Andrew's git / gitweb.git / read-tree.c
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read-tree.con commit Use Daniel's read-tree in the merge strategy 'resolve'. (2276aa6)
   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;
  15
  16static int head_idx = -1;
  17static int merge_size = 0;
  18
  19static struct object_list *trees = NULL;
  20
  21static struct cache_entry df_conflict_entry = { 
  22};
  23
  24static struct tree_entry_list df_conflict_list = {
  25        .name = NULL,
  26        .next = &df_conflict_list
  27};
  28
  29typedef int (*merge_fn_t)(struct cache_entry **src);
  30
  31static int entcmp(char *name1, int dir1, char *name2, int dir2)
  32{
  33        int len1 = strlen(name1);
  34        int len2 = strlen(name2);
  35        int len = len1 < len2 ? len1 : len2;
  36        int ret = memcmp(name1, name2, len);
  37        unsigned char c1, c2;
  38        if (ret)
  39                return ret;
  40        c1 = name1[len];
  41        c2 = name2[len];
  42        if (!c1 && dir1)
  43                c1 = '/';
  44        if (!c2 && dir2)
  45                c2 = '/';
  46        ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
  47        if (c1 && c2 && !ret)
  48                ret = len1 - len2;
  49        return ret;
  50}
  51
  52static int unpack_trees_rec(struct tree_entry_list **posns, int len,
  53                            const char *base, merge_fn_t fn, int *indpos)
  54{
  55        int baselen = strlen(base);
  56        int src_size = len + 1;
  57        do {
  58                int i;
  59                char *first;
  60                int firstdir = 0;
  61                int pathlen;
  62                unsigned ce_size;
  63                struct tree_entry_list **subposns;
  64                struct cache_entry **src;
  65                int any_files = 0;
  66                int any_dirs = 0;
  67                char *cache_name;
  68                int ce_stage;
  69
  70                /* Find the first name in the input. */
  71
  72                first = NULL;
  73                cache_name = NULL;
  74
  75                /* Check the cache */
  76                if (merge && *indpos < active_nr) {
  77                        /* This is a bit tricky: */
  78                        /* If the index has a subdirectory (with
  79                         * contents) as the first name, it'll get a
  80                         * filename like "foo/bar". But that's after
  81                         * "foo", so the entry in trees will get
  82                         * handled first, at which point we'll go into
  83                         * "foo", and deal with "bar" from the index,
  84                         * because the base will be "foo/". The only
  85                         * way we can actually have "foo/bar" first of
  86                         * all the things is if the trees don't
  87                         * contain "foo" at all, in which case we'll
  88                         * handle "foo/bar" without going into the
  89                         * directory, but that's fine (and will return
  90                         * an error anyway, with the added unknown
  91                         * file case.
  92                         */
  93
  94                        cache_name = active_cache[*indpos]->name;
  95                        if (strlen(cache_name) > baselen &&
  96                            !memcmp(cache_name, base, baselen)) {
  97                                cache_name += baselen;
  98                                first = cache_name;
  99                        } else {
 100                                cache_name = NULL;
 101                        }
 102                }
 103
 104#if DBRT_DEBUG > 1
 105                if (first)
 106                        printf("index %s\n", first);
 107#endif
 108                for (i = 0; i < len; i++) {
 109                        if (!posns[i] || posns[i] == &df_conflict_list)
 110                                continue;
 111#if DBRT_DEBUG > 1
 112                        printf("%d %s\n", i + 1, posns[i]->name);
 113#endif
 114                        if (!first || entcmp(first, firstdir,
 115                                             posns[i]->name, 
 116                                             posns[i]->directory) > 0) {
 117                                first = posns[i]->name;
 118                                firstdir = posns[i]->directory;
 119                        }
 120                }
 121                /* No name means we're done */
 122                if (!first)
 123                        return 0;
 124
 125                pathlen = strlen(first);
 126                ce_size = cache_entry_size(baselen + pathlen);
 127
 128                src = xmalloc(sizeof(struct cache_entry *) * src_size);
 129                memset(src, 0, sizeof(struct cache_entry *) * src_size);
 130
 131                subposns = xmalloc(sizeof(struct tree_list_entry *) * len);
