read-tree.con commit Merge branch 'jc/perl' (6b98579)
   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;
  18static int aggressive = 0;
  19
  20static int head_idx = -1;
  21static int merge_size = 0;
  22
  23static struct object_list *trees = NULL;
  24
  25static struct cache_entry df_conflict_entry = { 
  26};
  27
  28static struct tree_entry_list df_conflict_list = {
  29        .name = NULL,
  30        .next = &df_conflict_list
  31};
  32
  33typedef int (*merge_fn_t)(struct cache_entry **src);
  34
  35static int entcmp(char *name1, int dir1, char *name2, int dir2)
  36{
  37        int len1 = strlen(name1);
  38        int len2 = strlen(name2);
  39        int len = len1 < len2 ? len1 : len2;
  40        int ret = memcmp(name1, name2, len);
  41        unsigned char c1, c2;
  42        if (ret)
  43                return ret;
  44        c1 = name1[len];
  45        c2 = name2[len];
  46        if (!c1 && dir1)
  47                c1 = '/';
  48        if (!c2 && dir2)
  49                c2 = '/';
  50        ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
  51        if (c1 && c2 && !ret)
  52                ret = len1 - len2;
  53        return ret;
  54}
  55
  56static int unpack_trees_rec(struct tree_entry_list **posns, int len,
  57                            const char *base, merge_fn_t fn, int *indpos)
  58{
  59        int baselen = strlen(base);
  60        int src_size = len + 1;
  61        do {
  62                int i;
  63                char *first;
  64                int firstdir = 0;
  65                int pathlen;
  66                unsigned ce_size;
  67                struct tree_entry_list **subposns;
  68                struct cache_entry **src;
  69                int any_files = 0;
  70                int any_dirs = 0;
  71                char *cache_name;
  72                int ce_stage;
  73
  74                /* Find the first name in the input. */
  75
  76                first = NULL;
  77                cache_name = NULL;
  78
  79                /* Check the cache */
  80                if (merge && *indpos < active_nr) {
  81                        /* This is a bit tricky: */
  82                        /* If the index has a subdirectory (with
  83                         * contents) as the first name, it'll get a
  84                         * filename like "foo/bar". But that's after
  85                         * "foo", so the entry in trees will get
  86                         * handled first, at which point we'll go into
  87                         * "foo", and deal with "bar" from the index,
  88                         * because the base will be "foo/". The only
  89                         * way we can actually have "foo/bar" first of
  90                         * all the things is if the trees don't
  91                         * contain "foo" at all, in which case we'll
  92                         * handle "foo/bar" without going into the
  93                         * directory, but that's fine (and will return
  94                         * an error anyway, with the added unknown
  95                         * file case.
  96                         */
  97
  98                        cache_name = active_cache[*indpos]->name;
  99                        if (strlen(cache_name) > baselen &&
 100                            !memcmp(cache_name, base, baselen)) {
 101                                cache_name += baselen;
 102                                first = cache_name;
 103                        } else {
 104                                cache_name = NULL;
 105                        }
 106                }
 107
 108#if DBRT_DEBUG > 1
 109                if (first)
 110                        printf("index %s\n", first);
 111#endif
 112                for (i = 0; i < len; i++) {
 113                        if (!posns[i] || posns[i] == &df_conflict_list)
 114                                continue;
 115#if DBRT_DEBUG > 1
 116                        printf("%d %s\n", i + 1, posns[i]->name);
 117#endif
 118                        if (!first || entcmp(first, firstdir,
 119                                             posns[i]->name, 
 120                                             posns[i]->directory) > 0) {
 121                                first = posns[i]->name;
 122                                firstdir = posns[i]->directory;
 123                        }
 124                }
 125                /* No name means we're done */
 126                if (!first)
 127                        return 0;
 128
 129                pathlen = strlen(first);
 130                ce_size = cache_entry_size(baselen + pathlen);
 131
 132                src = xmalloc(sizeof(struct cache_entry *) * src_size);
 133                memset(src, 0, sizeof(struct cache_entry *) * src_size);
 134
 135                subposns = xmalloc(sizeof(struct tree_list_entry *) * len);
