Andrew's git / gitweb.git / read-tree.c
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read-tree.con commit git push -f documentation (f0fff36)
   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
  13static int merge = 0;
  14static int update = 0;
  15static int index_only = 0;
  16static int nontrivial_merge = 0;
  17static int trivial_merges_only = 0;
  18
  19static int head_idx = -1;
  20static int merge_size = 0;
  21
  22static struct object_list *trees = NULL;
  23
  24static struct cache_entry df_conflict_entry = { 
  25};
  26
  27static struct tree_entry_list df_conflict_list = {
  28        .name = NULL,
  29        .next = &df_conflict_list
  30};
  31
  32typedef int (*merge_fn_t)(struct cache_entry **src);
  33
  34static int entcmp(char *name1, int dir1, char *name2, int dir2)
  35{
  36        int len1 = strlen(name1);
  37        int len2 = strlen(name2);
  38        int len = len1 < len2 ? len1 : len2;
  39        int ret = memcmp(name1, name2, len);
  40        unsigned char c1, c2;
  41        if (ret)
  42                return ret;
  43        c1 = name1[len];
  44        c2 = name2[len];
  45        if (!c1 && dir1)
  46                c1 = '/';
  47        if (!c2 && dir2)
  48                c2 = '/';
  49        ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
  50        if (c1 && c2 && !ret)
  51                ret = len1 - len2;
  52        return ret;
  53}
  54
  55static int unpack_trees_rec(struct tree_entry_list **posns, int len,
  56                            const char *base, merge_fn_t fn, int *indpos)
  57{
  58        int baselen = strlen(base);
  59        int src_size = len + 1;
  60        do {
  61                int i;
  62                char *first;
  63                int firstdir = 0;
  64                int pathlen;
  65                unsigned ce_size;
  66                struct tree_entry_list **subposns;
  67                struct cache_entry **src;
  68                int any_files = 0;
  69                int any_dirs = 0;
  70                char *cache_name;
  71                int ce_stage;
  72
  73                /* Find the first name in the input. */
  74
  75                first = NULL;
  76                cache_name = NULL;
  77
  78                /* Check the cache */
  79                if (merge && *indpos < active_nr) {
  80                        /* This is a bit tricky: */
  81                        /* If the index has a subdirectory (with
  82                         * contents) as the first name, it'll get a
  83                         * filename like "foo/bar". But that's after
  84                         * "foo", so the entry in trees will get
  85                         * handled first, at which point we'll go into
  86                         * "foo", and deal with "bar" from the index,
  87                         * because the base will be "foo/". The only
  88                         * way we can actually have "foo/bar" first of
  89                         * all the things is if the trees don't
  90                         * contain "foo" at all, in which case we'll
  91                         * handle "foo/bar" without going into the
  92                         * directory, but that's fine (and will return
  93                         * an error anyway, with the added unknown
  94                         * file case.
  95                         */
  96
  97                        cache_name = active_cache[*indpos]->name;
  98                        if (strlen(cache_name) > baselen &&
  99                            !memcmp(cache_name, base, baselen)) {
 100                                cache_name += baselen;
 101                                first = cache_name;
 102                        } else {
 103                                cache_name = NULL;
 104                        }
 105                }
 106
 107#if DBRT_DEBUG > 1
 108                if (first)
 109                        printf("index %s\n", first);
 110#endif
 111                for (i = 0; i < len; i++) {
 112                        if (!posns[i] || posns[i] == &df_conflict_list)
 113                                continue;
 114#if DBRT_DEBUG > 1
 115                        printf("%d %s\n", i + 1, posns[i]->name);
 116#endif
 117                        if (!first || entcmp(first, firstdir,
 118                                             posns[i]->name, 
 119                                             posns[i]->directory) > 0) {
 120                                first = posns[i]->name;
 121                                firstdir = posns[i]->directory;
 122                        }
 123                }
 124                /* No name means we're done */
 125                if (!first)
 126                        return 0;
 127
 128                pathlen = strlen(first);
 129                ce_size = cache_entry_size(baselen + pathlen);
 130
 131                src = xmalloc(sizeof(struct cache_entry *) * src_size);
 132                memset(src, 0, sizeof(struct cache_entry *) * src_size);