 132                memset(subposns, 0, sizeof(struct tree_list_entry *) * len);
 133
 134                if (cache_name && !strcmp(cache_name, first)) {
 135                        any_files = 1;
 136                        src[0] = active_cache[*indpos];
 137                        remove_cache_entry_at(*indpos);
 138                }
 139
 140                for (i = 0; i < len; i++) {
 141                        struct cache_entry *ce;
 142
 143                        if (!posns[i] ||
 144                            (posns[i] != &df_conflict_list &&
 145                             strcmp(first, posns[i]->name))) {
 146                                continue;
 147                        }
 148
 149                        if (posns[i] == &df_conflict_list) {
 150                                src[i + merge] = &df_conflict_entry;
 151                                continue;
 152                        }
 153
 154                        if (posns[i]->directory) {
 155                                any_dirs = 1;
 156                                parse_tree(posns[i]->item.tree);
 157                                subposns[i] = posns[i]->item.tree->entries;
 158                                posns[i] = posns[i]->next;
 159                                src[i + merge] = &df_conflict_entry;
 160                                continue;
 161                        }
 162
 163                        if (!merge)
 164                                ce_stage = 0;
 165                        else if (i + 1 < head_idx)
 166                                ce_stage = 1;
 167                        else if (i + 1 > head_idx)
 168                                ce_stage = 3;
 169                        else
 170                                ce_stage = 2;
 171
 172                        ce = xmalloc(ce_size);
 173                        memset(ce, 0, ce_size);
 174                        ce->ce_mode = create_ce_mode(posns[i]->mode);
 175                        ce->ce_flags = create_ce_flags(baselen + pathlen,
 176                                                       ce_stage);
 177                        memcpy(ce->name, base, baselen);
 178                        memcpy(ce->name + baselen, first, pathlen + 1);
 179
 180                        any_files = 1;
 181
 182                        memcpy(ce->sha1, posns[i]->item.any->sha1, 20);
 183                        src[i + merge] = ce;
 184                        subposns[i] = &df_conflict_list;
 185                        posns[i] = posns[i]->next;
 186                }
 187                if (any_files) {
 188                        if (merge) {
 189                                int ret;
 190
 191#if DBRT_DEBUG > 1
 192                                printf("%s:\n", first);
 193                                for (i = 0; i < src_size; i++) {
 194                                        printf(" %d ", i);
 195                                        if (src[i])
 196                                                printf("%s\n", sha1_to_hex(src[i]->sha1));
 197                                        else
 198                                                printf("\n");
 199                                }
 200#endif
 201                                ret = fn(src);
 202                                
 203#if DBRT_DEBUG > 1
 204                                printf("Added %d entries\n", ret);
 205#endif
 206                                *indpos += ret;
 207                        } else {
 208                                for (i = 0; i < src_size; i++) {
 209                                        if (src[i]) {
 210                                                add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
 211                                        }
 212                                }
 213                        }
 214                }
 215                if (any_dirs) {
 216                        char *newbase = xmalloc(baselen + 2 + pathlen);
 217                        memcpy(newbase, base, baselen);
 218                        memcpy(newbase + baselen, first, pathlen);
 219                        newbase[baselen + pathlen] = '/';
 220                        newbase[baselen + pathlen + 1] = '\0';
 221                        if (unpack_trees_rec(subposns, len, newbase, fn,
 222                                             indpos))
 223                                return -1;
 224                        free(newbase);
 225                }
 226                free(subposns);
 227                free(src);
 228        } while (1);
 229}
 230
 231static void reject_merge(struct cache_entry *ce)
 232{
 233        die("Entry '%s' would be overwritten by merge. Cannot merge.", 
 234            ce->name);
 235}
 236
 237static void check_updates(struct cache_entry **src, int nr)
 238{
 239        static struct checkout state = {
 240                .base_dir = "",
 241                .force = 1,
 242                .quiet = 1,
 243                .refresh_cache = 1,
 244        };