 136                memset(subposns, 0, sizeof(struct tree_list_entry *) * len);
 137
 138                if (cache_name && !strcmp(cache_name, first)) {
 139                        any_files = 1;
 140                        src[0] = active_cache[*indpos];
 141                        remove_cache_entry_at(*indpos);
 142                }
 143
 144                for (i = 0; i < len; i++) {
 145                        struct cache_entry *ce;
 146
 147                        if (!posns[i] ||
 148                            (posns[i] != &df_conflict_list &&
 149                             strcmp(first, posns[i]->name))) {
 150                                continue;
 151                        }
 152
 153                        if (posns[i] == &df_conflict_list) {
 154                                src[i + merge] = &df_conflict_entry;
 155                                continue;
 156                        }
 157
 158                        if (posns[i]->directory) {
 159                                any_dirs = 1;
 160                                parse_tree(posns[i]->item.tree);
 161                                subposns[i] = posns[i]->item.tree->entries;
 162                                posns[i] = posns[i]->next;
 163                                src[i + merge] = &df_conflict_entry;
 164                                continue;
 165                        }
 166
 167                        if (!merge)
 168                                ce_stage = 0;
 169                        else if (i + 1 < head_idx)
 170                                ce_stage = 1;
 171                        else if (i + 1 > head_idx)
 172                                ce_stage = 3;
 173                        else
 174                                ce_stage = 2;
 175
 176                        ce = xmalloc(ce_size);
 177                        memset(ce, 0, ce_size);
 178                        ce->ce_mode = create_ce_mode(posns[i]->mode);
 179                        ce->ce_flags = create_ce_flags(baselen + pathlen,
 180                                                       ce_stage);
 181                        memcpy(ce->name, base, baselen);
 182                        memcpy(ce->name + baselen, first, pathlen + 1);
 183
 184                        any_files = 1;
 185
 186                        memcpy(ce->sha1, posns[i]->item.any->sha1, 20);
 187                        src[i + merge] = ce;
 188                        subposns[i] = &df_conflict_list;
 189                        posns[i] = posns[i]->next;
 190                }
 191                if (any_files) {
 192                        if (merge) {
 193                                int ret;
 194
 195#if DBRT_DEBUG > 1
 196                                printf("%s:\n", first);
 197                                for (i = 0; i < src_size; i++) {
 198                                        printf(" %d ", i);
 199                                        if (src[i])
 200                                                printf("%s\n", sha1_to_hex(src[i]->sha1));
 201                                        else
 202                                                printf("\n");
 203                                }
 204#endif
 205                                ret = fn(src);
 206                                
 207#if DBRT_DEBUG > 1
 208                                printf("Added %d entries\n", ret);
 209#endif
 210                                *indpos += ret;
 211                        } else {
 212                                for (i = 0; i < src_size; i++) {
 213                                        if (src[i]) {
 214                                                add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
 215                                        }
 216                                }
 217                        }
 218                }
 219                if (any_dirs) {
 220                        char *newbase = xmalloc(baselen + 2 + pathlen);
 221                        memcpy(newbase, base, baselen);
 222                        memcpy(newbase + baselen, first, pathlen);
 223                        newbase[baselen + pathlen] = '/';
 224                        newbase[baselen + pathlen + 1] = '\0';
 225                        if (unpack_trees_rec(subposns, len, newbase, fn,
 226                                             indpos))
 227                                return -1;
 228                        free(newbase);
 229                }
 230                free(subposns);
 231                free(src);
 232        } while (1);
 233}
 234
 235static void reject_merge(struct cache_entry *ce)
 236{
 237        die("Entry '%s' would be overwritten by merge. Cannot merge.", 
 238            ce->name);
 239}
 240
 241/* Unlink the last component and attempt to remove leading
 242 * directories, in case this unlink is the removal of the
 243 * last entry in the directory -- empty directories are removed.