 133
 134                subposns = xmalloc(sizeof(struct tree_list_entry *) * len);
 135                memset(subposns, 0, sizeof(struct tree_list_entry *) * len);
 136
 137                if (cache_name && !strcmp(cache_name, first)) {
 138                        any_files = 1;
 139                        src[0] = active_cache[*indpos];
 140                        remove_cache_entry_at(*indpos);
 141                }
 142
 143                for (i = 0; i < len; i++) {
 144                        struct cache_entry *ce;
 145
 146                        if (!posns[i] ||
 147                            (posns[i] != &df_conflict_list &&
 148                             strcmp(first, posns[i]->name))) {
 149                                continue;
 150                        }
 151
 152                        if (posns[i] == &df_conflict_list) {
 153                                src[i + merge] = &df_conflict_entry;
 154                                continue;
 155                        }
 156
 157                        if (posns[i]->directory) {
 158                                any_dirs = 1;
 159                                parse_tree(posns[i]->item.tree);
 160                                subposns[i] = posns[i]->item.tree->entries;
 161                                posns[i] = posns[i]->next;
 162                                src[i + merge] = &df_conflict_entry;
 163                                continue;
 164                        }
 165
 166                        if (!merge)
 167                                ce_stage = 0;
 168                        else if (i + 1 < head_idx)
 169                                ce_stage = 1;
 170                        else if (i + 1 > head_idx)
 171                                ce_stage = 3;
 172                        else
 173                                ce_stage = 2;
 174
 175                        ce = xmalloc(ce_size);
 176                        memset(ce, 0, ce_size);
 177                        ce->ce_mode = create_ce_mode(posns[i]->mode);
 178                        ce->ce_flags = create_ce_flags(baselen + pathlen,
 179                                                       ce_stage);
 180                        memcpy(ce->name, base, baselen);
 181                        memcpy(ce->name + baselen, first, pathlen + 1);
 182
 183                        any_files = 1;
 184
 185                        memcpy(ce->sha1, posns[i]->item.any->sha1, 20);
 186                        src[i + merge] = ce;
 187                        subposns[i] = &df_conflict_list;
 188                        posns[i] = posns[i]->next;
 189                }
 190                if (any_files) {
 191                        if (merge) {
 192                                int ret;
 193
 194#if DBRT_DEBUG > 1
 195                                printf("%s:\n", first);
 196                                for (i = 0; i < src_size; i++) {
 197                                        printf(" %d ", i);
 198                                        if (src[i])
 199                                                printf("%s\n", sha1_to_hex(src[i]->sha1));
 200                                        else
 201                                                printf("\n");
 202                                }
 203#endif
 204                                ret = fn(src);
 205                                
 206#if DBRT_DEBUG > 1
 207                                printf("Added %d entries\n", ret);
 208#endif
 209                                *indpos += ret;
 210                        } else {
 211                                for (i = 0; i < src_size; i++) {
 212                                        if (src[i]) {
 213                                                add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
 214                                        }
 215                                }
 216                        }
 217                }
 218                if (any_dirs) {
 219                        char *newbase = xmalloc(baselen + 2 + pathlen);
 220                        memcpy(newbase, base, baselen);
 221                        memcpy(newbase + baselen, first, pathlen);
 222                        newbase[baselen + pathlen] = '/';
 223                        newbase[baselen + pathlen + 1] = '\0';
 224                        if (unpack_trees_rec(subposns, len, newbase, fn,
 225                                             indpos))
 226                                return -1;
 227                        free(newbase);
 228                }
 229                free(subposns);
 230                free(src);
 231        } while (1);
 232}
 233
 234static void reject_merge(struct cache_entry *ce)
 235{
 236        die("Entry '%s' would be overwritten by merge. Cannot merge.", 
 237            ce->name);
 238}
 239
 240/* Unlink the last component and attempt to remove leading
 241 * directories, in case this unlink is the removal of the
 242 * last entry in the directory -- empty directories are removed.
