Andrew's git / gitweb.git / read-tree.c
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read-tree.con commit Merge part of 'jc/cache-tree' (5b5e4d6)
   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
  15static int merge = 0;
  16static int update = 0;
  17static int index_only = 0;
  18static int nontrivial_merge = 0;
  19static int trivial_merges_only = 0;
  20static int aggressive = 0;
  21static int verbose_update = 0;
  22static volatile int progress_update = 0;
  23
  24static int head_idx = -1;
  25static int merge_size = 0;
  26
  27static struct object_list *trees = NULL;
  28
  29static struct cache_entry df_conflict_entry = { 
  30};
  31
  32static struct tree_entry_list df_conflict_list = {
  33        .name = NULL,
  34        .next = &df_conflict_list
  35};
  36
  37typedef int (*merge_fn_t)(struct cache_entry **src);
  38
  39static int entcmp(char *name1, int dir1, char *name2, int dir2)
  40{
  41        int len1 = strlen(name1);
  42        int len2 = strlen(name2);
  43        int len = len1 < len2 ? len1 : len2;
  44        int ret = memcmp(name1, name2, len);
  45        unsigned char c1, c2;
  46        if (ret)
  47                return ret;
  48        c1 = name1[len];
  49        c2 = name2[len];
  50        if (!c1 && dir1)
  51                c1 = '/';
  52        if (!c2 && dir2)
  53                c2 = '/';
  54        ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
  55        if (c1 && c2 && !ret)
  56                ret = len1 - len2;
  57        return ret;
  58}
  59
  60static int unpack_trees_rec(struct tree_entry_list **posns, int len,
  61                            const char *base, merge_fn_t fn, int *indpos)
  62{
  63        int baselen = strlen(base);
  64        int src_size = len + 1;
  65        do {
  66                int i;
  67                char *first;
  68                int firstdir = 0;
  69                int pathlen;
  70                unsigned ce_size;
  71                struct tree_entry_list **subposns;
  72                struct cache_entry **src;
  73                int any_files = 0;
  74                int any_dirs = 0;
  75                char *cache_name;
  76                int ce_stage;
  77
  78                /* Find the first name in the input. */
  79
  80                first = NULL;
  81                cache_name = NULL;
  82
  83                /* Check the cache */
  84                if (merge && *indpos < active_nr) {
  85                        /* This is a bit tricky: */
  86                        /* If the index has a subdirectory (with
  87                         * contents) as the first name, it'll get a
  88                         * filename like "foo/bar". But that's after
  89                         * "foo", so the entry in trees will get
  90                         * handled first, at which point we'll go into
  91                         * "foo", and deal with "bar" from the index,
  92                         * because the base will be "foo/". The only
  93                         * way we can actually have "foo/bar" first of
  94                         * all the things is if the trees don't
  95                         * contain "foo" at all, in which case we'll
  96                         * handle "foo/bar" without going into the
  97                         * directory, but that's fine (and will return
  98                         * an error anyway, with the added unknown
  99                         * file case.
 100                         */
 101
 102                        cache_name = active_cache[*indpos]->name;
 103                        if (strlen(cache_name) > baselen &&
 104                            !memcmp(cache_name, base, baselen)) {
 105                                cache_name += baselen;
 106                                first = cache_name;
 107                        } else {
 108                                cache_name = NULL;
 109                        }
 110                }
 111
 112#if DBRT_DEBUG > 1
 113                if (first)
 114                        printf("index %s\n", first);
 115#endif
 116                for (i = 0; i < len; i++) {
 117                        if (!posns[i] || posns[i] == &df_conflict_list)
 118                                continue;
 119#if DBRT_DEBUG > 1
 120                        printf("%d %s\n", i + 1, posns[i]->name);
 121#endif
 122                        if (!first || entcmp(first, firstdir,
 123                                             posns[i]->name, 
 124                                             posns[i]->directory) > 0) {
 125                                first = posns[i]->name;
 126                                firstdir = posns[i]->directory;
 127                        }
 128                }
 129                /* No name means we're done */
 130                if (!first)
 131                        return 0;
 132
 133                pathlen = strlen(first);
 134                ce_size = cache_entry_size(baselen + pathlen);
