Andrew's git / gitweb.git / read-tree.c
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read-tree.con commit Yank writing-back support from gitfakemmap. (f48000f)
   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
 240static void check_updates(struct cache_entry **src, int nr)
 241{
 242        static struct checkout state = {
 243                .base_dir = "",
 244                .force = 1,
 245                .quiet = 1,
 246                .refresh_cache = 1,
 247        };
 248        unsigned short mask = htons(CE_UPDATE);
 249        while (nr--) {
 250                struct cache_entry *ce = *src++;
 251                if (!ce->ce_mode) {
 252                        if (update)
 253                                unlink(ce->name);
 254                        continue;
 255                }
 256                if (ce->ce_flags & mask) {
 257                        ce->ce_flags &= ~mask;
 258                        if (update)
 259                                checkout_entry(ce, &state);
 260                }
 261        }
 262}
 263
 264static int unpack_trees(merge_fn_t fn)
 265{
 266        int indpos = 0;
 267        unsigned len = object_list_length(trees);
 268        struct tree_entry_list **posns = 
 269                xmalloc(len * sizeof(struct tree_entry_list *));
 270        int i;
 271        struct object_list *posn = trees;
 272        merge_size = len;
 273        for (i = 0; i < len; i++) {
 274                posns[i] = ((struct tree *) posn->item)->entries;
 275                posn = posn->next;
 276        }
 277        if (unpack_trees_rec(posns, len, "", fn, &indpos))
 278                return -1;
 279
 280        if (trivial_merges_only && nontrivial_merge)
 281                die("Merge requires file-level merging");
 282
 283        check_updates(active_cache, active_nr);
 284        return 0;
 285}
 286
 287static int list_tree(unsigned char *sha1)
 288{
 289        struct tree *tree = parse_tree_indirect(sha1);
 290        if (!tree)
 291                return -1;
 292        object_list_append(&tree->object, &trees);
 293        return 0;
 294}
 295
 296static int same(struct cache_entry *a, struct cache_entry *b)
 297{
 298        if (!!a != !!b)
 299                return 0;
 300        if (!a && !b)
 301                return 1;
 302        return a->ce_mode == b->ce_mode && 
 303                !memcmp(a->sha1, b->sha1, 20);
 304}
 305
 306
 307/*
 308 * When a CE gets turned into an unmerged entry, we
 309 * want it to be up-to-date
 310 */
 311static void verify_uptodate(struct cache_entry *ce)
 312{
 313        struct stat st;
 314
 315        if (index_only)
 316                return;
 317
 318        if (!lstat(ce->name, &st)) {
 319                unsigned changed = ce_match_stat(ce, &st);
 320                if (!changed)
 321                        return;
 322                errno = 0;
 323        }
 324        if (errno == ENOENT)
 325                return;
 326        die("Entry '%s' not uptodate. Cannot merge.", ce->name);
 327}
 328
 329static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
 330{
 331        merge->ce_flags |= htons(CE_UPDATE);
 332        if (old) {
 333                /*
 334                 * See if we can re-use the old CE directly?
 335                 * That way we get the uptodate stat info.
 336                 *
 337                 * This also removes the UPDATE flag on
 338                 * a match.
 339                 */
 340                if (same(old, merge)) {
 341                        *merge = *old;
 342                } else {
 343                        verify_uptodate(old);
 344                }
 345        }
 346        merge->ce_flags &= ~htons(CE_STAGEMASK);
 347        add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
 348        return 1;
 349}
 350
 351static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
 352{
 353        if (old)
 354                verify_uptodate(old);
 355        ce->ce_mode = 0;
 356        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 357        return 1;
 358}
 359
 360static int keep_entry(struct cache_entry *ce)
 361{
 362        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
 363        return 1;
 364}
 365
 366#if DBRT_DEBUG
 367static void show_stage_entry(FILE *o,
 368                             const char *label, const struct cache_entry *ce)
 369{
 370        if (!ce)
 371                fprintf(o, "%s (missing)\n", label);
 372        else
 373                fprintf(o, "%s%06o %s %d\t%s\n",
 374                        label,
 375                        ntohl(ce->ce_mode),
 376                        sha1_to_hex(ce->sha1),
 377                        ce_stage(ce),
 378                        ce->name);
 379}
 380#endif
 381
 382static int threeway_merge(struct cache_entry **stages)
 383{
 384        struct cache_entry *index;
 385        struct cache_entry *head; 
 386        struct cache_entry *remote = stages[head_idx + 1];
 387        int count;
 388        int head_match = 0;
 389        int remote_match = 0;
 390
 391        int df_conflict_head = 0;
 392        int df_conflict_remote = 0;
 393
 394        int any_anc_missing = 0;
 395        int i;
 396
 397        for (i = 1; i < head_idx; i++) {
 398                if (!stages[i])
 399                        any_anc_missing = 1;
 400        }
 401
 402        index = stages[0];
 403        head = stages[head_idx];
 404
 405        if (head == &df_conflict_entry) {
 406                df_conflict_head = 1;
 407                head = NULL;
 408        }
 409
 410        if (remote == &df_conflict_entry) {
 411                df_conflict_remote = 1;
 412                remote = NULL;
 413        }
 414
 415        /* First, if there's a #16 situation, note that to prevent #13
 416         * and #14. 
