11902cd51da9d83952df03edc1aadffc41e3f05b
   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
  11/*
  12 * Error messages expected by scripts out of plumbing commands such as
  13 * read-tree.  Non-scripted Porcelain is not required to use these messages
  14 * and in fact are encouraged to reword them to better suit their particular
  15 * situation better.  See how "git checkout" replaces not_uptodate_file to
  16 * explain why it does not allow switching between branches when you have
  17 * local changes, for example.
  18 */
  19static struct unpack_trees_error_msgs unpack_plumbing_errors = {
  20        /* would_overwrite */
  21        "Entry '%s' would be overwritten by merge. Cannot merge.",
  22
  23        /* not_uptodate_file */
  24        "Entry '%s' not uptodate. Cannot merge.",
  25
  26        /* not_uptodate_dir */
  27        "Updating '%s' would lose untracked files in it",
  28
  29        /* would_lose_untracked */
  30        "Untracked working tree file '%s' would be %s by merge.",
  31
  32        /* bind_overlap */
  33        "Entry '%s' overlaps with '%s'.  Cannot bind.",
  34};
  35
  36#define ERRORMSG(o,fld) \
  37        ( ((o) && (o)->msgs.fld) \
  38        ? ((o)->msgs.fld) \
  39        : (unpack_plumbing_errors.fld) )
  40
  41static void add_entry(struct unpack_trees_options *o, struct cache_entry *ce,
  42        unsigned int set, unsigned int clear)
  43{
  44        unsigned int size = ce_size(ce);
  45        struct cache_entry *new = xmalloc(size);
  46
  47        clear |= CE_HASHED | CE_UNHASHED;
  48
  49        memcpy(new, ce, size);
  50        new->next = NULL;
  51        new->ce_flags = (new->ce_flags & ~clear) | set;
  52        add_index_entry(&o->result, new, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE|ADD_CACHE_SKIP_DFCHECK);
  53}
  54
  55/*
  56 * Unlink the last component and schedule the leading directories for
  57 * removal, such that empty directories get removed.
  58 */
  59static void unlink_entry(struct cache_entry *ce)
  60{
  61        if (has_symlink_or_noent_leading_path(ce->name, ce_namelen(ce)))
  62                return;
  63        if (unlink(ce->name))
  64                return;
  65        schedule_dir_for_removal(ce->name, ce_namelen(ce));
  66}
  67
  68static struct checkout state;
  69static int check_updates(struct unpack_trees_options *o)
  70{
  71        unsigned cnt = 0, total = 0;
  72        struct progress *progress = NULL;
  73        struct index_state *index = &o->result;
  74        int i;
  75        int errs = 0;
  76
  77        if (o->update && o->verbose_update) {
  78                for (total = cnt = 0; cnt < index->cache_nr; cnt++) {
  79                        struct cache_entry *ce = index->cache[cnt];
  80                        if (ce->ce_flags & (CE_UPDATE | CE_REMOVE))
  81                                total++;
  82                }
  83
  84                progress = start_progress_delay("Checking out files",
  85                                                total, 50, 1);
  86                cnt = 0;
  87        }
  88
  89        for (i = 0; i < index->cache_nr; i++) {
  90                struct cache_entry *ce = index->cache[i];
  91
  92                if (ce->ce_flags & CE_REMOVE) {
  93                        display_progress(progress, ++cnt);
  94                        if (o->update)
  95                                unlink_entry(ce);
  96                }
  97        }
  98        remove_marked_cache_entries(&o->result);
  99        remove_scheduled_dirs();
 100
 101        for (i = 0; i < index->cache_nr; i++) {
 102                struct cache_entry *ce = index->cache[i];
 103
 104                if (ce->ce_flags & CE_UPDATE) {
 105                        display_progress(progress, ++cnt);
 106                        ce->ce_flags &= ~CE_UPDATE;
 107                        if (o->update) {
 108                                errs |= checkout_entry(ce, &state, NULL);
 109                        }
 110                }
 111        }
 112        stop_progress(&progress);
 113        return errs != 0;
 114}
 115
 116static inline int call_unpack_fn(struct cache_entry **src, struct unpack_trees_options *o)
 117{
 118        int ret = o->fn(src, o);
 119        if (ret > 0)
 120                ret = 0;
