Andrew's git / gitweb.git / builtin-read-tree.c
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builtin-read-tree.con commit git-svn: migrate out of contrib (60d02cc)
   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
  18static int reset = 0;
  19static int merge = 0;
  20static int update = 0;
  21static int index_only = 0;
  22static int nontrivial_merge = 0;
  23static int trivial_merges_only = 0;
  24static int aggressive = 0;
  25static int verbose_update = 0;
  26static volatile int progress_update = 0;
  27static const char *prefix = NULL;
  28
  29static int head_idx = -1;
  30static int merge_size = 0;
  31
  32static struct object_list *trees = NULL;
  33
  34static struct cache_entry df_conflict_entry;
  35
  36struct tree_entry_list {
  37        struct tree_entry_list *next;
  38        unsigned directory : 1;
  39        unsigned executable : 1;
  40        unsigned symlink : 1;
  41        unsigned int mode;
  42        const char *name;
  43        const unsigned char *sha1;
  44};
  45
  46static struct tree_entry_list df_conflict_list = {
  47        .name = NULL,
  48        .next = &df_conflict_list
  49};
  50
  51typedef int (*merge_fn_t)(struct cache_entry **src);
  52
  53static struct tree_entry_list *create_tree_entry_list(struct tree *tree)
  54{
  55        struct tree_desc desc;
  56        struct name_entry one;
  57        struct tree_entry_list *ret = NULL;
  58        struct tree_entry_list **list_p = &ret;
  59
  60        desc.buf = tree->buffer;
  61        desc.size = tree->size;
  62
  63        while (tree_entry(&desc, &one)) {
  64                struct tree_entry_list *entry;
  65
  66                entry = xmalloc(sizeof(struct tree_entry_list));
  67                entry->name = one.path;
  68                entry->sha1 = one.sha1;
  69                entry->mode = one.mode;
  70                entry->directory = S_ISDIR(one.mode) != 0;
  71                entry->executable = (one.mode & S_IXUSR) != 0;
  72                entry->symlink = S_ISLNK(one.mode) != 0;
  73                entry->next = NULL;
  74
  75                *list_p = entry;
  76                list_p = &entry->next;
  77        }
  78        return ret;
  79}
  80
  81static int entcmp(const char *name1, int dir1, const char *name2, int dir2)
  82{
  83        int len1 = strlen(name1);
  84        int len2 = strlen(name2);
  85        int len = len1 < len2 ? len1 : len2;
  86        int ret = memcmp(name1, name2, len);
  87        unsigned char c1, c2;
  88        if (ret)
  89                return ret;
  90        c1 = name1[len];
  91        c2 = name2[len];
  92        if (!c1 && dir1)
  93                c1 = '/';
  94        if (!c2 && dir2)
  95                c2 = '/';
  96        ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
  97        if (c1 && c2 && !ret)
  98                ret = len1 - len2;
  99        return ret;
 100}
 101
 102static int unpack_trees_rec(struct tree_entry_list **posns, int len,
 103                            const char *base, merge_fn_t fn, int *indpos)
 104{
 105        int baselen = strlen(base);
 106        int src_size = len + 1;
 107        do {
 108                int i;
 109                const char *first;
 110                int firstdir = 0;
 111                int pathlen;
 112                unsigned ce_size;
 113                struct tree_entry_list **subposns;
 114                struct cache_entry **src;
 115                int any_files = 0;
 116                int any_dirs = 0;
 117                char *cache_name;
 118                int ce_stage;
 119
 120                /* Find the first name in the input. */
 121
 122                first = NULL;
 123                cache_name = NULL;
 124
 125                /* Check the cache */
 126                if (merge && *indpos < active_nr) {
 127                        /* This is a bit tricky: */
 128                        /* If the index has a subdirectory (with
 129                         * contents) as the first name, it'll get a
 130                         * filename like "foo/bar". But that's after
 131                         * "foo", so the entry in trees will get
 132                         * handled first, at which point we'll go into
 133                         * "foo", and deal with "bar" from the index,
 134                         * because the base will be "foo/". The only
 135                         * way we can actually have "foo/bar" first of
 136                         * all the things is if the trees don't
 137                         * contain "foo" at all, in which case we'll
 138                         * handle "foo/bar" without going into the
 139                         * directory, but that's fine (and will return
 140                         * an error anyway, with the added unknown
 141                         * file case.
