git.oblomov.eu Git - git/blob - cache-tree.c

   1 #include "cache.h"
   2 #include "lockfile.h"
   3 #include "tree.h"
   4 #include "tree-walk.h"
   5 #include "cache-tree.h"
   6
   7 #ifndef DEBUG
   8 #define DEBUG 0
   9 #endif
  10
  11 struct cache_tree *cache_tree(void)
  12 {
  13         struct cache_tree *it = xcalloc(1, sizeof(struct cache_tree));
  14         it->entry_count = -1;
  15         return it;
  16 }
  17
  18 void cache_tree_free(struct cache_tree **it_p)
  19 {
  20         int i;
  21         struct cache_tree *it = *it_p;
  22
  23         if (!it)
  24                 return;
  25         for (i = 0; i < it->subtree_nr; i++)
  26                 if (it->down[i]) {
  27                         cache_tree_free(&it->down[i]->cache_tree);
  28                         free(it->down[i]);
  29                 }
  30         free(it->down);
  31         free(it);
  32         *it_p = NULL;
  33 }
  34
  35 static int subtree_name_cmp(const char *one, int onelen,
  36                             const char *two, int twolen)
  37 {
  38         if (onelen < twolen)
  39                 return -1;
  40         if (twolen < onelen)
  41                 return 1;
  42         return memcmp(one, two, onelen);
  43 }
  44
  45 static int subtree_pos(struct cache_tree *it, const char *path, int pathlen)
  46 {
  47         struct cache_tree_sub **down = it->down;
  48         int lo, hi;
  49         lo = 0;
  50         hi = it->subtree_nr;
  51         while (lo < hi) {
  52                 int mi = (lo + hi) / 2;
  53                 struct cache_tree_sub *mdl = down[mi];
  54                 int cmp = subtree_name_cmp(path, pathlen,
  55                                            mdl->name, mdl->namelen);
  56                 if (!cmp)
  57                         return mi;
  58                 if (cmp < 0)
  59                         hi = mi;
  60                 else
  61                         lo = mi + 1;
  62         }
  63         return -lo-1;
  64 }
  65
  66 static struct cache_tree_sub *find_subtree(struct cache_tree *it,
  67                                            const char *path,
  68                                            int pathlen,
  69                                            int create)
  70 {
  71         struct cache_tree_sub *down;
  72         int pos = subtree_pos(it, path, pathlen);
  73         if (0 <= pos)
  74                 return it->down[pos];
  75         if (!create)
  76                 return NULL;
  77
  78         pos = -pos-1;
  79         ALLOC_GROW(it->down, it->subtree_nr + 1, it->subtree_alloc);
  80         it->subtree_nr++;
  81
  82         FLEX_ALLOC_MEM(down, name, path, pathlen);
  83         down->cache_tree = NULL;
  84         down->namelen = pathlen;
  85
  86         if (pos < it->subtree_nr)
  87                 memmove(it->down + pos + 1,
  88                         it->down + pos,
  89                         sizeof(down) * (it->subtree_nr - pos - 1));
  90         it->down[pos] = down;
  91         return down;
  92 }
  93
  94 struct cache_tree_sub *cache_tree_sub(struct cache_tree *it, const char *path)
  95 {
  96         int pathlen = strlen(path);
  97         return find_subtree(it, path, pathlen, 1);
  98 }
  99
 100 static int do_invalidate_path(struct cache_tree *it, const char *path)
 101 {
 102         /* a/b/c
 103          * ==> invalidate self
 104          * ==> find "a", have it invalidate "b/c"
 105          * a
 106          * ==> invalidate self
 107          * ==> if "a" exists as a subtree, remove it.