 244 */
 245static void unlink_entry(char *name)
 246{
 247        char *cp, *prev;
 248
 249        if (unlink(name))
 250                return;
 251        prev = NULL;
 252        while (1) {
 253                int status;
 254                cp = strrchr(name, '/');
 255                if (prev)
 256                        *prev = '/';
 257                if (!cp)
 258                        break;
 259
 260                *cp = 0;
 261                status = rmdir(name);
 262                if (status) {
 263                        *cp = '/';
 264                        break;
 265                }
 266                prev = cp;
 267        }
 268}
 269
 270static void check_updates(struct cache_entry **src, int nr)
 271{
 272        static struct checkout state = {
 273                .base_dir = "",
 274                .force = 1,
 275                .quiet = 1,
 276                .refresh_cache = 1,
 277        };
 278        unsigned short mask = htons(CE_UPDATE);
 279        while (nr--) {
 280                struct cache_entry *ce = *src++;
 281                if (!ce->ce_mode) {
 282                        if (update)
 283                                unlink_entry(ce->name);
 284                        continue;
 285                }
 286                if (ce->ce_flags & mask) {
 287                        ce->ce_flags &= ~mask;
 288                        if (update)
 289                                checkout_entry(ce, &state);
 290                }
 291        }
 292}
 293
 294static int unpack_trees(merge_fn_t fn)
 295{
 296        int indpos = 0;
 297        unsigned len = object_list_length(trees);
 298        struct tree_entry_list **posns;
 299        int i;
 300        struct object_list *posn = trees;
 301        merge_size = len;
 302
 303        if (len) {
 304                posns = xmalloc(len * sizeof(struct tree_entry_list *));
 305                for (i = 0; i < len; i++) {
 306                        posns[i] = ((struct tree *) posn->item)->entries;
 307                        posn = posn->next;
 308                }
 309                if (unpack_trees_rec(posns, len, "", fn, &indpos))
 310                        return -1;
 311        }
 312
 313        if (trivial_merges_only && nontrivial_merge)
 314                die("Merge requires file-level merging");
 315
 316        check_updates(active_cache, active_nr);
 317        return 0;
 318}
 319
 320static int list_tree(unsigned char *sha1)
 321{
 322        struct tree *tree = parse_tree_indirect(sha1);
 323        if (!tree)
 324                return -1;
 325        object_list_append(&tree->object, &trees);
 326        return 0;
 327}
 328
 329static int same(struct cache_entry *a, struct cache_entry *b)
 330{
 331        if (!!a != !!b)
 332                return 0;
 333        if (!a && !b)
 334                return 1;
 335        return a->ce_mode == b->ce_mode && 
 336                !memcmp(a->sha1, b->sha1, 20);
 337}
 338
 339
 340/*
 341 * When a CE gets turned into an unmerged entry, we
 342 * want it to be up-to-date
 343 */
 344static void verify_uptodate(struct cache_entry *ce)
 345{
 346        struct stat st;
 347
 348        if (index_only)
 349                return;
 350
 351        if (!lstat(ce->name, &st)) {
 352                unsigned changed = ce_match_stat(ce, &st, 1);
 353                if (!changed)
 354                        return;
 355                errno = 0;
 356        }
 357        if (errno == ENOENT)
 358                return;
 359        die("Entry '%s' not uptodate. Cannot merge.", ce->name);
 360}
 361
 362static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
 363{
 364        merge->ce_flags |= htons(CE_UPDATE);
 365        if (old) {
 366                /*
 367                 * See if we can re-use the old CE directly?
 368                 * That way we get the uptodate stat info.
 369                 *
 370                 * This also removes the UPDATE flag on
 371                 * a match.