 142                         */
 143
 144                        cache_name = active_cache[*indpos]->name;
 145                        if (strlen(cache_name) > baselen &&
 146                            !memcmp(cache_name, base, baselen)) {
 147                                cache_name += baselen;
 148                                first = cache_name;
 149                        } else {
 150                                cache_name = NULL;
 151                        }
 152                }
 153
 154#if DBRT_DEBUG > 1
 155                if (first)
 156                        printf("index %s\n", first);
 157#endif
 158                for (i = 0; i < len; i++) {
 159                        if (!posns[i] || posns[i] == &df_conflict_list)
 160                                continue;
 161#if DBRT_DEBUG > 1
 162                        printf("%d %s\n", i + 1, posns[i]->name);
 163#endif
 164                        if (!first || entcmp(first, firstdir,
 165                                             posns[i]->name, 
 166                                             posns[i]->directory) > 0) {
 167                                first = posns[i]->name;
 168                                firstdir = posns[i]->directory;
 169                        }
 170                }
 171                /* No name means we're done */
 172                if (!first)
 173                        return 0;
 174
 175                pathlen = strlen(first);
 176                ce_size = cache_entry_size(baselen + pathlen);
 177
 178                src = xcalloc(src_size, sizeof(struct cache_entry *));
 179
 180                subposns = xcalloc(len, sizeof(struct tree_list_entry *));
 181
 182                if (cache_name && !strcmp(cache_name, first)) {
 183                        any_files = 1;
 184                        src[0] = active_cache[*indpos];
 185                        remove_cache_entry_at(*indpos);
 186                }
 187
 188                for (i = 0; i < len; i++) {
 189                        struct cache_entry *ce;
 190
 191                        if (!posns[i] ||
 192                            (posns[i] != &df_conflict_list &&
 193                             strcmp(first, posns[i]->name))) {
 194                                continue;
 195                        }
 196
 197                        if (posns[i] == &df_conflict_list) {
 198                                src[i + merge] = &df_conflict_entry;
 199                                continue;
 200                        }
 201
 202                        if (posns[i]->directory) {
 203                                struct tree *tree = lookup_tree(posns[i]->sha1);
 204                                any_dirs = 1;
 205                                parse_tree(tree);
 206                                subposns[i] = create_tree_entry_list(tree);
 207                                posns[i] = posns[i]->next;
 208                                src[i + merge] = &df_conflict_entry;
 209                                continue;
 210                        }
 211
 212                        if (!merge)
 213                                ce_stage = 0;
 214                        else if (i + 1 < head_idx)
 215                                ce_stage = 1;
 216                        else if (i + 1 > head_idx)
 217                                ce_stage = 3;
 218                        else
 219                                ce_stage = 2;
 220
 221                        ce = xcalloc(1, ce_size);
 222                        ce->ce_mode = create_ce_mode(posns[i]->mode);
 223                        ce->ce_flags = create_ce_flags(baselen + pathlen,
 224                                                       ce_stage);
 225                        memcpy(ce->name, base, baselen);
 226                        memcpy(ce->name + baselen, first, pathlen + 1);
 227
 228                        any_files = 1;
 229
 230                        memcpy(ce->sha1, posns[i]->sha1, 20);
 231                        src[i + merge] = ce;
 232                        subposns[i] = &df_conflict_list;
 233                        posns[i] = posns[i]->next;
 234                }
 235                if (any_files) {
 236                        if (merge) {
 237                                int ret;
 238
 239#if DBRT_DEBUG > 1
 240                                printf("%s:\n", first);
 241                                for (i = 0; i < src_size; i++) {
 242                                        printf(" %d ", i);
 243                                        if (src[i])
 244                                                printf("%s\n", sha1_to_hex(src[i]->sha1));
 245                                        else
 246                                                printf("\n");
 247                                }
 248#endif
 249                                ret = fn(src);
 250                                
 251#if DBRT_DEBUG > 1
 252                                printf("Added %d entries\n", ret);
 253#endif
 254                                *indpos += ret;
 255                        } else {
 256                                for (i = 0; i < src_size; i++) {
 257                                        if (src[i]) {
 258                                                add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
 259                                        }
 260                                }
 261                        }
 262                }
 263                if (any_dirs) {
 264                        char *newbase = xmalloc(baselen + 2 + pathlen);
 265                        memcpy(newbase, base, baselen);
 266                        memcpy(newbase + baselen, first, pathlen);
 267                        newbase[baselen + pathlen] = '/';
 268                        newbase[baselen + pathlen + 1] = '\0';
 269                        if (unpack_trees_rec(subposns, len, newbase, fn,
 270                                             indpos))
 271                                return -1;
 272                        free(newbase);
 273                }
 274                free(subposns);
 275                free(src);
 276        } while (1);
 277}
 278
 279static void reject_merge(struct cache_entry *ce)
 280{
 281        die("Entry '%s' would be overwritten by merge. Cannot merge.", 
 282            ce->name);
 283}
 284
 285/* Unlink the last component and attempt to remove leading
 286 * directories, in case this unlink is the removal of the
 287 * last entry in the directory -- empty directories are removed.
