builtin-read-tree.c

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