 372                 */
 373                if (same(old, merge)) {
 374                        *merge = *old;
 375                } else {
 376                        verify_uptodate(old);
 377                }
 378        }
 379        merge->ce_flags &= ~htons(CE_STAGEMASK);
 380        add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
 381        return 1;
 382}
 383
 384static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
 385{
 386        if (old)
 387                verify_uptodate(old);
 388        ce->ce_mode = 0;
 389        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 390        return 1;
 391}
 392
 393static int keep_entry(struct cache_entry *ce)
 394{
 395        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 396        return 1;
 397}
 398
 399#if DBRT_DEBUG
 400static void show_stage_entry(FILE *o,
 401                             const char *label, const struct cache_entry *ce)
 402{
 403        if (!ce)
 404                fprintf(o, "%s (missing)\n", label);
 405        else
 406                fprintf(o, "%s%06o %s %d\t%s\n",
 407                        label,
 408                        ntohl(ce->ce_mode),
 409                        sha1_to_hex(ce->sha1),
 410                        ce_stage(ce),
 411                        ce->name);
 412}
 413#endif
 414
 415static int threeway_merge(struct cache_entry **stages)
 416{
 417        struct cache_entry *index;
 418        struct cache_entry *head; 
 419        struct cache_entry *remote = stages[head_idx + 1];
 420        int count;
 421        int head_match = 0;
 422        int remote_match = 0;
 423
 424        int df_conflict_head = 0;
 425        int df_conflict_remote = 0;
 426
 427        int any_anc_missing = 0;
 428        int no_anc_exists = 1;
 429        int i;
 430
 431        for (i = 1; i < head_idx; i++) {
 432                if (!stages[i])
 433                        any_anc_missing = 1;
 434                else
 435                        no_anc_exists = 0;
 436        }
 437
 438        index = stages[0];
 439        head = stages[head_idx];
 440
 441        if (head == &df_conflict_entry) {
 442                df_conflict_head = 1;
 443                head = NULL;
 444        }
 445
 446        if (remote == &df_conflict_entry) {
 447                df_conflict_remote = 1;
 448                remote = NULL;
 449        }
 450
 451        /* First, if there's a #16 situation, note that to prevent #13
 452         * and #14. 
 453         */
 454        if (!same(remote, head)) {
 455                for (i = 1; i < head_idx; i++) {
 456                        if (same(stages[i], head)) {
 457                                head_match = i;
 458                        }
 459                        if (same(stages[i], remote)) {
 460                                remote_match = i;
 461                        }
 462                }
 463        }
 464
 465        /* We start with cases where the index is allowed to match
 466         * something other than the head: #14(ALT) and #2ALT, where it
 467         * is permitted to match the result instead.
 468         */
 469        /* #14, #14ALT, #2ALT */
 470        if (remote && !df_conflict_head && head_match && !remote_match) {
 471                if (index && !same(index, remote) && !same(index, head))
 472                        reject_merge(index);
 473                return merged_entry(remote, index);
 474        }
 475        /*
 476         * If we have an entry in the index cache, then we want to
 477         * make sure that it matches head.
 478         */
 479        if (index && !same(index, head)) {
 480                reject_merge(index);
 481        }
 482
 483        if (head) {
 484                /* #5ALT, #15 */
 485                if (same(head, remote))
 486                        return merged_entry(head, index);
 487                /* #13, #3ALT */
 488                if (!df_conflict_remote && remote_match && !head_match)
 489                        return merged_entry(head, index);
 490        }
 491
 492        /* #1 */
 493        if (!head && !remote && any_anc_missing)
 494                return 0;
 495
 496        /* Under the new "aggressive" rule, we resolve mostly trivial
 497         * cases that we historically had git-merge-one-file resolve.
 498         */
 499        if (aggressive) {
 500                int head_deleted = !head && !df_conflict_head;
 501                int remote_deleted = !remote && !df_conflict_remote;
 502                /*
 503                 * Deleted in both.
 504                 * Deleted in one and unchanged in the other.
 505                 */
 506                if ((head_deleted && remote_deleted) ||
 507                    (head_deleted && remote && remote_match) ||
 508                    (remote_deleted && head && head_match))
 509                        return 0;
 510
 511                /*
 512                 * Added in both, identically.