 288 */
 289static void unlink_entry(char *name)
 290{
 291        char *cp, *prev;
 292
 293        if (unlink(name))
 294                return;
 295        prev = NULL;
 296        while (1) {
 297                int status;
 298                cp = strrchr(name, '/');
 299                if (prev)
 300                        *prev = '/';
 301                if (!cp)
 302                        break;
 303
 304                *cp = 0;
 305                status = rmdir(name);
 306                if (status) {
 307                        *cp = '/';
 308                        break;
 309                }
 310                prev = cp;
 311        }
 312}
 313
 314static void progress_interval(int signum)
 315{
 316        progress_update = 1;
 317}
 318
 319static void setup_progress_signal(void)
 320{
 321        struct sigaction sa;
 322        struct itimerval v;
 323
 324        memset(&sa, 0, sizeof(sa));
 325        sa.sa_handler = progress_interval;
 326        sigemptyset(&sa.sa_mask);
 327        sa.sa_flags = SA_RESTART;
 328        sigaction(SIGALRM, &sa, NULL);
 329
 330        v.it_interval.tv_sec = 1;
 331        v.it_interval.tv_usec = 0;
 332        v.it_value = v.it_interval;
 333        setitimer(ITIMER_REAL, &v, NULL);
 334}
 335
 336static void check_updates(struct cache_entry **src, int nr)
 337{
 338        static struct checkout state = {
 339                .base_dir = "",
 340                .force = 1,
 341                .quiet = 1,
 342                .refresh_cache = 1,
 343        };
 344        unsigned short mask = htons(CE_UPDATE);
 345        unsigned last_percent = 200, cnt = 0, total = 0;
 346
 347        if (update && verbose_update) {
 348                for (total = cnt = 0; cnt < nr; cnt++) {
 349                        struct cache_entry *ce = src[cnt];
 350                        if (!ce->ce_mode || ce->ce_flags & mask)
 351                                total++;
 352                }
 353
 354                /* Don't bother doing this for very small updates */
 355                if (total < 250)
 356                        total = 0;
 357
 358                if (total) {
 359                        fprintf(stderr, "Checking files out...\n");
 360                        setup_progress_signal();
 361                        progress_update = 1;
 362                }
 363                cnt = 0;
 364        }
 365
 366        while (nr--) {
 367                struct cache_entry *ce = *src++;
 368
 369                if (total) {
 370                        if (!ce->ce_mode || ce->ce_flags & mask) {
 371                                unsigned percent;
 372                                cnt++;
 373                                percent = (cnt * 100) / total;
 374                                if (percent != last_percent ||
 375                                    progress_update) {
 376                                        fprintf(stderr, "%4u%% (%u/%u) done\r",
 377                                                percent, cnt, total);
 378                                        last_percent = percent;
 379                                        progress_update = 0;
 380                                }
 381                        }
 382                }
 383                if (!ce->ce_mode) {
 384                        if (update)
 385                                unlink_entry(ce->name);
 386                        continue;
 387                }
 388                if (ce->ce_flags & mask) {
 389                        ce->ce_flags &= ~mask;
 390                        if (update)