 108          */
 109         const char *slash;
 110         int namelen;
 111         struct cache_tree_sub *down;
 112
 113 #if DEBUG
 114         fprintf(stderr, "cache-tree invalidate <%s>\n", path);
 115 #endif
 116
 117         if (!it)
 118                 return 0;
 119         slash = strchrnul(path, '/');
 120         namelen = slash - path;
 121         it->entry_count = -1;
 122         if (!*slash) {
 123                 int pos;
 124                 pos = subtree_pos(it, path, namelen);
 125                 if (0 <= pos) {
 126                         cache_tree_free(&it->down[pos]->cache_tree);
 127                         free(it->down[pos]);
 128                         /* 0 1 2 3 4 5
 129                          *       ^     ^subtree_nr = 6
 130                          *       pos
 131                          * move 4 and 5 up one place (2 entries)
 132                          * 2 = 6 - 3 - 1 = subtree_nr - pos - 1
 133                          */
 134                         memmove(it->down+pos, it->down+pos+1,
 135                                 sizeof(struct cache_tree_sub *) *
 136                                 (it->subtree_nr - pos - 1));
 137                         it->subtree_nr--;
 138                 }
 139                 return 1;
 140         }
 141         down = find_subtree(it, path, namelen, 0);
 142         if (down)
 143                 do_invalidate_path(down->cache_tree, slash + 1);
 144         return 1;
 145 }
 146
 147 void cache_tree_invalidate_path(struct index_state *istate, const char *path)
 148 {
 149         if (do_invalidate_path(istate->cache_tree, path))
 150                 istate->cache_changed |= CACHE_TREE_CHANGED;
 151 }
 152
 153 static int verify_cache(struct cache_entry **cache,
 154                         int entries, int flags)
 155 {
 156         int i, funny;
 157         int silent = flags & WRITE_TREE_SILENT;
 158
 159         /* Verify that the tree is merged */
 160         funny = 0;
 161         for (i = 0; i < entries; i++) {
 162                 const struct cache_entry *ce = cache[i];
 163                 if (ce_stage(ce)) {
 164                         if (silent)
 165                                 return -1;
 166                         if (10 < ++funny) {
 167                                 fprintf(stderr, "...\n");
 168                                 break;
 169                         }
 170                         fprintf(stderr, "%s: unmerged (%s)\n",
 171                                 ce->name, oid_to_hex(&ce->oid));
 172                 }
 173         }
 174         if (funny)
 175                 return -1;
 176
 177         /* Also verify that the cache does not have path and path/file
 178          * at the same time.  At this point we know the cache has only
 179          * stage 0 entries.
 180          */
 181         funny = 0;
 182         for (i = 0; i < entries - 1; i++) {
 183                 /* path/file always comes after path because of the way
 184                  * the cache is sorted.  Also path can appear only once,
 185                  * which means conflicting one would immediately follow.
 186                  */
 187                 const char *this_name = cache[i]->name;
 188                 const char *next_name = cache[i+1]->name;
 189                 int this_len = strlen(this_name);
 190                 if (this_len < strlen(next_name) &&
 191                     strncmp(this_name, next_name, this_len) == 0 &&
 192                     next_name[this_len] == '/') {
 193                         if (10 < ++funny) {
 194                                 fprintf(stderr, "...\n");
 195                                 break;
 196                         }
 197                         fprintf(stderr, "You have both %s and %s\n",
 198                                 this_name, next_name);
 199                 }
 200         }
 201         if (funny)
 202                 return -1;
 203         return 0;
 204 }
 205
 206 static void discard_unused_subtrees(struct cache_tree *it)
 207 {
 208         struct cache_tree_sub **down = it->down;
