c2 = name2[len];
  98         if (!c1 && dir1)
  99                 c1 = '/';
 100         if (!c2 && dir2)
 101                 c2 = '/';
 102         ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
 103         if (c1 && c2 && !ret)
 104                 ret = len1 - len2;
 105         return ret;
 106 }
 107
 108 static int unpack_trees_rec(struct tree_entry_list **posns, int len,
 109                             const char *base, merge_fn_t fn, int *indpos)
 110 {
 111         int baselen = strlen(base);
 112         int src_size = len + 1;
 113         do {
 114                 int i;
 115                 const char *first;
 116                 int firstdir = 0;
 117                 int pathlen;
 118                 unsigned ce_size;
 119                 struct tree_entry_list **subposns;
 120                 struct cache_entry **src;
 121                 int any_files = 0;
 122                 int any_dirs = 0;
 123                 char *cache_name;
 124                 int ce_stage;
 125
 126                 /* Find the first name in the input. */
 127
 128                 first = NULL;
 129                 cache_name = NULL;
 130
 131                 /* Check the cache */
 132                 if (merge && *indpos < active_nr) {
 133                         /* This is a bit tricky: */
 134                         /* If the index has a subdirectory (with
 135                          * contents) as the first name, it'll get a
 136                          * filename like "foo/bar". But that's after
 137                          * "foo", so the entry in trees will get
 138                          * handled first, at which point we'll go into
 139                          * "foo", and deal with "bar" from the index,
 140                          * because the base will be "foo/". The only
 141                          * way we can actually have "foo/bar" first of
 142                          * all the things is if the trees don't
 143                          * contain "foo" at all, in which case we'll
 144                          * handle "foo/bar" without going into the
 145                          * directory, but that's fine (and will return
 146                          * an error anyway, with the added unknown
 147                          * file case.
 148                          */
 149
 150                         cache_name = active_cache[*indpos]->name;
 151                         if (strlen(cache_name) > baselen &&
 152                             !memcmp(cache_name, base, baselen)) {
 153                                 cache_name += baselen;
 154                                 first = cache_name;
 155                         } else {
 156                                 cache_name = NULL;
 157                         }
 158                 }
 159
 160 #if DBRT_DEBUG > 1
 161                 if (first)
 162                         printf("index %s\n", first);
 163 #endif
 164                 for (i = 0; i < len; i++) {
 165                         if (!posns[i] || posns[i] == &df_conflict_list)
 166                                 continue;
 167 #if DBRT_DEBUG > 1
 168                         printf("%d %s\n", i + 1, posns[i]->name);
 169 #endif
 170                         if (!first || entcmp(first, firstdir,
 171                                              posns[i]->name,
 172                                              posns[i]->directory) > 0) {
 173                                 first = posns[i]->name;
 174                                 firstdir = posns[i]->directory;
 175                         }
 176                 }
 177                 /* No name means we're done */
 178                 if (!first)
 179                         return 0;
 180
 181                 pathlen = strlen(first);
 182                 ce_size = cache_entry_size(baselen + pathlen);
 183
 184                 src = xcalloc(src_size, sizeof(struct cache_entry *));
 185
 186                 subposns = xcalloc(len, sizeof(struct tree_list_entry *));
 187
 188                 if (cache_name && !strcmp(cache_name, first)) {
 189                         any_files = 1;
 190                         src[0] = active_cache[*indpos];
 191                         remove_cache_entry_at(*indpos);
 192                 }
 193
 194                 for (i = 0; i < len; i++) {
 195                         struct cache_entry *ce;
 196
 197                         if (!posns[i] ||
 198                             (posns[i] != &df_conflict_list &&
