cb8f84796862ba7f3aee42981585441085e9060a
   1#define NO_THE_INDEX_COMPATIBILITY_MACROS
   2#include "cache.h"
   3#include "dir.h"
   4#include "tree.h"
   5#include "tree-walk.h"
   6#include "cache-tree.h"
   7#include "unpack-trees.h"
   8#include "progress.h"
   9#include "refs.h"
  10
  11static inline void remove_entry(int remove, struct unpack_trees_options *o)
  12{
  13        if (remove >= 0)
  14                remove_index_entry_at(o->index, remove);
  15}
  16
  17/* Unlink the last component and attempt to remove leading
  18 * directories, in case this unlink is the removal of the
  19 * last entry in the directory -- empty directories are removed.
  20 */
  21static void unlink_entry(char *name, char *last_symlink)
  22{
  23        char *cp, *prev;
  24
  25        if (has_symlink_leading_path(name, last_symlink))
  26                return;
  27        if (unlink(name))
  28                return;
  29        prev = NULL;
  30        while (1) {
  31                int status;
  32                cp = strrchr(name, '/');
  33                if (prev)
  34                        *prev = '/';
  35                if (!cp)
  36                        break;
  37
  38                *cp = 0;
  39                status = rmdir(name);
  40                if (status) {
  41                        *cp = '/';
  42                        break;
  43                }
  44                prev = cp;
  45        }
  46}
  47
  48static struct checkout state;
  49static void check_updates(struct unpack_trees_options *o)
  50{
  51        unsigned cnt = 0, total = 0;
  52        struct progress *progress = NULL;
  53        char last_symlink[PATH_MAX];
  54        int i;
  55
  56        if (o->update && o->verbose_update) {
  57                for (total = cnt = 0; cnt < o->index->cache_nr; cnt++) {
  58                        struct cache_entry *ce = o->index->cache[cnt];
  59                        if (ce->ce_flags & (CE_UPDATE | CE_REMOVE))
  60                                total++;
  61                }
  62
  63                progress = start_progress_delay("Checking out files",
  64                                                total, 50, 1);
  65                cnt = 0;
  66        }
  67
  68        *last_symlink = '\0';
  69        for (i = 0; i < o->index->cache_nr; i++) {
  70                struct cache_entry *ce = o->index->cache[i];
  71
  72                if (ce->ce_flags & (CE_UPDATE | CE_REMOVE))
  73                        display_progress(progress, ++cnt);
  74                if (ce->ce_flags & CE_REMOVE) {
  75                        if (o->update)
  76                                unlink_entry(ce->name, last_symlink);
  77                        remove_index_entry_at(o->index, i);
  78                        i--;
  79                        continue;
  80                }
  81                if (ce->ce_flags & CE_UPDATE) {
  82                        ce->ce_flags &= ~CE_UPDATE;
  83                        if (o->update) {
  84                                checkout_entry(ce, &state, NULL);
  85                                *last_symlink = '\0';
  86                        }
  87                }
  88        }
  89        stop_progress(&progress);
  90}
  91
  92static inline int call_unpack_fn(struct cache_entry **src, struct unpack_trees_options *o, int remove)
  93{
  94        int ret = o->fn(src, o, remove);
  95        if (ret > 0) {
  96                o->pos += ret;
  97                ret = 0;
  98        }
  99        return ret;
 100}
 101
 102static int unpack_index_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 103{
 104        struct cache_entry *src[5] = { ce, };
 105        if (ce_stage(ce)) {
 106                if (o->skip_unmerged) {
 107                        o->pos++;
 108                } else {
 109                        remove_entry(o->pos, o);
 110                }
 111                return 0;
 112        }
 113        return call_unpack_fn(src, o, o->pos);
 114}
 115
 116int traverse_trees_recursive(int n, unsigned long dirmask, unsigned long df_conflicts, struct name_entry *names, struct traverse_info *info)
 117{
 118        int i;
 119        struct tree_desc t[3];
 120        struct traverse_info newinfo;
 121        struct name_entry *p;
 122
 123        p = names;
 124        while (!p->mode)
 125                p++;
 126
 127        newinfo = *info;
 128        newinfo.prev = info;
 129        newinfo.name = *p;
 130        newinfo.pathlen += tree_entry_len(p->path, p->sha1) + 1;
 131        newinfo.conflicts |= df_conflicts;
 132
 133        for (i = 0; i < n; i++, dirmask >>= 1) {
 134                const unsigned char *sha1 = NULL;
 135                if (dirmask & 1)
 136                        sha1 = names[i].sha1;
 137                fill_tree_descriptor(t+i, sha1);
 138        }
 139        traverse_trees(n, t, &newinfo);
 140        return 0;
 141}
 142
 143/*
 144 * Compare the traverse-path to the cache entry without actually
 145 * having to generate the textual representation of the traverse
 146 * path.
