unpack-trees.c

   1 #define NO_THE_INDEX_COMPATIBILITY_MACROS
   2 #include "cache.h"
   3 #include "argv-array.h"
   4 #include "repository.h"
   5 #include "config.h"
   6 #include "dir.h"
   7 #include "tree.h"
   8 #include "tree-walk.h"
   9 #include "cache-tree.h"
  10 #include "unpack-trees.h"
  11 #include "progress.h"
  12 #include "refs.h"
  13 #include "attr.h"
  14 #include "split-index.h"
  15 #include "dir.h"
  16 #include "submodule.h"
  17 #include "submodule-config.h"
  18 #include "fsmonitor.h"
  19 #include "fetch-object.h"
  20
  21 /*
  22  * Error messages expected by scripts out of plumbing commands such as
  23  * read-tree.  Non-scripted Porcelain is not required to use these messages
  24  * and in fact are encouraged to reword them to better suit their particular
  25  * situation better.  See how "git checkout" and "git merge" replaces
  26  * them using setup_unpack_trees_porcelain(), for example.
  27  */
  28 static const char *unpack_plumbing_errors[NB_UNPACK_TREES_ERROR_TYPES] = {
  29         /* ERROR_WOULD_OVERWRITE */
  30         "Entry '%s' would be overwritten by merge. Cannot merge.",
  31
  32         /* ERROR_NOT_UPTODATE_FILE */
  33         "Entry '%s' not uptodate. Cannot merge.",
  34
  35         /* ERROR_NOT_UPTODATE_DIR */
  36         "Updating '%s' would lose untracked files in it",
  37
  38         /* ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN */
  39         "Untracked working tree file '%s' would be overwritten by merge.",
  40
  41         /* ERROR_WOULD_LOSE_UNTRACKED_REMOVED */
  42         "Untracked working tree file '%s' would be removed by merge.",
  43
  44         /* ERROR_BIND_OVERLAP */
  45         "Entry '%s' overlaps with '%s'.  Cannot bind.",
  46
  47         /* ERROR_SPARSE_NOT_UPTODATE_FILE */
  48         "Entry '%s' not uptodate. Cannot update sparse checkout.",
  49
  50         /* ERROR_WOULD_LOSE_ORPHANED_OVERWRITTEN */
  51         "Working tree file '%s' would be overwritten by sparse checkout update.",
  52
  53         /* ERROR_WOULD_LOSE_ORPHANED_REMOVED */
  54         "Working tree file '%s' would be removed by sparse checkout update.",
  55
  56         /* ERROR_WOULD_LOSE_SUBMODULE */
  57         "Submodule '%s' cannot checkout new HEAD.",
  58 };
  59
  60 #define ERRORMSG(o,type) \
  61         ( ((o) && (o)->msgs[(type)]) \
  62           ? ((o)->msgs[(type)])      \
  63           : (unpack_plumbing_errors[(type)]) )
  64
  65 static const char *super_prefixed(const char *path)
  66 {
  67         /*
  68          * It is necessary and sufficient to have two static buffers
  69          * here, as the return value of this function is fed to
  70          * error() using the unpack_*_errors[] templates we see above.
  71          */
  72         static struct strbuf buf[2] = {STRBUF_INIT, STRBUF_INIT};
  73         static int super_prefix_len = -1;
  74         static unsigned idx = ARRAY_SIZE(buf) - 1;
  75
  76         if (super_prefix_len < 0) {
  77                 const char *super_prefix = get_super_prefix();
  78                 if (!super_prefix) {
  79                         super_prefix_len = 0;
  80                 } else {
  81                         int i;
  82                         for (i = 0; i < ARRAY_SIZE(buf); i++)
  83                                 strbuf_addstr(&buf[i], super_prefix);
  84                         super_prefix_len = buf[0].len;
  85                 }
  86         }
  87
  88         if (!super_prefix_len)
  89                 return path;
  90
  91         if (++idx >= ARRAY_SIZE(buf))
  92                 idx = 0;
  93
  94         strbuf_setlen(&buf[idx], super_prefix_len);
  95         strbuf_addstr(&buf[idx], path);
  96
  97         return buf[idx].buf;
  98 }
  99
 100 void setup_unpack_trees_porcelain(struct unpack_trees_options *opts,
 101                                   const char *cmd)
 102 {
 103         int i;
 104         const char **msgs = opts->msgs;
 105         const char *msg;
 106
 107         argv_array_init(&opts->msgs_to_free);
 108
 109         if (!strcmp(cmd, "checkout"))
 110                 msg = advice_commit_before_merge
 111                       ? _("Your local changes to the following files would be overwritten by checkout:\n%%s"
 112                           "Please commit your changes or stash them before you switch branches.")
 113                       : _("Your local changes to the following files would be overwritten by checkout:\n%%s");
 114         else if (!strcmp(cmd, "merge"))
 115                 msg = advice_commit_before_merge
 116                       ? _("Your local changes to the following files would be overwritten by merge:\n%%s"
 117                           "Please commit your changes or stash them before you merge.")
 118                       : _("Your local changes to the following files would be overwritten by merge:\n%%s");
 119         else
 120                 msg = advice_commit_before_merge
 121                       ? _("Your local changes to the following files would be overwritten by %s:\n%%s"
 122                           "Please commit your changes or stash them before you %s.")
 123                       : _("Your local changes to the following files would be overwritten by %s:\n%%s");
 124         msgs[ERROR_WOULD_OVERWRITE] = msgs[ERROR_NOT_UPTODATE_FILE] =
 125                 argv_array_pushf(&opts->msgs_to_free, msg, cmd, cmd);
 126
 127         msgs[ERROR_NOT_UPTODATE_DIR] =
 128                 _("Updating the following directories would lose untracked files in them:\n%s");
 129
 130         if (!strcmp(cmd, "checkout"))
 131                 msg = advice_commit_before_merge
 132                       ? _("The following untracked working tree files would be removed by checkout:\n%%s"
 133                           "Please move or remove them before you switch branches.")
 134                       : _("The following untracked working tree files would be removed by checkout:\n%%s");
 135         else if (!strcmp(cmd, "merge"))
 136                 msg = advice_commit_before_merge
 137                       ? _("The following untracked working tree files would be removed by merge:\n%%s"
 138                           "Please move or remove them before you merge.")
 139                       : _("The following untracked working tree files would be removed by merge:\n%%s");
 140         else
 141                 msg = advice_commit_before_merge
 142                       ? _("The following untracked working tree files would be removed by %s:\n%%s"
 143                           "Please move or remove them before you %s.")
 144                       : _("The following untracked working tree files would be removed by %s:\n%%s");
 145         msgs[ERROR_WOULD_LOSE_UNTRACKED_REMOVED] =
 146                 argv_array_pushf(&opts->msgs_to_free, msg, cmd, cmd);
 147
 148         if (!strcmp(cmd, "checkout"))
 149                 msg = advice_commit_before_merge
 150                       ? _("The following untracked working tree files would be overwritten by checkout:\n%%s"
 151                           "Please move or remove them before you switch branches.")
 152                       : _("The following untracked working tree files would be overwritten by checkout:\n%%s");
 153         else if (!strcmp(cmd, "merge"))
 154                 msg = advice_commit_before_merge
 155                       ? _("The following untracked working tree files would be overwritten by merge:\n%%s"
 156                           "Please move or remove them before you merge.")
 157                       : _("The following untracked working tree files would be overwritten by merge:\n%%s");
 158         else
 159                 msg = advice_commit_before_merge
 160                       ? _("The following untracked working tree files would be overwritten by %s:\n%%s"
 161                           "Please move or remove them before you %s.")
 162                       : _("The following untracked working tree files would be overwritten by %s:\n%%s");
 163         msgs[ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN] =
 164                 argv_array_pushf(&opts->msgs_to_free, msg, cmd, cmd);
 165
 166         /*
 167          * Special case: ERROR_BIND_OVERLAP refers to a pair of paths, we
 168          * cannot easily display it as a list.
