path.c

   1 /*
   2  * Utilities for paths and pathnames
   3  */
   4 #include "cache.h"
   5 #include "strbuf.h"
   6 #include "string-list.h"
   7 #include "dir.h"
   8 #include "worktree.h"
   9 #include "submodule-config.h"
  10
  11 static int get_st_mode_bits(const char *path, int *mode)
  12 {
  13         struct stat st;
  14         if (lstat(path, &st) < 0)
  15                 return -1;
  16         *mode = st.st_mode;
  17         return 0;
  18 }
  19
  20 static char bad_path[] = "/bad-path/";
  21
  22 static struct strbuf *get_pathname(void)
  23 {
  24         static struct strbuf pathname_array[4] = {
  25                 STRBUF_INIT, STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
  26         };
  27         static int index;
  28         struct strbuf *sb = &pathname_array[index];
  29         index = (index + 1) % ARRAY_SIZE(pathname_array);
  30         strbuf_reset(sb);
  31         return sb;
  32 }
  33
  34 static char *cleanup_path(char *path)
  35 {
  36         /* Clean it up */
  37         if (!memcmp(path, "./", 2)) {
  38                 path += 2;
  39                 while (*path == '/')
  40                         path++;
  41         }
  42         return path;
  43 }
  44
  45 static void strbuf_cleanup_path(struct strbuf *sb)
  46 {
  47         char *path = cleanup_path(sb->buf);
  48         if (path > sb->buf)
  49                 strbuf_remove(sb, 0, path - sb->buf);
  50 }
  51
  52 char *mksnpath(char *buf, size_t n, const char *fmt, ...)
  53 {
  54         va_list args;
  55         unsigned len;
  56
  57         va_start(args, fmt);
  58         len = vsnprintf(buf, n, fmt, args);
  59         va_end(args);
  60         if (len >= n) {
  61                 strlcpy(buf, bad_path, n);
  62                 return buf;
  63         }
  64         return cleanup_path(buf);
  65 }
  66
  67 static int dir_prefix(const char *buf, const char *dir)
  68 {
  69         int len = strlen(dir);
  70         return !strncmp(buf, dir, len) &&
  71                 (is_dir_sep(buf[len]) || buf[len] == '\0');
  72 }
  73
  74 /* $buf =~ m|$dir/+$file| but without regex */
  75 static int is_dir_file(const char *buf, const char *dir, const char *file)
  76 {
  77         int len = strlen(dir);
  78         if (strncmp(buf, dir, len) || !is_dir_sep(buf[len]))
  79                 return 0;
  80         while (is_dir_sep(buf[len]))
  81                 len++;
  82         return !strcmp(buf + len, file);
  83 }
  84
  85 static void replace_dir(struct strbuf *buf, int len, const char *newdir)
  86 {
  87         int newlen = strlen(newdir);
  88         int need_sep = (buf->buf[len] && !is_dir_sep(buf->buf[len])) &&
  89                 !is_dir_sep(newdir[newlen - 1]);
  90         if (need_sep)
  91                 len--;   /* keep one char, to be replaced with '/'  */
  92         strbuf_splice(buf, 0, len, newdir, newlen);
  93         if (need_sep)
  94                 buf->buf[newlen] = '/';
  95 }
  96
  97 struct common_dir {
  98         /* Not considered garbage for report_linked_checkout_garbage */
  99         unsigned ignore_garbage:1;
 100         unsigned is_dir:1;
 101         /* Not common even though its parent is */
 102         unsigned exclude:1;
 103         const char *dirname;
 104 };
 105
 106 static struct common_dir common_list[] = {
 107         { 0, 1, 0, "branches" },
 108         { 0, 1, 0, "hooks" },
 109         { 0, 1, 0, "info" },
 110         { 0, 0, 1, "info/sparse-checkout" },
 111         { 1, 1, 0, "logs" },
 112         { 1, 1, 1, "logs/HEAD" },
 113         { 0, 1, 1, "logs/refs/bisect" },
 114         { 0, 1, 0, "lost-found" },
 115         { 0, 1, 0, "objects" },
 116         { 0, 1, 0, "refs" },
 117         { 0, 1, 1, "refs/bisect" },
 118         { 0, 1, 0, "remotes" },
 119         { 0, 1, 0, "worktrees" },
 120         { 0, 1, 0, "rr-cache" },
 121         { 0, 1, 0, "svn" },
 122         { 0, 0, 0, "config" },
 123         { 1, 0, 0, "gc.pid" },
 124         { 0, 0, 0, "packed-refs" },
 125         { 0, 0, 0, "shallow" },
 126         { 0, 0, 0, NULL }
 127 };
 128
 129 /*
 130  * A compressed trie.  A trie node consists of zero or more characters that
 131  * are common to all elements with this prefix, optionally followed by some
 132  * children.  If value is not NULL, the trie node is a terminal node.
