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                         MOVE_ARRAY(it->down + pos, it->down + pos + 1,
 135                                    it->subtree_nr - pos - 1);
 136                         it->subtree_nr--;
 137                 }
 138                 return 1;
 139         }
 140         down = find_subtree(it, path, namelen, 0);
 141         if (down)
 142                 do_invalidate_path(down->cache_tree, slash + 1);
 143         return 1;
 144 }
 145
 146 void cache_tree_invalidate_path(struct index_state *istate, const char *path)
 147 {
 148         if (do_invalidate_path(istate->cache_tree, path))
 149                 istate->cache_changed |= CACHE_TREE_CHANGED;
 150 }
 151
 152 static int verify_cache(struct cache_entry **cache,
 153                         int entries, int flags)
 154 {
 155         int i, funny;
 156         int silent = flags & WRITE_TREE_SILENT;
 157
 158         /* Verify that the tree is merged */
 159         funny = 0;
 160         for (i = 0; i < entries; i++) {
 161                 const struct cache_entry *ce = cache[i];
 162                 if (ce_stage(ce)) {
 163                         if (silent)
 164                                 return -1;
 165                         if (10 < ++funny) {
 166                                 fprintf(stderr, "...\n");
 167                                 break;
 168                         }
 169                         fprintf(stderr, "%s: unmerged (%s)\n",
 170                                 ce->name, oid_to_hex(&ce->oid));
 171                 }
 172         }
 173         if (funny)
 174                 return -1;
 175
 176         /* Also verify that the cache does not have path and path/file
 177          * at the same time.  At this point we know the cache has only
 178          * stage 0 entries.
 179          */
 180         funny = 0;
 181         for (i = 0; i < entries - 1; i++) {
 182                 /* path/file always comes after path because of the way
 183                  * the cache is sorted.  Also path can appear only once,
 184                  * which means conflicting one would immediately follow.
 185                  */
 186                 const char *this_name = cache[i]->name;
 187                 const char *next_name = cache[i+1]->name;
 188                 int this_len = strlen(this_name);
 189                 if (this_len < strlen(next_name) &&
 190                     strncmp(this_name, next_name, this_len) == 0 &&
 191                     next_name[this_len] == '/') {
 192                         if (10 < ++funny) {
 193                                 fprintf(stderr, "...\n");
 194                                 break;
 195                         }
 196                         fprintf(stderr, "You have both %s and %s\n",
 197                                 this_name, next_name);
 198                 }
 199         }
 200         if (funny)
 201                 return -1;
 202         return 0;
 203 }
 204
 205 static void discard_unused_subtrees(struct cache_tree *it)
 206 {
 207         struct cache_tree_sub **down = it->down;
 208         int nr = it->subtree_nr;
 209         int dst, src;
 210         for (dst = src = 0; src < nr; src++) {
 211                 struct cache_tree_sub *s = down[src];
 212                 if (s->used)
 213                         down[dst++] = s;
 214                 else {
 215                         cache_tree_free(&s->cache_tree);
 216                         free(s);
 217                         it->subtree_nr--;
 218                 }
 219         }
 220 }
 221
 222 int cache_tree_fully_valid(struct cache_tree *it)
 223 {
 224         int i;
 225         if (!it)
 226                 return 0;
 227         if (it->entry_count < 0 || !has_sha1_file(it->oid.hash))
 228                 return 0;
 229         for (i = 0; i < it->subtree_nr; i++) {
 230                 if (!cache_tree_fully_valid(it->down[i]->cache_tree))
 231                         return 0;
 232         }
 233         return 1;
 234 }
 235
 236 static int update_one(struct cache_tree *it,
 237                       struct cache_entry **cache,
 238                       int entries,
 239                       const char *base,
 240                       int baselen,
 241                       int *skip_count,
 242                       int flags)
 243 {
 244         struct strbuf buffer;
 245         int missing_ok = flags & WRITE_TREE_MISSING_OK;
 246         int dryrun = flags & WRITE_TREE_DRY_RUN;
 247         int repair = flags & WRITE_TREE_REPAIR;
 248         int to_invalidate = 0;
 249         int i;
 250
 251         assert(!(dryrun && repair));
 252
 253         *skip_count = 0;
 254
 255         if (0 <= it->entry_count && has_sha1_file(it->oid.hash))
 256                 return it->entry_count;
 257
 258         /*
 259          * We first scan for subtrees and update them; we start by
 260          * marking existing subtrees -- the ones that are unmarked
 261          * should not be in the result.