 147 *
 148 * NOTE! This *only* compares up to the size of the traverse path
 149 * itself - the caller needs to do the final check for the cache
 150 * entry having more data at the end!
 151 */
 152static int do_compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
 153{
 154        int len, pathlen, ce_len;
 155        const char *ce_name;
 156
 157        if (info->prev) {
 158                int cmp = do_compare_entry(ce, info->prev, &info->name);
 159                if (cmp)
 160                        return cmp;
 161        }
 162        pathlen = info->pathlen;
 163        ce_len = ce_namelen(ce);
 164
 165        /* If ce_len < pathlen then we must have previously hit "name == directory" entry */
 166        if (ce_len < pathlen)
 167                return -1;
 168
 169        ce_len -= pathlen;
 170        ce_name = ce->name + pathlen;
 171
 172        len = tree_entry_len(n->path, n->sha1);
 173        return df_name_compare(ce_name, ce_len, S_IFREG, n->path, len, n->mode);
 174}
 175
 176static int compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
 177{
 178        int cmp = do_compare_entry(ce, info, n);
 179        if (cmp)
 180                return cmp;
 181
 182        /*
 183         * Even if the beginning compared identically, the ce should
 184         * compare as bigger than a directory leading up to it!
 185         */
 186        return ce_namelen(ce) > traverse_path_len(info, n);
 187}
 188
 189static struct cache_entry *create_ce_entry(const struct traverse_info *info, const struct name_entry *n, int stage)
 190{
 191        int len = traverse_path_len(info, n);
 192        struct cache_entry *ce = xcalloc(1, cache_entry_size(len));
 193
 194        ce->ce_mode = create_ce_mode(n->mode);
 195        ce->ce_flags = create_ce_flags(len, stage);
 196        hashcpy(ce->sha1, n->sha1);
 197        make_traverse_path(ce->name, info, n);
 198
 199        return ce;
 200}
 201
 202static int unpack_nondirectories(int n, unsigned long mask, unsigned long dirmask, struct cache_entry *src[5],
 203        const struct name_entry *names, const struct traverse_info *info, int remove)
 204{
 205        int i;
 206        struct unpack_trees_options *o = info->data;
 207        unsigned long conflicts;
 208
 209        /* Do we have *only* directories? Nothing to do */
 210        if (mask == dirmask && !src[0])
 211                return 0;
 212
 213        conflicts = info->conflicts;
 214        if (o->merge)
 215                conflicts >>= 1;
 216        conflicts |= dirmask;
 217
 218        /*
 219         * Ok, we've filled in up to any potential index entry in src[0],
 220         * now do the rest.