 199                              strcmp(first, posns[i]->name))) {
 200                                 continue;
 201                         }
 202
 203                         if (posns[i] == &df_conflict_list) {
 204                                 src[i + merge] = &df_conflict_entry;
 205                                 continue;
 206                         }
 207
 208                         if (posns[i]->directory) {
 209                                 struct tree *tree = lookup_tree(posns[i]->sha1);
 210                                 any_dirs = 1;
 211                                 parse_tree(tree);
 212                                 subposns[i] = create_tree_entry_list(tree);
 213                                 posns[i] = posns[i]->next;
 214                                 src[i + merge] = &df_conflict_entry;
 215                                 continue;
 216                         }
 217
 218                         if (!merge)
 219                                 ce_stage = 0;
 220                         else if (i + 1 < head_idx)
 221                                 ce_stage = 1;
 222                         else if (i + 1 > head_idx)
 223                                 ce_stage = 3;
 224                         else
 225                                 ce_stage = 2;
 226
 227                         ce = xcalloc(1, ce_size);
 228                         ce->ce_mode = create_ce_mode(posns[i]->mode);
 229                         ce->ce_flags = create_ce_flags(baselen + pathlen,
 230                                                        ce_stage);
 231                         memcpy(ce->name, base, baselen);
 232                         memcpy(ce->name + baselen, first, pathlen + 1);
 233
 234                         any_files = 1;
 235
 236                         memcpy(ce->sha1, posns[i]->sha1, 20);
 237                         src[i + merge] = ce;
 238                         subposns[i] = &df_conflict_list;
 239                         posns[i] = posns[i]->next;
 240                 }
 241                 if (any_files) {
 242                         if (merge) {
 243                                 int ret;
 244
 245 #if DBRT_DEBUG > 1
 246                                 printf("%s:\n", first);
 247                                 for (i = 0; i < src_size; i++) {
 248                                         printf(" %d ", i);
 249                                         if (src[i])
 250                                                 printf("%s\n", sha1_to_hex(src[i]->sha1));
 251                                         else
 252                                                 printf("\n");
 253                                 }
 254 #endif
 255                                 ret = fn(src);
 256
 257 #if DBRT_DEBUG > 1
 258                                 printf("Added %d entries\n", ret);
 259 #endif
 260                                 *indpos += ret;
 261                         } else {
 262                                 for (i = 0; i < src_size; i++) {
 263                                         if (src[i]) {
 264                                                 add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
 265                                         }
 266                                 }
 267                         }
 268                 }
 269                 if (any_dirs) {
 270                         char *newbase = xmalloc(baselen + 2 + pathlen);
 271                         memcpy(newbase, base, baselen);
 272                         memcpy(newbase + baselen, first, pathlen);
 273                         newbase[baselen + pathlen] = '/';
 274                         newbase[baselen + pathlen + 1] = '\0';
 275                         if (unpack_trees_rec(subposns, len, newbase, fn,
 276                                              indpos))
 277                                 return -1;
 278                         free(newbase);
 279                 }
 280                 free(subposns);
 281                 free(src);
 282         } while (1);
 283 }
 284
 285 static void reject_merge(struct cache_entry *ce)
 286 {
 287         die("Entry '%s' would be overwritten by merge. Cannot merge.",
 288             ce->name);
 289 }
 290
 291 /* Unlink the last component and attempt to remove leading
 292  * directories, in case this unlink is the removal of the
 293  * last entry in the directory -- empty directories are removed.