 209         int nr = it->subtree_nr;
 210         int dst, src;
 211         for (dst = src = 0; src < nr; src++) {
 212                 struct cache_tree_sub *s = down[src];
 213                 if (s->used)
 214                         down[dst++] = s;
 215                 else {
 216                         cache_tree_free(&s->cache_tree);
 217                         free(s);
 218                         it->subtree_nr--;
 219                 }
 220         }
 221 }
 222
 223 int cache_tree_fully_valid(struct cache_tree *it)
 224 {
 225         int i;
 226         if (!it)
 227                 return 0;
 228         if (it->entry_count < 0 || !has_sha1_file(it->oid.hash))
 229                 return 0;
 230         for (i = 0; i < it->subtree_nr; i++) {
 231                 if (!cache_tree_fully_valid(it->down[i]->cache_tree))
 232                         return 0;
 233         }
 234         return 1;
 235 }
 236
 237 static int update_one(struct cache_tree *it,
 238                       struct cache_entry **cache,
 239                       int entries,
 240                       const char *base,
 241                       int baselen,
 242                       int *skip_count,
 243                       int flags)
 244 {
 245         struct strbuf buffer;
 246         int missing_ok = flags & WRITE_TREE_MISSING_OK;
 247         int dryrun = flags & WRITE_TREE_DRY_RUN;
 248         int repair = flags & WRITE_TREE_REPAIR;
 249         int to_invalidate = 0;
 250         int i;
 251
 252         assert(!(dryrun && repair));
 253
 254         *skip_count = 0;
 255
 256         if (0 <= it->entry_count && has_sha1_file(it->oid.hash))
 257                 return it->entry_count;
 258
 259         /*
 260          * We first scan for subtrees and update them; we start by
 261          * marking existing subtrees -- the ones that are unmarked
 262          * should not be in the result.
 263          */
 264         for (i = 0; i < it->subtree_nr; i++)
 265                 it->down[i]->used = 0;
 266
 267         /*
 268          * Find the subtrees and update them.
 269          */
 270         i = 0;
 271         while (i < entries) {
 272                 const struct cache_entry *ce = cache[i];
 273                 struct cache_tree_sub *sub;
 274                 const char *path, *slash;
 275                 int pathlen, sublen, subcnt, subskip;
 276
 277                 path = ce->name;
 278                 pathlen = ce_namelen(ce);
 279                 if (pathlen <= baselen || memcmp(base, path, baselen))
 280                         break; /* at the end of this level */
 281
 282                 slash = strchr(path + baselen, '/');
 283                 if (!slash) {
 284                         i++;
 285                         continue;
 286                 }
 287                 /*
 288                  * a/bbb/c (base = a/, slash = /c)
 289                  * ==>
 290                  * path+baselen = bbb/c, sublen = 3
 291                  */
 292                 sublen = slash - (path + baselen);
 293                 sub = find_subtree(it, path + baselen, sublen, 1);
 294                 if (!sub->cache_tree)
 295                         sub->cache_tree = cache_tree();
 296                 subcnt = update_one(sub->cache_tree,
 297                                     cache + i, entries - i,
 298                                     path,
 299                                     baselen + sublen + 1,
 300                                     &subskip,
 301                                     flags);
 302                 if (subcnt < 0)
 303                         return subcnt;
 304                 if (!subcnt)
 305                         die("index cache-tree records empty sub-tree");
 306                 i += subcnt;
 307                 sub->count = subcnt; /* to be used in the next loop */
 308                 *skip_count += subskip;
 309                 sub->used = 1;
 310         }
 311
 312         discard_unused_subtrees(it);
 313
 314         /*
 315          * Then write out the tree object for this level.