 262          */
 263         for (i = 0; i < it->subtree_nr; i++)
 264                 it->down[i]->used = 0;
 265
 266         /*
 267          * Find the subtrees and update them.
 268          */
 269         i = 0;
 270         while (i < entries) {
 271                 const struct cache_entry *ce = cache[i];
 272                 struct cache_tree_sub *sub;
 273                 const char *path, *slash;
 274                 int pathlen, sublen, subcnt, subskip;
 275
 276                 path = ce->name;
 277                 pathlen = ce_namelen(ce);
 278                 if (pathlen <= baselen || memcmp(base, path, baselen))
 279                         break; /* at the end of this level */
 280
 281                 slash = strchr(path + baselen, '/');
 282                 if (!slash) {
 283                         i++;
 284                         continue;
 285                 }
 286                 /*
 287                  * a/bbb/c (base = a/, slash = /c)
 288                  * ==>
 289                  * path+baselen = bbb/c, sublen = 3
 290                  */
 291                 sublen = slash - (path + baselen);
 292                 sub = find_subtree(it, path + baselen, sublen, 1);
 293                 if (!sub->cache_tree)
 294                         sub->cache_tree = cache_tree();
 295                 subcnt = update_one(sub->cache_tree,
 296                                     cache + i, entries - i,
 297                                     path,
 298                                     baselen + sublen + 1,
 299                                     &subskip,
 300                                     flags);
 301                 if (subcnt < 0)
 302                         return subcnt;
 303                 if (!subcnt)
 304                         die("index cache-tree records empty sub-tree");
 305                 i += subcnt;
 306                 sub->count = subcnt; /* to be used in the next loop */
 307                 *skip_count += subskip;
 308                 sub->used = 1;
 309         }
 310
 311         discard_unused_subtrees(it);
 312
 313         /*
 314          * Then write out the tree object for this level.
 315          */
 316         strbuf_init(&buffer, 8192);
 317
 318         i = 0;
 319         while (i < entries) {
 320                 const struct cache_entry *ce = cache[i];
 321                 struct cache_tree_sub *sub = NULL;
 322                 const char *path, *slash;
 323                 int pathlen, entlen;
 324                 const unsigned char *sha1;
 325                 unsigned mode;
 326                 int expected_missing = 0;
 327                 int contains_ita = 0;
 328
 329                 path = ce->name;
 330                 pathlen = ce_namelen(ce);
 331                 if (pathlen <= baselen || memcmp(base, path, baselen))
 332                         break; /* at the end of this level */
 333
 334                 slash = strchr(path + baselen, '/');
 335                 if (slash) {
 336                         entlen = slash - (path + baselen);
 337                         sub = find_subtree(it, path + baselen, entlen, 0);
 338                         if (!sub)
 339                                 die("cache-tree.c: '%.*s' in '%s' not found",
 340                                     entlen, path + baselen, path);
 341                         i += sub->count;
 342                         sha1 = sub->cache_tree->oid.hash;
 343                         mode = S_IFDIR;
 344                         contains_ita = sub->cache_tree->entry_count < 0;
 345                         if (contains_ita) {
 346                                 to_invalidate = 1;
 347                                 expected_missing = 1;
 348                         }
 349                 }
 350                 else {
 351                         sha1 = ce->oid.hash;
 352                         mode = ce->ce_mode;
 353                         entlen = pathlen - baselen;
 354                         i++;
 355                 }
 356
 357                 if (is_null_sha1(sha1) ||
 358                     (mode != S_IFGITLINK && !missing_ok && !has_sha1_file(sha1))) {
 359                         strbuf_release(&buffer);
 360                         if (expected_missing)
 361                                 return -1;
 362                         return error("invalid object %06o %s for '%.*s'",
 363                                 mode, sha1_to_hex(sha1), entlen+baselen, path);
 364                 }
 365
 366                 /*
 367                  * CE_REMOVE entries are removed before the index is
 368                  * written to disk. Skip them to remain consistent
 369                  * with the future on-disk index.
 370                  */
 371                 if (ce->ce_flags & CE_REMOVE) {
 372                         *skip_count = *skip_count + 1;
 373                         continue;
 374                 }
 375
 376                 /*
 377                  * CE_INTENT_TO_ADD entries exist on on-disk index but
 378                  * they are not part of generated trees. Invalidate up
 379                  * to root to force cache-tree users to read elsewhere.