 294  */
 295 static void unlink_entry(char *name)
 296 {
 297         char *cp, *prev;
 298
 299         if (unlink(name))
 300                 return;
 301         prev = NULL;
 302         while (1) {
 303                 int status;
 304                 cp = strrchr(name, '/');
 305                 if (prev)
 306                         *prev = '/';
 307                 if (!cp)
 308                         break;
 309
 310                 *cp = 0;
 311                 status = rmdir(name);
 312                 if (status) {
 313                         *cp = '/';
 314                         break;
 315                 }
 316                 prev = cp;
 317         }
 318 }
 319
 320 static void progress_interval(int signum)
 321 {
 322         progress_update = 1;
 323 }
 324
 325 static void setup_progress_signal(void)
 326 {
 327         struct sigaction sa;
 328         struct itimerval v;
 329
 330         memset(&sa, 0, sizeof(sa));
 331         sa.sa_handler = progress_interval;
 332         sigemptyset(&sa.sa_mask);
 333         sa.sa_flags = SA_RESTART;
 334         sigaction(SIGALRM, &sa, NULL);
 335
 336         v.it_interval.tv_sec = 1;
 337         v.it_interval.tv_usec = 0;
 338         v.it_value = v.it_interval;
 339         setitimer(ITIMER_REAL, &v, NULL);
 340 }
 341
 342 static void check_updates(struct cache_entry **src, int nr)
 343 {
 344         static struct checkout state = {
 345                 .base_dir = "",
 346                 .force = 1,
 347                 .quiet = 1,
 348                 .refresh_cache = 1,
 349         };
 350         unsigned short mask = htons(CE_UPDATE);
 351         unsigned last_percent = 200, cnt = 0, total = 0;
 352
 353         if (update && verbose_update) {
 354                 for (total = cnt = 0; cnt < nr; cnt++) {
 355                         struct cache_entry *ce = src[cnt];
 356                         if (!ce->ce_mode || ce->ce_flags & mask)
 357                                 total++;
 358                 }
 359
 360                 /* Don't bother doing this for very small updates */
 361                 if (total < 250)
 362                         total = 0;
 363
 364                 if (total) {
 365                         fprintf(stderr, "Checking files out...\n");
 366                         setup_progress_signal();
 367                         progress_update = 1;
 368                 }
 369                 cnt = 0;
 370         }
 371
 372         while (nr--) {
 373                 struct cache_entry *ce = *src++;
 374
 375                 if (total) {
 376                         if (!ce->ce_mode || ce->ce_flags & mask) {
 377                                 unsigned percent;
 378                                 cnt++;
 379                                 percent = (cnt * 100) / total;
 380                                 if (percent != last_percent ||
 381                                     progress_update) {
 382                                         fprintf(stderr, "%4u%% (%u/%u) done\r",
 383                                                 percent, cnt, total);
 384                                         last_percent = percent;
 385                                 }
 386                         }
 387                 }
 388                 if (!ce->ce_mode) {
 389                         if (update)
 390                                 unlink_entry(ce->name);
 391                         continue;
 392                 }
 393                 if (ce->ce_flags & mask) {
 394                         ce->ce_flags &= ~mask;
 395                         if (update)
 396                                 checkout_entry(ce, &state, NULL);
 397                 }
 398         }
 399         if (total) {
 400                 signal(SIGALRM, SIG_IGN);
 401                 fputc('\n', stderr);
 402         }
 403 }
 404
 405 static int unpack_trees(merge_fn_t fn)
 406 {
 407         int indpos = 0;
 408         unsigned len = object_list_length(trees);
 409         struct tree_entry_list **posns;
 410         int i;
 411         struct object_list *posn = trees;
 412         merge_size = len;
 413
 414         if (len) {
 415                 posns = xmalloc(len * sizeof(struct tree_entry_list *));
 416                 for (i = 0; i < len; i++) {
 417                         posns[i] = create_tree_entry_list((struct tree *) posn->item);
 418                         posn = posn->next;
 419                 }
 420                 if (unpack_trees_rec(posns, len, prefix ? prefix : "",
 421                                      fn, &indpos))
 422                         return -1;
 423         }
 424
 425         if (trivial_merges_only && nontrivial_merge)
 426                 die("Merge requires file-level merging");
 427
 428         check_updates(active_cache, active_nr);
 429         return 0;
 430 }
 431
 432 static int list_tree(unsigned char *sha1)
 433 {
 434         struct tree *tree = parse_tree_indirect(sha1);
 435         if (!tree)
 436                 return -1;
 437         object_list_append(&tree->object, &trees);
 438         return 0;
 439 }
 440
 441 static int same(struct cache_entry *a, struct cache_entry *b)
 442 {
 443         if (!!a != !!b)
 444                 return 0;