 169          */
 170         msgs[ERROR_BIND_OVERLAP] = _("Entry '%s' overlaps with '%s'.  Cannot bind.");
 171
 172         msgs[ERROR_SPARSE_NOT_UPTODATE_FILE] =
 173                 _("Cannot update sparse checkout: the following entries are not up to date:\n%s");
 174         msgs[ERROR_WOULD_LOSE_ORPHANED_OVERWRITTEN] =
 175                 _("The following working tree files would be overwritten by sparse checkout update:\n%s");
 176         msgs[ERROR_WOULD_LOSE_ORPHANED_REMOVED] =
 177                 _("The following working tree files would be removed by sparse checkout update:\n%s");
 178         msgs[ERROR_WOULD_LOSE_SUBMODULE] =
 179                 _("Cannot update submodule:\n%s");
 180
 181         opts->show_all_errors = 1;
 182         /* rejected paths may not have a static buffer */
 183         for (i = 0; i < ARRAY_SIZE(opts->unpack_rejects); i++)
 184                 opts->unpack_rejects[i].strdup_strings = 1;
 185 }
 186
 187 void clear_unpack_trees_porcelain(struct unpack_trees_options *opts)
 188 {
 189         argv_array_clear(&opts->msgs_to_free);
 190         memset(opts->msgs, 0, sizeof(opts->msgs));
 191 }
 192
 193 static int do_add_entry(struct unpack_trees_options *o, struct cache_entry *ce,
 194                          unsigned int set, unsigned int clear)
 195 {
 196         clear |= CE_HASHED;
 197
 198         if (set & CE_REMOVE)
 199                 set |= CE_WT_REMOVE;
 200
 201         ce->ce_flags = (ce->ce_flags & ~clear) | set;
 202         return add_index_entry(&o->result, ce,
 203                                ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
 204 }
 205
 206 static struct cache_entry *dup_entry(const struct cache_entry *ce)
 207 {
 208         unsigned int size = ce_size(ce);
 209         struct cache_entry *new_entry = xmalloc(size);
 210
 211         memcpy(new_entry, ce, size);
 212         return new_entry;
 213 }
 214
 215 static void add_entry(struct unpack_trees_options *o,
 216                       const struct cache_entry *ce,
 217                       unsigned int set, unsigned int clear)
 218 {
 219         do_add_entry(o, dup_entry(ce), set, clear);
 220 }
 221
 222 /*
 223  * add error messages on path <path>
 224  * corresponding to the type <e> with the message <msg>
 225  * indicating if it should be display in porcelain or not
 226  */
 227 static int add_rejected_path(struct unpack_trees_options *o,
 228                              enum unpack_trees_error_types e,
 229                              const char *path)
 230 {
 231         if (!o->show_all_errors)
 232                 return error(ERRORMSG(o, e), super_prefixed(path));
 233
 234         /*
 235          * Otherwise, insert in a list for future display by
 236          * display_error_msgs()
 237          */
 238         string_list_append(&o->unpack_rejects[e], path);
 239         return -1;
 240 }
 241
 242 /*
 243  * display all the error messages stored in a nice way
 244  */
 245 static void display_error_msgs(struct unpack_trees_options *o)
 246 {
 247         int e, i;
 248         int something_displayed = 0;
 249         for (e = 0; e < NB_UNPACK_TREES_ERROR_TYPES; e++) {
 250                 struct string_list *rejects = &o->unpack_rejects[e];
 251                 if (rejects->nr > 0) {
 252                         struct strbuf path = STRBUF_INIT;
 253                         something_displayed = 1;
 254                         for (i = 0; i < rejects->nr; i++)
 255                                 strbuf_addf(&path, "\t%s\n", rejects->items[i].string);
 256                         error(ERRORMSG(o, e), super_prefixed(path.buf));
 257                         strbuf_release(&path);
 258                 }
 259                 string_list_clear(rejects, 0);
 260         }
 261         if (something_displayed)
 262                 fprintf(stderr, _("Aborting\n"));
 263 }
 264
 265 static int check_submodule_move_head(const struct cache_entry *ce,
 266                                      const char *old_id,
 267                                      const char *new_id,
 268                                      struct unpack_trees_options *o)
 269 {
 270         unsigned flags = SUBMODULE_MOVE_HEAD_DRY_RUN;
 271         const struct submodule *sub = submodule_from_ce(ce);
 272
 273         if (!sub)
 274                 return 0;
 275
 276         if (o->reset)
 277                 flags |= SUBMODULE_MOVE_HEAD_FORCE;
 278
 279         if (submodule_move_head(ce->name, old_id, new_id, flags))
 280                 return o->gently ? -1 :
 281                                    add_rejected_path(o, ERROR_WOULD_LOSE_SUBMODULE, ce->name);
 282         return 0;
 283 }
 284
 285 /*
 286  * Preform the loading of the repository's gitmodules file.  This function is
 287  * used by 'check_update()' to perform loading of the gitmodules file in two
 288  * differnt situations:
 289  * (1) before removing entries from the working tree if the gitmodules file has
 290  *     been marked for removal.  This situation is specified by 'state' == NULL.
 291  * (2) before checking out entries to the working tree if the gitmodules file
 292  *     has been marked for update.  This situation is specified by 'state' != NULL.
 293  */
 294 static void load_gitmodules_file(struct index_state *index,
 295                                  struct checkout *state)
 296 {
 297         int pos = index_name_pos(index, GITMODULES_FILE, strlen(GITMODULES_FILE));
 298
 299         if (pos >= 0) {
 300                 struct cache_entry *ce = index->cache[pos];
 301                 if (!state && ce->ce_flags & CE_WT_REMOVE) {
 302                         repo_read_gitmodules(the_repository);
 303                 } else if (state && (ce->ce_flags & CE_UPDATE)) {
 304                         submodule_free(the_repository);
 305                         checkout_entry(ce, state, NULL);
 306                         repo_read_gitmodules(the_repository);
 307                 }
 308         }
 309 }
 310
 311 /*
 312  * Unlink the last component and schedule the leading directories for
 313  * removal, such that empty directories get removed.
 314  */
 315 static void unlink_entry(const struct cache_entry *ce)
 316 {
 317         const struct submodule *sub = submodule_from_ce(ce);
 318         if (sub) {
 319                 /* state.force is set at the caller. */
 320                 submodule_move_head(ce->name, "HEAD", NULL,
 321                                     SUBMODULE_MOVE_HEAD_FORCE);
 322         }
 323         if (!check_leading_path(ce->name, ce_namelen(ce)))
 324                 return;
 325         if (remove_or_warn(ce->ce_mode, ce->name))
 326                 return;
 327         schedule_dir_for_removal(ce->name, ce_namelen(ce));
 328 }
 329
 330 static struct progress *get_progress(struct unpack_trees_options *o)
 331 {
 332         unsigned cnt = 0, total = 0;
 333         struct index_state *index = &o->result;
 334
 335         if (!o->update || !o->verbose_update)
 336                 return NULL;
 337
 338         for (; cnt < index->cache_nr; cnt++) {
 339                 const struct cache_entry *ce = index->cache[cnt];
 340                 if (ce->ce_flags & (CE_UPDATE | CE_WT_REMOVE))
 341                         total++;
 342         }
 343
 344         return start_delayed_progress(_("Checking out files"), total);
 345 }
 346
 347 static int check_updates(struct unpack_trees_options *o)
 348 {
 349         unsigned cnt = 0;
 350         int errs = 0;
 351         struct progress *progress = NULL;
 352         struct index_state *index = &o->result;
 353         struct checkout state = CHECKOUT_INIT;
 354         int i;
 355
 356         state.force = 1;
 357         state.quiet = 1;
 358         state.refresh_cache = 1;
 359         state.istate = index;
 360
 361         progress = get_progress(o);
 362
 363         if (o->update)
 364                 git_attr_set_direction(GIT_ATTR_CHECKOUT, index);
 365
 366         if (should_update_submodules() && o->update && !o->dry_run)
 367                 load_gitmodules_file(index, NULL);
 368
 369         for (i = 0; i < index->cache_nr; i++) {
 370                 const struct cache_entry *ce = index->cache[i];
 371
 372                 if (ce->ce_flags & CE_WT_REMOVE) {
 373                         display_progress(progress, ++cnt);
 374                         if (o->update && !o->dry_run)
 375                                 unlink_entry(ce);
 376                 }
 377         }
 378         remove_marked_cache_entries(index);
 379         remove_scheduled_dirs();
 380
 381         if (should_update_submodules() && o->update && !o->dry_run)
 382                 load_gitmodules_file(index, &state);
 383
 384         enable_delayed_checkout(&state);
 385         if (repository_format_partial_clone && o->update && !o->dry_run) {
 386                 /*
 387                  * Prefetch the objects that are to be checked out in the loop
 388                  * below.
 389                  */
 390                 struct oid_array to_fetch = OID_ARRAY_INIT;
 391                 int fetch_if_missing_store = fetch_if_missing;
 392                 fetch_if_missing = 0;
 393                 for (i = 0; i < index->cache_nr; i++) {
 394                         struct cache_entry *ce = index->cache[i];
 395                         if ((ce->ce_flags & CE_UPDATE) &&
 396                             !S_ISGITLINK(ce->ce_mode)) {
 397                                 if (!has_object_file(&ce->oid))
 398                                         oid_array_append(&to_fetch, &ce->oid);
 399                         }
 400                 }
 401                 if (to_fetch.nr)
 402                         fetch_objects(repository_format_partial_clone,
 403                                       &to_fetch);
 404                 fetch_if_missing = fetch_if_missing_store;
 405                 oid_array_clear(&to_fetch);
 406         }
 407         for (i = 0; i < index->cache_nr; i++) {
 408                 struct cache_entry *ce = index->cache[i];
 409
 410                 if (ce->ce_flags & CE_UPDATE) {
 411                         if (ce->ce_flags & CE_WT_REMOVE)
 412                                 BUG("both update and delete flags are set on %s",
 413                                     ce->name);
 414                         display_progress(progress, ++cnt);
 415                         ce->ce_flags &= ~CE_UPDATE;
 416                         if (o->update && !o->dry_run) {
 417                                 errs |= checkout_entry(ce, &state, NULL);
 418                         }
 419                 }
 420         }
 421         stop_progress(&progress);
 422         errs |= finish_delayed_checkout(&state);
 423         if (o->update)
 424                 git_attr_set_direction(GIT_ATTR_CHECKIN, NULL);
 425         return errs != 0;
 426 }
 427
 428 static int verify_uptodate_sparse(const struct cache_entry *ce,
 429                                   struct unpack_trees_options *o);
 430 static int verify_absent_sparse(const struct cache_entry *ce,
 431                                 enum unpack_trees_error_types,
 432                                 struct unpack_trees_options *o);
 433
 434 static int apply_sparse_checkout(struct index_state *istate,
 435                                  struct cache_entry *ce,
 436                                  struct unpack_trees_options *o)
 437 {
 438         int was_skip_worktree = ce_skip_worktree(ce);
 439
 440         if (ce->ce_flags & CE_NEW_SKIP_WORKTREE)
 441                 ce->ce_flags |= CE_SKIP_WORKTREE;
 442         else
 443                 ce->ce_flags &= ~CE_SKIP_WORKTREE;
 444         if (was_skip_worktree != ce_skip_worktree(ce)) {
 445                 ce->ce_flags |= CE_UPDATE_IN_BASE;
 446                 mark_fsmonitor_invalid(istate, ce);
 447                 istate->cache_changed |= CE_ENTRY_CHANGED;
 448         }
 449
 450         /*
 451          * if (!was_skip_worktree && !ce_skip_worktree()) {
 452          *      This is perfectly normal. Move on;
 453          * }
 454          */
 455
 456         /*
 457          * Merge strategies may set CE_UPDATE|CE_REMOVE outside checkout
 458          * area as a result of ce_skip_worktree() shortcuts in
 459          * verify_absent() and verify_uptodate().
 460          * Make sure they don't modify worktree if they are already
 461          * outside checkout area
 462          */
 463         if (was_skip_worktree && ce_skip_worktree(ce)) {
 464                 ce->ce_flags &= ~CE_UPDATE;
 465
 466                 /*
 467                  * By default, when CE_REMOVE is on, CE_WT_REMOVE is also
 468                  * on to get that file removed from both index and worktree.
 469                  * If that file is already outside worktree area, don't
 470                  * bother remove it.
