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