 445         if (!a && !b)
 446                 return 1;
 447         return a->ce_mode == b->ce_mode &&
 448                 !memcmp(a->sha1, b->sha1, 20);
 449 }
 450
 451
 452 /*
 453  * When a CE gets turned into an unmerged entry, we
 454  * want it to be up-to-date
 455  */
 456 static void verify_uptodate(struct cache_entry *ce)
 457 {
 458         struct stat st;
 459
 460         if (index_only || reset)
 461                 return;
 462
 463         if (!lstat(ce->name, &st)) {
 464                 unsigned changed = ce_match_stat(ce, &st, 1);
 465                 if (!changed)
 466                         return;
 467                 errno = 0;
 468         }
 469         if (reset) {
 470                 ce->ce_flags |= htons(CE_UPDATE);
 471                 return;
 472         }
 473         if (errno == ENOENT)
 474                 return;
 475         die("Entry '%s' not uptodate. Cannot merge.", ce->name);
 476 }
 477
 478 static void invalidate_ce_path(struct cache_entry *ce)
 479 {
 480         if (ce)
 481                 cache_tree_invalidate_path(active_cache_tree, ce->name);
 482 }
 483
 484 /*
 485  * We do not want to remove or overwrite a working tree file that
 486  * is not tracked.
 487  */
 488 static void verify_absent(const char *path, const char *action)
 489 {
 490         struct stat st;
 491
 492         if (index_only || reset || !update)
 493                 return;
 494         if (!lstat(path, &st))
 495                 die("Untracked working tree file '%s' "
 496                     "would be %s by merge.", path, action);
 497 }
 498
 499 static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
 500 {
 501         merge->ce_flags |= htons(CE_UPDATE);
 502         if (old) {
 503                 /*
 504                  * See if we can re-use the old CE directly?
 505                  * That way we get the uptodate stat info.
 506                  *
 507                  * This also removes the UPDATE flag on
 508                  * a match.
 509                  */
 510                 if (same(old, merge)) {
 511                         *merge = *old;
 512                 } else {
 513                         verify_uptodate(old);
 514                         invalidate_ce_path(old);
 515                 }
 516         }
 517         else {
 518                 verify_absent(merge->name, "overwritten");
 519                 invalidate_ce_path(merge);
 520         }
 521
 522         merge->ce_flags &= ~htons(CE_STAGEMASK);
 523         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
 524         return 1;
 525 }
 526
 527 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
 528 {
 529         if (old)
 530                 verify_uptodate(old);
 531         else
 532                 verify_absent(ce->name, "removed");
 533         ce->ce_mode = 0;
 534         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 535         invalidate_ce_path(ce);
 536         return 1;
 537 }
 538
 539 static int keep_entry(struct cache_entry *ce)
 540 {
 541         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 542         return 1;
 543 }
 544
 545 #if DBRT_DEBUG
 546 static void show_stage_entry(FILE *o,
 547                              const char *label, const struct cache_entry *ce)
 548 {
 549         if (!ce)
 550                 fprintf(o, "%s (missing)\n", label);
 551         else
 552                 fprintf(o, "%s%06o %s %d\t%s\n",
 553                         label,
 554                         ntohl(ce->ce_mode),
 555                         sha1_to_hex(ce->sha1),
 556                         ce_stage(ce),
 557                         ce->name);
 558 }
 559 #endif
 560
 561 static int threeway_merge(struct cache_entry **stages)
 562 {
 563         struct cache_entry *index;
 564         struct cache_entry *head;
 565         struct cache_entry *remote = stages[head_idx + 1];
 566         int count;
 567         int head_match = 0;
 568         int remote_match = 0;
 569         const char *path = NULL;
 570
 571         int df_conflict_head = 0;
 572         int df_conflict_remote = 0;
 573
 574         int any_anc_missing = 0;
 575         int no_anc_exists = 1;
 576         int i;
 577
 578         for (i = 1; i < head_idx; i++) {
 579                 if (!stages[i])
 580                         any_anc_missing = 1;
 581                 else {
 582                         if (!path)
 583                                 path = stages[i]->name;
 584                         no_anc_exists = 0;
 585                 }
 586         }
 587
 588         index = stages[0];
 589         head = stages[head_idx];
 590
 591         if (head == &df_conflict_entry) {
 592                 df_conflict_head = 1;
 593                 head = NULL;
 594         }
 595
 596         if (remote == &df_conflict_entry) {
 597                 df_conflict_remote = 1;
 598                 remote = NULL;
 599         }
 600
 601         if (!path && index)
 602                 path = index->name;
 603         if (!path && head)
 604                 path = head->name;
 605         if (!path && remote)
 606                 path = remote->name;
 607
 608         /* First, if there's a #16 situation, note that to prevent #13
 609          * and #14.
