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 <sys/time.h>
  13 #include <signal.h>
  14 #include "builtin.h"
  15
  16 static int reset = 0;
  17 static int merge = 0;
  18 static int update = 0;
  19 static int index_only = 0;
  20 static int nontrivial_merge = 0;
  21 static int trivial_merges_only = 0;
  22 static int aggressive = 0;
  23 static int verbose_update = 0;
  24 static volatile int progress_update = 0;
  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, "", fn, &indpos))
 374                         return -1;
 375         }
 376
 377         if (trivial_merges_only && nontrivial_merge)
 378                 die("Merge requires file-level merging");
 379
 380         check_updates(active_cache, active_nr);
 381         return 0;
 382 }
 383
 384 static int list_tree(unsigned char *sha1)
 385 {
 386         struct tree *tree = parse_tree_indirect(sha1);
 387         if (!tree)
 388                 return -1;
 389         object_list_append(&tree->object, &trees);
 390         return 0;
 391 }
 392
 393 static int same(struct cache_entry *a, struct cache_entry *b)
 394 {
 395         if (!!a != !!b)
 396                 return 0;
 397         if (!a && !b)
 398                 return 1;
 399         return a->ce_mode == b->ce_mode &&
 400                 !memcmp(a->sha1, b->sha1, 20);
 401 }
 402
 403
 404 /*
 405  * When a CE gets turned into an unmerged entry, we
 406  * want it to be up-to-date
 407  */
 408 static void verify_uptodate(struct cache_entry *ce)
 409 {
 410         struct stat st;
 411
 412         if (index_only || reset)
 413                 return;
 414
 415         if (!lstat(ce->name, &st)) {
 416                 unsigned changed = ce_match_stat(ce, &st, 1);
 417                 if (!changed)
 418                         return;
 419                 errno = 0;
 420         }
 421         if (reset) {
 422                 ce->ce_flags |= htons(CE_UPDATE);
 423                 return;
 424         }
 425         if (errno == ENOENT)
 426                 return;
 427         die("Entry '%s' not uptodate. Cannot merge.", ce->name);
 428 }
 429
 430 /*
 431  * We do not want to remove or overwrite a working tree file that
 432  * is not tracked.
 433  */
 434 static void verify_absent(const char *path, const char *action)
 435 {
 436         struct stat st;
 437
 438         if (index_only || reset || !update)
 439                 return;
 440         if (!lstat(path, &st))
 441                 die("Untracked working tree file '%s' "
 442                     "would be %s by merge.", path, action);
 443 }
 444
 445 static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
 446 {
 447         merge->ce_flags |= htons(CE_UPDATE);
 448         if (old) {
 449                 /*
 450                  * See if we can re-use the old CE directly?
 451                  * That way we get the uptodate stat info.
 452                  *
 453                  * This also removes the UPDATE flag on
 454                  * a match.
 455                  */
 456                 if (same(old, merge)) {
 457                         *merge = *old;
 458                 } else {
 459                         verify_uptodate(old);
 460                 }
 461         }
 462         else
 463                 verify_absent(merge->name, "overwritten");
 464
 465         merge->ce_flags &= ~htons(CE_STAGEMASK);
 466         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
 467         return 1;
 468 }
 469
 470 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
 471 {
 472         if (old)
 473                 verify_uptodate(old);
 474         else
 475                 verify_absent(ce->name, "removed");
 476         ce->ce_mode = 0;
 477         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 478         return 1;
 479 }
 480
 481 static int keep_entry(struct cache_entry *ce)
 482 {
 483         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 484         return 1;
 485 }
 486
 487 #if DBRT_DEBUG
 488 static void show_stage_entry(FILE *o,
 489                              const char *label, const struct cache_entry *ce)
 490 {
 491         if (!ce)
 492                 fprintf(o, "%s (missing)\n", label);
 493         else
 494                 fprintf(o, "%s%06o %s %d\t%s\n",
 495                         label,
 496                         ntohl(ce->ce_mode),
 497                         sha1_to_hex(ce->sha1),
 498                         ce_stage(ce),
 499                         ce->name);
 500 }
 501 #endif
 502
 503 static int threeway_merge(struct cache_entry **stages)
 504 {
 505         struct cache_entry *index;