 471                  */
 472                 if (ce->ce_flags & CE_REMOVE)
 473                         ce->ce_flags &= ~CE_WT_REMOVE;
 474         }
 475
 476         if (!was_skip_worktree && ce_skip_worktree(ce)) {
 477                 /*
 478                  * If CE_UPDATE is set, verify_uptodate() must be called already
 479                  * also stat info may have lost after merged_entry() so calling
 480                  * verify_uptodate() again may fail
 481                  */
 482                 if (!(ce->ce_flags & CE_UPDATE) && verify_uptodate_sparse(ce, o))
 483                         return -1;
 484                 ce->ce_flags |= CE_WT_REMOVE;
 485                 ce->ce_flags &= ~CE_UPDATE;
 486         }
 487         if (was_skip_worktree && !ce_skip_worktree(ce)) {
 488                 if (verify_absent_sparse(ce, ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN, o))
 489                         return -1;
 490                 ce->ce_flags |= CE_UPDATE;
 491         }
 492         return 0;
 493 }
 494
 495 static inline int call_unpack_fn(const struct cache_entry * const *src,
 496                                  struct unpack_trees_options *o)
 497 {
 498         int ret = o->fn(src, o);
 499         if (ret > 0)
 500                 ret = 0;
 501         return ret;
 502 }
 503
 504 static void mark_ce_used(struct cache_entry *ce, struct unpack_trees_options *o)
 505 {
 506         ce->ce_flags |= CE_UNPACKED;
 507
 508         if (o->cache_bottom < o->src_index->cache_nr &&
 509             o->src_index->cache[o->cache_bottom] == ce) {
 510                 int bottom = o->cache_bottom;
 511                 while (bottom < o->src_index->cache_nr &&
 512                        o->src_index->cache[bottom]->ce_flags & CE_UNPACKED)
 513                         bottom++;
 514                 o->cache_bottom = bottom;
 515         }
 516 }
 517
 518 static void mark_all_ce_unused(struct index_state *index)
 519 {
 520         int i;
 521         for (i = 0; i < index->cache_nr; i++)
 522                 index->cache[i]->ce_flags &= ~(CE_UNPACKED | CE_ADDED | CE_NEW_SKIP_WORKTREE);
 523 }
 524
 525 static int locate_in_src_index(const struct cache_entry *ce,
 526                                struct unpack_trees_options *o)
 527 {
 528         struct index_state *index = o->src_index;
 529         int len = ce_namelen(ce);
 530         int pos = index_name_pos(index, ce->name, len);
 531         if (pos < 0)
 532                 pos = -1 - pos;
 533         return pos;
 534 }
 535
 536 /*
 537  * We call unpack_index_entry() with an unmerged cache entry
 538  * only in diff-index, and it wants a single callback.  Skip
 539  * the other unmerged entry with the same name.
 540  */
 541 static void mark_ce_used_same_name(struct cache_entry *ce,
 542                                    struct unpack_trees_options *o)
 543 {
 544         struct index_state *index = o->src_index;
 545         int len = ce_namelen(ce);
 546         int pos;
 547
 548         for (pos = locate_in_src_index(ce, o); pos < index->cache_nr; pos++) {
 549                 struct cache_entry *next = index->cache[pos];
 550                 if (len != ce_namelen(next) ||
 551                     memcmp(ce->name, next->name, len))
 552                         break;
 553                 mark_ce_used(next, o);
 554         }
 555 }
 556
 557 static struct cache_entry *next_cache_entry(struct unpack_trees_options *o)
 558 {
 559         const struct index_state *index = o->src_index;
 560         int pos = o->cache_bottom;
 561
 562         while (pos < index->cache_nr) {
 563                 struct cache_entry *ce = index->cache[pos];
 564                 if (!(ce->ce_flags & CE_UNPACKED))
 565                         return ce;
 566                 pos++;
 567         }
 568         return NULL;
 569 }
 570
 571 static void add_same_unmerged(const struct cache_entry *ce,
 572                               struct unpack_trees_options *o)
 573 {
 574         struct index_state *index = o->src_index;
 575         int len = ce_namelen(ce);
 576         int pos = index_name_pos(index, ce->name, len);
 577
 578         if (0 <= pos)
 579                 die("programming error in a caller of mark_ce_used_same_name");
 580         for (pos = -pos - 1; pos < index->cache_nr; pos++) {
 581                 struct cache_entry *next = index->cache[pos];
 582                 if (len != ce_namelen(next) ||
 583                     memcmp(ce->name, next->name, len))
 584                         break;
 585                 add_entry(o, next, 0, 0);
 586                 mark_ce_used(next, o);
 587         }
 588 }
 589
 590 static int unpack_index_entry(struct cache_entry *ce,
 591                               struct unpack_trees_options *o)
 592 {
 593         const struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
 594         int ret;
 595
 596         src[0] = ce;
 597
 598         mark_ce_used(ce, o);
 599         if (ce_stage(ce)) {
 600                 if (o->skip_unmerged) {
 601                         add_entry(o, ce, 0, 0);
 602                         return 0;
 603                 }
 604         }
 605         ret = call_unpack_fn(src, o);
 606         if (ce_stage(ce))
 607                 mark_ce_used_same_name(ce, o);
 608         return ret;
 609 }
 610
 611 static int find_cache_pos(struct traverse_info *, const struct name_entry *);
 612
 613 static void restore_cache_bottom(struct traverse_info *info, int bottom)
 614 {
 615         struct unpack_trees_options *o = info->data;
 616
 617         if (o->diff_index_cached)
 618                 return;
 619         o->cache_bottom = bottom;
 620 }
 621
 622 static int switch_cache_bottom(struct traverse_info *info)
 623 {
 624         struct unpack_trees_options *o = info->data;
 625         int ret, pos;
 626
 627         if (o->diff_index_cached)
 628                 return 0;
 629         ret = o->cache_bottom;
 630         pos = find_cache_pos(info->prev, &info->name);
 631
 632         if (pos < -1)
 633                 o->cache_bottom = -2 - pos;
 634         else if (pos < 0)
 635                 o->cache_bottom = o->src_index->cache_nr;
 636         return ret;
 637 }
 638
 639 static inline int are_same_oid(struct name_entry *name_j, struct name_entry *name_k)
 640 {
 641         return name_j->oid && name_k->oid && !oidcmp(name_j->oid, name_k->oid);
 642 }
 643
 644 static int traverse_trees_recursive(int n, unsigned long dirmask,
 645                                     unsigned long df_conflicts,
 646                                     struct name_entry *names,
 647                                     struct traverse_info *info)
 648 {
 649         int i, ret, bottom;
 650         int nr_buf = 0;
 651         struct tree_desc t[MAX_UNPACK_TREES];
 652         void *buf[MAX_UNPACK_TREES];
 653         struct traverse_info newinfo;
 654         struct name_entry *p;
 655
 656         p = names;
 657         while (!p->mode)
 658                 p++;
 659
 660         newinfo = *info;
 661         newinfo.prev = info;
 662         newinfo.pathspec = info->pathspec;
 663         newinfo.name = *p;
 664         newinfo.pathlen += tree_entry_len(p) + 1;
 665         newinfo.df_conflicts |= df_conflicts;
 666
 667         /*
 668          * Fetch the tree from the ODB for each peer directory in the
 669          * n commits.
 670          *
 671          * For 2- and 3-way traversals, we try to avoid hitting the
 672          * ODB twice for the same OID.  This should yield a nice speed
 673          * up in checkouts and merges when the commits are similar.
 674          *
 675          * We don't bother doing the full O(n^2) search for larger n,
 676          * because wider traversals don't happen that often and we
 677          * avoid the search setup.
 678          *
 679          * When 2 peer OIDs are the same, we just copy the tree
 680          * descriptor data.  This implicitly borrows the buffer
 681          * data from the earlier cell.
 682          */
 683         for (i = 0; i < n; i++, dirmask >>= 1) {
 684                 if (i > 0 && are_same_oid(&names[i], &names[i - 1]))
 685                         t[i] = t[i - 1];
 686                 else if (i > 1 && are_same_oid(&names[i], &names[i - 2]))
 687                         t[i] = t[i - 2];
 688                 else {
 689                         const struct object_id *oid = NULL;
 690                         if (dirmask & 1)
 691                                 oid = names[i].oid;
 692                         buf[nr_buf++] = fill_tree_descriptor(t + i, oid);
 693                 }
 694         }
 695
 696         bottom = switch_cache_bottom(&newinfo);
 697         ret = traverse_trees(n, t, &newinfo);
 698         restore_cache_bottom(&newinfo, bottom);
 699
 700         for (i = 0; i < nr_buf; i++)
 701                 free(buf[i]);
 702
 703         return ret;
 704 }
 705
 706 /*
 707  * Compare the traverse-path to the cache entry without actually
 708  * having to generate the textual representation of the traverse
 709  * path.
 710  *
 711  * NOTE! This *only* compares up to the size of the traverse path
 712  * itself - the caller needs to do the final check for the cache
 713  * entry having more data at the end!
 714  */
 715 static int do_compare_entry_piecewise(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
 716 {
 717         int len, pathlen, ce_len;
 718         const char *ce_name;
 719
 720         if (info->prev) {
 721                 int cmp = do_compare_entry_piecewise(ce, info->prev,
 722                                                      &info->name);
 723                 if (cmp)
 724                         return cmp;
 725         }
 726         pathlen = info->pathlen;
 727         ce_len = ce_namelen(ce);
 728
 729         /* If ce_len < pathlen then we must have previously hit "name == directory" entry */
 730         if (ce_len < pathlen)
 731                 return -1;
 732
 733         ce_len -= pathlen;
 734         ce_name = ce->name + pathlen;
 735
 736         len = tree_entry_len(n);
 737         return df_name_compare(ce_name, ce_len, S_IFREG, n->path, len, n->mode);
 738 }
 739
 740 static int do_compare_entry(const struct cache_entry *ce,
 741                             const struct traverse_info *info,
 742                             const struct name_entry *n)
 743 {
 744         int len, pathlen, ce_len;
 745         const char *ce_name;
 746         int cmp;
 747
 748         /*
 749          * If we have not precomputed the traverse path, it is quicker
 750          * to avoid doing so.  But if we have precomputed it,
 751          * it is quicker to use the precomputed version.