 245        unsigned short mask = htons(CE_UPDATE);
 246        while (nr--) {
 247                struct cache_entry *ce = *src++;
 248                if (!ce->ce_mode) {
 249                        if (update)
 250                                unlink(ce->name);
 251                        continue;
 252                }
 253                if (ce->ce_flags & mask) {
 254                        ce->ce_flags &= ~mask;
 255                        if (update)
 256                                checkout_entry(ce, &state);
 257                }
 258        }
 259}
 260
 261static int unpack_trees(merge_fn_t fn)
 262{
 263        int indpos = 0;
 264        unsigned len = object_list_length(trees);
 265        struct tree_entry_list **posns = 
 266                xmalloc(len * sizeof(struct tree_entry_list *));
 267        int i;
 268        struct object_list *posn = trees;
 269        merge_size = len;
 270        for (i = 0; i < len; i++) {
 271                posns[i] = ((struct tree *) posn->item)->entries;
 272                posn = posn->next;
 273        }
 274        if (unpack_trees_rec(posns, len, "", fn, &indpos))
 275                return -1;
 276
 277        check_updates(active_cache, active_nr);
 278        return 0;
 279}
 280
 281static int list_tree(unsigned char *sha1)
 282{
 283        struct tree *tree = parse_tree_indirect(sha1);
 284        if (!tree)
 285                return -1;
 286        object_list_append(&tree->object, &trees);
 287        return 0;
 288}
 289
 290static int same(struct cache_entry *a, struct cache_entry *b)
 291{
 292        if (!!a != !!b)
 293                return 0;
 294        if (!a && !b)
 295                return 1;
 296        return a->ce_mode == b->ce_mode && 
 297                !memcmp(a->sha1, b->sha1, 20);
 298}
 299
 300
 301/*
 302 * When a CE gets turned into an unmerged entry, we
 303 * want it to be up-to-date
 304 */
 305static void verify_uptodate(struct cache_entry *ce)
 306{
 307        struct stat st;
 308
 309        if (!lstat(ce->name, &st)) {
 310                unsigned changed = ce_match_stat(ce, &st);
 311                if (!changed)
 312                        return;
 313                errno = 0;
 314        }
 315        if (errno == ENOENT)
 316                return;
 317        die("Entry '%s' not uptodate. Cannot merge.", ce->name);
 318}
 319
 320static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
 321{
 322        merge->ce_flags |= htons(CE_UPDATE);
 323        if (old) {
 324                /*
 325                 * See if we can re-use the old CE directly?
 326                 * That way we get the uptodate stat info.
 327                 *
 328                 * This also removes the UPDATE flag on
 329                 * a match.
 330                 */
 331                if (same(old, merge)) {
 332                        *merge = *old;
 333                } else {
 334                        verify_uptodate(old);
 335                }
 336        }
 337        merge->ce_flags &= ~htons(CE_STAGEMASK);
 338        add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
 339        return 1;
 340}
 341
 342static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
 343{
 344        if (old)
 345                verify_uptodate(old);
 346        ce->ce_mode = 0;
 347        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 348        return 1;
 349}
 350
 351static int keep_entry(struct cache_entry *ce)
 352{
 353        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 354        return 1;
 355}
 356
 357#if DBRT_DEBUG
 358static void show_stage_entry(FILE *o,
 359                             const char *label, const struct cache_entry *ce)
 360{
 361        fprintf(stderr, "%s%06o %s %d\t%s\n",
 362                label,
 363                ntohl(ce->ce_mode),
 364                sha1_to_hex(ce->sha1),
 365                ce_stage(ce),
 366                ce->name);
 367}
 368#endif
 369
 370static int threeway_merge(struct cache_entry **stages)
 371{
 372        struct cache_entry *index;
 373        struct cache_entry *head; 
 374        struct cache_entry *remote = stages[head_idx + 1];
 375        int count;
 376        int head_match = 0;
 377        int remote_match = 0;
 378
 379        int df_conflict_head = 0;
 380        int df_conflict_remote = 0;
 381
 382        int any_anc_missing = 0;
 383        int i;
 384
 385        for (i = 1; i < head_idx; i++) {
 386                if (!stages[i])
 387                        any_anc_missing = 1;
 388        }
 389
 390        index = stages[0];
 391        head = stages[head_idx];
 392
 393        if (head == &df_conflict_entry) {
 394                df_conflict_head = 1;
 395                head = NULL;
 396        }
 397
 398        if (remote == &df_conflict_entry) {
 399                df_conflict_remote = 1;
 400                remote = NULL;
 401        }
 402
 403        /* First, if there's a #16 situation, note that to prevent #13
 404         * and #14. 