 121        return ret;
 122}
 123
 124static int unpack_index_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 125{
 126        struct cache_entry *src[5] = { ce, };
 127
 128        o->pos++;
 129        if (ce_stage(ce)) {
 130                if (o->skip_unmerged) {
 131                        add_entry(o, ce, 0, 0);
 132                        return 0;
 133                }
 134        }
 135        return call_unpack_fn(src, o);
 136}
 137
 138int traverse_trees_recursive(int n, unsigned long dirmask, unsigned long df_conflicts, struct name_entry *names, struct traverse_info *info)
 139{
 140        int i;
 141        struct tree_desc t[MAX_UNPACK_TREES];
 142        struct traverse_info newinfo;
 143        struct name_entry *p;
 144
 145        p = names;
 146        while (!p->mode)
 147                p++;
 148
 149        newinfo = *info;
 150        newinfo.prev = info;
 151        newinfo.name = *p;
 152        newinfo.pathlen += tree_entry_len(p->path, p->sha1) + 1;
 153        newinfo.conflicts |= df_conflicts;
 154
 155        for (i = 0; i < n; i++, dirmask >>= 1) {
 156                const unsigned char *sha1 = NULL;
 157                if (dirmask & 1)
 158                        sha1 = names[i].sha1;
 159                fill_tree_descriptor(t+i, sha1);
 160        }
 161        return traverse_trees(n, t, &newinfo);
 162}
 163
 164/*
 165 * Compare the traverse-path to the cache entry without actually
 166 * having to generate the textual representation of the traverse
 167 * path.
 168 *
 169 * NOTE! This *only* compares up to the size of the traverse path
 170 * itself - the caller needs to do the final check for the cache
 171 * entry having more data at the end!
 172 */
 173static int do_compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
 174{
 175        int len, pathlen, ce_len;
 176        const char *ce_name;
 177
 178        if (info->prev) {
 179                int cmp = do_compare_entry(ce, info->prev, &info->name);
 180                if (cmp)
 181                        return cmp;
 182        }
 183        pathlen = info->pathlen;
 184        ce_len = ce_namelen(ce);
 185
 186        /* If ce_len < pathlen then we must have previously hit "name == directory" entry */
 187        if (ce_len < pathlen)
 188                return -1;
 189
 190        ce_len -= pathlen;
 191        ce_name = ce->name + pathlen;
 192
 193        len = tree_entry_len(n->path, n->sha1);
 194        return df_name_compare(ce_name, ce_len, S_IFREG, n->path, len, n->mode);
 195}
 196
 197static int compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
 198{
 199        int cmp = do_compare_entry(ce, info, n);
 200        if (cmp)
 201                return cmp;
 202
 203        /*
 204         * Even if the beginning compared identically, the ce should
 205         * compare as bigger than a directory leading up to it!
 206         */
 207        return ce_namelen(ce) > traverse_path_len(info, n);
 208}
 209
 210static struct cache_entry *create_ce_entry(const struct traverse_info *info, const struct name_entry *n, int stage)
 211{
 212        int len = traverse_path_len(info, n);
 213        struct cache_entry *ce = xcalloc(1, cache_entry_size(len));
 214
 215        ce->ce_mode = create_ce_mode(n->mode);
 216        ce->ce_flags = create_ce_flags(len, stage);
 217        hashcpy(ce->sha1, n->sha1);
 218        make_traverse_path(ce->name, info, n);
 219
 220        return ce;
 221}
 222
 223static int unpack_nondirectories(int n, unsigned long mask,
 224                                 unsigned long dirmask,
 225                                 struct cache_entry **src,
 226                                 const struct name_entry *names,
 227                                 const struct traverse_info *info)
 228{
 229        int i;
 230        struct unpack_trees_options *o = info->data;
 231        unsigned long conflicts;
 232
 233        /* Do we have *only* directories? Nothing to do */
 234        if (mask == dirmask && !src[0])
 235                return 0;
 236
 237        conflicts = info->conflicts;
 238        if (o->merge)
 239                conflicts >>= 1;
 240        conflicts |= dirmask;
 241
 242        /*
 243         * Ok, we've filled in up to any potential index entry in src[0],
 244         * now do the rest.