 380                  */
 381                 if (!sub && ce_intent_to_add(ce)) {
 382                         to_invalidate = 1;
 383                         continue;
 384                 }
 385
 386                 /*
 387                  * "sub" can be an empty tree if all subentries are i-t-a.
 388                  */
 389                 if (contains_ita && !hashcmp(sha1, EMPTY_TREE_SHA1_BIN))
 390                         continue;
 391
 392                 strbuf_grow(&buffer, entlen + 100);
 393                 strbuf_addf(&buffer, "%o %.*s%c", mode, entlen, path + baselen, '\0');
 394                 strbuf_add(&buffer, sha1, 20);
 395
 396 #if DEBUG
 397                 fprintf(stderr, "cache-tree update-one %o %.*s\n",
 398                         mode, entlen, path + baselen);
 399 #endif
 400         }
 401
 402         if (repair) {
 403                 unsigned char sha1[20];
 404                 hash_sha1_file(buffer.buf, buffer.len, tree_type, sha1);
 405                 if (has_sha1_file(sha1))
 406                         hashcpy(it->oid.hash, sha1);
 407                 else
 408                         to_invalidate = 1;
 409         } else if (dryrun)
 410                 hash_sha1_file(buffer.buf, buffer.len, tree_type,
 411                                it->oid.hash);
 412         else if (write_sha1_file(buffer.buf, buffer.len, tree_type, it->oid.hash)) {
 413                 strbuf_release(&buffer);
 414                 return -1;
 415         }
 416
 417         strbuf_release(&buffer);
 418         it->entry_count = to_invalidate ? -1 : i - *skip_count;
 419 #if DEBUG
 420         fprintf(stderr, "cache-tree update-one (%d ent, %d subtree) %s\n",
 421                 it->entry_count, it->subtree_nr,
 422                 oid_to_hex(&it->oid));
 423 #endif
 424         return i;
 425 }
 426
 427 int cache_tree_update(struct index_state *istate, int flags)
 428 {
 429         struct cache_tree *it = istate->cache_tree;
 430         struct cache_entry **cache = istate->cache;
 431         int entries = istate->cache_nr;
 432         int skip, i = verify_cache(cache, entries, flags);
 433
 434         if (i)
 435                 return i;
 436         i = update_one(it, cache, entries, "", 0, &skip, flags);
 437         if (i < 0)
 438                 return i;
 439         istate->cache_changed |= CACHE_TREE_CHANGED;
 440         return 0;
 441 }
 442
 443 static void write_one(struct strbuf *buffer, struct cache_tree *it,
 444                       const char *path, int pathlen)
 445 {
 446         int i;
 447
 448         /* One "cache-tree" entry consists of the following:
 449          * path (NUL terminated)
 450          * entry_count, subtree_nr ("%d %d\n")
 451          * tree-sha1 (missing if invalid)
 452          * subtree_nr "cache-tree" entries for subtrees.
 453          */
 454         strbuf_grow(buffer, pathlen + 100);
 455         strbuf_add(buffer, path, pathlen);
 456         strbuf_addf(buffer, "%c%d %d\n", 0, it->entry_count, it->subtree_nr);
 457
 458 #if DEBUG
 459         if (0 <= it->entry_count)
 460                 fprintf(stderr, "cache-tree <%.*s> (%d ent, %d subtree) %s\n",
 461                         pathlen, path, it->entry_count, it->subtree_nr,
 462                         oid_to_hex(&it->oid));
 463         else
 464                 fprintf(stderr, "cache-tree <%.*s> (%d subtree) invalid\n",
 465                         pathlen, path, it->subtree_nr);
 466 #endif
 467
 468         if (0 <= it->entry_count) {
 469                 strbuf_add(buffer, it->oid.hash, 20);
 470         }
 471         for (i = 0; i < it->subtree_nr; i++) {
 472                 struct cache_tree_sub *down = it->down[i];
 473                 if (i) {
 474                         struct cache_tree_sub *prev = it->down[i-1];
 475                         if (subtree_name_cmp(down->name, down->namelen,
 476                                              prev->name, prev->namelen) <= 0)
 477                                 die("fatal - unsorted cache subtree");
 478                 }
 479                 write_one(buffer, down->cache_tree, down->name, down->namelen);
 480         }
 481 }
 482
 483 void cache_tree_write(struct strbuf *sb, struct cache_tree *root)
 484 {
 485         write_one(sb, root, "", 0);
 486 }
 487
 488 static struct cache_tree *read_one(const char **buffer, unsigned long *size_p)
 489 {
 490         const char *buf = *buffer;
 491         unsigned long size = *size_p;
 492         const char *cp;
 493         char *ep;
 494         struct cache_tree *it;
 495         int i, subtree_nr;
 496
 497         it = NULL;
 498         /* skip name, but make sure name exists */
 499         while (size && *buf) {
 500                 size--;
 501                 buf++;
 502         }
 503         if (!size)
 504                 goto free_return;
 505         buf++; size--;
 506         it = cache_tree();