 417         */
 418        if (!same(remote, head)) {
 419                for (i = 1; i < head_idx; i++) {
 420                        if (same(stages[i], head)) {
 421                                head_match = i;
 422                        }
 423                        if (same(stages[i], remote)) {
 424                                remote_match = i;
 425                        }
 426                }
 427        }
 428
 429        /* We start with cases where the index is allowed to match
 430         * something other than the head: #14(ALT) and #2ALT, where it
 431         * is permitted to match the result instead.
 432         */
 433        /* #14, #14ALT, #2ALT */
 434        if (remote && !df_conflict_head && head_match && !remote_match) {
 435                if (index && !same(index, remote) && !same(index, head))
 436                        reject_merge(index);
 437                return merged_entry(remote, index);
 438        }
 439        /*
 440         * If we have an entry in the index cache, then we want to
 441         * make sure that it matches head.
 442         */
 443        if (index && !same(index, head)) {
 444                reject_merge(index);
 445        }
 446
 447        if (head) {
 448                /* #5ALT, #15 */
 449                if (same(head, remote))
 450                        return merged_entry(head, index);
 451                /* #13, #3ALT */
 452                if (!df_conflict_remote && remote_match && !head_match)
 453                        return merged_entry(head, index);
 454        }
 455
 456        /* #1 */
 457        if (!head && !remote && any_anc_missing)
 458                return 0;
 459
 460        /* Below are "no merge" cases, which require that the index be
 461         * up-to-date to avoid the files getting overwritten with
 462         * conflict resolution files. 
 463         */
 464        if (index) {
 465                verify_uptodate(index);
 466        }
 467
 468        nontrivial_merge = 1;
 469
 470        /* #2, #3, #4, #6, #7, #9, #11. */
 471        count = 0;
 472        if (!head_match || !remote_match) {
 473                for (i = 1; i < head_idx; i++) {
 474                        if (stages[i]) {
 475                                keep_entry(stages[i]);
 476                                count++;
 477                                break;
 478                        }
 479                }
 480        }
 481#if DBRT_DEBUG
 482        else {
 483                fprintf(stderr, "read-tree: warning #16 detected\n");
 484                show_stage_entry(stderr, "head   ", stages[head_match]);
 485                show_stage_entry(stderr, "remote ", stages[remote_match]);
 486        }
 487#endif
 488        if (head) { count += keep_entry(head); }
 489        if (remote) { count += keep_entry(remote); }
 490        return count;
 491}
 492
 493/*
 494 * Two-way merge.
 495 *
 496 * The rule is to "carry forward" what is in the index without losing
 497 * information across a "fast forward", favoring a successful merge
 498 * over a merge failure when it makes sense.  For details of the
 499 * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 500 *
 501 */
 502static int twoway_merge(struct cache_entry **src)
 503{
 504        struct cache_entry *current = src[0];
 505        struct cache_entry *oldtree = src[1], *newtree = src[2];
 506
 507        if (merge_size != 2)
 508                return error("Cannot do a twoway merge of %d trees\n",
 509                             merge_size);
 510
 511        if (current) {
 512                if ((!oldtree && !newtree) || /* 4 and 5 */
 513                    (!oldtree && newtree &&
 514                     same(current, newtree)) || /* 6 and 7 */
 515                    (oldtree && newtree &&
 516                     same(oldtree, newtree)) || /* 14 and 15 */
 517                    (oldtree && newtree &&
 518                     !same(oldtree, newtree) && /* 18 and 19*/
 519                     same(current, newtree))) {
 520                        return keep_entry(current);
 521                }
 522                else if (oldtree && !newtree && same(current, oldtree)) {
 523                        /* 10 or 11 */
 524                        return deleted_entry(oldtree, current);
 525                }
 526                else if (oldtree && newtree &&
 527                         same(current, oldtree) && !same(current, newtree)) {
 528                        /* 20 or 21 */
 529                        return merged_entry(newtree, current);
 530                }
 531                else {
 532                        /* all other failures */
 533                        if (oldtree)
 534                                reject_merge(oldtree);
 535                        if (current)
 536                                reject_merge(current);
 537                        if (newtree)
 538                                reject_merge(newtree);
 539                        return -1;
 540                }
 541        }
 542        else if (newtree)
 543                return merged_entry(newtree, current);
 544        else
 545                return deleted_entry(oldtree, current);
 546}
 547
 548/*
 549 * One-way merge.