 245         */
 246        for (i = 0; i < n; i++) {
 247                int stage;
 248                unsigned int bit = 1ul << i;
 249                if (conflicts & bit) {
 250                        src[i + o->merge] = o->df_conflict_entry;
 251                        continue;
 252                }
 253                if (!(mask & bit))
 254                        continue;
 255                if (!o->merge)
 256                        stage = 0;
 257                else if (i + 1 < o->head_idx)
 258                        stage = 1;
 259                else if (i + 1 > o->head_idx)
 260                        stage = 3;
 261                else
 262                        stage = 2;
 263                src[i + o->merge] = create_ce_entry(info, names + i, stage);
 264        }
 265
 266        if (o->merge)
 267                return call_unpack_fn(src, o);
 268
 269        n += o->merge;
 270        for (i = 0; i < n; i++)
 271                add_entry(o, src[i], 0, 0);
 272        return 0;
 273}
 274
 275static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *names, struct traverse_info *info)
 276{
 277        struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
 278        struct unpack_trees_options *o = info->data;
 279        const struct name_entry *p = names;
 280
 281        /* Find first entry with a real name (we could use "mask" too) */
 282        while (!p->mode)
 283                p++;
 284
 285        /* Are we supposed to look at the index too? */
 286        if (o->merge) {
 287                while (o->pos < o->src_index->cache_nr) {
 288                        struct cache_entry *ce = o->src_index->cache[o->pos];
 289                        int cmp = compare_entry(ce, info, p);
 290                        if (cmp < 0) {
 291                                if (unpack_index_entry(ce, o) < 0)
 292                                        return -1;
 293                                continue;
 294                        }
 295                        if (!cmp) {
 296                                o->pos++;
 297                                if (ce_stage(ce)) {
 298                                        /*
 299                                         * If we skip unmerged index entries, we'll skip this
 300                                         * entry *and* the tree entries associated with it!
 301                                         */
 302                                        if (o->skip_unmerged) {
 303                                                add_entry(o, ce, 0, 0);
 304                                                return mask;
 305                                        }
 306                                }
 307                                src[0] = ce;
 308                        }
 309                        break;
 310                }
 311        }
 312
 313        if (unpack_nondirectories(n, mask, dirmask, src, names, info) < 0)
 314                return -1;
 315
 316        /* Now handle any directories.. */
 317        if (dirmask) {
 318                unsigned long conflicts = mask & ~dirmask;
 319                if (o->merge) {
 320                        conflicts <<= 1;
 321                        if (src[0])
 322                                conflicts |= 1;
 323                }
 324                if (traverse_trees_recursive(n, dirmask, conflicts,
 325                                             names, info) < 0)
 326                        return -1;
 327                return mask;
 328        }
 329
 330        return mask;
 331}
 332
 333static int unpack_failed(struct unpack_trees_options *o, const char *message)
 334{
 335        discard_index(&o->result);
 336        if (!o->gently) {
 337                if (message)
 338                        return error("%s", message);
 339                return -1;
 340        }
 341        return -1;
 342}
 343
 344/*
 345 * N-way merge "len" trees.  Returns 0 on success, -1 on failure to manipulate the
 346 * resulting index, -2 on failure to reflect the changes to the work tree.