 513                 */
 514                if (no_anc_exists && head && remote && same(head, remote))
 515                        return merged_entry(head, index);
 516
 517        }
 518
 519        /* Below are "no merge" cases, which require that the index be
 520         * up-to-date to avoid the files getting overwritten with
 521         * conflict resolution files. 
 522         */
 523        if (index) {
 524                verify_uptodate(index);
 525        }
 526
 527        nontrivial_merge = 1;
 528
 529        /* #2, #3, #4, #6, #7, #9, #11. */
 530        count = 0;
 531        if (!head_match || !remote_match) {
 532                for (i = 1; i < head_idx; i++) {
 533                        if (stages[i]) {
 534                                keep_entry(stages[i]);
 535                                count++;
 536                                break;
 537                        }
 538                }
 539        }
 540#if DBRT_DEBUG
 541        else {
 542                fprintf(stderr, "read-tree: warning #16 detected\n");
 543                show_stage_entry(stderr, "head   ", stages[head_match]);
 544                show_stage_entry(stderr, "remote ", stages[remote_match]);
 545        }
 546#endif
 547        if (head) { count += keep_entry(head); }
 548        if (remote) { count += keep_entry(remote); }
 549        return count;
 550}
 551
 552/*
 553 * Two-way merge.
 554 *
 555 * The rule is to "carry forward" what is in the index without losing
 556 * information across a "fast forward", favoring a successful merge
 557 * over a merge failure when it makes sense.  For details of the
 558 * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 559 *
 560 */
 561static int twoway_merge(struct cache_entry **src)
 562{
 563        struct cache_entry *current = src[0];
 564        struct cache_entry *oldtree = src[1], *newtree = src[2];
 565
 566        if (merge_size != 2)
 567                return error("Cannot do a twoway merge of %d trees\n",
 568                             merge_size);
 569
 570        if (current) {
 571                if ((!oldtree && !newtree) || /* 4 and 5 */
 572                    (!oldtree && newtree &&
 573                     same(current, newtree)) || /* 6 and 7 */
 574                    (oldtree && newtree &&
 575                     same(oldtree, newtree)) || /* 14 and 15 */
 576                    (oldtree && newtree &&
 577                     !same(oldtree, newtree) && /* 18 and 19*/
 578                     same(current, newtree))) {
 579                        return keep_entry(current);
 580                }
 581                else if (oldtree && !newtree && same(current, oldtree)) {
 582                        /* 10 or 11 */
 583                        return deleted_entry(oldtree, current);
 584                }
 585                else if (oldtree && newtree &&
 586                         same(current, oldtree) && !same(current, newtree)) {
 587                        /* 20 or 21 */
 588                        return merged_entry(newtree, current);
 589                }
 590                else {
 591                        /* all other failures */
 592                        if (oldtree)
 593                                reject_merge(oldtree);
 594                        if (current)
 595                                reject_merge(current);
 596                        if (newtree)
 597                                reject_merge(newtree);
 598                        return -1;
 599                }
 600        }
 601        else if (newtree)
 602                return merged_entry(newtree, current);
 603        else
 604                return deleted_entry(oldtree, current);
 605}
 606
 607/*
 608 * One-way merge.