 221         */
 222        for (i = 0; i < n; i++) {
 223                int stage;
 224                unsigned int bit = 1ul << i;
 225                if (conflicts & bit) {
 226                        src[i + o->merge] = o->df_conflict_entry;
 227                        continue;
 228                }
 229                if (!(mask & bit))
 230                        continue;
 231                if (!o->merge)
 232                        stage = 0;
 233                else if (i + 1 < o->head_idx)
 234                        stage = 1;
 235                else if (i + 1 > o->head_idx)
 236                        stage = 3;
 237                else
 238                        stage = 2;
 239                src[i + o->merge] = create_ce_entry(info, names + i, stage);
 240        }
 241
 242        if (o->merge)
 243                return call_unpack_fn(src, o, remove);
 244
 245        n += o->merge;
 246        remove_entry(remove, o);
 247        for (i = 0; i < n; i++)
 248                add_index_entry(o->index, src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
 249        return 0;
 250}
 251
 252static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *names, struct traverse_info *info)
 253{
 254        struct cache_entry *src[5] = { NULL, };
 255        struct unpack_trees_options *o = info->data;
 256        int remove = -1;
 257        const struct name_entry *p = names;
 258
 259        /* Find first entry with a real name (we could use "mask" too) */
 260        while (!p->mode)
 261                p++;
 262
 263        /* Are we supposed to look at the index too? */
 264        if (o->merge) {
 265                while (o->pos < o->index->cache_nr) {
 266                        struct cache_entry *ce = o->index->cache[o->pos];
 267                        int cmp = compare_entry(ce, info, p);
 268                        if (cmp < 0) {
 269                                if (unpack_index_entry(ce, o) < 0)
 270                                        return -1;
 271                                continue;
 272                        }
 273                        if (!cmp) {
 274                                if (ce_stage(ce)) {
 275                                        /*
 276                                         * If we skip unmerged index entries, we'll skip this
 277                                         * entry *and* the tree entries associated with it!
 278                                         */
 279                                        if (o->skip_unmerged)
 280                                                return mask;
 281                                        remove_entry(o->pos, o);
 282                                        continue;
 283                                }
 284                                src[0] = ce;
 285                                remove = o->pos;
 286                        }
 287                        break;
 288                }
 289        }
 290
 291        if (unpack_nondirectories(n, mask, dirmask, src, names, info, remove) < 0)
 292                return -1;
 293
 294        /* Now handle any directories.. */
 295        if (dirmask) {
 296                unsigned long conflicts = mask & ~dirmask;
 297                if (o->merge) {
 298                        conflicts <<= 1;
 299                        if (src[0])
 300                                conflicts |= 1;
 301                }
 302                traverse_trees_recursive(n, dirmask, conflicts, names, info);
 303                return mask;
 304        }
 305
 306        return mask;
 307}
 308
 309static int unpack_failed(struct unpack_trees_options *o, const char *message)
 310{
 311        if (!o->gently) {
 312                if (message)
 313                        return error(message);
 314                return -1;
 315        }
 316        discard_index(o->index);
 317        read_index(o->index);
 318        return -1;
 319}
 320
 321int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
 322{
 323        static struct cache_entry *dfc;
 324
 325        if (len > 4)
 326                die("unpack_trees takes at most four trees");
 327        memset(&state, 0, sizeof(state));
 328        state.base_dir = "";
 329        state.force = 1;
 330        state.quiet = 1;
 331        state.refresh_cache = 1;
 332
 333        o->merge_size = len;
 334
 335        if (!dfc)
 336                dfc = xcalloc(1, sizeof(struct cache_entry) + 1);
 337        o->df_conflict_entry = dfc;
 338
 339        if (len) {
 340                const char *prefix = o->prefix ? o->prefix : "";
 341                struct traverse_info info;
 342
 343                setup_traverse_info(&info, prefix);
 344                info.fn = unpack_callback;
 345                info.data = o;
 346
 347                if (traverse_trees(len, t, &info) < 0)