 391                                checkout_entry(ce, &state, NULL);
 392                }
 393        }
 394        if (total) {
 395                signal(SIGALRM, SIG_IGN);
 396                fputc('\n', stderr);
 397        }
 398}
 399
 400static int unpack_trees(merge_fn_t fn)
 401{
 402        int indpos = 0;
 403        unsigned len = object_list_length(trees);
 404        struct tree_entry_list **posns;
 405        int i;
 406        struct object_list *posn = trees;
 407        merge_size = len;
 408
 409        if (len) {
 410                posns = xmalloc(len * sizeof(struct tree_entry_list *));
 411                for (i = 0; i < len; i++) {
 412                        posns[i] = create_tree_entry_list((struct tree *) posn->item);
 413                        posn = posn->next;
 414                }
 415                if (unpack_trees_rec(posns, len, prefix ? prefix : "",
 416                                     fn, &indpos))
 417                        return -1;
 418        }
 419
 420        if (trivial_merges_only && nontrivial_merge)
 421                die("Merge requires file-level merging");
 422
 423        check_updates(active_cache, active_nr);
 424        return 0;
 425}
 426
 427static int list_tree(unsigned char *sha1)
 428{
 429        struct tree *tree = parse_tree_indirect(sha1);
 430        if (!tree)
 431                return -1;
 432        object_list_append(&tree->object, &trees);
 433        return 0;
 434}
 435
 436static int same(struct cache_entry *a, struct cache_entry *b)
 437{
 438        if (!!a != !!b)
 439                return 0;
 440        if (!a && !b)
 441                return 1;
 442        return a->ce_mode == b->ce_mode && 
 443                !memcmp(a->sha1, b->sha1, 20);
 444}
 445
 446
 447/*
 448 * When a CE gets turned into an unmerged entry, we
 449 * want it to be up-to-date
 450 */
 451static void verify_uptodate(struct cache_entry *ce)
 452{
 453        struct stat st;
 454
 455        if (index_only || reset)
 456                return;
 457
 458        if (!lstat(ce->name, &st)) {
 459                unsigned changed = ce_match_stat(ce, &st, 1);
 460                if (!changed)
 461                        return;
 462                errno = 0;
 463        }
 464        if (reset) {
 465                ce->ce_flags |= htons(CE_UPDATE);
 466                return;
 467        }
 468        if (errno == ENOENT)
 469                return;
 470        die("Entry '%s' not uptodate. Cannot merge.", ce->name);
 471}
 472
 473static void invalidate_ce_path(struct cache_entry *ce)
 474{
 475        if (ce)
 476                cache_tree_invalidate_path(active_cache_tree, ce->name);
 477}
 478
 479/*
 480 * We do not want to remove or overwrite a working tree file that
 481 * is not tracked.
 482 */
 483static void verify_absent(const char *path, const char *action)
 484{
 485        struct stat st;
 486
 487        if (index_only || reset || !update)
 488                return;
 489        if (!lstat(path, &st))
 490                die("Untracked working tree file '%s' "
 491                    "would be %s by merge.", path, action);
 492}
 493
 494static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
 495{
 496        merge->ce_flags |= htons(CE_UPDATE);
 497        if (old) {
 498                /*
 499                 * See if we can re-use the old CE directly?
 500                 * That way we get the uptodate stat info.
 501                 *
 502                 * This also removes the UPDATE flag on
 503                 * a match.