 133  *
 134  * For example, consider the following set of strings:
 135  * abc
 136  * def
 137  * definite
 138  * definition
 139  *
 140  * The trie would look like:
 141  * root: len = 0, children a and d non-NULL, value = NULL.
 142  *    a: len = 2, contents = bc, value = (data for "abc")
 143  *    d: len = 2, contents = ef, children i non-NULL, value = (data for "def")
 144  *       i: len = 3, contents = nit, children e and i non-NULL, value = NULL
 145  *           e: len = 0, children all NULL, value = (data for "definite")
 146  *           i: len = 2, contents = on, children all NULL,
 147  *              value = (data for "definition")
 148  */
 149 struct trie {
 150         struct trie *children[256];
 151         int len;
 152         char *contents;
 153         void *value;
 154 };
 155
 156 static struct trie *make_trie_node(const char *key, void *value)
 157 {
 158         struct trie *new_node = xcalloc(1, sizeof(*new_node));
 159         new_node->len = strlen(key);
 160         if (new_node->len) {
 161                 new_node->contents = xmalloc(new_node->len);
 162                 memcpy(new_node->contents, key, new_node->len);
 163         }
 164         new_node->value = value;
 165         return new_node;
 166 }
 167
 168 /*
 169  * Add a key/value pair to a trie.  The key is assumed to be \0-terminated.
 170  * If there was an existing value for this key, return it.
 171  */
 172 static void *add_to_trie(struct trie *root, const char *key, void *value)
 173 {
 174         struct trie *child;
 175         void *old;
 176         int i;
 177
 178         if (!*key) {
 179                 /* we have reached the end of the key */
 180                 old = root->value;
 181                 root->value = value;
 182                 return old;
 183         }
 184
 185         for (i = 0; i < root->len; i++) {
 186                 if (root->contents[i] == key[i])
 187                         continue;
 188
 189                 /*
 190                  * Split this node: child will contain this node's
 191                  * existing children.
 192                  */
 193                 child = malloc(sizeof(*child));
 194                 memcpy(child->children, root->children, sizeof(root->children));
 195
 196                 child->len = root->len - i - 1;
 197                 if (child->len) {
 198                         child->contents = xstrndup(root->contents + i + 1,
 199                                                    child->len);
 200                 }
 201                 child->value = root->value;
 202                 root->value = NULL;
 203                 root->len = i;
 204
 205                 memset(root->children, 0, sizeof(root->children));
 206                 root->children[(unsigned char)root->contents[i]] = child;
 207
 208                 /* This is the newly-added child. */
 209                 root->children[(unsigned char)key[i]] =
 210                         make_trie_node(key + i + 1, value);
 211                 return NULL;
 212         }
 213
 214         /* We have matched the entire compressed section */
 215         if (key[i]) {
 216                 child = root->children[(unsigned char)key[root->len]];
 217                 if (child) {
 218                         return add_to_trie(child, key + root->len + 1, value);
 219                 } else {
 220                         child = make_trie_node(key + root->len + 1, value);
 221                         root->children[(unsigned char)key[root->len]] = child;
 222                         return NULL;
 223                 }
 224         }
 225
 226         old = root->value;
 227         root->value = value;
 228         return old;
 229 }
 230
 231 typedef int (*match_fn)(const char *unmatched, void *data, void *baton);
 232
 233 /*
 234  * Search a trie for some key.  Find the longest /-or-\0-terminated
 235  * prefix of the key for which the trie contains a value.  Call fn
 236  * with the unmatched portion of the key and the found value, and
 237  * return its return value.  If there is no such prefix, return -1.