 348                        return unpack_failed(o, NULL);
 349        }
 350
 351        /* Any left-over entries in the index? */
 352        if (o->merge) {
 353                while (o->pos < o->index->cache_nr) {
 354                        struct cache_entry *ce = o->index->cache[o->pos];
 355                        if (unpack_index_entry(ce, o) < 0)
 356                                return unpack_failed(o, NULL);
 357                }
 358        }
 359
 360        if (o->trivial_merges_only && o->nontrivial_merge)
 361                return unpack_failed(o, "Merge requires file-level merging");
 362
 363        check_updates(o);
 364        return 0;
 365}
 366
 367/* Here come the merge functions */
 368
 369static int reject_merge(struct cache_entry *ce)
 370{
 371        return error("Entry '%s' would be overwritten by merge. Cannot merge.",
 372                     ce->name);
 373}
 374
 375static int same(struct cache_entry *a, struct cache_entry *b)
 376{
 377        if (!!a != !!b)
 378                return 0;
 379        if (!a && !b)
 380                return 1;
 381        return a->ce_mode == b->ce_mode &&
 382               !hashcmp(a->sha1, b->sha1);
 383}
 384
 385
 386/*
 387 * When a CE gets turned into an unmerged entry, we
 388 * want it to be up-to-date
 389 */
 390static int verify_uptodate(struct cache_entry *ce,
 391                struct unpack_trees_options *o)
 392{
 393        struct stat st;
 394
 395        if (o->index_only || o->reset)
 396                return 0;
 397
 398        if (!lstat(ce->name, &st)) {
 399                unsigned changed = ie_match_stat(o->index, ce, &st, CE_MATCH_IGNORE_VALID);
 400                if (!changed)
 401                        return 0;
 402                /*
 403                 * NEEDSWORK: the current default policy is to allow
 404                 * submodule to be out of sync wrt the supermodule
 405                 * index.  This needs to be tightened later for
 406                 * submodules that are marked to be automatically
 407                 * checked out.
 408                 */
 409                if (S_ISGITLINK(ce->ce_mode))
 410                        return 0;
 411                errno = 0;
 412        }
 413        if (errno == ENOENT)
 414                return 0;
 415        return o->gently ? -1 :
 416                error("Entry '%s' not uptodate. Cannot merge.", ce->name);
 417}
 418
 419static void invalidate_ce_path(struct cache_entry *ce, struct unpack_trees_options *o)
 420{
 421        if (ce)
 422                cache_tree_invalidate_path(o->index->cache_tree, ce->name);
 423}
 424
 425/*
 426 * Check that checking out ce->sha1 in subdir ce->name is not
 427 * going to overwrite any working files.
 428 *
 429 * Currently, git does not checkout subprojects during a superproject
 430 * checkout, so it is not going to overwrite anything.
 431 */
 432static int verify_clean_submodule(struct cache_entry *ce, const char *action,
 433                                      struct unpack_trees_options *o)
 434{
 435        return 0;
 436}
 437
 438static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
 439                                      struct unpack_trees_options *o)
 440{
 441        /*
 442         * we are about to extract "ce->name"; we would not want to lose
 443         * anything in the existing directory there.
 444         */
 445        int namelen;
 446        int pos, i;
 447        struct dir_struct d;
 448        char *pathbuf;
 449        int cnt = 0;
 450        unsigned char sha1[20];
 451
 452        if (S_ISGITLINK(ce->ce_mode) &&
 453            resolve_gitlink_ref(ce->name, "HEAD", sha1) == 0) {
 454                /* If we are not going to update the submodule, then
 455                 * we don't care.
 456                 */
 457                if (!hashcmp(sha1, ce->sha1))
 458                        return 0;
 459                return verify_clean_submodule(ce, action, o);
 460        }
 461
 462        /*
 463         * First let's make sure we do not have a local modification
 464         * in that directory.
 465         */
 466        namelen = strlen(ce->name);
 467        pos = index_name_pos(o->index, ce->name, namelen);
 468        if (0 <= pos)
 469                return cnt; /* we have it as nondirectory */
 470        pos = -pos - 1;
 471        for (i = pos; i < o->index->cache_nr; i++) {
 472                struct cache_entry *ce = o->index->cache[i];
 473                int len = ce_namelen(ce);
 474                if (len < namelen ||
 475                    strncmp(ce->name, ce->name, namelen) ||
 476                    ce->name[namelen] != '/')
 477                        break;
 478                /*
 479                 * ce->name is an entry in the subdirectory.