 752          */
 753         if (!info->traverse_path)
 754                 return do_compare_entry_piecewise(ce, info, n);
 755
 756         cmp = strncmp(ce->name, info->traverse_path, info->pathlen);
 757         if (cmp)
 758                 return cmp;
 759
 760         pathlen = info->pathlen;
 761         ce_len = ce_namelen(ce);
 762
 763         if (ce_len < pathlen)
 764                 return -1;
 765
 766         ce_len -= pathlen;
 767         ce_name = ce->name + pathlen;
 768
 769         len = tree_entry_len(n);
 770         return df_name_compare(ce_name, ce_len, S_IFREG, n->path, len, n->mode);
 771 }
 772
 773 static int compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
 774 {
 775         int cmp = do_compare_entry(ce, info, n);
 776         if (cmp)
 777                 return cmp;
 778
 779         /*
 780          * Even if the beginning compared identically, the ce should
 781          * compare as bigger than a directory leading up to it!
 782          */
 783         return ce_namelen(ce) > traverse_path_len(info, n);
 784 }
 785
 786 static int ce_in_traverse_path(const struct cache_entry *ce,
 787                                const struct traverse_info *info)
 788 {
 789         if (!info->prev)
 790                 return 1;
 791         if (do_compare_entry(ce, info->prev, &info->name))
 792                 return 0;
 793         /*
 794          * If ce (blob) is the same name as the path (which is a tree
 795          * we will be descending into), it won't be inside it.
 796          */
 797         return (info->pathlen < ce_namelen(ce));
 798 }
 799
 800 static struct cache_entry *create_ce_entry(const struct traverse_info *info, const struct name_entry *n, int stage)
 801 {
 802         int len = traverse_path_len(info, n);
 803         struct cache_entry *ce = xcalloc(1, cache_entry_size(len));
 804
 805         ce->ce_mode = create_ce_mode(n->mode);
 806         ce->ce_flags = create_ce_flags(stage);
 807         ce->ce_namelen = len;
 808         oidcpy(&ce->oid, n->oid);
 809         make_traverse_path(ce->name, info, n);
 810
 811         return ce;
 812 }
 813
 814 static int unpack_nondirectories(int n, unsigned long mask,
 815                                  unsigned long dirmask,
 816                                  struct cache_entry **src,
 817                                  const struct name_entry *names,
 818                                  const struct traverse_info *info)
 819 {
 820         int i;
 821         struct unpack_trees_options *o = info->data;
 822         unsigned long conflicts = info->df_conflicts | dirmask;
 823
 824         /* Do we have *only* directories? Nothing to do */
 825         if (mask == dirmask && !src[0])
 826                 return 0;
 827
 828         /*
 829          * Ok, we've filled in up to any potential index entry in src[0],
 830          * now do the rest.
 831          */
 832         for (i = 0; i < n; i++) {
 833                 int stage;
 834                 unsigned int bit = 1ul << i;
 835                 if (conflicts & bit) {
 836                         src[i + o->merge] = o->df_conflict_entry;
 837                         continue;
 838                 }
 839                 if (!(mask & bit))
 840                         continue;
 841                 if (!o->merge)
 842                         stage = 0;
 843                 else if (i + 1 < o->head_idx)
 844                         stage = 1;
 845                 else if (i + 1 > o->head_idx)
 846                         stage = 3;
 847                 else
 848                         stage = 2;
 849                 src[i + o->merge] = create_ce_entry(info, names + i, stage);
 850         }
 851
 852         if (o->merge) {
 853                 int rc = call_unpack_fn((const struct cache_entry * const *)src,
 854                                         o);
 855                 for (i = 0; i < n; i++) {
 856                         struct cache_entry *ce = src[i + o->merge];
 857                         if (ce != o->df_conflict_entry)
 858                                 free(ce);
 859                 }
 860                 return rc;
 861         }
 862
 863         for (i = 0; i < n; i++)
 864                 if (src[i] && src[i] != o->df_conflict_entry)
 865                         if (do_add_entry(o, src[i], 0, 0))
 866                                 return -1;
 867
 868         return 0;
 869 }
 870
 871 static int unpack_failed(struct unpack_trees_options *o, const char *message)
 872 {
 873         discard_index(&o->result);
 874         if (!o->gently && !o->exiting_early) {
 875                 if (message)
 876                         return error("%s", message);
 877                 return -1;
 878         }
 879         return -1;
 880 }
 881
 882 /*
 883  * The tree traversal is looking at name p.  If we have a matching entry,
 884  * return it.  If name p is a directory in the index, do not return
 885  * anything, as we will want to match it when the traversal descends into
 886  * the directory.
 887  */
 888 static int find_cache_pos(struct traverse_info *info,
 889                           const struct name_entry *p)
 890 {
 891         int pos;
 892         struct unpack_trees_options *o = info->data;
 893         struct index_state *index = o->src_index;
 894         int pfxlen = info->pathlen;
 895         int p_len = tree_entry_len(p);
 896
 897         for (pos = o->cache_bottom; pos < index->cache_nr; pos++) {
 898                 const struct cache_entry *ce = index->cache[pos];
 899                 const char *ce_name, *ce_slash;
 900                 int cmp, ce_len;
 901
 902                 if (ce->ce_flags & CE_UNPACKED) {
 903                         /*
 904                          * cache_bottom entry is already unpacked, so
 905                          * we can never match it; don't check it
 906                          * again.
 907                          */
 908                         if (pos == o->cache_bottom)
 909                                 ++o->cache_bottom;
 910                         continue;
 911                 }
 912                 if (!ce_in_traverse_path(ce, info)) {
 913                         /*
 914                          * Check if we can skip future cache checks
 915                          * (because we're already past all possible
 916                          * entries in the traverse path).
 917                          */
 918                         if (info->traverse_path) {
 919                                 if (strncmp(ce->name, info->traverse_path,
 920                                             info->pathlen) > 0)
 921                                         break;
 922                         }
 923                         continue;
 924                 }
 925                 ce_name = ce->name + pfxlen;
 926                 ce_slash = strchr(ce_name, '/');
 927                 if (ce_slash)
 928                         ce_len = ce_slash - ce_name;
 929                 else
 930                         ce_len = ce_namelen(ce) - pfxlen;
 931                 cmp = name_compare(p->path, p_len, ce_name, ce_len);
 932                 /*
 933                  * Exact match; if we have a directory we need to
 934                  * delay returning it.
 935                  */
 936                 if (!cmp)
 937                         return ce_slash ? -2 - pos : pos;
 938                 if (0 < cmp)
 939                         continue; /* keep looking */
 940                 /*
 941                  * ce_name sorts after p->path; could it be that we
 942                  * have files under p->path directory in the index?
 943                  * E.g.  ce_name == "t-i", and p->path == "t"; we may
 944                  * have "t/a" in the index.
 945                  */
 946                 if (p_len < ce_len && !memcmp(ce_name, p->path, p_len) &&
 947                     ce_name[p_len] < '/')
 948                         continue; /* keep looking */
 949                 break;
 950         }
 951         return -1;
 952 }
 953
 954 static struct cache_entry *find_cache_entry(struct traverse_info *info,
 955                                             const struct name_entry *p)
 956 {
 957         int pos = find_cache_pos(info, p);
 958         struct unpack_trees_options *o = info->data;
 959
 960         if (0 <= pos)
 961                 return o->src_index->cache[pos];
 962         else
 963                 return NULL;
 964 }
 965
 966 static void debug_path(struct traverse_info *info)
 967 {
 968         if (info->prev) {
 969                 debug_path(info->prev);
 970                 if (*info->prev->name.path)
 971                         putchar('/');
 972         }
 973         printf("%s", info->name.path);
 974 }
 975
 976 static void debug_name_entry(int i, struct name_entry *n)
 977 {
 978         printf("ent#%d %06o %s\n", i,
 979                n->path ? n->mode : 0,
 980                n->path ? n->path : "(missing)");
 981 }
 982
 983 static void debug_unpack_callback(int n,
 984                                   unsigned long mask,
 985                                   unsigned long dirmask,
 986                                   struct name_entry *names,
 987                                   struct traverse_info *info)
 988 {
 989         int i;
 990         printf("* unpack mask %lu, dirmask %lu, cnt %d ",
 991                mask, dirmask, n);
 992         debug_path(info);
 993         putchar('\n');
 994         for (i = 0; i < n; i++)
 995                 debug_name_entry(i, names + i);
 996 }
 997
 998 static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *names, struct traverse_info *info)
 999 {
1000         struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
1001         struct unpack_trees_options *o = info->data;
1002         const struct name_entry *p = names;
1003
1004         /* Find first entry with a real name (we could use "mask" too) */
1005         while (!p->mode)
1006                 p++;
1007
1008         if (o->debug_unpack)
1009                 debug_unpack_callback(n, mask, dirmask, names, info);
1010
1011         /* Are we supposed to look at the index too? */
1012         if (o->merge) {
1013                 while (1) {
1014                         int cmp;
1015                         struct cache_entry *ce;
1016
1017                         if (o->diff_index_cached)
1018                                 ce = next_cache_entry(o);
1019                         else
1020                                 ce = find_cache_entry(info, p);
1021
1022                         if (!ce)
1023                                 break;
1024                         cmp = compare_entry(ce, info, p);
1025                         if (cmp < 0) {
1026                                 if (unpack_index_entry(ce, o) < 0)
1027                                         return unpack_failed(o, NULL);
1028                                 continue;
1029                         }
1030                         if (!cmp) {
1031                                 if (ce_stage(ce)) {
1032                                         /*
1033                                          * If we skip unmerged index
1034                                          * entries, we'll skip this
1035                                          * entry *and* the tree
1036                                          * entries associated with it!
1037                                          */
1038                                         if (o->skip_unmerged) {
1039                                                 add_same_unmerged(ce, o);
1040                                                 return mask;
1041                                         }
1042                                 }
1043                                 src[0] = ce;
1044                         }
1045                         break;
1046                 }
1047         }
1048
1049         if (unpack_nondirectories(n, mask, dirmask, src, names, info) < 0)
1050                 return -1;
1051
1052         if (o->merge && src[0]) {
1053                 if (ce_stage(src[0]))
1054                         mark_ce_used_same_name(src[0], o);
1055                 else
1056                         mark_ce_used(src[0], o);
1057         }
1058
1059         /* Now handle any directories.. */
1060         if (dirmask) {
1061                 /* special case: "diff-index --cached" looking at a tree */
1062                 if (o->diff_index_cached &&
1063                     n == 1 && dirmask == 1 && S_ISDIR(names->mode)) {
1064                         int matches;
1065                         matches = cache_tree_matches_traversal(o->src_index->cache_tree,
1066                                                                names, info);
1067                         /*
1068                          * Everything under the name matches; skip the
1069                          * entire hierarchy.  diff_index_cached codepath
1070                          * special cases D/F conflicts in such a way that
1071                          * it does not do any look-ahead, so this is safe.