 504                 */
 505                if (same(old, merge)) {
 506                        *merge = *old;
 507                } else {
 508                        verify_uptodate(old);
 509                        invalidate_ce_path(old);
 510                }
 511        }
 512        else {
 513                verify_absent(merge->name, "overwritten");
 514                invalidate_ce_path(merge);
 515        }
 516
 517        merge->ce_flags &= ~htons(CE_STAGEMASK);
 518        add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
 519        return 1;
 520}
 521
 522static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
 523{
 524        if (old)
 525                verify_uptodate(old);
 526        else
 527                verify_absent(ce->name, "removed");
 528        ce->ce_mode = 0;
 529        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 530        invalidate_ce_path(ce);
 531        return 1;
 532}
 533
 534static int keep_entry(struct cache_entry *ce)
 535{
 536        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 537        return 1;
 538}
 539
 540#if DBRT_DEBUG
 541static void show_stage_entry(FILE *o,
 542                             const char *label, const struct cache_entry *ce)
 543{
 544        if (!ce)
 545                fprintf(o, "%s (missing)\n", label);
 546        else
 547                fprintf(o, "%s%06o %s %d\t%s\n",
 548                        label,
 549                        ntohl(ce->ce_mode),
 550                        sha1_to_hex(ce->sha1),
 551                        ce_stage(ce),
 552                        ce->name);
 553}
 554#endif
 555
 556static int threeway_merge(struct cache_entry **stages)
 557{
 558        struct cache_entry *index;
 559        struct cache_entry *head; 
 560        struct cache_entry *remote = stages[head_idx + 1];
 561        int count;
 562        int head_match = 0;
 563        int remote_match = 0;
 564        const char *path = NULL;
 565
 566        int df_conflict_head = 0;
 567        int df_conflict_remote = 0;
 568
 569        int any_anc_missing = 0;
 570        int no_anc_exists = 1;
 571        int i;
 572
 573        for (i = 1; i < head_idx; i++) {
 574                if (!stages[i])
 575                        any_anc_missing = 1;
 576                else {
 577                        if (!path)
 578                                path = stages[i]->name;
 579                        no_anc_exists = 0;
 580                }
 581        }
 582
 583        index = stages[0];
 584        head = stages[head_idx];
 585
 586        if (head == &df_conflict_entry) {
 587                df_conflict_head = 1;
 588                head = NULL;
 589        }
 590
 591        if (remote == &df_conflict_entry) {
 592                df_conflict_remote = 1;
 593                remote = NULL;
 594        }
 595
 596        if (!path && index)
 597                path = index->name;
 598        if (!path && head)
 599                path = head->name;
 600        if (!path && remote)
 601                path = remote->name;
 602
 603        /* First, if there's a #16 situation, note that to prevent #13
 604         * and #14.
 605         */
 606        if (!same(remote, head)) {
 607                for (i = 1; i < head_idx; i++) {
 608                        if (same(stages[i], head)) {
 609                                head_match = i;
 610                        }
 611                        if (same(stages[i], remote)) {
 612                                remote_match = i;
 613                        }
 614                }
 615        }
 616
 617        /* We start with cases where the index is allowed to match
 618         * something other than the head: #14(ALT) and #2ALT, where it
 619         * is permitted to match the result instead.
 620         */
 621        /* #14, #14ALT, #2ALT */
 622        if (remote && !df_conflict_head && head_match && !remote_match) {
 623                if (index && !same(index, remote) && !same(index, head))
 624                        reject_merge(index);
 625                return merged_entry(remote, index);
 626        }
 627        /*
 628         * If we have an entry in the index cache, then we want to
 629         * make sure that it matches head.
 630         */
 631        if (index && !same(index, head)) {
 632                reject_merge(index);
 633        }
 634
 635        if (head) {
 636                /* #5ALT, #15 */
 637                if (same(head, remote))
 638                        return merged_entry(head, index);
 639                /* #13, #3ALT */
 640                if (!df_conflict_remote && remote_match && !head_match)
 641                        return merged_entry(head, index);
 642        }
 643
 644        /* #1 */
 645        if (!head && !remote && any_anc_missing)
 646                return 0;
 647
 648        /* Under the new "aggressive" rule, we resolve mostly trivial
 649         * cases that we historically had git-merge-one-file resolve.
 650         */
 651        if (aggressive) {
 652                int head_deleted = !head && !df_conflict_head;
 653                int remote_deleted = !remote && !df_conflict_remote;
 654                /*
 655                 * Deleted in both.
 656                 * Deleted in one and unchanged in the other.
 657                 */
 658                if ((head_deleted && remote_deleted) ||
 659                    (head_deleted && remote && remote_match) ||
 660                    (remote_deleted && head && head_match)) {
 661                        if (index)
 662                                return deleted_entry(index, index);
 663                        else if (path)
 664                                verify_absent(path, "removed");
 665                        return 0;
 666                }
 667                /*
 668                 * Added in both, identically.