 480                 */
 481                if (!ce_stage(ce)) {
 482                        if (verify_uptodate(ce, o))
 483                                return -1;
 484                        ce->ce_flags |= CE_REMOVE;
 485                }
 486                cnt++;
 487        }
 488
 489        /*
 490         * Then we need to make sure that we do not lose a locally
 491         * present file that is not ignored.
 492         */
 493        pathbuf = xmalloc(namelen + 2);
 494        memcpy(pathbuf, ce->name, namelen);
 495        strcpy(pathbuf+namelen, "/");
 496
 497        memset(&d, 0, sizeof(d));
 498        if (o->dir)
 499                d.exclude_per_dir = o->dir->exclude_per_dir;
 500        i = read_directory(&d, ce->name, pathbuf, namelen+1, NULL);
 501        if (i)
 502                return o->gently ? -1 :
 503                        error("Updating '%s' would lose untracked files in it",
 504                              ce->name);
 505        free(pathbuf);
 506        return cnt;
 507}
 508
 509/*
 510 * We do not want to remove or overwrite a working tree file that
 511 * is not tracked, unless it is ignored.
 512 */
 513static int verify_absent(struct cache_entry *ce, const char *action,
 514                         struct unpack_trees_options *o)
 515{
 516        struct stat st;
 517
 518        if (o->index_only || o->reset || !o->update)
 519                return 0;
 520
 521        if (has_symlink_leading_path(ce->name, NULL))
 522                return 0;
 523
 524        if (!lstat(ce->name, &st)) {
 525                int cnt;
 526                int dtype = ce_to_dtype(ce);
 527
 528                if (o->dir && excluded(o->dir, ce->name, &dtype))
 529                        /*
 530                         * ce->name is explicitly excluded, so it is Ok to
 531                         * overwrite it.
 532                         */
 533                        return 0;
 534                if (S_ISDIR(st.st_mode)) {
 535                        /*
 536                         * We are checking out path "foo" and
 537                         * found "foo/." in the working tree.
 538                         * This is tricky -- if we have modified
 539                         * files that are in "foo/" we would lose
 540                         * it.
 541                         */
 542                        cnt = verify_clean_subdirectory(ce, action, o);
 543
 544                        /*
 545                         * If this removed entries from the index,
 546                         * what that means is:
 547                         *
 548                         * (1) the caller unpack_trees_rec() saw path/foo
 549                         * in the index, and it has not removed it because
 550                         * it thinks it is handling 'path' as blob with
 551                         * D/F conflict;
 552                         * (2) we will return "ok, we placed a merged entry
 553                         * in the index" which would cause o->pos to be
 554                         * incremented by one;
 555                         * (3) however, original o->pos now has 'path/foo'
 556                         * marked with "to be removed".
 557                         *
 558                         * We need to increment it by the number of
 559                         * deleted entries here.
 560                         */
 561                        o->pos += cnt;
 562                        return 0;
 563                }
 564
 565                /*
 566                 * The previous round may already have decided to
 567                 * delete this path, which is in a subdirectory that
 568                 * is being replaced with a blob.
 569                 */
 570                cnt = index_name_pos(o->index, ce->name, strlen(ce->name));
 571                if (0 <= cnt) {
 572                        struct cache_entry *ce = o->index->cache[cnt];
 573                        if (ce->ce_flags & CE_REMOVE)
 574                                return 0;
 575                }
 576
 577                return o->gently ? -1 :
 578                        error("Untracked working tree file '%s' "
 579                              "would be %s by merge.", ce->name, action);
 580        }
 581        return 0;
 582}
 583
 584static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
 585                struct unpack_trees_options *o)
 586{
 587        merge->ce_flags |= CE_UPDATE;
 588        if (old) {
 589                /*
 590                 * See if we can re-use the old CE directly?