 347 */
 348int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
 349{
 350        int ret;
 351        static struct cache_entry *dfc;
 352
 353        if (len > MAX_UNPACK_TREES)
 354                die("unpack_trees takes at most %d trees", MAX_UNPACK_TREES);
 355        memset(&state, 0, sizeof(state));
 356        state.base_dir = "";
 357        state.force = 1;
 358        state.quiet = 1;
 359        state.refresh_cache = 1;
 360
 361        memset(&o->result, 0, sizeof(o->result));
 362        o->result.initialized = 1;
 363        if (o->src_index) {
 364                o->result.timestamp.sec = o->src_index->timestamp.sec;
 365#ifdef USE_NSEC
 366                o->result.timestamp.nsec = o->src_index->timestamp.nsec;
 367#endif
 368        }
 369        o->merge_size = len;
 370
 371        if (!dfc)
 372                dfc = xcalloc(1, cache_entry_size(0));
 373        o->df_conflict_entry = dfc;
 374
 375        if (len) {
 376                const char *prefix = o->prefix ? o->prefix : "";
 377                struct traverse_info info;
 378
 379                setup_traverse_info(&info, prefix);
 380                info.fn = unpack_callback;
 381                info.data = o;
 382
 383                if (traverse_trees(len, t, &info) < 0)
 384                        return unpack_failed(o, NULL);
 385        }
 386
 387        /* Any left-over entries in the index? */
 388        if (o->merge) {
 389                while (o->pos < o->src_index->cache_nr) {
 390                        struct cache_entry *ce = o->src_index->cache[o->pos];
 391                        if (unpack_index_entry(ce, o) < 0)
 392                                return unpack_failed(o, NULL);
 393                }
 394        }
 395
 396        if (o->trivial_merges_only && o->nontrivial_merge)
 397                return unpack_failed(o, "Merge requires file-level merging");
 398
 399        o->src_index = NULL;
 400        ret = check_updates(o) ? (-2) : 0;
 401        if (o->dst_index)
 402                *o->dst_index = o->result;
 403        return ret;
 404}
 405
 406/* Here come the merge functions */
 407
 408static int reject_merge(struct cache_entry *ce, struct unpack_trees_options *o)
 409{
 410        return error(ERRORMSG(o, would_overwrite), ce->name);
 411}
 412
 413static int same(struct cache_entry *a, struct cache_entry *b)
 414{
 415        if (!!a != !!b)
 416                return 0;
 417        if (!a && !b)
 418                return 1;
 419        return a->ce_mode == b->ce_mode &&
 420               !hashcmp(a->sha1, b->sha1);
 421}
 422
 423
 424/*
 425 * When a CE gets turned into an unmerged entry, we
 426 * want it to be up-to-date
 427 */
 428static int verify_uptodate(struct cache_entry *ce,
 429                struct unpack_trees_options *o)
 430{
 431        struct stat st;
 432
 433        if (o->index_only || o->reset)
 434                return 0;
 435
 436        if (!lstat(ce->name, &st)) {
 437                unsigned changed = ie_match_stat(o->src_index, ce, &st, CE_MATCH_IGNORE_VALID);
 438                if (!changed)
 439                        return 0;
 440                /*
 441                 * NEEDSWORK: the current default policy is to allow
 442                 * submodule to be out of sync wrt the supermodule
 443                 * index.  This needs to be tightened later for
 444                 * submodules that are marked to be automatically
 445                 * checked out.
 446                 */
 447                if (S_ISGITLINK(ce->ce_mode))
 448                        return 0;
 449                errno = 0;
 450        }
 451        if (errno == ENOENT)
 452                return 0;
 453        return o->gently ? -1 :
 454                error(ERRORMSG(o, not_uptodate_file), ce->name);
 455}
 456
 457static void invalidate_ce_path(struct cache_entry *ce, struct unpack_trees_options *o)
 458{
 459        if (ce)
 460                cache_tree_invalidate_path(o->src_index->cache_tree, ce->name);
 461}
 462
 463/*
 464 * Check that checking out ce->sha1 in subdir ce->name is not
 465 * going to overwrite any working files.
 466 *
 467 * Currently, git does not checkout subprojects during a superproject
 468 * checkout, so it is not going to overwrite anything.
 469 */
 470static int verify_clean_submodule(struct cache_entry *ce, const char *action,
 471                                      struct unpack_trees_options *o)
 472{
 473        return 0;
 474}
 475
 476static int verify_clean_subdirectory(struct cache_entry *ce, const char *action,
 477                                      struct unpack_trees_options *o)
 478{
 479        /*
 480         * we are about to extract "ce->name"; we would not want to lose
 481         * anything in the existing directory there.
 482         */
 483        int namelen;
 484        int i;
 485        struct dir_struct d;
 486        char *pathbuf;
 487        int cnt = 0;
 488        unsigned char sha1[20];
 489
 490        if (S_ISGITLINK(ce->ce_mode) &&
 491            resolve_gitlink_ref(ce->name, "HEAD", sha1) == 0) {
 492                /* If we are not going to update the submodule, then
 493                 * we don't care.
 494                 */
 495                if (!hashcmp(sha1, ce->sha1))
 496                        return 0;
 497                return verify_clean_submodule(ce, action, o);
 498        }
 499
 500        /*
 501         * First let's make sure we do not have a local modification
 502         * in that directory.