 405         */
 406        if (!same(remote, head)) {
 407                for (i = 1; i < head_idx; i++) {
 408                        if (same(stages[i], head)) {
 409                                head_match = i;
 410                        }
 411                        if (same(stages[i], remote)) {
 412                                remote_match = i;
 413                        }
 414                }
 415        }
 416
 417        /* We start with cases where the index is allowed to match
 418         * something other than the head: #14(ALT) and #2ALT, where it
 419         * is permitted to match the result instead.
 420         */
 421        /* #14, #14ALT, #2ALT */
 422        if (remote && !df_conflict_head && head_match && !remote_match) {
 423                if (index && !same(index, remote) && !same(index, head))
 424                        reject_merge(index);
 425                return merged_entry(remote, index);
 426        }
 427        /*
 428         * If we have an entry in the index cache, then we want to
 429         * make sure that it matches head.
 430         */
 431        if (index && !same(index, head)) {
 432                reject_merge(index);
 433        }
 434
 435        if (head) {
 436                /* #5ALT, #15 */
 437                if (same(head, remote))
 438                        return merged_entry(head, index);
 439                /* #13, #3ALT */
 440                if (!df_conflict_remote && remote_match && !head_match)
 441                        return merged_entry(head, index);
 442        }
 443
 444        /* #1 */
 445        if (!head && !remote && any_anc_missing)
 446                return 0;
 447
 448        /* Below are "no merge" cases, which require that the index be
 449         * up-to-date to avoid the files getting overwritten with
 450         * conflict resolution files. 
 451         */
 452        if (index) {
 453                verify_uptodate(index);
 454        }
 455
 456        /* #2, #3, #4, #6, #7, #9, #11. */
 457        count = 0;
 458        if (!head_match || !remote_match) {
 459                for (i = 1; i < head_idx; i++) {
 460                        if (stages[i]) {
 461                                keep_entry(stages[i]);
 462                                count++;
 463                                break;
 464                        }
 465                }
 466        }
 467#if DBRT_DEBUG
 468        else {
 469                fprintf(stderr, "read-tree: warning #16 detected\n");
 470                show_stage_entry(stderr, "head   ", stages[head_match]);
 471                show_stage_entry(stderr, "remote ", stages[remote_match]);
 472        }
 473#endif
 474        if (head) { count += keep_entry(head); }
 475        if (remote) { count += keep_entry(remote); }
 476        return count;
 477}
 478
 479/*
 480 * Two-way merge.
 481 *
 482 * The rule is to "carry forward" what is in the index without losing
 483 * information across a "fast forward", favoring a successful merge
 484 * over a merge failure when it makes sense.  For details of the
 485 * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 486 *
 487 */
 488static int twoway_merge(struct cache_entry **src)
 489{
 490        struct cache_entry *current = src[0];
 491        struct cache_entry *oldtree = src[1], *newtree = src[2];
 492
 493        if (merge_size != 2)
 494                return error("Cannot do a twoway merge of %d trees\n",
 495                             merge_size);
 496
 497        if (current) {
 498                if ((!oldtree && !newtree) || /* 4 and 5 */
 499                    (!oldtree && newtree &&
 500                     same(current, newtree)) || /* 6 and 7 */
 501                    (oldtree && newtree &&
 502                     same(oldtree, newtree)) || /* 14 and 15 */
 503                    (oldtree && newtree &&
 504                     !same(oldtree, newtree) && /* 18 and 19*/
 505                     same(current, newtree))) {
 506                        return keep_entry(current);
 507                }
 508                else if (oldtree && !newtree && same(current, oldtree)) {
 509                        /* 10 or 11 */
 510                        return deleted_entry(oldtree, current);
 511                }
 512                else if (oldtree && newtree &&
 513                         same(current, oldtree) && !same(current, newtree)) {
 514                        /* 20 or 21 */
 515                        return merged_entry(newtree, current);
 516                }
 517                else {
 518                        /* all other failures */
 519                        if (oldtree)
 520                                reject_merge(oldtree);
 521                        if (current)
 522                                reject_merge(current);
 523                        if (newtree)
 524                                reject_merge(newtree);
 525                        return -1;
 526                }
 527        }
 528        else if (newtree)
 529                return merged_entry(newtree, current);
 530        else
 531                return deleted_entry(oldtree, current);
 532}
 533
 534/*
 535 * One-way merge.