 610          */
 611         if (!same(remote, head)) {
 612                 for (i = 1; i < head_idx; i++) {
 613                         if (same(stages[i], head)) {
 614                                 head_match = i;
 615                         }
 616                         if (same(stages[i], remote)) {
 617                                 remote_match = i;
 618                         }
 619                 }
 620         }
 621
 622         /* We start with cases where the index is allowed to match
 623          * something other than the head: #14(ALT) and #2ALT, where it
 624          * is permitted to match the result instead.
 625          */
 626         /* #14, #14ALT, #2ALT */
 627         if (remote && !df_conflict_head && head_match && !remote_match) {
 628                 if (index && !same(index, remote) && !same(index, head))
 629                         reject_merge(index);
 630                 return merged_entry(remote, index);
 631         }
 632         /*
 633          * If we have an entry in the index cache, then we want to
 634          * make sure that it matches head.
 635          */
 636         if (index && !same(index, head)) {
 637                 reject_merge(index);
 638         }
 639
 640         if (head) {
 641                 /* #5ALT, #15 */
 642                 if (same(head, remote))
 643                         return merged_entry(head, index);
 644                 /* #13, #3ALT */
 645                 if (!df_conflict_remote && remote_match && !head_match)
 646                         return merged_entry(head, index);
 647         }
 648
 649         /* #1 */
 650         if (!head && !remote && any_anc_missing)
 651                 return 0;
 652
 653         /* Under the new "aggressive" rule, we resolve mostly trivial
 654          * cases that we historically had git-merge-one-file resolve.
 655          */
 656         if (aggressive) {
 657                 int head_deleted = !head && !df_conflict_head;
 658                 int remote_deleted = !remote && !df_conflict_remote;
 659                 /*
 660                  * Deleted in both.
 661                  * Deleted in one and unchanged in the other.
 662                  */
 663                 if ((head_deleted && remote_deleted) ||
 664                     (head_deleted && remote && remote_match) ||
 665                     (remote_deleted && head && head_match)) {
 666                         if (index)
 667                                 return deleted_entry(index, index);
 668                         else if (path)
 669                                 verify_absent(path, "removed");
 670                         return 0;
 671                 }
 672                 /*
 673                  * Added in both, identically.
 674                  */
 675                 if (no_anc_exists && head && remote && same(head, remote))
 676                         return merged_entry(head, index);
 677
 678         }
 679
 680         /* Below are "no merge" cases, which require that the index be
 681          * up-to-date to avoid the files getting overwritten with
 682          * conflict resolution files.
 683          */
 684         if (index) {
 685                 verify_uptodate(index);
 686         }
 687         else if (path)
 688                 verify_absent(path, "overwritten");
 689
 690         nontrivial_merge = 1;
 691
 692         /* #2, #3, #4, #6, #7, #9, #11. */
 693         count = 0;
 694         if (!head_match || !remote_match) {
 695                 for (i = 1; i < head_idx; i++) {
 696                         if (stages[i]) {
 697                                 keep_entry(stages[i]);
 698                                 count++;
 699                                 break;
 700                         }
 701                 }
 702         }
 703 #if DBRT_DEBUG
 704         else {
 705                 fprintf(stderr, "read-tree: warning #16 detected\n");
 706                 show_stage_entry(stderr, "head   ", stages[head_match]);
 707                 show_stage_entry(stderr, "remote ", stages[remote_match]);
 708         }
 709 #endif
 710         if (head) { count += keep_entry(head); }
 711         if (remote) { count += keep_entry(remote); }
 712         return count;
 713 }
 714
 715 /*
 716  * Two-way merge.