 316          */
 317         strbuf_init(&buffer, 8192);
 318
 319         i = 0;
 320         while (i < entries) {
 321                 const struct cache_entry *ce = cache[i];
 322                 struct cache_tree_sub *sub = NULL;
 323                 const char *path, *slash;
 324                 int pathlen, entlen;
 325                 const unsigned char *sha1;
 326                 unsigned mode;
 327                 int expected_missing = 0;
 328                 int contains_ita = 0;
 329
 330                 path = ce->name;
 331                 pathlen = ce_namelen(ce);
 332                 if (pathlen <= baselen || memcmp(base, path, baselen))
 333                         break; /* at the end of this level */
 334
 335                 slash = strchr(path + baselen, '/');
 336                 if (slash) {
 337                         entlen = slash - (path + baselen);
 338                         sub = find_subtree(it, path + baselen, entlen, 0);
 339                         if (!sub)
 340                                 die("cache-tree.c: '%.*s' in '%s' not found",
 341                                     entlen, path + baselen, path);
 342                         i += sub->count;
 343                         sha1 = sub->cache_tree->oid.hash;
 344                         mode = S_IFDIR;
 345                         contains_ita = sub->cache_tree->entry_count < 0;
 346                         if (contains_ita) {
 347                                 to_invalidate = 1;
 348                                 expected_missing = 1;
 349                         }
 350                 }
 351                 else {
 352                         sha1 = ce->oid.hash;
 353                         mode = ce->ce_mode;
 354                         entlen = pathlen - baselen;
 355                         i++;
 356                 }
 357
 358                 if (is_null_sha1(sha1) ||
 359                     (mode != S_IFGITLINK && !missing_ok && !has_sha1_file(sha1))) {
 360                         strbuf_release(&buffer);
 361                         if (expected_missing)
 362                                 return -1;
 363                         return error("invalid object %06o %s for '%.*s'",
 364                                 mode, sha1_to_hex(sha1), entlen+baselen, path);
 365                 }
 366
 367                 /*
 368                  * CE_REMOVE entries are removed before the index is
 369                  * written to disk. Skip them to remain consistent
 370                  * with the future on-disk index.
 371                  */
 372                 if (ce->ce_flags & CE_REMOVE) {
 373                         *skip_count = *skip_count + 1;
 374                         continue;
 375                 }
 376
 377                 /*
 378                  * CE_INTENT_TO_ADD entries exist on on-disk index but
 379                  * they are not part of generated trees. Invalidate up
 380                  * to root to force cache-tree users to read elsewhere.
 381                  */
 382                 if (!sub && ce_intent_to_add(ce)) {
 383                         to_invalidate = 1;
 384                         continue;
 385                 }
 386
 387                 /*
 388                  * "sub" can be an empty tree if all subentries are i-t-a.
 389                  */
 390                 if (contains_ita && !hashcmp(sha1, EMPTY_TREE_SHA1_BIN))
 391                         continue;
 392
 393                 strbuf_grow(&buffer, entlen + 100);
 394                 strbuf_addf(&buffer, "%o %.*s%c", mode, entlen, path + baselen, '\0');
 395                 strbuf_add(&buffer, sha1, 20);
 396
 397 #if DEBUG
 398                 fprintf(stderr, "cache-tree update-one %o %.*s\n",
 399                         mode, entlen, path + baselen);
 400 #endif
 401         }
 402
 403         if (repair) {
 404                 unsigned char sha1[20];
 405                 hash_sha1_file(buffer.buf, buffer.len, tree_type, sha1);
 406                 if (has_sha1_file(sha1))
 407                         hashcpy(it->oid.hash, sha1);
 408                 else
 409                         to_invalidate = 1;
 410         } else if (dryrun)
 411                 hash_sha1_file(buffer.buf, buffer.len, tree_type,
 412                                it->oid.hash);
 413         else if (write_sha1_file(buffer.buf, buffer.len, tree_type, it->oid.hash)) {
 414                 strbuf_release(&buffer);
 415                 return -1;
 416         }
 417
 418         strbuf_release(&buffer);
 419         it->entry_count = to_invalidate ? -1 : i - *skip_count;
 420 #if DEBUG
 421         fprintf(stderr, "cache-tree update-one (%d ent, %d subtree) %s\n",
 422                 it->entry_count, it->subtree_nr,
 423                 oid_to_hex(&it->oid));
 424 #endif
 425         return i;
 426 }
 427
 428 int cache_tree_update(struct index_state *istate, int flags)
 429 {
 430         struct cache_tree *it = istate->cache_tree;
 431         struct cache_entry **cache = istate->cache;
 432         int entries = istate->cache_nr;
 433         int skip, i = verify_cache(cache, entries, flags);
 434
 435         if (i)
 436                 return i;
 437         i = update_one(it, cache, entries, "", 0, &skip, flags);
 438         if (i < 0)
 439                 return i;
 440         istate->cache_changed |= CACHE_TREE_CHANGED;
 441         return 0;
 442 }
 443
 444 static void write_one(struct strbuf *buffer, struct cache_tree *it,
 445                       const char *path, int pathlen)
 446 {
 447         int i;
 448
 449         /* One "cache-tree" entry consists of the following:
 450          * path (NUL terminated)
 451          * entry_count, subtree_nr ("%d %d\n")
 452          * tree-sha1 (missing if invalid)
 453          * subtree_nr "cache-tree" entries for subtrees.