 135
 136                src = xcalloc(src_size, sizeof(struct cache_entry *));
 137
 138                subposns = xcalloc(len, sizeof(struct tree_list_entry *));
 139
 140                if (cache_name && !strcmp(cache_name, first)) {
 141                        any_files = 1;
 142                        src[0] = active_cache[*indpos];
 143                        remove_cache_entry_at(*indpos);
 144                }
 145
 146                for (i = 0; i < len; i++) {
 147                        struct cache_entry *ce;
 148
 149                        if (!posns[i] ||
 150                            (posns[i] != &df_conflict_list &&
 151                             strcmp(first, posns[i]->name))) {
 152                                continue;
 153                        }
 154
 155                        if (posns[i] == &df_conflict_list) {
 156                                src[i + merge] = &df_conflict_entry;
 157                                continue;
 158                        }
 159
 160                        if (posns[i]->directory) {
 161                                any_dirs = 1;
 162                                parse_tree(posns[i]->item.tree);
 163                                subposns[i] = posns[i]->item.tree->entries;
 164                                posns[i] = posns[i]->next;
 165                                src[i + merge] = &df_conflict_entry;
 166                                continue;
 167                        }
 168
 169                        if (!merge)
 170                                ce_stage = 0;
 171                        else if (i + 1 < head_idx)
 172                                ce_stage = 1;
 173                        else if (i + 1 > head_idx)
 174                                ce_stage = 3;
 175                        else
 176                                ce_stage = 2;
 177
 178                        ce = xcalloc(1, ce_size);
 179                        ce->ce_mode = create_ce_mode(posns[i]->mode);
 180                        ce->ce_flags = create_ce_flags(baselen + pathlen,
 181                                                       ce_stage);
 182                        memcpy(ce->name, base, baselen);
 183                        memcpy(ce->name + baselen, first, pathlen + 1);
 184
 185                        any_files = 1;
 186
 187                        memcpy(ce->sha1, posns[i]->item.any->sha1, 20);
 188                        src[i + merge] = ce;
 189                        subposns[i] = &df_conflict_list;
 190                        posns[i] = posns[i]->next;
 191                }
 192                if (any_files) {
 193                        if (merge) {
 194                                int ret;
 195
 196#if DBRT_DEBUG > 1
 197                                printf("%s:\n", first);
 198                                for (i = 0; i < src_size; i++) {
 199                                        printf(" %d ", i);
 200                                        if (src[i])
 201                                                printf("%s\n", sha1_to_hex(src[i]->sha1));
 202                                        else
 203                                                printf("\n");
 204                                }
 205#endif
 206                                ret = fn(src);
 207                                
 208#if DBRT_DEBUG > 1
 209                                printf("Added %d entries\n", ret);
 210#endif
 211                                *indpos += ret;
 212                        } else {
 213                                for (i = 0; i < src_size; i++) {
 214                                        if (src[i]) {
 215                                                add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
 216                                        }
 217                                }
 218                        }
 219                }
 220                if (any_dirs) {
 221                        char *newbase = xmalloc(baselen + 2 + pathlen);
 222                        memcpy(newbase, base, baselen);
 223                        memcpy(newbase + baselen, first, pathlen);
 224                        newbase[baselen + pathlen] = '/';
 225                        newbase[baselen + pathlen + 1] = '\0';
 226                        if (unpack_trees_rec(subposns, len, newbase, fn,
 227                                             indpos))
 228                                return -1;
 229                        free(newbase);
 230                }
 231                free(subposns);
 232                free(src);
 233        } while (1);
 234}
 235
 236static void reject_merge(struct cache_entry *ce)
 237{
 238        die("Entry '%s' would be overwritten by merge. Cannot merge.", 
 239            ce->name);
 240}
 241
 242/* Unlink the last component and attempt to remove leading
 243 * directories, in case this unlink is the removal of the
 244 * last entry in the directory -- empty directories are removed.