 669                 */
 670                if (no_anc_exists && head && remote && same(head, remote))
 671                        return merged_entry(head, index);
 672
 673        }
 674
 675        /* Below are "no merge" cases, which require that the index be
 676         * up-to-date to avoid the files getting overwritten with
 677         * conflict resolution files. 
 678         */
 679        if (index) {
 680                verify_uptodate(index);
 681        }
 682        else if (path)
 683                verify_absent(path, "overwritten");
 684
 685        nontrivial_merge = 1;
 686
 687        /* #2, #3, #4, #6, #7, #9, #11. */
 688        count = 0;
 689        if (!head_match || !remote_match) {
 690                for (i = 1; i < head_idx; i++) {
 691                        if (stages[i]) {
 692                                keep_entry(stages[i]);
 693                                count++;
 694                                break;
 695                        }
 696                }
 697        }
 698#if DBRT_DEBUG
 699        else {
 700                fprintf(stderr, "read-tree: warning #16 detected\n");
 701                show_stage_entry(stderr, "head   ", stages[head_match]);
 702                show_stage_entry(stderr, "remote ", stages[remote_match]);
 703        }
 704#endif
 705        if (head) { count += keep_entry(head); }
 706        if (remote) { count += keep_entry(remote); }
 707        return count;
 708}
 709
 710/*
 711 * Two-way merge.
 712 *
 713 * The rule is to "carry forward" what is in the index without losing
 714 * information across a "fast forward", favoring a successful merge
 715 * over a merge failure when it makes sense.  For details of the
 716 * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 717 *
 718 */
 719static int twoway_merge(struct cache_entry **src)
 720{
 721        struct cache_entry *current = src[0];
 722        struct cache_entry *oldtree = src[1], *newtree = src[2];
 723
 724        if (merge_size != 2)
 725                return error("Cannot do a twoway merge of %d trees",
 726                             merge_size);
 727
 728        if (current) {
 729                if ((!oldtree && !newtree) || /* 4 and 5 */
 730                    (!oldtree && newtree &&
 731                     same(current, newtree)) || /* 6 and 7 */
 732                    (oldtree && newtree &&
 733                     same(oldtree, newtree)) || /* 14 and 15 */
 734                    (oldtree && newtree &&
 735                     !same(oldtree, newtree) && /* 18 and 19*/
 736                     same(current, newtree))) {
 737                        return keep_entry(current);
 738                }
 739                else if (oldtree && !newtree && same(current, oldtree)) {
 740                        /* 10 or 11 */
 741                        return deleted_entry(oldtree, current);
 742                }
 743                else if (oldtree && newtree &&
 744                         same(current, oldtree) && !same(current, newtree)) {
 745                        /* 20 or 21 */
 746                        return merged_entry(newtree, current);
 747                }
 748                else {
 749                        /* all other failures */
 750                        if (oldtree)
 751                                reject_merge(oldtree);
 752                        if (current)
 753                                reject_merge(current);
 754                        if (newtree)
 755                                reject_merge(newtree);
 756                        return -1;
 757                }
 758        }
 759        else if (newtree)
 760                return merged_entry(newtree, current);
 761        else
 762                return deleted_entry(oldtree, current);
 763}
 764
 765/*
 766 * Bind merge.
 767 *
 768 * Keep the index entries at stage0, collapse stage1 but make sure
 769 * stage0 does not have anything there.
 770 */
 771static int bind_merge(struct cache_entry **src)
 772{
 773        struct cache_entry *old = src[0];
 774        struct cache_entry *a = src[1];
 775
 776        if (merge_size != 1)
 777                return error("Cannot do a bind merge of %d trees\n",
 778                             merge_size);
 779        if (a && old)
 780                die("Entry '%s' overlaps.  Cannot bind.", a->name);
 781        if (!a)
 782                return keep_entry(old);
 783        else
 784                return merged_entry(a, NULL);
 785}
 786
 787/*
 788 * One-way merge.