 238  *
 239  * The key is partially normalized: consecutive slashes are skipped.
 240  *
 241  * For example, consider the trie containing only [refs,
 242  * refs/worktree] (both with values).
 243  *
 244  * | key             | unmatched  | val from node | return value |
 245  * |-----------------|------------|---------------|--------------|
 246  * | a               | not called | n/a           | -1           |
 247  * | refs            | \0         | refs          | as per fn    |
 248  * | refs/           | /          | refs          | as per fn    |
 249  * | refs/w          | /w         | refs          | as per fn    |
 250  * | refs/worktree   | \0         | refs/worktree | as per fn    |
 251  * | refs/worktree/  | /          | refs/worktree | as per fn    |
 252  * | refs/worktree/a | /a         | refs/worktree | as per fn    |
 253  * |-----------------|------------|---------------|--------------|
 254  *
 255  */
 256 static int trie_find(struct trie *root, const char *key, match_fn fn,
 257                      void *baton)
 258 {
 259         int i;
 260         int result;
 261         struct trie *child;
 262
 263         if (!*key) {
 264                 /* we have reached the end of the key */
 265                 if (root->value && !root->len)
 266                         return fn(key, root->value, baton);
 267                 else
 268                         return -1;
 269         }
 270
 271         for (i = 0; i < root->len; i++) {
 272                 /* Partial path normalization: skip consecutive slashes. */
 273                 if (key[i] == '/' && key[i+1] == '/') {
 274                         key++;
 275                         continue;
 276                 }
 277                 if (root->contents[i] != key[i])
 278                         return -1;
 279         }
 280
 281         /* Matched the entire compressed section */
 282         key += i;
 283         if (!*key)
 284                 /* End of key */
 285                 return fn(key, root->value, baton);
 286
 287         /* Partial path normalization: skip consecutive slashes */
 288         while (key[0] == '/' && key[1] == '/')
 289                 key++;
 290
 291         child = root->children[(unsigned char)*key];
 292         if (child)
 293                 result = trie_find(child, key + 1, fn, baton);
 294         else
 295                 result = -1;
 296
 297         if (result >= 0 || (*key != '/' && *key != 0))
 298                 return result;
 299         if (root->value)
 300                 return fn(key, root->value, baton);
 301         else
 302                 return -1;
 303 }
 304
 305 static struct trie common_trie;
 306 static int common_trie_done_setup;
 307
 308 static void init_common_trie(void)
 309 {
 310         struct common_dir *p;
 311
 312         if (common_trie_done_setup)
 313                 return;
 314
 315         for (p = common_list; p->dirname; p++)
 316                 add_to_trie(&common_trie, p->dirname, p);
 317
 318         common_trie_done_setup = 1;
 319 }
 320
 321 /*
 322  * Helper function for update_common_dir: returns 1 if the dir
 323  * prefix is common.