 243 */
 244static void unlink_entry(char *name)
 245{
 246        char *cp, *prev;
 247
 248        if (unlink(name))
 249                return;
 250        prev = NULL;
 251        while (1) {
 252                int status;
 253                cp = strrchr(name, '/');
 254                if (prev)
 255                        *prev = '/';
 256                if (!cp)
 257                        break;
 258
 259                *cp = 0;
 260                status = rmdir(name);
 261                if (status) {
 262                        *cp = '/';
 263                        break;
 264                }
 265                prev = cp;
 266        }
 267}
 268
 269static void check_updates(struct cache_entry **src, int nr)
 270{
 271        static struct checkout state = {
 272                .base_dir = "",
 273                .force = 1,
 274                .quiet = 1,
 275                .refresh_cache = 1,
 276        };
 277        unsigned short mask = htons(CE_UPDATE);
 278        while (nr--) {
 279                struct cache_entry *ce = *src++;
 280                if (!ce->ce_mode) {
 281                        if (update)
 282                                unlink_entry(ce->name);
 283                        continue;
 284                }
 285                if (ce->ce_flags & mask) {
 286                        ce->ce_flags &= ~mask;
 287                        if (update)
 288                                checkout_entry(ce, &state);
 289                }
 290        }
 291}
 292
 293static int unpack_trees(merge_fn_t fn)
 294{
 295        int indpos = 0;
 296        unsigned len = object_list_length(trees);
 297        struct tree_entry_list **posns;
 298        int i;
 299        struct object_list *posn = trees;
 300        merge_size = len;
 301
 302        if (len) {
 303                posns = xmalloc(len * sizeof(struct tree_entry_list *));
 304                for (i = 0; i < len; i++) {
 305                        posns[i] = ((struct tree *) posn->item)->entries;
 306                        posn = posn->next;
 307                }
 308                if (unpack_trees_rec(posns, len, "", fn, &indpos))
 309                        return -1;
 310        }
 311
 312        if (trivial_merges_only && nontrivial_merge)
 313                die("Merge requires file-level merging");
 314
 315        check_updates(active_cache, active_nr);
 316        return 0;
 317}
 318
 319static int list_tree(unsigned char *sha1)
 320{
 321        struct tree *tree = parse_tree_indirect(sha1);
 322        if (!tree)
 323                return -1;
 324        object_list_append(&tree->object, &trees);
 325        return 0;
 326}
 327
 328static int same(struct cache_entry *a, struct cache_entry *b)
 329{
 330        if (!!a != !!b)
 331                return 0;
 332        if (!a && !b)
 333                return 1;
 334        return a->ce_mode == b->ce_mode && 
 335                !memcmp(a->sha1, b->sha1, 20);
 336}
 337
 338
 339/*
 340 * When a CE gets turned into an unmerged entry, we
 341 * want it to be up-to-date
 342 */
 343static void verify_uptodate(struct cache_entry *ce)
 344{
 345        struct stat st;
 346
 347        if (index_only)
 348                return;
 349
 350        if (!lstat(ce->name, &st)) {
 351                unsigned changed = ce_match_stat(ce, &st);
 352                if (!changed)
 353                        return;
 354                errno = 0;
 355        }
 356        if (errno == ENOENT)
 357                return;
 358        die("Entry '%s' not uptodate. Cannot merge.", ce->name);
 359}
 360
 361static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
 362{
 363        merge->ce_flags |= htons(CE_UPDATE);
 364        if (old) {
 365                /*
 366                 * See if we can re-use the old CE directly?
 367                 * That way we get the uptodate stat info.
 368                 *
 369                 * This also removes the UPDATE flag on
 370                 * a match.
 371                 */
 372                if (same(old, merge)) {
 373                        *merge = *old;
 374                } else {
 375                        verify_uptodate(old);
 376                }
 377        }
 378        merge->ce_flags &= ~htons(CE_STAGEMASK);
 379        add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
 380        return 1;
 381}
 382
 383static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
 384{
 385        if (old)
 386                verify_uptodate(old);
 387        ce->ce_mode = 0;
 388        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 389        return 1;
 390}
 391
 392static int keep_entry(struct cache_entry *ce)
 393{
 394        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 395        return 1;
 396}
 397
 398#if DBRT_DEBUG
 399static void show_stage_entry(FILE *o,
 400                             const char *label, const struct cache_entry *ce)
 401{
 402        if (!ce)
 403                fprintf(o, "%s (missing)\n", label);
 404        else
 405                fprintf(o, "%s%06o %s %d\t%s\n",
 406                        label,
 407                        ntohl(ce->ce_mode),
 408                        sha1_to_hex(ce->sha1),
 409                        ce_stage(ce),
 410                        ce->name);
 411}
 412#endif
 413
 414static int threeway_merge(struct cache_entry **stages)
 415{
 416        struct cache_entry *index;
 417        struct cache_entry *head; 
 418        struct cache_entry *remote = stages[head_idx + 1];
 419        int count;
 420        int head_match = 0;
 421        int remote_match = 0;
 422
 423        int df_conflict_head = 0;
 424        int df_conflict_remote = 0;
 425
 426        int any_anc_missing = 0;
 427        int i;
 428
 429        for (i = 1; i < head_idx; i++) {
 430                if (!stages[i])
 431                        any_anc_missing = 1;
 432        }
 433
 434        index = stages[0];
 435        head = stages[head_idx];
 436
 437        if (head == &df_conflict_entry) {
 438                df_conflict_head = 1;
 439                head = NULL;
 440        }
 441
 442        if (remote == &df_conflict_entry) {
 443                df_conflict_remote = 1;
 444                remote = NULL;
 445        }
 446
 447        /* First, if there's a #16 situation, note that to prevent #13
 448         * and #14. 