 507
 508         cp = buf;
 509         it->entry_count = strtol(cp, &ep, 10);
 510         if (cp == ep)
 511                 goto free_return;
 512         cp = ep;
 513         subtree_nr = strtol(cp, &ep, 10);
 514         if (cp == ep)
 515                 goto free_return;
 516         while (size && *buf && *buf != '\n') {
 517                 size--;
 518                 buf++;
 519         }
 520         if (!size)
 521                 goto free_return;
 522         buf++; size--;
 523         if (0 <= it->entry_count) {
 524                 if (size < 20)
 525                         goto free_return;
 526                 hashcpy(it->oid.hash, (const unsigned char*)buf);
 527                 buf += 20;
 528                 size -= 20;
 529         }
 530
 531 #if DEBUG
 532         if (0 <= it->entry_count)
 533                 fprintf(stderr, "cache-tree <%s> (%d ent, %d subtree) %s\n",
 534                         *buffer, it->entry_count, subtree_nr,
 535                         oid_to_hex(&it->oid));
 536         else
 537                 fprintf(stderr, "cache-tree <%s> (%d subtrees) invalid\n",
 538                         *buffer, subtree_nr);
 539 #endif
 540
 541         /*
 542          * Just a heuristic -- we do not add directories that often but
 543          * we do not want to have to extend it immediately when we do,
 544          * hence +2.
 545          */
 546         it->subtree_alloc = subtree_nr + 2;
 547         it->down = xcalloc(it->subtree_alloc, sizeof(struct cache_tree_sub *));
 548         for (i = 0; i < subtree_nr; i++) {
 549                 /* read each subtree */
 550                 struct cache_tree *sub;
 551                 struct cache_tree_sub *subtree;
 552                 const char *name = buf;
 553
 554                 sub = read_one(&buf, &size);
 555                 if (!sub)
 556                         goto free_return;
 557                 subtree = cache_tree_sub(it, name);
 558                 subtree->cache_tree = sub;
 559         }
 560         if (subtree_nr != it->subtree_nr)
 561                 die("cache-tree: internal error");
 562         *buffer = buf;
 563         *size_p = size;
 564         return it;
 565
 566  free_return:
 567         cache_tree_free(&it);
 568         return NULL;
 569 }
 570
 571 struct cache_tree *cache_tree_read(const char *buffer, unsigned long size)
 572 {
 573         if (buffer[0])
 574                 return NULL; /* not the whole tree */
 575         return read_one(&buffer, &size);
 576 }
 577
 578 static struct cache_tree *cache_tree_find(struct cache_tree *it, const char *path)
 579 {
 580         if (!it)
 581                 return NULL;
 582         while (*path) {
 583                 const char *slash;
 584                 struct cache_tree_sub *sub;
 585
 586                 slash = strchrnul(path, '/');
 587                 /*
 588                  * Between path and slash is the name of the subtree
 589                  * to look for.
 590                  */
 591                 sub = find_subtree(it, path, slash - path, 0);
 592                 if (!sub)
 593                         return NULL;
 594                 it = sub->cache_tree;
 595
 596                 path = slash;
 597                 while (*path == '/')
 598                         path++;
 599         }
 600         return it;
 601 }
 602
 603 int write_index_as_tree(unsigned char *sha1, struct index_state *index_state, const char *index_path, int flags, const char *prefix)
 604 {
 605         int entries, was_valid, newfd;
 606         struct lock_file *lock_file;
 607         int ret = 0;
 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                 ret = WRITE_TREE_UNREADABLE_INDEX;
 620                 goto out;
 621         }
 622         if (flags & WRITE_TREE_IGNORE_CACHE_TREE)
 623                 cache_tree_free(&index_state->cache_tree);
 624
 625         if (!index_state->cache_tree)
 626                 index_state->cache_tree = cache_tree();
 627
 628         was_valid = cache_tree_fully_valid(index_state->cache_tree);
 629         if (!was_valid) {
 630                 if (cache_tree_update(index_state, flags) < 0) {
 631                         ret = WRITE_TREE_UNMERGED_INDEX;
 632                         goto out;
 633                 }
 634                 if (0 <= newfd) {
 635                         if (!write_locked_index(index_state, lock_file, COMMIT_LOCK))
 636                                 newfd = -1;
 637                 }
 638                 /* Not being able to write is fine -- we are only interested
 639                  * in updating the cache-tree part, and if the next caller
 640                  * ends up using the old index with unupdated cache-tree part
 641                  * it misses the work we did here, but that is just a
 642                  * performance penalty and not a big deal.