 591                 * That way we get the uptodate stat info.
 592                 *
 593                 * This also removes the UPDATE flag on
 594                 * a match.
 595                 */
 596                if (same(old, merge)) {
 597                        copy_cache_entry(merge, old);
 598                } else {
 599                        if (verify_uptodate(old, o))
 600                                return -1;
 601                        invalidate_ce_path(old, o);
 602                }
 603        }
 604        else {
 605                if (verify_absent(merge, "overwritten", o))
 606                        return -1;
 607                invalidate_ce_path(merge, o);
 608        }
 609
 610        merge->ce_flags &= ~CE_STAGEMASK;
 611        add_index_entry(o->index, merge, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 612        return 1;
 613}
 614
 615static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
 616                struct unpack_trees_options *o)
 617{
 618        if (old) {
 619                if (verify_uptodate(old, o))
 620                        return -1;
 621        } else
 622                if (verify_absent(ce, "removed", o))
 623                        return -1;
 624        ce->ce_flags |= CE_REMOVE;
 625        add_index_entry(o->index, ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 626        invalidate_ce_path(ce, o);
 627        return 1;
 628}
 629
 630static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 631{
 632        add_index_entry(o->index, ce, ADD_CACHE_OK_TO_ADD);
 633        return 1;
 634}
 635
 636#if DBRT_DEBUG
 637static void show_stage_entry(FILE *o,
 638                             const char *label, const struct cache_entry *ce)
 639{
 640        if (!ce)
 641                fprintf(o, "%s (missing)\n", label);
 642        else
 643                fprintf(o, "%s%06o %s %d\t%s\n",
 644                        label,
 645                        ce->ce_mode,
 646                        sha1_to_hex(ce->sha1),
 647                        ce_stage(ce),
 648                        ce->name);
 649}
 650#endif
 651
 652int threeway_merge(struct cache_entry **stages,
 653                struct unpack_trees_options *o,
 654                int remove)
 655{
 656        struct cache_entry *index;
 657        struct cache_entry *head;
 658        struct cache_entry *remote = stages[o->head_idx + 1];
 659        int count;
 660        int head_match = 0;
 661        int remote_match = 0;
 662
 663        int df_conflict_head = 0;
 664        int df_conflict_remote = 0;
 665
 666        int any_anc_missing = 0;
 667        int no_anc_exists = 1;
 668        int i;
 669
 670        for (i = 1; i < o->head_idx; i++) {
 671                if (!stages[i] || stages[i] == o->df_conflict_entry)
 672                        any_anc_missing = 1;
 673                else
 674                        no_anc_exists = 0;
 675        }
 676
 677        index = stages[0];
 678        head = stages[o->head_idx];
 679
 680        if (head == o->df_conflict_entry) {
 681                df_conflict_head = 1;
 682                head = NULL;
 683        }
 684
 685        if (remote == o->df_conflict_entry) {
 686                df_conflict_remote = 1;
 687                remote = NULL;
 688        }
 689
 690        /* First, if there's a #16 situation, note that to prevent #13
 691         * and #14.
 692         */
 693        if (!same(remote, head)) {
 694                for (i = 1; i < o->head_idx; i++) {
 695                        if (same(stages[i], head)) {
 696                                head_match = i;
 697                        }
 698                        if (same(stages[i], remote)) {
 699                                remote_match = i;
 700                        }
 701                }
 702        }
 703
 704        /* We start with cases where the index is allowed to match
 705         * something other than the head: #14(ALT) and #2ALT, where it
 706         * is permitted to match the result instead.