1072                          */
1073                         if (matches) {
1074                                 o->cache_bottom += matches;
1075                                 return mask;
1076                         }
1077                 }
1078
1079                 if (traverse_trees_recursive(n, dirmask, mask & ~dirmask,
1080                                              names, info) < 0)
1081                         return -1;
1082                 return mask;
1083         }
1084
1085         return mask;
1086 }
1087
1088 static int clear_ce_flags_1(struct cache_entry **cache, int nr,
1089                             struct strbuf *prefix,
1090                             int select_mask, int clear_mask,
1091                             struct exclude_list *el, int defval);
1092
1093 /* Whole directory matching */
1094 static int clear_ce_flags_dir(struct cache_entry **cache, int nr,
1095                               struct strbuf *prefix,
1096                               char *basename,
1097                               int select_mask, int clear_mask,
1098                               struct exclude_list *el, int defval)
1099 {
1100         struct cache_entry **cache_end;
1101         int dtype = DT_DIR;
1102         int ret = is_excluded_from_list(prefix->buf, prefix->len,
1103                                         basename, &dtype, el, &the_index);
1104         int rc;
1105
1106         strbuf_addch(prefix, '/');
1107
1108         /* If undecided, use matching result of parent dir in defval */
1109         if (ret < 0)
1110                 ret = defval;
1111
1112         for (cache_end = cache; cache_end != cache + nr; cache_end++) {
1113                 struct cache_entry *ce = *cache_end;
1114                 if (strncmp(ce->name, prefix->buf, prefix->len))
1115                         break;
1116         }
1117
1118         /*
1119          * TODO: check el, if there are no patterns that may conflict
1120          * with ret (iow, we know in advance the incl/excl
1121          * decision for the entire directory), clear flag here without
1122          * calling clear_ce_flags_1(). That function will call
1123          * the expensive is_excluded_from_list() on every entry.
1124          */
1125         rc = clear_ce_flags_1(cache, cache_end - cache,
1126                               prefix,
1127                               select_mask, clear_mask,
1128                               el, ret);
1129         strbuf_setlen(prefix, prefix->len - 1);
1130         return rc;
1131 }
1132
1133 /*
1134  * Traverse the index, find every entry that matches according to
1135  * o->el. Do "ce_flags &= ~clear_mask" on those entries. Return the
1136  * number of traversed entries.
1137  *
1138  * If select_mask is non-zero, only entries whose ce_flags has on of
1139  * those bits enabled are traversed.
1140  *
1141  * cache        : pointer to an index entry
1142  * prefix_len   : an offset to its path
1143  *
1144  * The current path ("prefix") including the trailing '/' is
1145  *   cache[0]->name[0..(prefix_len-1)]
1146  * Top level path has prefix_len zero.
1147  */
1148 static int clear_ce_flags_1(struct cache_entry **cache, int nr,
1149                             struct strbuf *prefix,
1150                             int select_mask, int clear_mask,
1151                             struct exclude_list *el, int defval)
1152 {
1153         struct cache_entry **cache_end = cache + nr;
1154
1155         /*
1156          * Process all entries that have the given prefix and meet
1157          * select_mask condition
1158          */
1159         while(cache != cache_end) {
1160                 struct cache_entry *ce = *cache;
1161                 const char *name, *slash;
1162                 int len, dtype, ret;
1163
1164                 if (select_mask && !(ce->ce_flags & select_mask)) {
1165                         cache++;
1166                         continue;
1167                 }
1168
1169                 if (prefix->len && strncmp(ce->name, prefix->buf, prefix->len))
1170                         break;
1171
1172                 name = ce->name + prefix->len;
1173                 slash = strchr(name, '/');
1174
1175                 /* If it's a directory, try whole directory match first */
1176                 if (slash) {
1177                         int processed;
1178
1179                         len = slash - name;
1180                         strbuf_add(prefix, name, len);
1181
1182                         processed = clear_ce_flags_dir(cache, cache_end - cache,
1183                                                        prefix,
1184                                                        prefix->buf + prefix->len - len,
1185                                                        select_mask, clear_mask,
1186                                                        el, defval);
1187
1188                         /* clear_c_f_dir eats a whole dir already? */
1189                         if (processed) {
1190                                 cache += processed;
1191                                 strbuf_setlen(prefix, prefix->len - len);
1192                                 continue;
1193                         }
1194
1195                         strbuf_addch(prefix, '/');
1196                         cache += clear_ce_flags_1(cache, cache_end - cache,
1197                                                   prefix,
1198                                                   select_mask, clear_mask, el, defval);
1199                         strbuf_setlen(prefix, prefix->len - len - 1);
1200                         continue;
1201                 }
1202
1203                 /* Non-directory */
1204                 dtype = ce_to_dtype(ce);
1205                 ret = is_excluded_from_list(ce->name, ce_namelen(ce),
1206                                             name, &dtype, el, &the_index);
1207                 if (ret < 0)
1208                         ret = defval;
1209                 if (ret > 0)
1210                         ce->ce_flags &= ~clear_mask;
1211                 cache++;
1212         }
1213         return nr - (cache_end - cache);
1214 }
1215
1216 static int clear_ce_flags(struct cache_entry **cache, int nr,
1217                             int select_mask, int clear_mask,
1218                             struct exclude_list *el)
1219 {
1220         static struct strbuf prefix = STRBUF_INIT;
1221
1222         strbuf_reset(&prefix);
1223
1224         return clear_ce_flags_1(cache, nr,
1225                                 &prefix,
1226                                 select_mask, clear_mask,
1227                                 el, 0);
1228 }
1229
1230 /*
1231  * Set/Clear CE_NEW_SKIP_WORKTREE according to $GIT_DIR/info/sparse-checkout
1232  */
1233 static void mark_new_skip_worktree(struct exclude_list *el,
1234                                    struct index_state *the_index,
1235                                    int select_flag, int skip_wt_flag)
1236 {
1237         int i;
1238
1239         /*
1240          * 1. Pretend the narrowest worktree: only unmerged entries
1241          * are checked out
1242          */
1243         for (i = 0; i < the_index->cache_nr; i++) {
1244                 struct cache_entry *ce = the_index->cache[i];
1245
1246                 if (select_flag && !(ce->ce_flags & select_flag))
1247                         continue;
1248
1249                 if (!ce_stage(ce))
1250                         ce->ce_flags |= skip_wt_flag;
1251                 else
1252                         ce->ce_flags &= ~skip_wt_flag;
1253         }
1254
1255         /*
1256          * 2. Widen worktree according to sparse-checkout file.
1257          * Matched entries will have skip_wt_flag cleared (i.e. "in")
1258          */
1259         clear_ce_flags(the_index->cache, the_index->cache_nr,
1260                        select_flag, skip_wt_flag, el);
1261 }
1262
1263 static int verify_absent(const struct cache_entry *,
1264                          enum unpack_trees_error_types,
1265                          struct unpack_trees_options *);
1266 /*
1267  * N-way merge "len" trees.  Returns 0 on success, -1 on failure to manipulate the
1268  * resulting index, -2 on failure to reflect the changes to the work tree.
1269  *
1270  * CE_ADDED, CE_UNPACKED and CE_NEW_SKIP_WORKTREE are used internally
1271  */
1272 int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
1273 {
1274         int i, ret;
1275         static struct cache_entry *dfc;
1276         struct exclude_list el;
1277
1278         if (len > MAX_UNPACK_TREES)
1279                 die("unpack_trees takes at most %d trees", MAX_UNPACK_TREES);
1280
1281         memset(&el, 0, sizeof(el));
1282         if (!core_apply_sparse_checkout || !o->update)
1283                 o->skip_sparse_checkout = 1;
1284         if (!o->skip_sparse_checkout) {
1285                 char *sparse = git_pathdup("info/sparse-checkout");
1286                 if (add_excludes_from_file_to_list(sparse, "", 0, &el, NULL) < 0)
1287                         o->skip_sparse_checkout = 1;
1288                 else
1289                         o->el = &el;
1290                 free(sparse);
1291         }
1292
1293         memset(&o->result, 0, sizeof(o->result));
1294         o->result.initialized = 1;
1295         o->result.timestamp.sec = o->src_index->timestamp.sec;
1296         o->result.timestamp.nsec = o->src_index->timestamp.nsec;
1297         o->result.version = o->src_index->version;
1298         if (!o->src_index->split_index) {
1299                 o->result.split_index = NULL;
1300         } else if (o->src_index == o->dst_index) {
1301                 /*
1302                  * o->dst_index (and thus o->src_index) will be discarded
1303                  * and overwritten with o->result at the end of this function,
1304                  * so just use src_index's split_index to avoid having to
1305                  * create a new one.
1306                  */
1307                 o->result.split_index = o->src_index->split_index;
1308                 o->result.split_index->refcount++;
1309         } else {
1310                 o->result.split_index = init_split_index(&o->result);
1311         }
1312         oidcpy(&o->result.oid, &o->src_index->oid);
1313         o->merge_size = len;
1314         mark_all_ce_unused(o->src_index);
1315
1316         /*
1317          * Sparse checkout loop #1: set NEW_SKIP_WORKTREE on existing entries
1318          */
1319         if (!o->skip_sparse_checkout)
1320                 mark_new_skip_worktree(o->el, o->src_index, 0, CE_NEW_SKIP_WORKTREE);
1321
1322         if (!dfc)
1323                 dfc = xcalloc(1, cache_entry_size(0));
1324         o->df_conflict_entry = dfc;
1325
1326         if (len) {
1327                 const char *prefix = o->prefix ? o->prefix : "";
1328                 struct traverse_info info;
1329
1330                 setup_traverse_info(&info, prefix);
1331                 info.fn = unpack_callback;
1332                 info.data = o;
1333                 info.show_all_errors = o->show_all_errors;
1334                 info.pathspec = o->pathspec;
1335
1336                 if (o->prefix) {
1337                         /*
1338                          * Unpack existing index entries that sort before the
1339                          * prefix the tree is spliced into.  Note that o->merge
1340                          * is always true in this case.