 449         */
 450        if (!same(remote, head)) {
 451                for (i = 1; i < head_idx; i++) {
 452                        if (same(stages[i], head)) {
 453                                head_match = i;
 454                        }
 455                        if (same(stages[i], remote)) {
 456                                remote_match = i;
 457                        }
 458                }
 459        }
 460
 461        /* We start with cases where the index is allowed to match
 462         * something other than the head: #14(ALT) and #2ALT, where it
 463         * is permitted to match the result instead.
 464         */
 465        /* #14, #14ALT, #2ALT */
 466        if (remote && !df_conflict_head && head_match && !remote_match) {
 467                if (index && !same(index, remote) && !same(index, head))
 468                        reject_merge(index);
 469                return merged_entry(remote, index);
 470        }
 471        /*
 472         * If we have an entry in the index cache, then we want to
 473         * make sure that it matches head.
 474         */
 475        if (index && !same(index, head)) {
 476                reject_merge(index);
 477        }
 478
 479        if (head) {
 480                /* #5ALT, #15 */
 481                if (same(head, remote))
 482                        return merged_entry(head, index);
 483                /* #13, #3ALT */
 484                if (!df_conflict_remote && remote_match && !head_match)
 485                        return merged_entry(head, index);
 486        }
 487
 488        /* #1 */
 489        if (!head && !remote && any_anc_missing)
 490                return 0;
 491
 492        /* Below are "no merge" cases, which require that the index be
 493         * up-to-date to avoid the files getting overwritten with
 494         * conflict resolution files. 
 495         */
 496        if (index) {
 497                verify_uptodate(index);
 498        }
 499
 500        nontrivial_merge = 1;
 501
 502        /* #2, #3, #4, #6, #7, #9, #11. */
 503        count = 0;
 504        if (!head_match || !remote_match) {
 505                for (i = 1; i < head_idx; i++) {
 506                        if (stages[i]) {
 507                                keep_entry(stages[i]);
 508                                count++;
 509                                break;
 510                        }
 511                }
 512        }
 513#if DBRT_DEBUG
 514        else {
 515                fprintf(stderr, "read-tree: warning #16 detected\n");
 516                show_stage_entry(stderr, "head   ", stages[head_match]);
 517                show_stage_entry(stderr, "remote ", stages[remote_match]);
 518        }
 519#endif
 520        if (head) { count += keep_entry(head); }
 521        if (remote) { count += keep_entry(remote); }
 522        return count;
 523}
 524
 525/*
 526 * Two-way merge.
 527 *
 528 * The rule is to "carry forward" what is in the index without losing
 529 * information across a "fast forward", favoring a successful merge
 530 * over a merge failure when it makes sense.  For details of the
 531 * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 532 *
 533 */
 534static int twoway_merge(struct cache_entry **src)
 535{
 536        struct cache_entry *current = src[0];
 537        struct cache_entry *oldtree = src[1], *newtree = src[2];
 538
 539        if (merge_size != 2)
 540                return error("Cannot do a twoway merge of %d trees\n",
 541                             merge_size);
 542
 543        if (current) {
 544                if ((!oldtree && !newtree) || /* 4 and 5 */
 545                    (!oldtree && newtree &&
 546                     same(current, newtree)) || /* 6 and 7 */
 547                    (oldtree && newtree &&
 548                     same(oldtree, newtree)) || /* 14 and 15 */
 549                    (oldtree && newtree &&
 550                     !same(oldtree, newtree) && /* 18 and 19*/
 551                     same(current, newtree))) {
 552                        return keep_entry(current);
 553                }
 554                else if (oldtree && !newtree && same(current, oldtree)) {
 555                        /* 10 or 11 */
 556                        return deleted_entry(oldtree, current);
 557                }
 558                else if (oldtree && newtree &&
 559                         same(current, oldtree) && !same(current, newtree)) {
 560                        /* 20 or 21 */
 561                        return merged_entry(newtree, current);
 562                }
 563                else {
 564                        /* all other failures */
 565                        if (oldtree)
 566                                reject_merge(oldtree);
 567                        if (current)
 568                                reject_merge(current);
 569                        if (newtree)
 570                                reject_merge(newtree);
 571                        return -1;
 572                }
 573        }
 574        else if (newtree)
 575                return merged_entry(newtree, current);
 576        else
 577                return deleted_entry(oldtree, current);
 578}
 579
 580/*
 581 * One-way merge.