 707         */
 708        /* #14, #14ALT, #2ALT */
 709        if (remote && !df_conflict_head && head_match && !remote_match) {
 710                if (index && !same(index, remote) && !same(index, head))
 711                        return o->gently ? -1 : reject_merge(index);
 712                return merged_entry(remote, index, o);
 713        }
 714        /*
 715         * If we have an entry in the index cache, then we want to
 716         * make sure that it matches head.
 717         */
 718        if (index && !same(index, head))
 719                return o->gently ? -1 : reject_merge(index);
 720
 721        if (head) {
 722                /* #5ALT, #15 */
 723                if (same(head, remote))
 724                        return merged_entry(head, index, o);
 725                /* #13, #3ALT */
 726                if (!df_conflict_remote && remote_match && !head_match)
 727                        return merged_entry(head, index, o);
 728        }
 729
 730        /* #1 */
 731        if (!head && !remote && any_anc_missing) {
 732                remove_entry(remove, o);
 733                return 0;
 734        }
 735
 736        /* Under the new "aggressive" rule, we resolve mostly trivial
 737         * cases that we historically had git-merge-one-file resolve.
 738         */
 739        if (o->aggressive) {
 740                int head_deleted = !head && !df_conflict_head;
 741                int remote_deleted = !remote && !df_conflict_remote;
 742                struct cache_entry *ce = NULL;
 743
 744                if (index)
 745                        ce = index;
 746                else if (head)
 747                        ce = head;
 748                else if (remote)
 749                        ce = remote;
 750                else {
 751                        for (i = 1; i < o->head_idx; i++) {
 752                                if (stages[i] && stages[i] != o->df_conflict_entry) {
 753                                        ce = stages[i];
 754                                        break;
 755                                }
 756                        }
 757                }
 758
 759                /*
 760                 * Deleted in both.
 761                 * Deleted in one and unchanged in the other.
 762                 */
 763                if ((head_deleted && remote_deleted) ||
 764                    (head_deleted && remote && remote_match) ||
 765                    (remote_deleted && head && head_match)) {
 766                        remove_entry(remove, o);
 767                        if (index)
 768                                return deleted_entry(index, index, o);
 769                        else if (ce && !head_deleted) {
 770                                if (verify_absent(ce, "removed", o))
 771                                        return -1;
 772                        }
 773                        return 0;
 774                }
 775                /*
 776                 * Added in both, identically.
 777                 */
 778                if (no_anc_exists && head && remote && same(head, remote))
 779                        return merged_entry(head, index, o);
 780
 781        }
 782
 783        /* Below are "no merge" cases, which require that the index be
 784         * up-to-date to avoid the files getting overwritten with
 785         * conflict resolution files.
 786         */
 787        if (index) {
 788                if (verify_uptodate(index, o))
 789                        return -1;
 790        }
 791
 792        remove_entry(remove, o);
 793        o->nontrivial_merge = 1;
 794
 795        /* #2, #3, #4, #6, #7, #9, #10, #11. */
 796        count = 0;
 797        if (!head_match || !remote_match) {
 798                for (i = 1; i < o->head_idx; i++) {
 799                        if (stages[i] && stages[i] != o->df_conflict_entry) {
 800                                keep_entry(stages[i], o);
 801                                count++;
 802                                break;
 803                        }
 804                }
 805        }
 806#if DBRT_DEBUG
 807        else {
 808                fprintf(stderr, "read-tree: warning #16 detected\n");
 809                show_stage_entry(stderr, "head   ", stages[head_match]);
 810                show_stage_entry(stderr, "remote ", stages[remote_match]);
 811        }
 812#endif
 813        if (head) { count += keep_entry(head, o); }
 814        if (remote) { count += keep_entry(remote, o); }
 815        return count;
 816}
 817
 818/*
 819 * Two-way merge.