 717  *
 718  * The rule is to "carry forward" what is in the index without losing
 719  * information across a "fast forward", favoring a successful merge
 720  * over a merge failure when it makes sense.  For details of the
 721  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 722  *
 723  */
 724 static int twoway_merge(struct cache_entry **src)
 725 {
 726         struct cache_entry *current = src[0];
 727         struct cache_entry *oldtree = src[1], *newtree = src[2];
 728
 729         if (merge_size != 2)
 730                 return error("Cannot do a twoway merge of %d trees",
 731                              merge_size);
 732
 733         if (current) {
 734                 if ((!oldtree && !newtree) || /* 4 and 5 */
 735                     (!oldtree && newtree &&
 736                      same(current, newtree)) || /* 6 and 7 */
 737                     (oldtree && newtree &&
 738                      same(oldtree, newtree)) || /* 14 and 15 */
 739                     (oldtree && newtree &&
 740                      !same(oldtree, newtree) && /* 18 and 19*/
 741                      same(current, newtree))) {
 742                         return keep_entry(current);
 743                 }
 744                 else if (oldtree && !newtree && same(current, oldtree)) {
 745                         /* 10 or 11 */
 746                         return deleted_entry(oldtree, current);
 747                 }
 748                 else if (oldtree && newtree &&
 749                          same(current, oldtree) && !same(current, newtree)) {
 750                         /* 20 or 21 */
 751                         return merged_entry(newtree, current);
 752                 }
 753                 else {
 754                         /* all other failures */
 755                         if (oldtree)
 756                                 reject_merge(oldtree);
 757                         if (current)
 758                                 reject_merge(current);
 759                         if (newtree)
 760                                 reject_merge(newtree);
 761                         return -1;
 762                 }
 763         }
 764         else if (newtree)
 765                 return merged_entry(newtree, current);
 766         else
 767                 return deleted_entry(oldtree, current);
 768 }
 769
 770 /*
 771  * Bind merge.
 772  *
 773  * Keep the index entries at stage0, collapse stage1 but make sure
 774  * stage0 does not have anything there.
 775  */
 776 static int bind_merge(struct cache_entry **src)
 777 {
 778         struct cache_entry *old = src[0];
 779         struct cache_entry *a = src[1];
 780
 781         if (merge_size != 1)
 782                 return error("Cannot do a bind merge of %d trees\n",
 783                              merge_size);
 784         if (a && old)
 785                 die("Entry '%s' overlaps.  Cannot bind.", a->name);
 786         if (!a)
 787                 return keep_entry(old);
 788         else
 789                 return merged_entry(a, NULL);
 790 }
 791
 792 /*
 793  * One-way merge.