 789 *
 790 * The rule is:
 791 * - take the stat information from stage0, take the data from stage1
 792 */
 793static int oneway_merge(struct cache_entry **src)
 794{
 795        struct cache_entry *old = src[0];
 796        struct cache_entry *a = src[1];
 797
 798        if (merge_size != 1)
 799                return error("Cannot do a oneway merge of %d trees",
 800                             merge_size);
 801
 802        if (!a)
 803                return deleted_entry(old, old);
 804        if (old && same(old, a)) {
 805                if (reset) {
 806                        struct stat st;
 807                        if (lstat(old->name, &st) ||
 808                            ce_match_stat(old, &st, 1))
 809                                old->ce_flags |= htons(CE_UPDATE);
 810                }
 811                return keep_entry(old);
 812        }
 813        return merged_entry(a, old);
 814}
 815
 816static int read_cache_unmerged(void)
 817{
 818        int i;
 819        struct cache_entry **dst;
 820        struct cache_entry *last = NULL;
 821
 822        read_cache();
 823        dst = active_cache;
 824        for (i = 0; i < active_nr; i++) {
 825                struct cache_entry *ce = active_cache[i];
 826                if (ce_stage(ce)) {
 827                        if (last && !strcmp(ce->name, last->name))
 828                                continue;
 829                        invalidate_ce_path(ce);
 830                        last = ce;
 831                        ce->ce_mode = 0;
 832                        ce->ce_flags &= ~htons(CE_STAGEMASK);
 833                }
 834                *dst++ = ce;
 835        }
 836        active_nr = dst - active_cache;
 837        return !!last;
 838}
 839
 840static void prime_cache_tree_rec(struct cache_tree *it, struct tree *tree)
 841{
 842        struct tree_desc desc;
 843        struct name_entry entry;
 844        int cnt;
 845
 846        memcpy(it->sha1, tree->object.sha1, 20);
 847        desc.buf = tree->buffer;
 848        desc.size = tree->size;
 849        cnt = 0;
 850        while (tree_entry(&desc, &entry)) {
 851                if (!S_ISDIR(entry.mode))
 852                        cnt++;
 853                else {
 854                        struct cache_tree_sub *sub;
 855                        struct tree *subtree = lookup_tree(entry.sha1);
 856                        if (!subtree->object.parsed)
 857                                parse_tree(subtree);
 858                        sub = cache_tree_sub(it, entry.path);
 859                        sub->cache_tree = cache_tree();
 860                        prime_cache_tree_rec(sub->cache_tree, subtree);
 861                        cnt += sub->cache_tree->entry_count;
 862                }
 863        }
 864        it->entry_count = cnt;
 865}
 866
 867static void prime_cache_tree(void)
 868{
 869        struct tree *tree = (struct tree *)trees->item;
 870        if (!tree)
 871                return;
 872        active_cache_tree = cache_tree();
 873        prime_cache_tree_rec(active_cache_tree, tree);
 874
 875}
 876
 877static const char read_tree_usage[] = "git-read-tree (<sha> | [[-m [--aggressive] | --reset | --prefix=<prefix>] [-u | -i]] <sha1> [<sha2> [<sha3>]])";
 878
 879static struct lock_file lock_file;
 880
 881int cmd_read_tree(int argc, const char **argv, char **envp)
 882{
 883        int i, newfd, stage = 0;
 884        unsigned char sha1[20];
 885        merge_fn_t fn = NULL;
 886
 887        setup_git_directory();
 888        git_config(git_default_config);
 889
 890        newfd = hold_lock_file_for_update(&lock_file, get_index_file());
 891        if (newfd < 0)
 892                die("unable to create new index file");
 893
 894        git_config(git_default_config);
 895
 896        merge = 0;
 897        reset = 0;
 898        for (i = 1; i < argc; i++) {
 899                const char *arg = argv[i];
 900
 901                /* "-u" means "update", meaning that a merge will update
 902                 * the working tree.
 903                 */
 904                if (!strcmp(arg, "-u")) {
 905                        update = 1;
 906                        continue;
 907                }
 908
 909                if (!strcmp(arg, "-v")) {
 910                        verbose_update = 1;
 911                        continue;
 912                }
 913
 914                /* "-i" means "index only", meaning that a merge will
 915                 * not even look at the working tree.
 916                 */
 917                if (!strcmp(arg, "-i")) {
 918                        index_only = 1;
 919                        continue;
 920                }
 921
 922                /* "--prefix=<subdirectory>/" means keep the current index
 923                 *  entries and put the entries from the tree under the
 924                 * given subdirectory.