 324  */
 325 static int check_common(const char *unmatched, void *value, void *baton)
 326 {
 327         struct common_dir *dir = value;
 328
 329         if (!dir)
 330                 return 0;
 331
 332         if (dir->is_dir && (unmatched[0] == 0 || unmatched[0] == '/'))
 333                 return !dir->exclude;
 334
 335         if (!dir->is_dir && unmatched[0] == 0)
 336                 return !dir->exclude;
 337
 338         return 0;
 339 }
 340
 341 static void update_common_dir(struct strbuf *buf, int git_dir_len,
 342                               const char *common_dir)
 343 {
 344         char *base = buf->buf + git_dir_len;
 345         init_common_trie();
 346         if (!common_dir)
 347                 common_dir = get_git_common_dir();
 348         if (trie_find(&common_trie, base, check_common, NULL) > 0)
 349                 replace_dir(buf, git_dir_len, common_dir);
 350 }
 351
 352 void report_linked_checkout_garbage(void)
 353 {
 354         struct strbuf sb = STRBUF_INIT;
 355         const struct common_dir *p;
 356         int len;
 357
 358         if (!git_common_dir_env)
 359                 return;
 360         strbuf_addf(&sb, "%s/", get_git_dir());
 361         len = sb.len;
 362         for (p = common_list; p->dirname; p++) {
 363                 const char *path = p->dirname;
 364                 if (p->ignore_garbage)
 365                         continue;
 366                 strbuf_setlen(&sb, len);
 367                 strbuf_addstr(&sb, path);
 368                 if (file_exists(sb.buf))
 369                         report_garbage(PACKDIR_FILE_GARBAGE, sb.buf);
 370         }
 371         strbuf_release(&sb);
 372 }
 373
 374 static void adjust_git_path(struct strbuf *buf, int git_dir_len)
 375 {
 376         const char *base = buf->buf + git_dir_len;
 377         if (git_graft_env && is_dir_file(base, "info", "grafts"))
 378                 strbuf_splice(buf, 0, buf->len,
 379                               get_graft_file(), strlen(get_graft_file()));
 380         else if (git_index_env && !strcmp(base, "index"))
 381                 strbuf_splice(buf, 0, buf->len,
 382                               get_index_file(), strlen(get_index_file()));
 383         else if (git_db_env && dir_prefix(base, "objects"))
 384                 replace_dir(buf, git_dir_len + 7, get_object_directory());
 385         else if (git_hooks_path && dir_prefix(base, "hooks"))
 386                 replace_dir(buf, git_dir_len + 5, git_hooks_path);
 387         else if (git_common_dir_env)
 388                 update_common_dir(buf, git_dir_len, NULL);
 389 }
 390
 391 static void do_git_path(const struct worktree *wt, struct strbuf *buf,
 392                         const char *fmt, va_list args)
 393 {
 394         int gitdir_len;
 395         strbuf_addstr(buf, get_worktree_git_dir(wt));
 396         if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 397                 strbuf_addch(buf, '/');
 398         gitdir_len = buf->len;
 399         strbuf_vaddf(buf, fmt, args);
 400         adjust_git_path(buf, gitdir_len);
 401         strbuf_cleanup_path(buf);
 402 }
 403
 404 char *git_path_buf(struct strbuf *buf, const char *fmt, ...)
 405 {
 406         va_list args;
 407         strbuf_reset(buf);
 408         va_start(args, fmt);
 409         do_git_path(NULL, buf, fmt, args);
 410         va_end(args);
 411         return buf->buf;
 412 }
 413
 414 void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
 415 {
 416         va_list args;
 417         va_start(args, fmt);
 418         do_git_path(NULL, sb, fmt, args);
 419         va_end(args);
 420 }
 421
 422 const char *git_path(const char *fmt, ...)
 423 {
 424         struct strbuf *pathname = get_pathname();
 425         va_list args;
 426         va_start(args, fmt);
 427         do_git_path(NULL, pathname, fmt, args);
 428         va_end(args);
 429         return pathname->buf;
 430 }
 431
 432 char *git_pathdup(const char *fmt, ...)
 433 {
 434         struct strbuf path = STRBUF_INIT;
 435         va_list args;
 436         va_start(args, fmt);
 437         do_git_path(NULL, &path, fmt, args);
 438         va_end(args);
 439         return strbuf_detach(&path, NULL);
 440 }
 441
 442 char *mkpathdup(const char *fmt, ...)