 245 */
 246static void unlink_entry(char *name)
 247{
 248        char *cp, *prev;
 249
 250        if (unlink(name))
 251                return;
 252        prev = NULL;
 253        while (1) {
 254                int status;
 255                cp = strrchr(name, '/');
 256                if (prev)
 257                        *prev = '/';
 258                if (!cp)
 259                        break;
 260
 261                *cp = 0;
 262                status = rmdir(name);
 263                if (status) {
 264                        *cp = '/';
 265                        break;
 266                }
 267                prev = cp;
 268        }
 269}
 270
 271static void progress_interval(int signum)
 272{
 273        progress_update = 1;
 274}
 275
 276static void setup_progress_signal(void)
 277{
 278        struct sigaction sa;
 279        struct itimerval v;
 280
 281        memset(&sa, 0, sizeof(sa));
 282        sa.sa_handler = progress_interval;
 283        sigemptyset(&sa.sa_mask);
 284        sa.sa_flags = SA_RESTART;
 285        sigaction(SIGALRM, &sa, NULL);
 286
 287        v.it_interval.tv_sec = 1;
 288        v.it_interval.tv_usec = 0;
 289        v.it_value = v.it_interval;
 290        setitimer(ITIMER_REAL, &v, NULL);
 291}
 292
 293static void check_updates(struct cache_entry **src, int nr)
 294{
 295        static struct checkout state = {
 296                .base_dir = "",
 297                .force = 1,
 298                .quiet = 1,
 299                .refresh_cache = 1,
 300        };
 301        unsigned short mask = htons(CE_UPDATE);
 302        unsigned last_percent = 200, cnt = 0, total = 0;
 303
 304        if (update && verbose_update) {
 305                for (total = cnt = 0; cnt < nr; cnt++) {
 306                        struct cache_entry *ce = src[cnt];
 307                        if (!ce->ce_mode || ce->ce_flags & mask)
 308                                total++;
 309                }
 310
 311                /* Don't bother doing this for very small updates */
 312                if (total < 250)
 313                        total = 0;
 314
 315                if (total) {
 316                        fprintf(stderr, "Checking files out...\n");
 317                        setup_progress_signal();
 318                        progress_update = 1;
 319                }
 320                cnt = 0;
 321        }
 322
 323        while (nr--) {
 324                struct cache_entry *ce = *src++;
 325
 326                if (total) {
 327                        if (!ce->ce_mode || ce->ce_flags & mask) {
 328                                unsigned percent;
 329                                cnt++;
 330                                percent = (cnt * 100) / total;
 331                                if (percent != last_percent ||
 332                                    progress_update) {
 333                                        fprintf(stderr, "%4u%% (%u/%u) done\r",
 334                                                percent, cnt, total);
 335                                        last_percent = percent;
 336                                }
 337                        }
 338                }
 339                if (!ce->ce_mode) {
 340                        if (update)
 341                                unlink_entry(ce->name);
 342                        continue;
 343                }
 344                if (ce->ce_flags & mask) {
 345                        ce->ce_flags &= ~mask;
 346                        if (update)
 347                                checkout_entry(ce, &state, NULL);
 348                }
 349        }
 350        if (total) {
 351                signal(SIGALRM, SIG_IGN);
 352                fputc('\n', stderr);
 353        }
 354}
 355
 356static int unpack_trees(merge_fn_t fn)
 357{
 358        int indpos = 0;
 359        unsigned len = object_list_length(trees);
 360        struct tree_entry_list **posns;
 361        int i;
 362        struct object_list *posn = trees;
 363        merge_size = len;
 364
 365        if (len) {
 366                posns = xmalloc(len * sizeof(struct tree_entry_list *));
 367                for (i = 0; i < len; i++) {
 368                        posns[i] = ((struct tree *) posn->item)->entries;
 369                        posn = posn->next;
 370                }
 371                if (unpack_trees_rec(posns, len, "", fn, &indpos))
 372                        return -1;
 373        }
 374
 375        if (trivial_merges_only && nontrivial_merge)
 376                die("Merge requires file-level merging");
 377
 378        check_updates(active_cache, active_nr);
 379        return 0;
 380}
 381
 382static int list_tree(unsigned char *sha1)
 383{
 384        struct tree *tree = parse_tree_indirect(sha1);
 385        if (!tree)
 386                return -1;
 387        object_list_append(&tree->object, &trees);
 388        return 0;
 389}
 390
 391static int same(struct cache_entry *a, struct cache_entry *b)
 392{
 393        if (!!a != !!b)
 394                return 0;
 395        if (!a && !b)
 396                return 1;
 397        return a->ce_mode == b->ce_mode && 
 398                !memcmp(a->sha1, b->sha1, 20);
 399}
 400
 401
 402/*
 403 * When a CE gets turned into an unmerged entry, we
 404 * want it to be up-to-date
 405 */
 406static void verify_uptodate(struct cache_entry *ce)
 407{
 408        struct stat st;
 409
 410        if (index_only)
 411                return;
 412
 413        if (!lstat(ce->name, &st)) {
 414                unsigned changed = ce_match_stat(ce, &st, 1);
 415                if (!changed)
 416                        return;
 417                errno = 0;
 418        }
 419        if (errno == ENOENT)
 420                return;
 421        die("Entry '%s' not uptodate. Cannot merge.", ce->name);
 422}
 423
 424static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
 425{
 426        merge->ce_flags |= htons(CE_UPDATE);
 427        if (old) {
 428                /*
 429                 * See if we can re-use the old CE directly?