 454          */
 455         strbuf_grow(buffer, pathlen + 100);
 456         strbuf_add(buffer, path, pathlen);
 457         strbuf_addf(buffer, "%c%d %d\n", 0, it->entry_count, it->subtree_nr);
 458
 459 #if DEBUG
 460         if (0 <= it->entry_count)
 461                 fprintf(stderr, "cache-tree <%.*s> (%d ent, %d subtree) %s\n",
 462                         pathlen, path, it->entry_count, it->subtree_nr,
 463                         oid_to_hex(&it->oid));
 464         else
 465                 fprintf(stderr, "cache-tree <%.*s> (%d subtree) invalid\n",
 466                         pathlen, path, it->subtree_nr);
 467 #endif
 468
 469         if (0 <= it->entry_count) {
 470                 strbuf_add(buffer, it->oid.hash, 20);
 471         }
 472         for (i = 0; i < it->subtree_nr; i++) {
 473                 struct cache_tree_sub *down = it->down[i];
 474                 if (i) {
 475                         struct cache_tree_sub *prev = it->down[i-1];
 476                         if (subtree_name_cmp(down->name, down->namelen,
 477                                              prev->name, prev->namelen) <= 0)
 478                                 die("fatal - unsorted cache subtree");
 479                 }
 480                 write_one(buffer, down->cache_tree, down->name, down->namelen);
 481         }
 482 }
 483
 484 void cache_tree_write(struct strbuf *sb, struct cache_tree *root)
 485 {
 486         write_one(sb, root, "", 0);
 487 }
 488
 489 static struct cache_tree *read_one(const char **buffer, unsigned long *size_p)
 490 {
 491         const char *buf = *buffer;
 492         unsigned long size = *size_p;
 493         const char *cp;
 494         char *ep;
 495         struct cache_tree *it;
 496         int i, subtree_nr;
 497
 498         it = NULL;
 499         /* skip name, but make sure name exists */
 500         while (size && *buf) {
 501                 size--;
 502                 buf++;
 503         }
 504         if (!size)
 505                 goto free_return;
 506         buf++; size--;
 507         it = cache_tree();
 508
 509         cp = buf;
 510         it->entry_count = strtol(cp, &ep, 10);
 511         if (cp == ep)
 512                 goto free_return;
 513         cp = ep;
 514         subtree_nr = strtol(cp, &ep, 10);
 515         if (cp == ep)
 516                 goto free_return;
 517         while (size && *buf && *buf != '\n') {
 518                 size--;
 519                 buf++;
 520         }
 521         if (!size)
 522                 goto free_return;
 523         buf++; size--;
 524         if (0 <= it->entry_count) {
 525                 if (size < 20)
 526                         goto free_return;
 527                 hashcpy(it->oid.hash, (const unsigned char*)buf);
 528                 buf += 20;
 529                 size -= 20;
 530         }
 531
 532 #if DEBUG
 533         if (0 <= it->entry_count)
 534                 fprintf(stderr, "cache-tree <%s> (%d ent, %d subtree) %s\n",
 535                         *buffer, it->entry_count, subtree_nr,
 536                         oid_to_hex(&it->oid));
 537         else
 538                 fprintf(stderr, "cache-tree <%s> (%d subtrees) invalid\n",
 539                         *buffer, subtree_nr);
 540 #endif
 541
 542         /*
 543          * Just a heuristic -- we do not add directories that often but
 544          * we do not want to have to extend it immediately when we do,
 545          * hence +2.