 503         */
 504        namelen = strlen(ce->name);
 505        for (i = o->pos; i < o->src_index->cache_nr; i++) {
 506                struct cache_entry *ce2 = o->src_index->cache[i];
 507                int len = ce_namelen(ce2);
 508                if (len < namelen ||
 509                    strncmp(ce->name, ce2->name, namelen) ||
 510                    ce2->name[namelen] != '/')
 511                        break;
 512                /*
 513                 * ce2->name is an entry in the subdirectory.
 514                 */
 515                if (!ce_stage(ce2)) {
 516                        if (verify_uptodate(ce2, o))
 517                                return -1;
 518                        add_entry(o, ce2, CE_REMOVE, 0);
 519                }
 520                cnt++;
 521        }
 522
 523        /*
 524         * Then we need to make sure that we do not lose a locally
 525         * present file that is not ignored.
 526         */
 527        pathbuf = xmalloc(namelen + 2);
 528        memcpy(pathbuf, ce->name, namelen);
 529        strcpy(pathbuf+namelen, "/");
 530
 531        memset(&d, 0, sizeof(d));
 532        if (o->dir)
 533                d.exclude_per_dir = o->dir->exclude_per_dir;
 534        i = read_directory(&d, ce->name, pathbuf, namelen+1, NULL);
 535        if (i)
 536                return o->gently ? -1 :
 537                        error(ERRORMSG(o, not_uptodate_dir), ce->name);
 538        free(pathbuf);
 539        return cnt;
 540}
 541
 542/*
 543 * This gets called when there was no index entry for the tree entry 'dst',
 544 * but we found a file in the working tree that 'lstat()' said was fine,
 545 * and we're on a case-insensitive filesystem.
 546 *
 547 * See if we can find a case-insensitive match in the index that also
 548 * matches the stat information, and assume it's that other file!
 549 */
 550static int icase_exists(struct unpack_trees_options *o, struct cache_entry *dst, struct stat *st)
 551{
 552        struct cache_entry *src;
 553
 554        src = index_name_exists(o->src_index, dst->name, ce_namelen(dst), 1);
 555        return src && !ie_match_stat(o->src_index, src, st, CE_MATCH_IGNORE_VALID);
 556}
 557
 558/*
 559 * We do not want to remove or overwrite a working tree file that
 560 * is not tracked, unless it is ignored.
 561 */
 562static int verify_absent(struct cache_entry *ce, const char *action,
 563                         struct unpack_trees_options *o)
 564{
 565        struct stat st;
 566
 567        if (o->index_only || o->reset || !o->update)
 568                return 0;
 569
 570        if (has_symlink_or_noent_leading_path(ce->name, ce_namelen(ce)))
 571                return 0;
 572
 573        if (!lstat(ce->name, &st)) {
 574                int ret;
 575                int dtype = ce_to_dtype(ce);
 576                struct cache_entry *result;
 577
 578                /*
 579                 * It may be that the 'lstat()' succeeded even though
 580                 * target 'ce' was absent, because there is an old
 581                 * entry that is different only in case..
 582                 *
 583                 * Ignore that lstat() if it matches.
 584                 */
 585                if (ignore_case && icase_exists(o, ce, &st))
 586                        return 0;
 587
 588                if (o->dir && excluded(o->dir, ce->name, &dtype))
 589                        /*
 590                         * ce->name is explicitly excluded, so it is Ok to
 591                         * overwrite it.
 592                         */
 593                        return 0;
 594                if (S_ISDIR(st.st_mode)) {
 595                        /*
 596                         * We are checking out path "foo" and
 597                         * found "foo/." in the working tree.
 598                         * This is tricky -- if we have modified
 599                         * files that are in "foo/" we would lose
 600                         * it.
 601                         */
 602                        ret = verify_clean_subdirectory(ce, action, o);
 603                        if (ret < 0)
 604                                return ret;
 605
 606                        /*
 607                         * If this removed entries from the index,
 608                         * what that means is:
 609                         *
 610                         * (1) the caller unpack_callback() saw path/foo
 611                         * in the index, and it has not removed it because
 612                         * it thinks it is handling 'path' as blob with
 613                         * D/F conflict;
 614                         * (2) we will return "ok, we placed a merged entry
 615                         * in the index" which would cause o->pos to be
 616                         * incremented by one;
 617                         * (3) however, original o->pos now has 'path/foo'
 618                         * marked with "to be removed".
