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