 609 *
 610 * The rule is:
 611 * - take the stat information from stage0, take the data from stage1
 612 */
 613static int oneway_merge(struct cache_entry **src)
 614{
 615        struct cache_entry *old = src[0];
 616        struct cache_entry *a = src[1];
 617
 618        if (merge_size != 1)
 619                return error("Cannot do a oneway merge of %d trees\n",
 620                             merge_size);
 621
 622        if (!a)
 623                return 0;
 624        if (old && same(old, a)) {
 625                return keep_entry(old);
 626        }
 627        return merged_entry(a, NULL);
 628}
 629
 630static int read_cache_unmerged(void)
 631{
 632        int i, deleted;
 633        struct cache_entry **dst;
 634
 635        read_cache();
 636        dst = active_cache;
 637        deleted = 0;
 638        for (i = 0; i < active_nr; i++) {
 639                struct cache_entry *ce = active_cache[i];
 640                if (ce_stage(ce)) {
 641                        deleted++;
 642                        continue;
 643                }
 644                if (deleted)
 645                        *dst = ce;
 646                dst++;
 647        }
 648        active_nr -= deleted;
 649        return deleted;
 650}
 651
 652static const char read_tree_usage[] = "git-read-tree (<sha> | -m [-u | -i] <sha1> [<sha2> [<sha3>]])";
 653
 654static struct cache_file cache_file;
 655
 656int main(int argc, char **argv)
 657{
 658        int i, newfd, reset, stage = 0;
 659        unsigned char sha1[20];
 660        merge_fn_t fn = NULL;
 661
 662        setup_git_directory();
 663
 664        newfd = hold_index_file_for_update(&cache_file, get_index_file());
 665        if (newfd < 0)
 666                die("unable to create new cachefile");
 667
 668        git_config(git_default_config);
 669
 670        merge = 0;
 671        reset = 0;
 672        for (i = 1; i < argc; i++) {
 673                const char *arg = argv[i];
 674
 675                /* "-u" means "update", meaning that a merge will update
 676                 * the working tree.
 677                 */
 678                if (!strcmp(arg, "-u")) {
 679                        update = 1;
 680                        continue;
 681                }
 682
 683                /* "-i" means "index only", meaning that a merge will
 684                 * not even look at the working tree.
 685                 */
 686                if (!strcmp(arg, "-i")) {
 687                        index_only = 1;
 688                        continue;
 689                }
 690
 691                /* This differs from "-m" in that we'll silently ignore unmerged entries */
 692                if (!strcmp(arg, "--reset")) {
 693                        if (stage || merge)
 694                                usage(read_tree_usage);
 695                        reset = 1;
 696                        merge = 1;
 697                        stage = 1;
 698                        read_cache_unmerged();
 699                        continue;
 700                }
 701
 702                if (!strcmp(arg, "--trivial")) {
 703                        trivial_merges_only = 1;
 704                        continue;
 705                }
 706
 707                if (!strcmp(arg, "--aggressive")) {
 708                        aggressive = 1;
 709                        continue;
 710                }
 711
 712                /* "-m" stands for "merge", meaning we start in stage 1 */
 713                if (!strcmp(arg, "-m")) {
 714                        if (stage || merge)
 715                                usage(read_tree_usage);
 716                        if (read_cache_unmerged())
 717                                die("you need to resolve your current index first");
 718                        stage = 1;
 719                        merge = 1;
 720                        continue;
 721                }
 722
 723                /* using -u and -i at the same time makes no sense */
 724                if (1 < index_only + update)
 725                        usage(read_tree_usage);
 726
 727                if (get_sha1(arg, sha1) < 0)
 728                        usage(read_tree_usage);
 729                if (list_tree(sha1) < 0)
 730                        die("failed to unpack tree object %s", arg);
 731                stage++;
 732        }
 733        if ((update||index_only) && !merge)
 734                usage(read_tree_usage);
 735
 736        if (merge) {
 737                if (stage < 2)
 738                        die("just how do you expect me to merge %d trees?", stage-1);
 739                switch (stage - 1) {
 740                case 1:
 741                        fn = oneway_merge;
 742                        break;
 743                case 2:
 744                        fn = twoway_merge;
 745                        break;
 746                case 3:
 747                        fn = threeway_merge;
 748                        break;
 749                default:
 750                        fn = threeway_merge;
 751                        break;
 752                }
 753
 754                if (stage - 1 >= 3)
 755                        head_idx = stage - 2;
 756                else
 757                        head_idx = 1;
 758        }
 759
 760        unpack_trees(fn);
 761        if (write_cache(newfd, active_cache, active_nr) ||
 762            commit_index_file(&cache_file))
 763                die("unable to write new index file");
 764        return 0;
 765}