 619                         *
 620                         * We need to increment it by the number of
 621                         * deleted entries here.
 622                         */
 623                        o->pos += ret;
 624                        return 0;
 625                }
 626
 627                /*
 628                 * The previous round may already have decided to
 629                 * delete this path, which is in a subdirectory that
 630                 * is being replaced with a blob.
 631                 */
 632                result = index_name_exists(&o->result, ce->name, ce_namelen(ce), 0);
 633                if (result) {
 634                        if (result->ce_flags & CE_REMOVE)
 635                                return 0;
 636                }
 637
 638                return o->gently ? -1 :
 639                        error(ERRORMSG(o, would_lose_untracked), ce->name, action);
 640        }
 641        return 0;
 642}
 643
 644static int merged_entry(struct cache_entry *merge, struct cache_entry *old,
 645                struct unpack_trees_options *o)
 646{
 647        int update = CE_UPDATE;
 648
 649        if (old) {
 650                /*
 651                 * See if we can re-use the old CE directly?
 652                 * That way we get the uptodate stat info.
 653                 *
 654                 * This also removes the UPDATE flag on a match; otherwise
 655                 * we will end up overwriting local changes in the work tree.
 656                 */
 657                if (same(old, merge)) {
 658                        copy_cache_entry(merge, old);
 659                        update = 0;
 660                } else {
 661                        if (verify_uptodate(old, o))
 662                                return -1;
 663                        invalidate_ce_path(old, o);
 664                }
 665        }
 666        else {
 667                if (verify_absent(merge, "overwritten", o))
 668                        return -1;
 669                invalidate_ce_path(merge, o);
 670        }
 671
 672        add_entry(o, merge, update, CE_STAGEMASK);
 673        return 1;
 674}
 675
 676static int deleted_entry(struct cache_entry *ce, struct cache_entry *old,
 677                struct unpack_trees_options *o)
 678{
 679        /* Did it exist in the index? */
 680        if (!old) {
 681                if (verify_absent(ce, "removed", o))
 682                        return -1;
 683                return 0;
 684        }
 685        if (verify_uptodate(old, o))
 686                return -1;
 687        add_entry(o, ce, CE_REMOVE, 0);
 688        invalidate_ce_path(ce, o);
 689        return 1;
 690}
 691
 692static int keep_entry(struct cache_entry *ce, struct unpack_trees_options *o)
 693{
 694        add_entry(o, ce, 0, 0);
 695        return 1;
 696}
 697
 698#if DBRT_DEBUG
 699static void show_stage_entry(FILE *o,
 700                             const char *label, const struct cache_entry *ce)
 701{
 702        if (!ce)
 703                fprintf(o, "%s (missing)\n", label);
 704        else
 705                fprintf(o, "%s%06o %s %d\t%s\n",
 706                        label,
 707                        ce->ce_mode,
 708                        sha1_to_hex(ce->sha1),
 709                        ce_stage(ce),
 710                        ce->name);
 711}
 712#endif
 713
 714int threeway_merge(struct cache_entry **stages, struct unpack_trees_options *o)
 715{
 716        struct cache_entry *index;
 717        struct cache_entry *head;
 718        struct cache_entry *remote = stages[o->head_idx + 1];
 719        int count;
 720        int head_match = 0;
 721        int remote_match = 0;
 722
 723        int df_conflict_head = 0;
 724        int df_conflict_remote = 0;
 725
 726        int any_anc_missing = 0;
 727        int no_anc_exists = 1;
 728        int i;
 729
 730        for (i = 1; i < o->head_idx; i++) {
 731                if (!stages[i] || stages[i] == o->df_conflict_entry)
 732                        any_anc_missing = 1;
 733                else
 734                        no_anc_exists = 0;
 735        }
 736
 737        index = stages[0];
 738        head = stages[o->head_idx];
 739
 740        if (head == o->df_conflict_entry) {
 741                df_conflict_head = 1;
 742                head = NULL;
 743        }
 744
 745        if (remote == o->df_conflict_entry) {
 746                df_conflict_remote = 1;
 747                remote = NULL;
 748        }
 749
 750        /* First, if there's a #16 situation, note that to prevent #13
 751         * and #14.