 643                  */
 644         }
 645
 646         if (prefix) {
 647                 struct cache_tree *subtree;
 648                 subtree = cache_tree_find(index_state->cache_tree, prefix);
 649                 if (!subtree) {
 650                         ret = WRITE_TREE_PREFIX_ERROR;
 651                         goto out;
 652                 }
 653                 hashcpy(sha1, subtree->oid.hash);
 654         }
 655         else
 656                 hashcpy(sha1, index_state->cache_tree->oid.hash);
 657
 658 out:
 659         if (0 <= newfd)
 660                 rollback_lock_file(lock_file);
 661         return ret;
 662 }
 663
 664 int write_cache_as_tree(unsigned char *sha1, int flags, const char *prefix)
 665 {
 666         return write_index_as_tree(sha1, &the_index, get_index_file(), flags, prefix);
 667 }
 668
 669 static void prime_cache_tree_rec(struct cache_tree *it, struct tree *tree)
 670 {
 671         struct tree_desc desc;
 672         struct name_entry entry;
 673         int cnt;
 674
 675         oidcpy(&it->oid, &tree->object.oid);
 676         init_tree_desc(&desc, tree->buffer, tree->size);
 677         cnt = 0;
 678         while (tree_entry(&desc, &entry)) {
 679                 if (!S_ISDIR(entry.mode))
 680                         cnt++;
 681                 else {
 682                         struct cache_tree_sub *sub;
 683                         struct tree *subtree = lookup_tree(entry.oid);
 684                         if (!subtree->object.parsed)
 685                                 parse_tree(subtree);
 686                         sub = cache_tree_sub(it, entry.path);
 687                         sub->cache_tree = cache_tree();
 688                         prime_cache_tree_rec(sub->cache_tree, subtree);
 689                         cnt += sub->cache_tree->entry_count;
 690                 }
 691         }
 692         it->entry_count = cnt;
 693 }
 694
 695 void prime_cache_tree(struct index_state *istate, struct tree *tree)
 696 {
 697         cache_tree_free(&istate->cache_tree);
 698         istate->cache_tree = cache_tree();
 699         prime_cache_tree_rec(istate->cache_tree, tree);
 700         istate->cache_changed |= CACHE_TREE_CHANGED;
 701 }
 702
 703 /*
 704  * find the cache_tree that corresponds to the current level without
 705  * exploding the full path into textual form.  The root of the
 706  * cache tree is given as "root", and our current level is "info".
 707  * (1) When at root level, info->prev is NULL, so it is "root" itself.
 708  * (2) Otherwise, find the cache_tree that corresponds to one level
 709  *     above us, and find ourselves in there.
 710  */
 711 static struct cache_tree *find_cache_tree_from_traversal(struct cache_tree *root,
 712                                                          struct traverse_info *info)
 713 {
 714         struct cache_tree *our_parent;
 715
 716         if (!info->prev)
 717                 return root;
 718         our_parent = find_cache_tree_from_traversal(root, info->prev);
 719         return cache_tree_find(our_parent, info->name.path);
 720 }
 721
 722 int cache_tree_matches_traversal(struct cache_tree *root,
 723                                  struct name_entry *ent,
 724                                  struct traverse_info *info)
 725 {
 726         struct cache_tree *it;
 727
 728         it = find_cache_tree_from_traversal(root, info);
 729         it = cache_tree_find(it, ent->path);
 730         if (it && it->entry_count > 0 && !oidcmp(ent->oid, &it->oid))
 731                 return it->entry_count;
 732         return 0;
 733 }
 734
 735 int update_main_cache_tree(int flags)
 736 {
 737         if (!the_index.cache_tree)
 738                 the_index.cache_tree = cache_tree();
 739         return cache_tree_update(&the_index, flags);
 740 }