 546          */
 547         it->subtree_alloc = subtree_nr + 2;
 548         it->down = xcalloc(it->subtree_alloc, sizeof(struct cache_tree_sub *));
 549         for (i = 0; i < subtree_nr; i++) {
 550                 /* read each subtree */
 551                 struct cache_tree *sub;
 552                 struct cache_tree_sub *subtree;
 553                 const char *name = buf;
 554
 555                 sub = read_one(&buf, &size);
 556                 if (!sub)
 557                         goto free_return;
 558                 subtree = cache_tree_sub(it, name);
 559                 subtree->cache_tree = sub;
 560         }
 561         if (subtree_nr != it->subtree_nr)
 562                 die("cache-tree: internal error");
 563         *buffer = buf;
 564         *size_p = size;
 565         return it;
 566
 567  free_return:
 568         cache_tree_free(&it);
 569         return NULL;
 570 }
 571
 572 struct cache_tree *cache_tree_read(const char *buffer, unsigned long size)
 573 {
 574         if (buffer[0])
 575                 return NULL; /* not the whole tree */
 576         return read_one(&buffer, &size);
 577 }
 578
 579 static struct cache_tree *cache_tree_find(struct cache_tree *it, const char *path)
 580 {
 581         if (!it)
 582                 return NULL;
 583         while (*path) {
 584                 const char *slash;
 585                 struct cache_tree_sub *sub;
 586
 587                 slash = strchrnul(path, '/');
 588                 /*
 589                  * Between path and slash is the name of the subtree
 590                  * to look for.
 591                  */
 592                 sub = find_subtree(it, path, slash - path, 0);
 593                 if (!sub)
 594                         return NULL;
 595                 it = sub->cache_tree;
 596
 597                 path = slash;
 598                 while (*path == '/')
 599                         path++;
 600         }
 601         return it;
 602 }
 603
 604 int write_index_as_tree(unsigned char *sha1, struct index_state *index_state, const char *index_path, int flags, const char *prefix)
 605 {
 606         int entries, was_valid, newfd;
 607         struct lock_file *lock_file;
 608
 609         /*
 610          * We can't free this memory, it becomes part of a linked list
 611          * parsed atexit()
 612          */
 613         lock_file = xcalloc(1, sizeof(struct lock_file));
 614
 615         newfd = hold_lock_file_for_update(lock_file, index_path, LOCK_DIE_ON_ERROR);
 616
 617         entries = read_index_from(index_state, index_path);
 618         if (entries < 0)
 619                 return WRITE_TREE_UNREADABLE_INDEX;
 620         if (flags & WRITE_TREE_IGNORE_CACHE_TREE)
 621                 cache_tree_free(&index_state->cache_tree);
 622
 623         if (!index_state->cache_tree)
 624                 index_state->cache_tree = cache_tree();
 625
 626         was_valid = cache_tree_fully_valid(index_state->cache_tree);
 627         if (!was_valid) {
 628                 if (cache_tree_update(index_state, flags) < 0)
 629                         return WRITE_TREE_UNMERGED_INDEX;
 630                 if (0 <= newfd) {
 631                         if (!write_locked_index(index_state, lock_file, COMMIT_LOCK))
 632                                 newfd = -1;
 633                 }
 634                 /* Not being able to write is fine -- we are only interested
 635                  * in updating the cache-tree part, and if the next caller
 636                  * ends up using the old index with unupdated cache-tree part
 637                  * it misses the work we did here, but that is just a
 638                  * performance penalty and not a big deal.