 430                 * That way we get the uptodate stat info.
 431                 *
 432                 * This also removes the UPDATE flag on
 433                 * a match.
 434                 */
 435                if (same(old, merge)) {
 436                        *merge = *old;
 437                } else {
 438                        verify_uptodate(old);
 439                }
 440        }
 441        merge->ce_flags &= ~htons(CE_STAGEMASK);
 442        add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
 443        return 1;
 444}
 445
 446static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
 447{
 448        if (old)
 449                verify_uptodate(old);
 450        ce->ce_mode = 0;
 451        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 452        return 1;
 453}
 454
 455static int keep_entry(struct cache_entry *ce)
 456{
 457        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 458        return 1;
 459}
 460
 461#if DBRT_DEBUG
 462static void show_stage_entry(FILE *o,
 463                             const char *label, const struct cache_entry *ce)
 464{
 465        if (!ce)
 466                fprintf(o, "%s (missing)\n", label);
 467        else
 468                fprintf(o, "%s%06o %s %d\t%s\n",
 469                        label,
 470                        ntohl(ce->ce_mode),
 471                        sha1_to_hex(ce->sha1),
 472                        ce_stage(ce),
 473                        ce->name);
 474}
 475#endif
 476
 477static int threeway_merge(struct cache_entry **stages)
 478{
 479        struct cache_entry *index;
 480        struct cache_entry *head; 
 481        struct cache_entry *remote = stages[head_idx + 1];
 482        int count;
 483        int head_match = 0;
 484        int remote_match = 0;
 485
 486        int df_conflict_head = 0;
 487        int df_conflict_remote = 0;
 488
 489        int any_anc_missing = 0;
 490        int no_anc_exists = 1;
 491        int i;
 492
 493        for (i = 1; i < head_idx; i++) {
 494                if (!stages[i])
 495                        any_anc_missing = 1;
 496                else
 497                        no_anc_exists = 0;
 498        }
 499
 500        index = stages[0];
 501        head = stages[head_idx];
 502
 503        if (head == &df_conflict_entry) {
 504                df_conflict_head = 1;
 505                head = NULL;
 506        }
 507
 508        if (remote == &df_conflict_entry) {
 509                df_conflict_remote = 1;
 510                remote = NULL;
 511        }
 512
 513        /* First, if there's a #16 situation, note that to prevent #13
 514         * and #14. 
 515         */
 516        if (!same(remote, head)) {
 517                for (i = 1; i < head_idx; i++) {
 518                        if (same(stages[i], head)) {
 519                                head_match = i;
 520                        }
 521                        if (same(stages[i], remote)) {
 522                                remote_match = i;
 523                        }
 524                }
 525        }
 526
 527        /* We start with cases where the index is allowed to match
 528         * something other than the head: #14(ALT) and #2ALT, where it
 529         * is permitted to match the result instead.
 530         */
 531        /* #14, #14ALT, #2ALT */
 532        if (remote && !df_conflict_head && head_match && !remote_match) {
 533                if (index && !same(index, remote) && !same(index, head))
 534                        reject_merge(index);
 535                return merged_entry(remote, index);
 536        }
 537        /*
 538         * If we have an entry in the index cache, then we want to
 539         * make sure that it matches head.
 540         */
 541        if (index && !same(index, head)) {
 542                reject_merge(index);
 543        }
 544
 545        if (head) {
 546                /* #5ALT, #15 */
 547                if (same(head, remote))
 548                        return merged_entry(head, index);
 549                /* #13, #3ALT */
 550                if (!df_conflict_remote && remote_match && !head_match)
 551                        return merged_entry(head, index);
 552        }
 553
 554        /* #1 */
 555        if (!head && !remote && any_anc_missing)
 556                return 0;
 557
 558        /* Under the new "aggressive" rule, we resolve mostly trivial
 559         * cases that we historically had git-merge-one-file resolve.
