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