1341                          */
1342                         while (1) {
1343                                 struct cache_entry *ce = next_cache_entry(o);
1344                                 if (!ce)
1345                                         break;
1346                                 if (ce_in_traverse_path(ce, &info))
1347                                         break;
1348                                 if (unpack_index_entry(ce, o) < 0)
1349                                         goto return_failed;
1350                         }
1351                 }
1352
1353                 if (traverse_trees(len, t, &info) < 0)
1354                         goto return_failed;
1355         }
1356
1357         /* Any left-over entries in the index? */
1358         if (o->merge) {
1359                 while (1) {
1360                         struct cache_entry *ce = next_cache_entry(o);
1361                         if (!ce)
1362                                 break;
1363                         if (unpack_index_entry(ce, o) < 0)
1364                                 goto return_failed;
1365                 }
1366         }
1367         mark_all_ce_unused(o->src_index);
1368
1369         if (o->trivial_merges_only && o->nontrivial_merge) {
1370                 ret = unpack_failed(o, "Merge requires file-level merging");
1371                 goto done;
1372         }
1373
1374         if (!o->skip_sparse_checkout) {
1375                 int empty_worktree = 1;
1376
1377                 /*
1378                  * Sparse checkout loop #2: set NEW_SKIP_WORKTREE on entries not in loop #1
1379                  * If the will have NEW_SKIP_WORKTREE, also set CE_SKIP_WORKTREE
1380                  * so apply_sparse_checkout() won't attempt to remove it from worktree
1381                  */
1382                 mark_new_skip_worktree(o->el, &o->result, CE_ADDED, CE_SKIP_WORKTREE | CE_NEW_SKIP_WORKTREE);
1383
1384                 ret = 0;
1385                 for (i = 0; i < o->result.cache_nr; i++) {
1386                         struct cache_entry *ce = o->result.cache[i];
1387
1388                         /*
1389                          * Entries marked with CE_ADDED in merged_entry() do not have
1390                          * verify_absent() check (the check is effectively disabled
1391                          * because CE_NEW_SKIP_WORKTREE is set unconditionally).
1392                          *
1393                          * Do the real check now because we have had
1394                          * correct CE_NEW_SKIP_WORKTREE
1395                          */
1396                         if (ce->ce_flags & CE_ADDED &&
1397                             verify_absent(ce, ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN, o)) {
1398                                 if (!o->show_all_errors)
1399                                         goto return_failed;
1400                                 ret = -1;
1401                         }
1402
1403                         if (apply_sparse_checkout(&o->result, ce, o)) {
1404                                 if (!o->show_all_errors)
1405                                         goto return_failed;
1406                                 ret = -1;
1407                         }
1408                         if (!ce_skip_worktree(ce))
1409                                 empty_worktree = 0;
1410
1411                 }
1412                 if (ret < 0)
1413                         goto return_failed;
1414                 /*
1415                  * Sparse checkout is meant to narrow down checkout area
1416                  * but it does not make sense to narrow down to empty working
1417                  * tree. This is usually a mistake in sparse checkout rules.
1418                  * Do not allow users to do that.
1419                  */
1420                 if (o->result.cache_nr && empty_worktree) {
1421                         ret = unpack_failed(o, "Sparse checkout leaves no entry on working directory");
1422                         goto done;
1423                 }
1424         }
1425
1426         ret = check_updates(o) ? (-2) : 0;
1427         if (o->dst_index) {
1428                 if (!ret) {
1429                         if (!o->result.cache_tree)
1430                                 o->result.cache_tree = cache_tree();
1431                         if (!cache_tree_fully_valid(o->result.cache_tree))
1432                                 cache_tree_update(&o->result,
1433                                                   WRITE_TREE_SILENT |
1434                                                   WRITE_TREE_REPAIR);
1435                 }
1436                 move_index_extensions(&o->result, o->src_index);
1437                 discard_index(o->dst_index);
1438                 *o->dst_index = o->result;
1439         } else {
1440                 discard_index(&o->result);
1441         }
1442         o->src_index = NULL;
1443
1444 done:
1445         clear_exclude_list(&el);
1446         return ret;
1447
1448 return_failed:
1449         if (o->show_all_errors)
1450                 display_error_msgs(o);
1451         mark_all_ce_unused(o->src_index);
1452         ret = unpack_failed(o, NULL);
1453         if (o->exiting_early)
1454                 ret = 0;
1455         goto done;
1456 }
1457
1458 /* Here come the merge functions */
1459
1460 static int reject_merge(const struct cache_entry *ce,
1461                         struct unpack_trees_options *o)
1462 {
1463         return o->gently ? -1 :
1464                 add_rejected_path(o, ERROR_WOULD_OVERWRITE, ce->name);
1465 }
1466
1467 static int same(const struct cache_entry *a, const struct cache_entry *b)
1468 {
1469         if (!!a != !!b)
1470                 return 0;
1471         if (!a && !b)
1472                 return 1;
1473         if ((a->ce_flags | b->ce_flags) & CE_CONFLICTED)
1474                 return 0;
1475         return a->ce_mode == b->ce_mode &&
1476                !oidcmp(&a->oid, &b->oid);
1477 }
1478
1479
1480 /*
1481  * When a CE gets turned into an unmerged entry, we
1482  * want it to be up-to-date
1483  */
1484 static int verify_uptodate_1(const struct cache_entry *ce,
1485                              struct unpack_trees_options *o,
1486                              enum unpack_trees_error_types error_type)
1487 {
1488         struct stat st;
1489
1490         if (o->index_only)
1491                 return 0;
1492
1493         /*
1494          * CE_VALID and CE_SKIP_WORKTREE cheat, we better check again
1495          * if this entry is truly up-to-date because this file may be
1496          * overwritten.
1497          */
1498         if ((ce->ce_flags & CE_VALID) || ce_skip_worktree(ce))
1499                 ; /* keep checking */
1500         else if (o->reset || ce_uptodate(ce))
1501                 return 0;
1502
1503         if (!lstat(ce->name, &st)) {
1504                 int flags = CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE;
1505                 unsigned changed = ie_match_stat(o->src_index, ce, &st, flags);
1506
1507                 if (submodule_from_ce(ce)) {
1508                         int r = check_submodule_move_head(ce,
1509                                 "HEAD", oid_to_hex(&ce->oid), o);
1510                         if (r)
1511                                 return o->gently ? -1 :
1512                                         add_rejected_path(o, error_type, ce->name);
1513                         return 0;
1514                 }
1515
1516                 if (!changed)
1517                         return 0;
1518                 /*
1519                  * Historic default policy was to allow submodule to be out
1520                  * of sync wrt the superproject index. If the submodule was
1521                  * not considered interesting above, we don't care here.
1522                  */
1523                 if (S_ISGITLINK(ce->ce_mode))
1524                         return 0;
1525
1526                 errno = 0;
1527         }
1528         if (errno == ENOENT)
1529                 return 0;
1530         return o->gently ? -1 :
1531                 add_rejected_path(o, error_type, ce->name);
1532 }
1533
1534 int verify_uptodate(const struct cache_entry *ce,
1535                     struct unpack_trees_options *o)
1536 {
1537         if (!o->skip_sparse_checkout && (ce->ce_flags & CE_NEW_SKIP_WORKTREE))
1538                 return 0;
1539         return verify_uptodate_1(ce, o, ERROR_NOT_UPTODATE_FILE);
1540 }
1541
1542 static int verify_uptodate_sparse(const struct cache_entry *ce,
1543                                   struct unpack_trees_options *o)
1544 {
1545         return verify_uptodate_1(ce, o, ERROR_SPARSE_NOT_UPTODATE_FILE);
1546 }
1547
1548 static void invalidate_ce_path(const struct cache_entry *ce,
1549                                struct unpack_trees_options *o)
1550 {
1551         if (!ce)
1552                 return;
1553         cache_tree_invalidate_path(o->src_index, ce->name);
1554         untracked_cache_invalidate_path(o->src_index, ce->name, 1);
1555 }
1556
1557 /*
1558  * Check that checking out ce->sha1 in subdir ce->name is not
1559  * going to overwrite any working files.
1560  *
1561  * Currently, git does not checkout subprojects during a superproject
1562  * checkout, so it is not going to overwrite anything.
1563  */
1564 static int verify_clean_submodule(const char *old_sha1,
1565                                   const struct cache_entry *ce,
1566                                   enum unpack_trees_error_types error_type,
1567                                   struct unpack_trees_options *o)
1568 {
1569         if (!submodule_from_ce(ce))
1570                 return 0;
1571
1572         return check_submodule_move_head(ce, old_sha1,
1573                                          oid_to_hex(&ce->oid), o);
1574 }
1575
1576 static int verify_clean_subdirectory(const struct cache_entry *ce,
1577                                      enum unpack_trees_error_types error_type,
1578                                      struct unpack_trees_options *o)
1579 {
1580         /*
1581          * we are about to extract "ce->name"; we would not want to lose
1582          * anything in the existing directory there.
1583          */
1584         int namelen;
1585         int i;
1586         struct dir_struct d;
1587         char *pathbuf;
1588         int cnt = 0;
1589
1590         if (S_ISGITLINK(ce->ce_mode)) {
1591                 struct object_id oid;
1592                 int sub_head = resolve_gitlink_ref(ce->name, "HEAD", &oid);
1593                 /*
1594                  * If we are not going to update the submodule, then
1595                  * we don't care.
1596                  */
1597                 if (!sub_head && !oidcmp(&oid, &ce->oid))
1598                         return 0;
1599                 return verify_clean_submodule(sub_head ? NULL : oid_to_hex(&oid),
1600                                               ce, error_type, o);
1601         }
1602
1603         /*
1604          * First let's make sure we do not have a local modification
1605          * in that directory.
1606          */
1607         namelen = ce_namelen(ce);
1608         for (i = locate_in_src_index(ce, o);
1609              i < o->src_index->cache_nr;
1610              i++) {
1611                 struct cache_entry *ce2 = o->src_index->cache[i];
1612                 int len = ce_namelen(ce2);
1613                 if (len < namelen ||
1614                     strncmp(ce->name, ce2->name, namelen) ||
1615                     ce2->name[namelen] != '/')
1616                         break;
1617                 /*
1618                  * ce2->name is an entry in the subdirectory to be
1619                  * removed.