 794  *
 795  * The rule is:
 796  * - take the stat information from stage0, take the data from stage1
 797  */
 798 static int oneway_merge(struct cache_entry **src)
 799 {
 800         struct cache_entry *old = src[0];
 801         struct cache_entry *a = src[1];
 802
 803         if (merge_size != 1)
 804                 return error("Cannot do a oneway merge of %d trees",
 805                              merge_size);
 806
 807         if (!a) {
 808                 invalidate_ce_path(old);
 809                 return deleted_entry(old, old);
 810         }
 811         if (old && same(old, a)) {
 812                 if (reset) {
 813                         struct stat st;
 814                         if (lstat(old->name, &st) ||
 815                             ce_match_stat(old, &st, 1))
 816                                 old->ce_flags |= htons(CE_UPDATE);
 817                 }
 818                 return keep_entry(old);
 819         }
 820         return merged_entry(a, old);
 821 }
 822
 823 static int read_cache_unmerged(void)
 824 {
 825         int i, deleted;
 826         struct cache_entry **dst;
 827
 828         read_cache();
 829         dst = active_cache;
 830         deleted = 0;
 831         for (i = 0; i < active_nr; i++) {
 832                 struct cache_entry *ce = active_cache[i];
 833                 if (ce_stage(ce)) {
 834                         deleted++;
 835                         invalidate_ce_path(ce);
 836                         continue;
 837                 }
 838                 if (deleted)
 839                         *dst = ce;
 840                 dst++;
 841         }
 842         active_nr -= deleted;
 843         return deleted;
 844 }
 845
 846 static void prime_cache_tree_rec(struct cache_tree *it, struct tree *tree)
 847 {
 848         struct tree_desc desc;
 849         int cnt;
 850
 851         memcpy(it->sha1, tree->object.sha1, 20);
 852         desc.buf = tree->buffer;
 853         desc.size = tree->size;
 854         cnt = 0;
 855         while (desc.size) {
 856                 unsigned mode;
 857                 const char *name;
 858                 const unsigned char *sha1;
 859
 860                 sha1 = tree_entry_extract(&desc, &name, &mode);
 861                 update_tree_entry(&desc);
 862                 if (!S_ISDIR(mode))
 863                         cnt++;
 864                 else {
 865                         struct cache_tree_sub *sub;
 866                         struct tree *subtree = lookup_tree(sha1);
 867                         if (!subtree->object.parsed)
 868                                 parse_tree(subtree);
 869                         sub = cache_tree_sub(it, name);
 870                         sub->cache_tree = cache_tree();
 871                         prime_cache_tree_rec(sub->cache_tree, subtree);
 872                         cnt += sub->cache_tree->entry_count;
 873                 }
 874         }
 875         it->entry_count = cnt;
 876 }
 877
 878 static void prime_cache_tree(void)
 879 {
 880         struct tree *tree = (struct tree *)trees->item;
 881         if (!tree)
 882                 return;
 883         active_cache_tree = cache_tree();
 884         prime_cache_tree_rec(active_cache_tree, tree);
 885
 886 }
 887
 888 static const char read_tree_usage[] = "git-read-tree (<sha> | [[-m [--aggressive] | --reset | --prefix=<prefix>] [-u | -i]] <sha1> [<sha2> [<sha3>]])";
 889
 890 static struct cache_file cache_file;
 891
 892 int cmd_read_tree(int argc, const char **argv, char **envp)
 893 {
 894         int i, newfd, stage = 0;
 895         unsigned char sha1[20];
 896         merge_fn_t fn = NULL;
 897
 898         setup_git_directory();
 899         git_config(git_default_config);
 900
 901         newfd = hold_index_file_for_update(&cache_file, get_index_file());
 902         if (newfd < 0)
 903                 die("unable to create new cachefile");
 904
 905         git_config(git_default_config);
 906
 907         merge = 0;
 908         reset = 0;
 909         for (i = 1; i < argc; i++) {
 910                 const char *arg = argv[i];
 911
 912                 /* "-u" means "update", meaning that a merge will update
 913                  * the working tree.
 914                  */
 915                 if (!strcmp(arg, "-u")) {
 916                         update = 1;
 917                         continue;
 918                 }
 919
 920                 if (!strcmp(arg, "-v")) {
 921                         verbose_update = 1;
 922                         continue;
 923                 }
 924
 925                 /* "-i" means "index only", meaning that a merge will
 926                  * not even look at the working tree.
 927                  */
 928                 if (!strcmp(arg, "-i")) {
 929                         index_only = 1;
 930                         continue;
 931                 }
 932
 933                 /* "--prefix=<subdirectory>/" means keep the current index
 934                  *  entries and put the entries from the tree under the
 935                  * given subdirectory.