 536 *
 537 * The rule is:
 538 * - take the stat information from stage0, take the data from stage1
 539 */
 540static int oneway_merge(struct cache_entry **src)
 541{
 542        struct cache_entry *old = src[0];
 543        struct cache_entry *a = src[1];
 544
 545        if (merge_size != 1)
 546                return error("Cannot do a oneway merge of %d trees\n",
 547                             merge_size);
 548
 549        if (!a)
 550                return 0;
 551        if (old && same(old, a)) {
 552                return keep_entry(old);
 553        }
 554        return merged_entry(a, NULL);
 555}
 556
 557static int read_cache_unmerged(void)
 558{
 559        int i, deleted;
 560        struct cache_entry **dst;
 561
 562        read_cache();
 563        dst = active_cache;
 564        deleted = 0;
 565        for (i = 0; i < active_nr; i++) {
 566                struct cache_entry *ce = active_cache[i];
 567                if (ce_stage(ce)) {
 568                        deleted++;
 569                        continue;
 570                }
 571                if (deleted)
 572                        *dst = ce;
 573                dst++;
 574        }
 575        active_nr -= deleted;
 576        return deleted;
 577}
 578
 579static const char read_tree_usage[] = "git-read-tree (<sha> | -m [-u] <sha1> [<sha2> [<sha3>]])";
 580
 581static struct cache_file cache_file;
 582
 583int main(int argc, char **argv)
 584{
 585        int i, newfd, reset, stage = 0;
 586        unsigned char sha1[20];
 587        merge_fn_t fn = NULL;
 588
 589        newfd = hold_index_file_for_update(&cache_file, get_index_file());
 590        if (newfd < 0)
 591                die("unable to create new cachefile");
 592
 593        merge = 0;
 594        reset = 0;
 595        for (i = 1; i < argc; i++) {
 596                const char *arg = argv[i];
 597
 598                /* "-u" means "update", meaning that a merge will update the working directory */
 599                if (!strcmp(arg, "-u")) {
 600                        update = 1;
 601                        continue;
 602                }
 603
 604                /* This differs from "-m" in that we'll silently ignore unmerged entries */
 605                if (!strcmp(arg, "--reset")) {
 606                        if (stage || merge)
 607                                usage(read_tree_usage);
 608                        reset = 1;
 609                        merge = 1;
 610                        stage = 1;
 611                        read_cache_unmerged();
 612                        continue;
 613                }
 614
 615                if (!strcmp(arg, "--head")) {
 616                        head_idx = stage - 1;
 617                        fn = threeway_merge;
 618                }
 619
 620                /* "-m" stands for "merge", meaning we start in stage 1 */
 621                if (!strcmp(arg, "-m")) {
 622                        if (stage || merge)
 623                                usage(read_tree_usage);
 624                        if (read_cache_unmerged())
 625                                die("you need to resolve your current index first");
 626                        stage = 1;
 627                        merge = 1;
 628                        continue;
 629                }
 630
 631                if (get_sha1(arg, sha1) < 0)
 632                        usage(read_tree_usage);
 633                if (list_tree(sha1) < 0)
 634                        die("failed to unpack tree object %s", arg);
 635                stage++;
 636        }
 637        if (update && !merge)
 638                usage(read_tree_usage);
 639        if (merge && !fn) {
 640                if (stage < 2)
 641                        die("just how do you expect me to merge %d trees?", stage-1);
 642                switch (stage - 1) {
 643                case 1:
 644                        fn = oneway_merge;
 645                        break;
 646                case 2:
 647                        fn = twoway_merge;
 648                        break;
 649                case 3:
 650                        fn = threeway_merge;
 651                        break;
 652                default:
 653                        fn = threeway_merge;
 654                        break;
 655                }
 656        }
 657
 658        if (head_idx < 0) {
 659                if (stage - 1 >= 3)
 660                        head_idx = stage - 2;
 661                else
 662                        head_idx = 1;
 663        }
 664
 665        unpack_trees(fn);
 666        if (write_cache(newfd, active_cache, active_nr) ||
 667            commit_index_file(&cache_file))
 668                die("unable to write new index file");
 669        return 0;
 670}