 506         struct cache_entry *head;
 507         struct cache_entry *remote = stages[head_idx + 1];
 508         int count;
 509         int head_match = 0;
 510         int remote_match = 0;
 511         const char *path = NULL;
 512
 513         int df_conflict_head = 0;
 514         int df_conflict_remote = 0;
 515
 516         int any_anc_missing = 0;
 517         int no_anc_exists = 1;
 518         int i;
 519
 520         for (i = 1; i < head_idx; i++) {
 521                 if (!stages[i])
 522                         any_anc_missing = 1;
 523                 else {
 524                         if (!path)
 525                                 path = stages[i]->name;
 526                         no_anc_exists = 0;
 527                 }
 528         }
 529
 530         index = stages[0];
 531         head = stages[head_idx];
 532
 533         if (head == &df_conflict_entry) {
 534                 df_conflict_head = 1;
 535                 head = NULL;
 536         }
 537
 538         if (remote == &df_conflict_entry) {
 539                 df_conflict_remote = 1;
 540                 remote = NULL;
 541         }
 542
 543         if (!path && index)
 544                 path = index->name;
 545         if (!path && head)
 546                 path = head->name;
 547         if (!path && remote)
 548                 path = remote->name;
 549
 550         /* First, if there's a #16 situation, note that to prevent #13
 551          * and #14.
 552          */
 553         if (!same(remote, head)) {
 554                 for (i = 1; i < head_idx; i++) {
 555                         if (same(stages[i], head)) {
 556                                 head_match = i;
 557                         }
 558                         if (same(stages[i], remote)) {
 559                                 remote_match = i;
 560                         }
 561                 }
 562         }
 563
 564         /* We start with cases where the index is allowed to match
 565          * something other than the head: #14(ALT) and #2ALT, where it
 566          * is permitted to match the result instead.
 567          */
 568         /* #14, #14ALT, #2ALT */
 569         if (remote && !df_conflict_head && head_match && !remote_match) {
 570                 if (index && !same(index, remote) && !same(index, head))
 571                         reject_merge(index);
 572                 return merged_entry(remote, index);
 573         }
 574         /*
 575          * If we have an entry in the index cache, then we want to
 576          * make sure that it matches head.
 577          */
 578         if (index && !same(index, head)) {
 579                 reject_merge(index);
 580         }
 581
 582         if (head) {
 583                 /* #5ALT, #15 */
 584                 if (same(head, remote))
 585                         return merged_entry(head, index);
 586                 /* #13, #3ALT */
 587                 if (!df_conflict_remote && remote_match && !head_match)
 588                         return merged_entry(head, index);
 589         }
 590
 591         /* #1 */
 592         if (!head && !remote && any_anc_missing)
 593                 return 0;
 594
 595         /* Under the new "aggressive" rule, we resolve mostly trivial
 596          * cases that we historically had git-merge-one-file resolve.
 597          */
 598         if (aggressive) {
 599                 int head_deleted = !head && !df_conflict_head;
 600                 int remote_deleted = !remote && !df_conflict_remote;
 601                 /*
 602                  * Deleted in both.
 603                  * Deleted in one and unchanged in the other.
 604                  */
 605                 if ((head_deleted && remote_deleted) ||
 606                     (head_deleted && remote && remote_match) ||
 607                     (remote_deleted && head && head_match)) {
 608                         if (index)
 609                                 return deleted_entry(index, index);
 610                         else if (path)
 611                                 verify_absent(path, "removed");
 612                         return 0;
 613                 }
 614                 /*
 615                  * Added in both, identically.
 616                  */
 617                 if (no_anc_exists && head && remote && same(head, remote))
 618                         return merged_entry(head, index);
 619
 620         }
 621
 622         /* Below are "no merge" cases, which require that the index be
 623          * up-to-date to avoid the files getting overwritten with
 624          * conflict resolution files.