 582 *
 583 * The rule is:
 584 * - take the stat information from stage0, take the data from stage1
 585 */
 586static int oneway_merge(struct cache_entry **src)
 587{
 588        struct cache_entry *old = src[0];
 589        struct cache_entry *a = src[1];
 590
 591        if (merge_size != 1)
 592                return error("Cannot do a oneway merge of %d trees\n",
 593                             merge_size);
 594
 595        if (!a)
 596                return 0;
 597        if (old && same(old, a)) {
 598                return keep_entry(old);
 599        }
 600        return merged_entry(a, NULL);
 601}
 602
 603static int read_cache_unmerged(void)
 604{
 605        int i, deleted;
 606        struct cache_entry **dst;
 607
 608        read_cache();
 609        dst = active_cache;
 610        deleted = 0;
 611        for (i = 0; i < active_nr; i++) {
 612                struct cache_entry *ce = active_cache[i];
 613                if (ce_stage(ce)) {
 614                        deleted++;
 615                        continue;
 616                }
 617                if (deleted)
 618                        *dst = ce;
 619                dst++;
 620        }
 621        active_nr -= deleted;
 622        return deleted;
 623}
 624
 625static const char read_tree_usage[] = "git-read-tree (<sha> | -m [-u | -i] <sha1> [<sha2> [<sha3>]])";
 626
 627static struct cache_file cache_file;
 628
 629int main(int argc, char **argv)
 630{
 631        int i, newfd, reset, stage = 0;
 632        unsigned char sha1[20];
 633        merge_fn_t fn = NULL;
 634
 635        setup_git_directory();
 636
 637        newfd = hold_index_file_for_update(&cache_file, get_index_file());
 638        if (newfd < 0)
 639                die("unable to create new cachefile");
 640
 641        git_config(git_default_config);
 642
 643        merge = 0;
 644        reset = 0;
 645        for (i = 1; i < argc; i++) {
 646                const char *arg = argv[i];
 647
 648                /* "-u" means "update", meaning that a merge will update
 649                 * the working tree.
 650                 */
 651                if (!strcmp(arg, "-u")) {
 652                        update = 1;
 653                        continue;
 654                }
 655
 656                /* "-i" means "index only", meaning that a merge will
 657                 * not even look at the working tree.
 658                 */
 659                if (!strcmp(arg, "-i")) {
 660                        index_only = 1;
 661                        continue;
 662                }
 663
 664                /* This differs from "-m" in that we'll silently ignore unmerged entries */
 665                if (!strcmp(arg, "--reset")) {
 666                        if (stage || merge)
 667                                usage(read_tree_usage);
 668                        reset = 1;
 669                        merge = 1;
 670                        stage = 1;
 671                        read_cache_unmerged();
 672                        continue;
 673                }
 674
 675                if (!strcmp(arg, "--trivial")) {
 676                        trivial_merges_only = 1;
 677                        continue;
 678                }
 679
 680                /* "-m" stands for "merge", meaning we start in stage 1 */
 681                if (!strcmp(arg, "-m")) {
 682                        if (stage || merge)
 683                                usage(read_tree_usage);
 684                        if (read_cache_unmerged())
 685                                die("you need to resolve your current index first");
 686                        stage = 1;
 687                        merge = 1;
 688                        continue;
 689                }
 690
 691                /* using -u and -i at the same time makes no sense */
 692                if (1 < index_only + update)
 693                        usage(read_tree_usage);
 694
 695                if (get_sha1(arg, sha1) < 0)
 696                        usage(read_tree_usage);
 697                if (list_tree(sha1) < 0)
 698                        die("failed to unpack tree object %s", arg);
 699                stage++;
 700        }
 701        if ((update||index_only) && !merge)
 702                usage(read_tree_usage);
 703
 704        if (merge) {
 705                if (stage < 2)
 706                        die("just how do you expect me to merge %d trees?", stage-1);
 707                switch (stage - 1) {
 708                case 1:
 709                        fn = oneway_merge;
 710                        break;
 711                case 2:
 712                        fn = twoway_merge;
 713                        break;
 714                case 3:
 715                        fn = threeway_merge;
 716                        break;
 717                default:
 718                        fn = threeway_merge;
 719                        break;
 720                }
 721
 722                if (stage - 1 >= 3)
 723                        head_idx = stage - 2;
 724                else
 725                        head_idx = 1;
 726        }
 727
 728        unpack_trees(fn);
 729        if (write_cache(newfd, active_cache, active_nr) ||
 730            commit_index_file(&cache_file))
 731                die("unable to write new index file");
 732        return 0;
 733}