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