 639                  */
 640         }
 641
 642         if (prefix) {
 643                 struct cache_tree *subtree;
 644                 subtree = cache_tree_find(index_state->cache_tree, prefix);
 645                 if (!subtree)
 646                         return WRITE_TREE_PREFIX_ERROR;
 647                 hashcpy(sha1, subtree->oid.hash);
 648         }
 649         else
 650                 hashcpy(sha1, index_state->cache_tree->oid.hash);
 651
 652         if (0 <= newfd)
 653                 rollback_lock_file(lock_file);
 654
 655         return 0;
 656 }
 657
 658 int write_cache_as_tree(unsigned char *sha1, int flags, const char *prefix)
 659 {
 660         return write_index_as_tree(sha1, &the_index, get_index_file(), flags, prefix);
 661 }
 662
 663 static void prime_cache_tree_rec(struct cache_tree *it, struct tree *tree)
 664 {
 665         struct tree_desc desc;
 666         struct name_entry entry;
 667         int cnt;
 668
 669         oidcpy(&it->oid, &tree->object.oid);
 670         init_tree_desc(&desc, tree->buffer, tree->size);
 671         cnt = 0;
 672         while (tree_entry(&desc, &entry)) {
 673                 if (!S_ISDIR(entry.mode))
 674                         cnt++;
 675                 else {
 676                         struct cache_tree_sub *sub;
 677                         struct tree *subtree = lookup_tree(entry.oid);
 678                         if (!subtree->object.parsed)
 679                                 parse_tree(subtree);
 680                         sub = cache_tree_sub(it, entry.path);
 681                         sub->cache_tree = cache_tree();
 682                         prime_cache_tree_rec(sub->cache_tree, subtree);
 683                         cnt += sub->cache_tree->entry_count;
 684                 }
 685         }
 686         it->entry_count = cnt;
 687 }
 688
 689 void prime_cache_tree(struct index_state *istate, struct tree *tree)
 690 {
 691         cache_tree_free(&istate->cache_tree);
 692         istate->cache_tree = cache_tree();
 693         prime_cache_tree_rec(istate->cache_tree, tree);
 694         istate->cache_changed |= CACHE_TREE_CHANGED;
 695 }
 696
 697 /*
 698  * find the cache_tree that corresponds to the current level without
 699  * exploding the full path into textual form.  The root of the
 700  * cache tree is given as "root", and our current level is "info".
 701  * (1) When at root level, info->prev is NULL, so it is "root" itself.
 702  * (2) Otherwise, find the cache_tree that corresponds to one level
 703  *     above us, and find ourselves in there.
 704  */
 705 static struct cache_tree *find_cache_tree_from_traversal(struct cache_tree *root,
 706                                                          struct traverse_info *info)
 707 {
 708         struct cache_tree *our_parent;
 709
 710         if (!info->prev)
 711                 return root;
 712         our_parent = find_cache_tree_from_traversal(root, info->prev);
 713         return cache_tree_find(our_parent, info->name.path);
 714 }
 715
 716 int cache_tree_matches_traversal(struct cache_tree *root,
 717                                  struct name_entry *ent,
 718                                  struct traverse_info *info)
 719 {
 720         struct cache_tree *it;
 721
 722         it = find_cache_tree_from_traversal(root, info);
 723         it = cache_tree_find(it, ent->path);
 724         if (it && it->entry_count > 0 && !oidcmp(ent->oid, &it->oid))
 725                 return it->entry_count;
 726         return 0;
 727 }
 728
 729 int update_main_cache_tree(int flags)
 730 {
 731         if (!the_index.cache_tree)
 732                 the_index.cache_tree = cache_tree();
 733         return cache_tree_update(&the_index, flags);
 734 }