 560         */
 561        if (aggressive) {
 562                int head_deleted = !head && !df_conflict_head;
 563                int remote_deleted = !remote && !df_conflict_remote;
 564                /*
 565                 * Deleted in both.
 566                 * Deleted in one and unchanged in the other.
 567                 */
 568                if ((head_deleted && remote_deleted) ||
 569                    (head_deleted && remote && remote_match) ||
 570                    (remote_deleted && head && head_match)) {
 571                        if (index)
 572                                return deleted_entry(index, index);
 573                        return 0;
 574                }
 575                /*
 576                 * Added in both, identically.
 577                 */
 578                if (no_anc_exists && head && remote && same(head, remote))
 579                        return merged_entry(head, index);
 580
 581        }
 582
 583        /* Below are "no merge" cases, which require that the index be
 584         * up-to-date to avoid the files getting overwritten with
 585         * conflict resolution files. 
 586         */
 587        if (index) {
 588                verify_uptodate(index);
 589        }
 590
 591        nontrivial_merge = 1;
 592
 593        /* #2, #3, #4, #6, #7, #9, #11. */
 594        count = 0;
 595        if (!head_match || !remote_match) {
 596                for (i = 1; i < head_idx; i++) {
 597                        if (stages[i]) {
 598                                keep_entry(stages[i]);
 599                                count++;
 600                                break;
 601                        }
 602                }
 603        }
 604#if DBRT_DEBUG
 605        else {
 606                fprintf(stderr, "read-tree: warning #16 detected\n");
 607                show_stage_entry(stderr, "head   ", stages[head_match]);
 608                show_stage_entry(stderr, "remote ", stages[remote_match]);
 609        }
 610#endif
 611        if (head) { count += keep_entry(head); }
 612        if (remote) { count += keep_entry(remote); }
 613        return count;
 614}
 615
 616/*
 617 * Two-way merge.
 618 *
 619 * The rule is to "carry forward" what is in the index without losing
 620 * information across a "fast forward", favoring a successful merge
 621 * over a merge failure when it makes sense.  For details of the
 622 * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 623 *
 624 */
 625static int twoway_merge(struct cache_entry **src)
 626{
 627        struct cache_entry *current = src[0];
 628        struct cache_entry *oldtree = src[1], *newtree = src[2];
 629
 630        if (merge_size != 2)
 631                return error("Cannot do a twoway merge of %d trees",
 632                             merge_size);
 633
 634        if (current) {
 635                if ((!oldtree && !newtree) || /* 4 and 5 */
 636                    (!oldtree && newtree &&
 637                     same(current, newtree)) || /* 6 and 7 */
 638                    (oldtree && newtree &&
 639                     same(oldtree, newtree)) || /* 14 and 15 */
 640                    (oldtree && newtree &&
 641                     !same(oldtree, newtree) && /* 18 and 19*/
 642                     same(current, newtree))) {
 643                        return keep_entry(current);
 644                }
 645                else if (oldtree && !newtree && same(current, oldtree)) {
 646                        /* 10 or 11 */
 647                        return deleted_entry(oldtree, current);
 648                }
 649                else if (oldtree && newtree &&
 650                         same(current, oldtree) && !same(current, newtree)) {
 651                        /* 20 or 21 */
 652                        return merged_entry(newtree, current);
 653                }
 654                else {
 655                        /* all other failures */
 656                        if (oldtree)
 657                                reject_merge(oldtree);
 658                        if (current)
 659                                reject_merge(current);
 660                        if (newtree)
 661                                reject_merge(newtree);
 662                        return -1;
 663                }
 664        }
 665        else if (newtree)
 666                return merged_entry(newtree, current);
 667        else
 668                return deleted_entry(oldtree, current);
 669}
 670
 671/*
 672 * One-way merge.
