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->sha1))
 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->sha1))
 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->sha1;
 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->sha1, sha1);
 408                 else
 409                         to_invalidate = 1;
 410         } else if (dryrun)
 411                 hash_sha1_file(buffer.buf, buffer.len, tree_type, it->sha1);
 412         else if (write_sha1_file(buffer.buf, buffer.len, tree_type, it->sha1)) {
 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                 sha1_to_hex(it->sha1));
 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                         sha1_to_hex(it->sha1));
 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->sha1, 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->sha1, (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                         sha1_to_hex(it->sha1));
 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
 608         /*
 609          * We can't free this memory, it becomes part of a linked list
 610          * parsed atexit()
 611          */
 612         lock_file = xcalloc(1, sizeof(struct lock_file));
 613
 614         newfd = hold_lock_file_for_update(lock_file, index_path, LOCK_DIE_ON_ERROR);
 615
 616         entries = read_index_from(index_state, index_path);
 617         if (entries < 0)
 618                 return WRITE_TREE_UNREADABLE_INDEX;
 619         if (flags & WRITE_TREE_IGNORE_CACHE_TREE)
 620                 cache_tree_free(&index_state->cache_tree);
 621
 622         if (!index_state->cache_tree)
 623                 index_state->cache_tree = cache_tree();
 624
 625         was_valid = cache_tree_fully_valid(index_state->cache_tree);
 626         if (!was_valid) {
 627                 if (cache_tree_update(index_state, flags) < 0)
 628                         return WRITE_TREE_UNMERGED_INDEX;
 629                 if (0 <= newfd) {
 630                         if (!write_locked_index(index_state, lock_file, COMMIT_LOCK))
 631                                 newfd = -1;
 632                 }
 633                 /* Not being able to write is fine -- we are only interested
 634                  * in updating the cache-tree part, and if the next caller
 635                  * ends up using the old index with unupdated cache-tree part
 636                  * it misses the work we did here, but that is just a
 637                  * performance penalty and not a big deal.
 638                  */
 639         }
 640
 641         if (prefix) {
 642                 struct cache_tree *subtree;
 643                 subtree = cache_tree_find(index_state->cache_tree, prefix);
 644                 if (!subtree)
 645                         return WRITE_TREE_PREFIX_ERROR;
 646                 hashcpy(sha1, subtree->sha1);
 647         }
 648         else
 649                 hashcpy(sha1, index_state->cache_tree->sha1);
 650
 651         if (0 <= newfd)
 652                 rollback_lock_file(lock_file);
 653
 654         return 0;
 655 }
 656
 657 int write_cache_as_tree(unsigned char *sha1, int flags, const char *prefix)
 658 {
 659         return write_index_as_tree(sha1, &the_index, get_index_file(), flags, prefix);
 660 }
 661
 662 static void prime_cache_tree_rec(struct cache_tree *it, struct tree *tree)
 663 {
 664         struct tree_desc desc;
 665         struct name_entry entry;
 666         int cnt;
 667
 668         hashcpy(it->sha1, tree->object.oid.hash);
 669         init_tree_desc(&desc, tree->buffer, tree->size);
 670         cnt = 0;
 671         while (tree_entry(&desc, &entry)) {
 672                 if (!S_ISDIR(entry.mode))
 673                         cnt++;
 674                 else {
 675                         struct cache_tree_sub *sub;
 676                         struct tree *subtree = lookup_tree(entry.oid->hash);
 677                         if (!subtree->object.parsed)
 678                                 parse_tree(subtree);
 679                         sub = cache_tree_sub(it, entry.path);
 680                         sub->cache_tree = cache_tree();
 681                         prime_cache_tree_rec(sub->cache_tree, subtree);
 682                         cnt += sub->cache_tree->entry_count;
 683                 }
 684         }
 685         it->entry_count = cnt;
 686 }
 687
 688 void prime_cache_tree(struct index_state *istate, struct tree *tree)
 689 {
 690         cache_tree_free(&istate->cache_tree);
 691         istate->cache_tree = cache_tree();
 692         prime_cache_tree_rec(istate->cache_tree, tree);
 693         istate->cache_changed |= CACHE_TREE_CHANGED;
 694 }
 695
 696 /*
 697  * find the cache_tree that corresponds to the current level without
 698  * exploding the full path into textual form.  The root of the
 699  * cache tree is given as "root", and our current level is "info".
 700  * (1) When at root level, info->prev is NULL, so it is "root" itself.
 701  * (2) Otherwise, find the cache_tree that corresponds to one level
 702  *     above us, and find ourselves in there.
 703  */
 704 static struct cache_tree *find_cache_tree_from_traversal(struct cache_tree *root,
 705                                                          struct traverse_info *info)
 706 {
 707         struct cache_tree *our_parent;
 708
 709         if (!info->prev)
 710                 return root;
 711         our_parent = find_cache_tree_from_traversal(root, info->prev);
 712         return cache_tree_find(our_parent, info->name.path);
 713 }
 714
 715 int cache_tree_matches_traversal(struct cache_tree *root,
 716                                  struct name_entry *ent,
 717                                  struct traverse_info *info)
 718 {
 719         struct cache_tree *it;
 720
 721         it = find_cache_tree_from_traversal(root, info);
 722         it = cache_tree_find(it, ent->path);
 723         if (it && it->entry_count > 0 && !hashcmp(ent->oid->hash, it->sha1))
 724                 return it->entry_count;
 725         return 0;
 726 }
 727
 728 int update_main_cache_tree(int flags)
 729 {
 730         if (!the_index.cache_tree)
 731                 the_index.cache_tree = cache_tree();
 732         return cache_tree_update(&the_index, flags);
 733 }