 936                  */
 937                 if (!strncmp(arg, "--prefix=", 9)) {
 938                         if (stage || merge || prefix)
 939                                 usage(read_tree_usage);
 940                         prefix = arg + 9;
 941                         merge = 1;
 942                         stage = 1;
 943                         if (read_cache_unmerged())
 944                                 die("you need to resolve your current index first");
 945                         continue;
 946                 }
 947
 948                 /* This differs from "-m" in that we'll silently ignore unmerged entries */
 949                 if (!strcmp(arg, "--reset")) {
 950                         if (stage || merge || prefix)
 951                                 usage(read_tree_usage);
 952                         reset = 1;
 953                         merge = 1;
 954                         stage = 1;
 955                         read_cache_unmerged();
 956                         continue;
 957                 }
 958
 959                 if (!strcmp(arg, "--trivial")) {
 960                         trivial_merges_only = 1;
 961                         continue;
 962                 }
 963
 964                 if (!strcmp(arg, "--aggressive")) {
 965                         aggressive = 1;
 966                         continue;
 967                 }
 968
 969                 /* "-m" stands for "merge", meaning we start in stage 1 */
 970                 if (!strcmp(arg, "-m")) {
 971                         if (stage || merge || prefix)
 972                                 usage(read_tree_usage);
 973                         if (read_cache_unmerged())
 974                                 die("you need to resolve your current index first");
 975                         stage = 1;
 976                         merge = 1;
 977                         continue;
 978                 }
 979
 980                 /* using -u and -i at the same time makes no sense */
 981                 if (1 < index_only + update)
 982                         usage(read_tree_usage);
 983
 984                 if (get_sha1(arg, sha1))
 985                         die("Not a valid object name %s", arg);
 986                 if (list_tree(sha1) < 0)
 987                         die("failed to unpack tree object %s", arg);
 988                 stage++;
 989         }
 990         if ((update||index_only) && !merge)
 991                 usage(read_tree_usage);
 992
 993         if (prefix) {
 994                 int pfxlen = strlen(prefix);
 995                 int pos;
 996                 if (prefix[pfxlen-1] != '/')
 997                         die("prefix must end with /");
 998                 if (stage != 2)
 999                         die("binding merge takes only one tree");
1000                 pos = cache_name_pos(prefix, pfxlen);
1001                 if (0 <= pos)
1002                         die("corrupt index file");
1003                 pos = -pos-1;
1004                 if (pos < active_nr &&
1005                     !strncmp(active_cache[pos]->name, prefix, pfxlen))
1006                         die("subdirectory '%s' already exists.", prefix);
1007                 pos = cache_name_pos(prefix, pfxlen-1);
1008                 if (0 <= pos)
1009                         die("file '%.*s' already exists.", pfxlen-1, prefix);
1010         }
1011
1012         if (merge) {
1013                 if (stage < 2)
1014                         die("just how do you expect me to merge %d trees?", stage-1);
1015                 switch (stage - 1) {
1016                 case 1:
1017                         fn = prefix ? bind_merge : oneway_merge;
1018                         break;
1019                 case 2:
1020                         fn = twoway_merge;
1021                         break;
1022                 case 3:
1023                 default:
1024                         fn = threeway_merge;
1025                         cache_tree_free(&active_cache_tree);
1026                         break;
1027                 }
1028
1029                 if (stage - 1 >= 3)
1030                         head_idx = stage - 2;
1031                 else
1032                         head_idx = 1;
1033         }
1034
1035         unpack_trees(fn);
1036
1037         /*
1038          * When reading only one tree (either the most basic form,
1039          * "-m ent" or "--reset ent" form), we can obtain a fully
1040          * valid cache-tree because the index must match exactly
1041          * what came from the tree.
1042          */
1043         if (trees && trees->item && (!merge || (stage == 2))) {
1044                 cache_tree_free(&active_cache_tree);
1045                 prime_cache_tree();
1046         }
1047
1048         if (write_cache(newfd, active_cache, active_nr) ||
1049             commit_index_file(&cache_file))
1050                 die("unable to write new index file");
1051         return 0;
1052 }