 625          */
 626         if (index) {
 627                 verify_uptodate(index);
 628         }
 629         else if (path)
 630                 verify_absent(path, "overwritten");
 631
 632         nontrivial_merge = 1;
 633
 634         /* #2, #3, #4, #6, #7, #9, #11. */
 635         count = 0;
 636         if (!head_match || !remote_match) {
 637                 for (i = 1; i < head_idx; i++) {
 638                         if (stages[i]) {
 639                                 keep_entry(stages[i]);
 640                                 count++;
 641                                 break;
 642                         }
 643                 }
 644         }
 645 #if DBRT_DEBUG
 646         else {
 647                 fprintf(stderr, "read-tree: warning #16 detected\n");
 648                 show_stage_entry(stderr, "head   ", stages[head_match]);
 649                 show_stage_entry(stderr, "remote ", stages[remote_match]);
 650         }
 651 #endif
 652         if (head) { count += keep_entry(head); }
 653         if (remote) { count += keep_entry(remote); }
 654         return count;
 655 }
 656
 657 /*
 658  * Two-way merge.
 659  *
 660  * The rule is to "carry forward" what is in the index without losing
 661  * information across a "fast forward", favoring a successful merge
 662  * over a merge failure when it makes sense.  For details of the
 663  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 664  *
 665  */
 666 static int twoway_merge(struct cache_entry **src)
 667 {
 668         struct cache_entry *current = src[0];
 669         struct cache_entry *oldtree = src[1], *newtree = src[2];
 670
 671         if (merge_size != 2)
 672                 return error("Cannot do a twoway merge of %d trees",
 673                              merge_size);
 674
 675         if (current) {
 676                 if ((!oldtree && !newtree) || /* 4 and 5 */
 677                     (!oldtree && newtree &&
 678                      same(current, newtree)) || /* 6 and 7 */
 679                     (oldtree && newtree &&
 680                      same(oldtree, newtree)) || /* 14 and 15 */
 681                     (oldtree && newtree &&
 682                      !same(oldtree, newtree) && /* 18 and 19*/
 683                      same(current, newtree))) {
 684                         return keep_entry(current);
 685                 }
 686                 else if (oldtree && !newtree && same(current, oldtree)) {
 687                         /* 10 or 11 */
 688                         return deleted_entry(oldtree, current);
 689                 }
 690                 else if (oldtree && newtree &&
 691                          same(current, oldtree) && !same(current, newtree)) {
 692                         /* 20 or 21 */
 693                         return merged_entry(newtree, current);
 694                 }
 695                 else {
 696                         /* all other failures */
 697                         if (oldtree)
 698                                 reject_merge(oldtree);
 699                         if (current)
 700                                 reject_merge(current);
 701                         if (newtree)
 702                                 reject_merge(newtree);
 703                         return -1;
 704                 }
 705         }
 706         else if (newtree)
 707                 return merged_entry(newtree, current);
 708         else
 709                 return deleted_entry(oldtree, current);
 710 }
 711
 712 /*
 713  * One-way merge.
 714  *
 715  * The rule is:
 716  * - take the stat information from stage0, take the data from stage1
 717  */
 718 static int oneway_merge(struct cache_entry **src)
 719 {
 720         struct cache_entry *old = src[0];
 721         struct cache_entry *a = src[1];
 722
 723         if (merge_size != 1)
 724                 return error("Cannot do a oneway merge of %d trees",
 725                              merge_size);
 726
 727         if (!a)
 728                 return deleted_entry(old, old);
 729         if (old && same(old, a)) {
 730                 if (reset) {
 731                         struct stat st;
 732                         if (lstat(old->name, &st) ||
 733                             ce_match_stat(old, &st, 1))
 734                                 old->ce_flags |= htons(CE_UPDATE);
 735                 }
 736                 return keep_entry(old);
 737         }
 738         return merged_entry(a, old);
 739 }
 740
 741 static int read_cache_unmerged(void)
 742 {
 743         int i, deleted;
 744         struct cache_entry **dst;
 745
 746         read_cache();
 747         dst = active_cache;
 748         deleted = 0;
 749         for (i = 0; i < active_nr; i++) {
 750                 struct cache_entry *ce = active_cache[i];
 751                 if (ce_stage(ce)) {
 752                         deleted++;
 753                         continue;
 754                 }
 755                 if (deleted)
 756                         *dst = ce;
 757                 dst++;
 758         }
 759         active_nr -= deleted;
 760         return deleted;
 761 }
 762
 763 static const char read_tree_usage[] = "git-read-tree (<sha> | -m [--aggressive] [-u | -i] <sha1> [<sha2> [<sha3>]])";
 764
 765 static struct cache_file cache_file;
 766
 767 int cmd_read_tree(int argc, const char **argv, char **envp)
 768 {
 769         int i, newfd, stage = 0;
 770         unsigned char sha1[20];
 771         merge_fn_t fn = NULL;
 772
 773         setup_git_directory();
 774         git_config(git_default_config);
 775
 776         newfd = hold_index_file_for_update(&cache_file, get_index_file());
 777         if (newfd < 0)
 778                 die("unable to create new cachefile");
 779
 780         git_config(git_default_config);
 781
 782         merge = 0;
 783         reset = 0;
 784         for (i = 1; i < argc; i++) {
 785                 const char *arg = argv[i];
 786
 787                 /* "-u" means "update", meaning that a merge will update
 788                  * the working tree.