 820 *
 821 * The rule is to "carry forward" what is in the index without losing
 822 * information across a "fast forward", favoring a successful merge
 823 * over a merge failure when it makes sense.  For details of the
 824 * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 825 *
 826 */
 827int twoway_merge(struct cache_entry **src,
 828                struct unpack_trees_options *o,
 829                int remove)
 830{
 831        struct cache_entry *current = src[0];
 832        struct cache_entry *oldtree = src[1];
 833        struct cache_entry *newtree = src[2];
 834
 835        if (o->merge_size != 2)
 836                return error("Cannot do a twoway merge of %d trees",
 837                             o->merge_size);
 838
 839        if (oldtree == o->df_conflict_entry)
 840                oldtree = NULL;
 841        if (newtree == o->df_conflict_entry)
 842                newtree = NULL;
 843
 844        if (current) {
 845                if ((!oldtree && !newtree) || /* 4 and 5 */
 846                    (!oldtree && newtree &&
 847                     same(current, newtree)) || /* 6 and 7 */
 848                    (oldtree && newtree &&
 849                     same(oldtree, newtree)) || /* 14 and 15 */
 850                    (oldtree && newtree &&
 851                     !same(oldtree, newtree) && /* 18 and 19 */
 852                     same(current, newtree))) {
 853                        return keep_entry(current, o);
 854                }
 855                else if (oldtree && !newtree && same(current, oldtree)) {
 856                        /* 10 or 11 */
 857                        remove_entry(remove, o);
 858                        return deleted_entry(oldtree, current, o);
 859                }
 860                else if (oldtree && newtree &&
 861                         same(current, oldtree) && !same(current, newtree)) {
 862                        /* 20 or 21 */
 863                        return merged_entry(newtree, current, o);
 864                }
 865                else {
 866                        /* all other failures */
 867                        remove_entry(remove, o);
 868                        if (oldtree)
 869                                return o->gently ? -1 : reject_merge(oldtree);
 870                        if (current)
 871                                return o->gently ? -1 : reject_merge(current);
 872                        if (newtree)
 873                                return o->gently ? -1 : reject_merge(newtree);
 874                        return -1;
 875                }
 876        }
 877        else if (newtree)
 878                return merged_entry(newtree, current, o);
 879        remove_entry(remove, o);
 880        return deleted_entry(oldtree, current, o);
 881}
 882
 883/*
 884 * Bind merge.
 885 *
 886 * Keep the index entries at stage0, collapse stage1 but make sure
 887 * stage0 does not have anything there.
 888 */
 889int bind_merge(struct cache_entry **src,
 890                struct unpack_trees_options *o,
 891                int remove)
 892{
 893        struct cache_entry *old = src[0];
 894        struct cache_entry *a = src[1];
 895
 896        if (o->merge_size != 1)
 897                return error("Cannot do a bind merge of %d trees\n",
 898                             o->merge_size);
 899        if (a && old)
 900                return o->gently ? -1 :
 901                        error("Entry '%s' overlaps.  Cannot bind.", a->name);
 902        if (!a)
 903                return keep_entry(old, o);
 904        else
 905                return merged_entry(a, NULL, o);
 906}
 907
 908/*
 909 * One-way merge.
 910 *
 911 * The rule is:
 912 * - take the stat information from stage0, take the data from stage1
 913 */
 914int oneway_merge(struct cache_entry **src,
 915                struct unpack_trees_options *o,
 916                int remove)
 917{
 918        struct cache_entry *old = src[0];
 919        struct cache_entry *a = src[1];
 920
 921        if (o->merge_size != 1)
 922                return error("Cannot do a oneway merge of %d trees",
 923                             o->merge_size);
 924
 925        if (!a) {
 926                remove_entry(remove, o);
 927                return deleted_entry(old, old, o);
 928        }
 929        if (old && same(old, a)) {
 930                if (o->reset) {
 931                        struct stat st;
 932                        if (lstat(old->name, &st) ||
 933                            ie_match_stat(o->index, old, &st, CE_MATCH_IGNORE_VALID))
 934                                old->ce_flags |= CE_UPDATE;
 935                }
 936                return keep_entry(old, o);
 937        }
 938        return merged_entry(a, old, o);
 939}