1620                  */
1621                 if (!ce_stage(ce2)) {
1622                         if (verify_uptodate(ce2, o))
1623                                 return -1;
1624                         add_entry(o, ce2, CE_REMOVE, 0);
1625                         mark_ce_used(ce2, o);
1626                 }
1627                 cnt++;
1628         }
1629
1630         /*
1631          * Then we need to make sure that we do not lose a locally
1632          * present file that is not ignored.
1633          */
1634         pathbuf = xstrfmt("%.*s/", namelen, ce->name);
1635
1636         memset(&d, 0, sizeof(d));
1637         if (o->dir)
1638                 d.exclude_per_dir = o->dir->exclude_per_dir;
1639         i = read_directory(&d, &the_index, pathbuf, namelen+1, NULL);
1640         if (i)
1641                 return o->gently ? -1 :
1642                         add_rejected_path(o, ERROR_NOT_UPTODATE_DIR, ce->name);
1643         free(pathbuf);
1644         return cnt;
1645 }
1646
1647 /*
1648  * This gets called when there was no index entry for the tree entry 'dst',
1649  * but we found a file in the working tree that 'lstat()' said was fine,
1650  * and we're on a case-insensitive filesystem.
1651  *
1652  * See if we can find a case-insensitive match in the index that also
1653  * matches the stat information, and assume it's that other file!
1654  */
1655 static int icase_exists(struct unpack_trees_options *o, const char *name, int len, struct stat *st)
1656 {
1657         const struct cache_entry *src;
1658
1659         src = index_file_exists(o->src_index, name, len, 1);
1660         return src && !ie_match_stat(o->src_index, src, st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE);
1661 }
1662
1663 static int check_ok_to_remove(const char *name, int len, int dtype,
1664                               const struct cache_entry *ce, struct stat *st,
1665                               enum unpack_trees_error_types error_type,
1666                               struct unpack_trees_options *o)
1667 {
1668         const struct cache_entry *result;
1669
1670         /*
1671          * It may be that the 'lstat()' succeeded even though
1672          * target 'ce' was absent, because there is an old
1673          * entry that is different only in case..
1674          *
1675          * Ignore that lstat() if it matches.
1676          */
1677         if (ignore_case && icase_exists(o, name, len, st))
1678                 return 0;
1679
1680         if (o->dir &&
1681             is_excluded(o->dir, &the_index, name, &dtype))
1682                 /*
1683                  * ce->name is explicitly excluded, so it is Ok to
1684                  * overwrite it.
1685                  */
1686                 return 0;
1687         if (S_ISDIR(st->st_mode)) {
1688                 /*
1689                  * We are checking out path "foo" and
1690                  * found "foo/." in the working tree.
1691                  * This is tricky -- if we have modified
1692                  * files that are in "foo/" we would lose
1693                  * them.
1694                  */
1695                 if (verify_clean_subdirectory(ce, error_type, o) < 0)
1696                         return -1;
1697                 return 0;
1698         }
1699
1700         /*
1701          * The previous round may already have decided to
1702          * delete this path, which is in a subdirectory that
1703          * is being replaced with a blob.
1704          */
1705         result = index_file_exists(&o->result, name, len, 0);
1706         if (result) {
1707                 if (result->ce_flags & CE_REMOVE)
1708                         return 0;
1709         }
1710
1711         return o->gently ? -1 :
1712                 add_rejected_path(o, error_type, name);
1713 }
1714
1715 /*
1716  * We do not want to remove or overwrite a working tree file that
1717  * is not tracked, unless it is ignored.
1718  */
1719 static int verify_absent_1(const struct cache_entry *ce,
1720                            enum unpack_trees_error_types error_type,
1721                            struct unpack_trees_options *o)
1722 {
1723         int len;
1724         struct stat st;
1725
1726         if (o->index_only || o->reset || !o->update)
1727                 return 0;
1728
1729         len = check_leading_path(ce->name, ce_namelen(ce));
1730         if (!len)
1731                 return 0;
1732         else if (len > 0) {
1733                 char *path;
1734                 int ret;
1735
1736                 path = xmemdupz(ce->name, len);
1737                 if (lstat(path, &st))
1738                         ret = error_errno("cannot stat '%s'", path);
1739                 else {
1740                         if (submodule_from_ce(ce))
1741                                 ret = check_submodule_move_head(ce,
1742                                                                 oid_to_hex(&ce->oid),
1743                                                                 NULL, o);
1744                         else
1745                                 ret = check_ok_to_remove(path, len, DT_UNKNOWN, NULL,
1746                                                          &st, error_type, o);
1747                 }
1748                 free(path);
1749                 return ret;
1750         } else if (lstat(ce->name, &st)) {
1751                 if (errno != ENOENT)
1752                         return error_errno("cannot stat '%s'", ce->name);
1753                 return 0;
1754         } else {
1755                 if (submodule_from_ce(ce))
1756                         return check_submodule_move_head(ce, oid_to_hex(&ce->oid),
1757                                                          NULL, o);
1758
1759                 return check_ok_to_remove(ce->name, ce_namelen(ce),
1760                                           ce_to_dtype(ce), ce, &st,
1761                                           error_type, o);
1762         }
1763 }
1764
1765 static int verify_absent(const struct cache_entry *ce,
1766                          enum unpack_trees_error_types error_type,
1767                          struct unpack_trees_options *o)
1768 {
1769         if (!o->skip_sparse_checkout && (ce->ce_flags & CE_NEW_SKIP_WORKTREE))
1770                 return 0;
1771         return verify_absent_1(ce, error_type, o);
1772 }
1773
1774 static int verify_absent_sparse(const struct cache_entry *ce,
1775                                 enum unpack_trees_error_types error_type,
1776                                 struct unpack_trees_options *o)
1777 {
1778         enum unpack_trees_error_types orphaned_error = error_type;
1779         if (orphaned_error == ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN)
1780                 orphaned_error = ERROR_WOULD_LOSE_ORPHANED_OVERWRITTEN;
1781
1782         return verify_absent_1(ce, orphaned_error, o);
1783 }
1784
1785 static int merged_entry(const struct cache_entry *ce,
1786                         const struct cache_entry *old,
1787                         struct unpack_trees_options *o)
1788 {
1789         int update = CE_UPDATE;
1790         struct cache_entry *merge = dup_entry(ce);
1791
1792         if (!old) {
1793                 /*
1794                  * New index entries. In sparse checkout, the following
1795                  * verify_absent() will be delayed until after
1796                  * traverse_trees() finishes in unpack_trees(), then:
1797                  *
1798                  *  - CE_NEW_SKIP_WORKTREE will be computed correctly
1799                  *  - verify_absent() be called again, this time with
1800                  *    correct CE_NEW_SKIP_WORKTREE
1801                  *
1802                  * verify_absent() call here does nothing in sparse
1803                  * checkout (i.e. o->skip_sparse_checkout == 0)
1804                  */
1805                 update |= CE_ADDED;
1806                 merge->ce_flags |= CE_NEW_SKIP_WORKTREE;
1807
1808                 if (verify_absent(merge,
1809                                   ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN, o)) {
1810                         free(merge);
1811                         return -1;
1812                 }
1813                 invalidate_ce_path(merge, o);
1814
1815                 if (submodule_from_ce(ce)) {
1816                         int ret = check_submodule_move_head(ce, NULL,
1817                                                             oid_to_hex(&ce->oid),
1818                                                             o);
1819                         if (ret)
1820                                 return ret;
1821                 }
1822
1823         } else if (!(old->ce_flags & CE_CONFLICTED)) {
1824                 /*
1825                  * See if we can re-use the old CE directly?
1826                  * That way we get the uptodate stat info.
1827                  *
1828                  * This also removes the UPDATE flag on a match; otherwise
1829                  * we will end up overwriting local changes in the work tree.
1830                  */
1831                 if (same(old, merge)) {
1832                         copy_cache_entry(merge, old);
1833                         update = 0;
1834                 } else {
1835                         if (verify_uptodate(old, o)) {
1836                                 free(merge);
1837                                 return -1;
1838                         }
1839                         /* Migrate old flags over */
1840                         update |= old->ce_flags & (CE_SKIP_WORKTREE | CE_NEW_SKIP_WORKTREE);
1841                         invalidate_ce_path(old, o);
1842                 }
1843
1844                 if (submodule_from_ce(ce)) {
1845                         int ret = check_submodule_move_head(ce, oid_to_hex(&old->oid),
1846                                                             oid_to_hex(&ce->oid),
1847                                                             o);
1848                         if (ret)
1849                                 return ret;
1850                 }
1851         } else {
1852                 /*
1853                  * Previously unmerged entry left as an existence
1854                  * marker by read_index_unmerged();
1855                  */
1856                 invalidate_ce_path(old, o);
1857         }
1858
1859         if (do_add_entry(o, merge, update, CE_STAGEMASK) < 0)
1860                 return -1;
1861         return 1;
1862 }
1863
1864 static int deleted_entry(const struct cache_entry *ce,
1865                          const struct cache_entry *old,
1866                          struct unpack_trees_options *o)
1867 {
1868         /* Did it exist in the index? */
1869         if (!old) {
1870                 if (verify_absent(ce, ERROR_WOULD_LOSE_UNTRACKED_REMOVED, o))
1871                         return -1;
1872                 return 0;
1873         }
1874         if (!(old->ce_flags & CE_CONFLICTED) && verify_uptodate(old, o))
1875                 return -1;
1876         add_entry(o, ce, CE_REMOVE, 0);
1877         invalidate_ce_path(ce, o);
1878         return 1;
1879 }
1880
1881 static int keep_entry(const struct cache_entry *ce,
1882                       struct unpack_trees_options *o)
1883 {
1884         add_entry(o, ce, 0, 0);
1885         return 1;
1886 }
1887
1888 #if DBRT_DEBUG
1889 static void show_stage_entry(FILE *o,
1890                              const char *label, const struct cache_entry *ce)
1891 {
1892         if (!ce)
1893                 fprintf(o, "%s (missing)\n", label);
1894         else
1895                 fprintf(o, "%s%06o %s %d\t%s\n",
1896                         label,
1897                         ce->ce_mode,
1898                         oid_to_hex(&ce->oid),
1899                         ce_stage(ce),
1900                         ce->name);
1901 }
1902 #endif
1903
1904 int threeway_merge(const struct cache_entry * const *stages,
1905                    struct unpack_trees_options *o)
1906 {
1907         const struct cache_entry *index;
1908         const struct cache_entry *head;
1909         const struct cache_entry *remote = stages[o->head_idx + 1];
1910         int count;
1911         int head_match = 0;
1912         int remote_match = 0;
1913
1914         int df_conflict_head = 0;
1915         int df_conflict_remote = 0;
1916
1917         int any_anc_missing = 0;
1918         int no_anc_exists = 1;
1919         int i;
1920
1921         for (i = 1; i < o->head_idx; i++) {
1922                 if (!stages[i] || stages[i] == o->df_conflict_entry)
1923                         any_anc_missing = 1;
1924                 else
1925                         no_anc_exists = 0;
1926         }
1927
1928         index = stages[0];
1929         head = stages[o->head_idx];
1930
1931         if (head == o->df_conflict_entry) {
1932                 df_conflict_head = 1;
1933                 head = NULL;
1934         }
1935
1936         if (remote == o->df_conflict_entry) {
1937                 df_conflict_remote = 1;
1938                 remote = NULL;
1939         }
1940
1941         /*
1942          * First, if there's a #16 situation, note that to prevent #13
1943          * and #14.