 789                  */
 790                 if (!strcmp(arg, "-u")) {
 791                         update = 1;
 792                         continue;
 793                 }
 794
 795                 if (!strcmp(arg, "-v")) {
 796                         verbose_update = 1;
 797                         continue;
 798                 }
 799
 800                 /* "-i" means "index only", meaning that a merge will
 801                  * not even look at the working tree.
 802                  */
 803                 if (!strcmp(arg, "-i")) {
 804                         index_only = 1;
 805                         continue;
 806                 }
 807
 808                 /* This differs from "-m" in that we'll silently ignore unmerged entries */
 809                 if (!strcmp(arg, "--reset")) {
 810                         if (stage || merge)
 811                                 usage(read_tree_usage);
 812                         reset = 1;
 813                         merge = 1;
 814                         stage = 1;
 815                         read_cache_unmerged();
 816                         continue;
 817                 }
 818
 819                 if (!strcmp(arg, "--trivial")) {
 820                         trivial_merges_only = 1;
 821                         continue;
 822                 }
 823
 824                 if (!strcmp(arg, "--aggressive")) {
 825                         aggressive = 1;
 826                         continue;
 827                 }
 828
 829                 /* "-m" stands for "merge", meaning we start in stage 1 */
 830                 if (!strcmp(arg, "-m")) {
 831                         if (stage || merge)
 832                                 usage(read_tree_usage);
 833                         if (read_cache_unmerged())
 834                                 die("you need to resolve your current index first");
 835                         stage = 1;
 836                         merge = 1;
 837                         continue;
 838                 }
 839
 840                 /* using -u and -i at the same time makes no sense */
 841                 if (1 < index_only + update)
 842                         usage(read_tree_usage);
 843
 844                 if (get_sha1(arg, sha1))
 845                         die("Not a valid object name %s", arg);
 846                 if (list_tree(sha1) < 0)
 847                         die("failed to unpack tree object %s", arg);
 848                 stage++;
 849         }
 850         if ((update||index_only) && !merge)
 851                 usage(read_tree_usage);
 852
 853         if (merge) {
 854                 if (stage < 2)
 855                         die("just how do you expect me to merge %d trees?", stage-1);
 856                 switch (stage - 1) {
 857                 case 1:
 858                         fn = oneway_merge;
 859                         break;
 860                 case 2:
 861                         fn = twoway_merge;
 862                         break;
 863                 case 3:
 864                         fn = threeway_merge;
 865                         break;
 866                 default:
 867                         fn = threeway_merge;
 868                         break;
 869                 }
 870
 871                 if (stage - 1 >= 3)
 872                         head_idx = stage - 2;
 873                 else
 874                         head_idx = 1;
 875         }
 876
 877         unpack_trees(fn);
 878         if (write_cache(newfd, active_cache, active_nr) ||
 879             commit_index_file(&cache_file))
 880                 die("unable to write new index file");
 881         return 0;
 882 }