 550 *
 551 * The rule is:
 552 * - take the stat information from stage0, take the data from stage1
 553 */
 554static int oneway_merge(struct cache_entry **src)
 555{
 556        struct cache_entry *old = src[0];
 557        struct cache_entry *a = src[1];
 558
 559        if (merge_size != 1)
 560                return error("Cannot do a oneway merge of %d trees\n",
 561                             merge_size);
 562
 563        if (!a)
 564                return 0;
 565        if (old && same(old, a)) {
 566                return keep_entry(old);
 567        }
 568        return merged_entry(a, NULL);
 569}
 570
 571static int read_cache_unmerged(void)
 572{
 573        int i, deleted;
 574        struct cache_entry **dst;
 575
 576        read_cache();
 577        dst = active_cache;
 578        deleted = 0;
 579        for (i = 0; i < active_nr; i++) {
 580                struct cache_entry *ce = active_cache[i];
 581                if (ce_stage(ce)) {
 582                        deleted++;
 583                        continue;
 584                }
 585                if (deleted)
 586                        *dst = ce;
 587                dst++;
 588        }
 589        active_nr -= deleted;
 590        return deleted;
 591}
 592
 593static const char read_tree_usage[] = "git-read-tree (<sha> | -m [-u | -i] <sha1> [<sha2> [<sha3>]])";
 594
 595static struct cache_file cache_file;
 596
 597int main(int argc, char **argv)
 598{
 599        int i, newfd, reset, stage = 0;
 600        unsigned char sha1[20];
 601        merge_fn_t fn = NULL;
 602
 603        newfd = hold_index_file_for_update(&cache_file, get_index_file());
 604        if (newfd < 0)
 605                die("unable to create new cachefile");
 606
 607        merge = 0;
 608        reset = 0;
 609        for (i = 1; i < argc; i++) {
 610                const char *arg = argv[i];
 611
 612                /* "-u" means "update", meaning that a merge will update
 613                 * the working tree.
 614                 */
 615                if (!strcmp(arg, "-u")) {
 616                        update = 1;
 617                        continue;
 618                }
 619
 620                /* "-i" means "index only", meaning that a merge will
 621                 * not even look at the working tree.
 622                 */
 623                if (!strcmp(arg, "-i")) {
 624                        index_only = 1;
 625                        continue;
 626                }
 627
 628                /* This differs from "-m" in that we'll silently ignore unmerged entries */
 629                if (!strcmp(arg, "--reset")) {
 630                        if (stage || merge)
 631                                usage(read_tree_usage);
 632                        reset = 1;
 633                        merge = 1;
 634                        stage = 1;
 635                        read_cache_unmerged();
 636                        continue;
 637                }
 638
 639                if (!strcmp(arg, "--trivial")) {
 640                        trivial_merges_only = 1;
 641                        continue;
 642                }
 643
 644                /* "-m" stands for "merge", meaning we start in stage 1 */
 645                if (!strcmp(arg, "-m")) {
 646                        if (stage || merge)
 647                                usage(read_tree_usage);
 648                        if (read_cache_unmerged())
 649                                die("you need to resolve your current index first");
 650                        stage = 1;
 651                        merge = 1;
 652                        continue;
 653                }
 654
 655                /* using -u and -i at the same time makes no sense */
 656                if (1 < index_only + update)
 657                        usage(read_tree_usage);
 658
 659                if (get_sha1(arg, sha1) < 0)
 660                        usage(read_tree_usage);
 661                if (list_tree(sha1) < 0)
 662                        die("failed to unpack tree object %s", arg);
 663                stage++;
 664        }
 665        if ((update||index_only) && !merge)
 666                usage(read_tree_usage);
 667
 668        if (merge) {
 669                if (stage < 2)
 670                        die("just how do you expect me to merge %d trees?", stage-1);
 671                switch (stage - 1) {
 672                case 1:
 673                        fn = oneway_merge;
 674                        break;
 675                case 2:
 676                        fn = twoway_merge;
 677                        break;
 678                case 3:
 679                        fn = threeway_merge;
 680                        break;
 681                default:
 682                        fn = threeway_merge;
 683                        break;
 684                }
 685
 686                if (stage - 1 >= 3)
 687                        head_idx = stage - 2;
 688                else
 689                        head_idx = 1;
 690        }
 691
 692        unpack_trees(fn);
 693        if (write_cache(newfd, active_cache, active_nr) ||
 694            commit_index_file(&cache_file))
 695                die("unable to write new index file");
 696        return 0;
 697}