 752         */
 753        if (!same(remote, head)) {
 754                for (i = 1; i < o->head_idx; i++) {
 755                        if (same(stages[i], head)) {
 756                                head_match = i;
 757                        }
 758                        if (same(stages[i], remote)) {
 759                                remote_match = i;
 760                        }
 761                }
 762        }
 763
 764        /* We start with cases where the index is allowed to match
 765         * something other than the head: #14(ALT) and #2ALT, where it
 766         * is permitted to match the result instead.
 767         */
 768        /* #14, #14ALT, #2ALT */
 769        if (remote && !df_conflict_head && head_match && !remote_match) {
 770                if (index && !same(index, remote) && !same(index, head))
 771                        return o->gently ? -1 : reject_merge(index, o);
 772                return merged_entry(remote, index, o);
 773        }
 774        /*
 775         * If we have an entry in the index cache, then we want to
 776         * make sure that it matches head.
 777         */
 778        if (index && !same(index, head))
 779                return o->gently ? -1 : reject_merge(index, o);
 780
 781        if (head) {
 782                /* #5ALT, #15 */
 783                if (same(head, remote))
 784                        return merged_entry(head, index, o);
 785                /* #13, #3ALT */
 786                if (!df_conflict_remote && remote_match && !head_match)
 787                        return merged_entry(head, index, o);
 788        }
 789
 790        /* #1 */
 791        if (!head && !remote && any_anc_missing)
 792                return 0;
 793
 794        /* Under the new "aggressive" rule, we resolve mostly trivial
 795         * cases that we historically had git-merge-one-file resolve.
 796         */
 797        if (o->aggressive) {
 798                int head_deleted = !head && !df_conflict_head;
 799                int remote_deleted = !remote && !df_conflict_remote;
 800                struct cache_entry *ce = NULL;
 801
 802                if (index)
 803                        ce = index;
 804                else if (head)
 805                        ce = head;
 806                else if (remote)
 807                        ce = remote;
 808                else {
 809                        for (i = 1; i < o->head_idx; i++) {
 810                                if (stages[i] && stages[i] != o->df_conflict_entry) {
 811                                        ce = stages[i];
 812                                        break;
 813                                }
 814                        }
 815                }
 816
 817                /*
 818                 * Deleted in both.
 819                 * Deleted in one and unchanged in the other.
 820                 */
 821                if ((head_deleted && remote_deleted) ||
 822                    (head_deleted && remote && remote_match) ||
 823                    (remote_deleted && head && head_match)) {
 824                        if (index)
 825                                return deleted_entry(index, index, o);
 826                        if (ce && !head_deleted) {
 827                                if (verify_absent(ce, "removed", o))
 828                                        return -1;
 829                        }
 830                        return 0;
 831                }
 832                /*
 833                 * Added in both, identically.
 834                 */
 835                if (no_anc_exists && head && remote && same(head, remote))
 836                        return merged_entry(head, index, o);
 837
 838        }
 839
 840        /* Below are "no merge" cases, which require that the index be
 841         * up-to-date to avoid the files getting overwritten with
 842         * conflict resolution files.
 843         */
 844        if (index) {
 845                if (verify_uptodate(index, o))
 846                        return -1;
 847        }
 848
 849        o->nontrivial_merge = 1;
 850
 851        /* #2, #3, #4, #6, #7, #9, #10, #11. */
 852        count = 0;
 853        if (!head_match || !remote_match) {
 854                for (i = 1; i < o->head_idx; i++) {
 855                        if (stages[i] && stages[i] != o->df_conflict_entry) {
 856                                keep_entry(stages[i], o);
 857                                count++;
 858                                break;
 859                        }
 860                }
 861        }
 862#if DBRT_DEBUG
 863        else {
 864                fprintf(stderr, "read-tree: warning #16 detected\n");
 865                show_stage_entry(stderr, "head   ", stages[head_match]);
 866                show_stage_entry(stderr, "remote ", stages[remote_match]);
 867        }
 868#endif
 869        if (head) { count += keep_entry(head, o); }
 870        if (remote) { count += keep_entry(remote, o); }
 871        return count;
 872}
 873
 874/*
 875 * Two-way merge.