 925                 */
 926                if (!strncmp(arg, "--prefix=", 9)) {
 927                        if (stage || merge || prefix)
 928                                usage(read_tree_usage);
 929                        prefix = arg + 9;
 930                        merge = 1;
 931                        stage = 1;
 932                        if (read_cache_unmerged())
 933                                die("you need to resolve your current index first");
 934                        continue;
 935                }
 936
 937                /* This differs from "-m" in that we'll silently ignore
 938                 * unmerged entries and overwrite working tree files that
 939                 * correspond to them.
 940                 */
 941                if (!strcmp(arg, "--reset")) {
 942                        if (stage || merge || prefix)
 943                                usage(read_tree_usage);
 944                        reset = 1;
 945                        merge = 1;
 946                        stage = 1;
 947                        read_cache_unmerged();
 948                        continue;
 949                }
 950
 951                if (!strcmp(arg, "--trivial")) {
 952                        trivial_merges_only = 1;
 953                        continue;
 954                }
 955
 956                if (!strcmp(arg, "--aggressive")) {
 957                        aggressive = 1;
 958                        continue;
 959                }
 960
 961                /* "-m" stands for "merge", meaning we start in stage 1 */
 962                if (!strcmp(arg, "-m")) {
 963                        if (stage || merge || prefix)
 964                                usage(read_tree_usage);
 965                        if (read_cache_unmerged())
 966                                die("you need to resolve your current index first");
 967                        stage = 1;
 968                        merge = 1;
 969                        continue;
 970                }
 971
 972                /* using -u and -i at the same time makes no sense */
 973                if (1 < index_only + update)
 974                        usage(read_tree_usage);
 975
 976                if (get_sha1(arg, sha1))
 977                        die("Not a valid object name %s", arg);
 978                if (list_tree(sha1) < 0)
 979                        die("failed to unpack tree object %s", arg);
 980                stage++;
 981        }
 982        if ((update||index_only) && !merge)
 983                usage(read_tree_usage);
 984
 985        if (prefix) {
 986                int pfxlen = strlen(prefix);
 987                int pos;
 988                if (prefix[pfxlen-1] != '/')
 989                        die("prefix must end with /");
 990                if (stage != 2)
 991                        die("binding merge takes only one tree");
 992                pos = cache_name_pos(prefix, pfxlen);
 993                if (0 <= pos)
 994                        die("corrupt index file");
 995                pos = -pos-1;
 996                if (pos < active_nr &&
 997                    !strncmp(active_cache[pos]->name, prefix, pfxlen))
 998                        die("subdirectory '%s' already exists.", prefix);
 999                pos = cache_name_pos(prefix, pfxlen-1);
1000                if (0 <= pos)
1001                        die("file '%.*s' already exists.", pfxlen-1, prefix);
1002        }
1003
1004        if (merge) {
1005                if (stage < 2)
1006                        die("just how do you expect me to merge %d trees?", stage-1);
1007                switch (stage - 1) {
1008                case 1:
1009                        fn = prefix ? bind_merge : oneway_merge;
1010                        break;
1011                case 2:
1012                        fn = twoway_merge;
1013                        break;
1014                case 3:
1015                default:
1016                        fn = threeway_merge;
1017                        cache_tree_free(&active_cache_tree);
1018                        break;
1019                }
1020
1021                if (stage - 1 >= 3)
1022                        head_idx = stage - 2;
1023                else
1024                        head_idx = 1;
1025        }
1026
1027        unpack_trees(fn);
1028
1029        /*
1030         * When reading only one tree (either the most basic form,
1031         * "-m ent" or "--reset ent" form), we can obtain a fully
1032         * valid cache-tree because the index must match exactly
1033         * what came from the tree.
1034         */
1035        if (trees && trees->item && !prefix && (!merge || (stage == 2))) {
1036                cache_tree_free(&active_cache_tree);
1037                prime_cache_tree();
1038        }
1039
1040        if (write_cache(newfd, active_cache, active_nr) ||
1041            commit_lock_file(&lock_file))
1042                die("unable to write new index file");
1043        return 0;
1044}