 673 *
 674 * The rule is:
 675 * - take the stat information from stage0, take the data from stage1
 676 */
 677static int oneway_merge(struct cache_entry **src)
 678{
 679        struct cache_entry *old = src[0];
 680        struct cache_entry *a = src[1];
 681
 682        if (merge_size != 1)
 683                return error("Cannot do a oneway merge of %d trees",
 684                             merge_size);
 685
 686        if (!a)
 687                return 0;
 688        if (old && same(old, a)) {
 689                return keep_entry(old);
 690        }
 691        return merged_entry(a, NULL);
 692}
 693
 694static int read_cache_unmerged(void)
 695{
 696        int i, deleted;
 697        struct cache_entry **dst;
 698
 699        read_cache();
 700        dst = active_cache;
 701        deleted = 0;
 702        for (i = 0; i < active_nr; i++) {
 703                struct cache_entry *ce = active_cache[i];
 704                if (ce_stage(ce)) {
 705                        deleted++;
 706                        continue;
 707                }
 708                if (deleted)
 709                        *dst = ce;
 710                dst++;
 711        }
 712        active_nr -= deleted;
 713        return deleted;
 714}
 715
 716static const char read_tree_usage[] = "git-read-tree (<sha> | -m [--aggressive] [-u | -i] <sha1> [<sha2> [<sha3>]])";
 717
 718static struct cache_file cache_file;
 719
 720int main(int argc, char **argv)
 721{
 722        int i, newfd, reset, stage = 0;
 723        unsigned char sha1[20];
 724        merge_fn_t fn = NULL;
 725
 726        setup_git_directory();
 727        git_config(git_default_config);
 728
 729        newfd = hold_index_file_for_update(&cache_file, get_index_file());
 730        if (newfd < 0)
 731                die("unable to create new cachefile");
 732
 733        git_config(git_default_config);
 734
 735        merge = 0;
 736        reset = 0;
 737        for (i = 1; i < argc; i++) {
 738                const char *arg = argv[i];
 739
 740                /* "-u" means "update", meaning that a merge will update
 741                 * the working tree.
 742                 */
 743                if (!strcmp(arg, "-u")) {
 744                        update = 1;
 745                        continue;
 746                }
 747
 748                if (!strcmp(arg, "-v")) {
 749                        verbose_update = 1;
 750                        continue;
 751                }
 752
 753                /* "-i" means "index only", meaning that a merge will
 754                 * not even look at the working tree.
 755                 */
 756                if (!strcmp(arg, "-i")) {
 757                        index_only = 1;
 758                        continue;
 759                }
 760
 761                /* This differs from "-m" in that we'll silently ignore unmerged entries */
 762                if (!strcmp(arg, "--reset")) {
 763                        if (stage || merge)
 764                                usage(read_tree_usage);
 765                        reset = 1;
 766                        merge = 1;
 767                        stage = 1;
 768                        read_cache_unmerged();
 769                        continue;
 770                }
 771
 772                if (!strcmp(arg, "--trivial")) {
 773                        trivial_merges_only = 1;
 774                        continue;
 775                }
 776
 777                if (!strcmp(arg, "--aggressive")) {
 778                        aggressive = 1;
 779                        continue;
 780                }
 781
 782                /* "-m" stands for "merge", meaning we start in stage 1 */
 783                if (!strcmp(arg, "-m")) {
 784                        if (stage || merge)
 785                                usage(read_tree_usage);
 786                        if (read_cache_unmerged())
 787                                die("you need to resolve your current index first");
 788                        stage = 1;
 789                        merge = 1;
 790                        continue;
 791                }
 792
 793                /* using -u and -i at the same time makes no sense */
 794                if (1 < index_only + update)
 795                        usage(read_tree_usage);
 796
 797                if (get_sha1(arg, sha1) < 0)
 798                        usage(read_tree_usage);
 799                if (list_tree(sha1) < 0)
 800                        die("failed to unpack tree object %s", arg);
 801                stage++;
 802        }
 803        if ((update||index_only) && !merge)
 804                usage(read_tree_usage);
 805
 806        if (merge) {
 807                if (stage < 2)
 808                        die("just how do you expect me to merge %d trees?", stage-1);
 809                switch (stage - 1) {
 810                case 1:
 811                        fn = oneway_merge;
 812                        break;
 813                case 2:
 814                        fn = twoway_merge;
 815                        break;
 816                case 3:
 817                        fn = threeway_merge;
 818                        break;
 819                default:
 820                        fn = threeway_merge;
 821                        break;
 822                }
 823
 824                if (stage - 1 >= 3)
 825                        head_idx = stage - 2;
 826                else
 827                        head_idx = 1;
 828        }
 829
 830        unpack_trees(fn);
 831        if (write_cache(newfd, active_cache, active_nr) ||
 832            commit_index_file(&cache_file))
 833                die("unable to write new index file");
 834        return 0;
 835}