 876 *
 877 * The rule is to "carry forward" what is in the index without losing
 878 * information across a "fast forward", favoring a successful merge
 879 * over a merge failure when it makes sense.  For details of the
 880 * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 881 *
 882 */
 883int twoway_merge(struct cache_entry **src, struct unpack_trees_options *o)
 884{
 885        struct cache_entry *current = src[0];
 886        struct cache_entry *oldtree = src[1];
 887        struct cache_entry *newtree = src[2];
 888
 889        if (o->merge_size != 2)
 890                return error("Cannot do a twoway merge of %d trees",
 891                             o->merge_size);
 892
 893        if (oldtree == o->df_conflict_entry)
 894                oldtree = NULL;
 895        if (newtree == o->df_conflict_entry)
 896                newtree = NULL;
 897
 898        if (current) {
 899                if ((!oldtree && !newtree) || /* 4 and 5 */
 900                    (!oldtree && newtree &&
 901                     same(current, newtree)) || /* 6 and 7 */
 902                    (oldtree && newtree &&
 903                     same(oldtree, newtree)) || /* 14 and 15 */
 904                    (oldtree && newtree &&
 905                     !same(oldtree, newtree) && /* 18 and 19 */
 906                     same(current, newtree))) {
 907                        return keep_entry(current, o);
 908                }
 909                else if (oldtree && !newtree && same(current, oldtree)) {
 910                        /* 10 or 11 */
 911                        return deleted_entry(oldtree, current, o);
 912                }
 913                else if (oldtree && newtree &&
 914                         same(current, oldtree) && !same(current, newtree)) {
 915                        /* 20 or 21 */
 916                        return merged_entry(newtree, current, o);
 917                }
 918                else {
 919                        /* all other failures */
 920                        if (oldtree)
 921                                return o->gently ? -1 : reject_merge(oldtree, o);
 922                        if (current)
 923                                return o->gently ? -1 : reject_merge(current, o);
 924                        if (newtree)
 925                                return o->gently ? -1 : reject_merge(newtree, o);
 926                        return -1;
 927                }
 928        }
 929        else if (newtree) {
 930                if (oldtree && !o->initial_checkout) {
 931                        /*
 932                         * deletion of the path was staged;
 933                         */
 934                        if (same(oldtree, newtree))
 935                                return 1;
 936                        return reject_merge(oldtree, o);
 937                }
 938                return merged_entry(newtree, current, o);
 939        }
 940        return deleted_entry(oldtree, current, o);
 941}
 942
 943/*
 944 * Bind merge.
 945 *
 946 * Keep the index entries at stage0, collapse stage1 but make sure
 947 * stage0 does not have anything there.
 948 */
 949int bind_merge(struct cache_entry **src,
 950                struct unpack_trees_options *o)
 951{
 952        struct cache_entry *old = src[0];
 953        struct cache_entry *a = src[1];
 954
 955        if (o->merge_size != 1)
 956                return error("Cannot do a bind merge of %d trees\n",
 957                             o->merge_size);
 958        if (a && old)
 959                return o->gently ? -1 :
 960                        error(ERRORMSG(o, bind_overlap), a->name, old->name);
 961        if (!a)
 962                return keep_entry(old, o);
 963        else
 964                return merged_entry(a, NULL, o);
 965}
 966
 967/*
 968 * One-way merge.
 969 *
 970 * The rule is:
 971 * - take the stat information from stage0, take the data from stage1
 972 */
 973int oneway_merge(struct cache_entry **src, struct unpack_trees_options *o)
 974{
 975        struct cache_entry *old = src[0];
 976        struct cache_entry *a = src[1];
 977
 978        if (o->merge_size != 1)
 979                return error("Cannot do a oneway merge of %d trees",
 980                             o->merge_size);
 981
 982        if (!a)
 983                return deleted_entry(old, old, o);
 984
 985        if (old && same(old, a)) {
 986                int update = 0;
 987                if (o->reset) {
 988                        struct stat st;
 989                        if (lstat(old->name, &st) ||
 990                            ie_match_stat(o->src_index, old, &st, CE_MATCH_IGNORE_VALID))
 991                                update |= CE_UPDATE;
 992                }
 993                add_entry(o, old, update, 0);
 994                return 0;
 995        }
 996        return merged_entry(a, old, o);
 997}