1944          */
1945         if (!same(remote, head)) {
1946                 for (i = 1; i < o->head_idx; i++) {
1947                         if (same(stages[i], head)) {
1948                                 head_match = i;
1949                         }
1950                         if (same(stages[i], remote)) {
1951                                 remote_match = i;
1952                         }
1953                 }
1954         }
1955
1956         /*
1957          * We start with cases where the index is allowed to match
1958          * something other than the head: #14(ALT) and #2ALT, where it
1959          * is permitted to match the result instead.
1960          */
1961         /* #14, #14ALT, #2ALT */
1962         if (remote && !df_conflict_head && head_match && !remote_match) {
1963                 if (index && !same(index, remote) && !same(index, head))
1964                         return reject_merge(index, o);
1965                 return merged_entry(remote, index, o);
1966         }
1967         /*
1968          * If we have an entry in the index cache, then we want to
1969          * make sure that it matches head.
1970          */
1971         if (index && !same(index, head))
1972                 return reject_merge(index, o);
1973
1974         if (head) {
1975                 /* #5ALT, #15 */
1976                 if (same(head, remote))
1977                         return merged_entry(head, index, o);
1978                 /* #13, #3ALT */
1979                 if (!df_conflict_remote && remote_match && !head_match)
1980                         return merged_entry(head, index, o);
1981         }
1982
1983         /* #1 */
1984         if (!head && !remote && any_anc_missing)
1985                 return 0;
1986
1987         /*
1988          * Under the "aggressive" rule, we resolve mostly trivial
1989          * cases that we historically had git-merge-one-file resolve.
1990          */
1991         if (o->aggressive) {
1992                 int head_deleted = !head;
1993                 int remote_deleted = !remote;
1994                 const struct cache_entry *ce = NULL;
1995
1996                 if (index)
1997                         ce = index;
1998                 else if (head)
1999                         ce = head;
2000                 else if (remote)
2001                         ce = remote;
2002                 else {
2003                         for (i = 1; i < o->head_idx; i++) {
2004                                 if (stages[i] && stages[i] != o->df_conflict_entry) {
2005                                         ce = stages[i];
2006                                         break;
2007                                 }
2008                         }
2009                 }
2010
2011                 /*
2012                  * Deleted in both.
2013                  * Deleted in one and unchanged in the other.
2014                  */
2015                 if ((head_deleted && remote_deleted) ||
2016                     (head_deleted && remote && remote_match) ||
2017                     (remote_deleted && head && head_match)) {
2018                         if (index)
2019                                 return deleted_entry(index, index, o);
2020                         if (ce && !head_deleted) {
2021                                 if (verify_absent(ce, ERROR_WOULD_LOSE_UNTRACKED_REMOVED, o))
2022                                         return -1;
2023                         }
2024                         return 0;
2025                 }
2026                 /*
2027                  * Added in both, identically.
2028                  */
2029                 if (no_anc_exists && head && remote && same(head, remote))
2030                         return merged_entry(head, index, o);
2031
2032         }
2033
2034         /* Below are "no merge" cases, which require that the index be
2035          * up-to-date to avoid the files getting overwritten with
2036          * conflict resolution files.
2037          */
2038         if (index) {
2039                 if (verify_uptodate(index, o))
2040                         return -1;
2041         }
2042
2043         o->nontrivial_merge = 1;
2044
2045         /* #2, #3, #4, #6, #7, #9, #10, #11. */
2046         count = 0;
2047         if (!head_match || !remote_match) {
2048                 for (i = 1; i < o->head_idx; i++) {
2049                         if (stages[i] && stages[i] != o->df_conflict_entry) {
2050                                 keep_entry(stages[i], o);
2051                                 count++;
2052                                 break;
2053                         }
2054                 }
2055         }
2056 #if DBRT_DEBUG
2057         else {
2058                 fprintf(stderr, "read-tree: warning #16 detected\n");
2059                 show_stage_entry(stderr, "head   ", stages[head_match]);
2060                 show_stage_entry(stderr, "remote ", stages[remote_match]);
2061         }
2062 #endif
2063         if (head) { count += keep_entry(head, o); }
2064         if (remote) { count += keep_entry(remote, o); }
2065         return count;
2066 }
2067
2068 /*
2069  * Two-way merge.
2070  *
2071  * The rule is to "carry forward" what is in the index without losing
2072  * information across a "fast-forward", favoring a successful merge
2073  * over a merge failure when it makes sense.  For details of the
2074  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
2075  *
2076  */
2077 int twoway_merge(const struct cache_entry * const *src,
2078                  struct unpack_trees_options *o)
2079 {
2080         const struct cache_entry *current = src[0];
2081         const struct cache_entry *oldtree = src[1];
2082         const struct cache_entry *newtree = src[2];
2083
2084         if (o->merge_size != 2)
2085                 return error("Cannot do a twoway merge of %d trees",
2086                              o->merge_size);
2087
2088         if (oldtree == o->df_conflict_entry)
2089                 oldtree = NULL;
2090         if (newtree == o->df_conflict_entry)
2091                 newtree = NULL;
2092
2093         if (current) {
2094                 if (current->ce_flags & CE_CONFLICTED) {
2095                         if (same(oldtree, newtree) || o->reset) {
2096                                 if (!newtree)
2097                                         return deleted_entry(current, current, o);
2098                                 else
2099                                         return merged_entry(newtree, current, o);
2100                         }
2101                         return reject_merge(current, o);
2102                 } else if ((!oldtree && !newtree) || /* 4 and 5 */
2103                          (!oldtree && newtree &&
2104                           same(current, newtree)) || /* 6 and 7 */
2105                          (oldtree && newtree &&
2106                           same(oldtree, newtree)) || /* 14 and 15 */
2107                          (oldtree && newtree &&
2108                           !same(oldtree, newtree) && /* 18 and 19 */
2109                           same(current, newtree))) {
2110                         return keep_entry(current, o);
2111                 } else if (oldtree && !newtree && same(current, oldtree)) {
2112                         /* 10 or 11 */
2113                         return deleted_entry(oldtree, current, o);
2114                 } else if (oldtree && newtree &&
2115                          same(current, oldtree) && !same(current, newtree)) {
2116                         /* 20 or 21 */
2117                         return merged_entry(newtree, current, o);
2118                 } else
2119                         return reject_merge(current, o);
2120         }
2121         else if (newtree) {
2122                 if (oldtree && !o->initial_checkout) {
2123                         /*
2124                          * deletion of the path was staged;
2125                          */
2126                         if (same(oldtree, newtree))
2127                                 return 1;
2128                         return reject_merge(oldtree, o);
2129                 }
2130                 return merged_entry(newtree, current, o);
2131         }
2132         return deleted_entry(oldtree, current, o);
2133 }
2134
2135 /*
2136  * Bind merge.
2137  *
2138  * Keep the index entries at stage0, collapse stage1 but make sure
2139  * stage0 does not have anything there.
2140  */
2141 int bind_merge(const struct cache_entry * const *src,
2142                struct unpack_trees_options *o)
2143 {
2144         const struct cache_entry *old = src[0];
2145         const struct cache_entry *a = src[1];
2146
2147         if (o->merge_size != 1)
2148                 return error("Cannot do a bind merge of %d trees",
2149                              o->merge_size);
2150         if (a && old)
2151                 return o->gently ? -1 :
2152                         error(ERRORMSG(o, ERROR_BIND_OVERLAP),
2153                               super_prefixed(a->name),
2154                               super_prefixed(old->name));
2155         if (!a)
2156                 return keep_entry(old, o);
2157         else
2158                 return merged_entry(a, NULL, o);
2159 }
2160
2161 /*
2162  * One-way merge.
2163  *
2164  * The rule is:
2165  * - take the stat information from stage0, take the data from stage1
2166  */
2167 int oneway_merge(const struct cache_entry * const *src,
2168                  struct unpack_trees_options *o)
2169 {
2170         const struct cache_entry *old = src[0];
2171         const struct cache_entry *a = src[1];
2172
2173         if (o->merge_size != 1)
2174                 return error("Cannot do a oneway merge of %d trees",
2175                              o->merge_size);
2176
2177         if (!a || a == o->df_conflict_entry)
2178                 return deleted_entry(old, old, o);
2179
2180         if (old && same(old, a)) {
2181                 int update = 0;
2182                 if (o->reset && o->update && !ce_uptodate(old) && !ce_skip_worktree(old)) {
2183                         struct stat st;
2184                         if (lstat(old->name, &st) ||
2185                             ie_match_stat(o->src_index, old, &st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE))
2186                                 update |= CE_UPDATE;
2187                 }
2188                 if (o->update && S_ISGITLINK(old->ce_mode) &&
2189                     should_update_submodules() && !verify_uptodate(old, o))
2190                         update |= CE_UPDATE;
2191                 add_entry(o, old, update, 0);
2192                 return 0;
2193         }
2194         return merged_entry(a, old, o);
2195 }