 443 {
 444         struct strbuf sb = STRBUF_INIT;
 445         va_list args;
 446         va_start(args, fmt);
 447         strbuf_vaddf(&sb, fmt, args);
 448         va_end(args);
 449         strbuf_cleanup_path(&sb);
 450         return strbuf_detach(&sb, NULL);
 451 }
 452
 453 const char *mkpath(const char *fmt, ...)
 454 {
 455         va_list args;
 456         struct strbuf *pathname = get_pathname();
 457         va_start(args, fmt);
 458         strbuf_vaddf(pathname, fmt, args);
 459         va_end(args);
 460         return cleanup_path(pathname->buf);
 461 }
 462
 463 const char *worktree_git_path(const struct worktree *wt, const char *fmt, ...)
 464 {
 465         struct strbuf *pathname = get_pathname();
 466         va_list args;
 467         va_start(args, fmt);
 468         do_git_path(wt, pathname, fmt, args);
 469         va_end(args);
 470         return pathname->buf;
 471 }
 472
 473 /* Returns 0 on success, negative on failure. */
 474 static int do_submodule_path(struct strbuf *buf, const char *path,
 475                              const char *fmt, va_list args)
 476 {
 477         struct strbuf git_submodule_common_dir = STRBUF_INIT;
 478         struct strbuf git_submodule_dir = STRBUF_INIT;
 479         int ret;
 480
 481         ret = submodule_to_gitdir(&git_submodule_dir, path);
 482         if (ret)
 483                 goto cleanup;
 484
 485         strbuf_complete(&git_submodule_dir, '/');
 486         strbuf_addbuf(buf, &git_submodule_dir);
 487         strbuf_vaddf(buf, fmt, args);
 488
 489         if (get_common_dir_noenv(&git_submodule_common_dir, git_submodule_dir.buf))
 490                 update_common_dir(buf, git_submodule_dir.len, git_submodule_common_dir.buf);
 491
 492         strbuf_cleanup_path(buf);
 493
 494 cleanup:
 495         strbuf_release(&git_submodule_dir);
 496         strbuf_release(&git_submodule_common_dir);
 497         return ret;
 498 }
 499
 500 char *git_pathdup_submodule(const char *path, const char *fmt, ...)
 501 {
 502         int err;
 503         va_list args;
 504         struct strbuf buf = STRBUF_INIT;
 505         va_start(args, fmt);
 506         err = do_submodule_path(&buf, path, fmt, args);
 507         va_end(args);
 508         if (err) {
 509                 strbuf_release(&buf);
 510                 return NULL;
 511         }
 512         return strbuf_detach(&buf, NULL);
 513 }
 514
 515 int strbuf_git_path_submodule(struct strbuf *buf, const char *path,
 516                               const char *fmt, ...)
 517 {
 518         int err;
 519         va_list args;
 520         va_start(args, fmt);
 521         err = do_submodule_path(buf, path, fmt, args);
 522         va_end(args);
 523
 524         return err;
 525 }
 526
 527 static void do_git_common_path(struct strbuf *buf,
 528                                const char *fmt,
 529                                va_list args)
 530 {
 531         strbuf_addstr(buf, get_git_common_dir());
 532         if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 533                 strbuf_addch(buf, '/');
 534         strbuf_vaddf(buf, fmt, args);
 535         strbuf_cleanup_path(buf);
 536 }
 537
 538 const char *git_common_path(const char *fmt, ...)
 539 {
 540         struct strbuf *pathname = get_pathname();
 541         va_list args;
 542         va_start(args, fmt);
 543         do_git_common_path(pathname, fmt, args);
 544         va_end(args);
 545         return pathname->buf;
 546 }
 547
 548 void strbuf_git_common_path(struct strbuf *sb, const char *fmt, ...)
 549 {
 550         va_list args;
 551         va_start(args, fmt);
 552         do_git_common_path(sb, fmt, args);
 553         va_end(args);
 554 }
 555
 556 int validate_headref(const char *path)
 557 {
 558         struct stat st;
 559         char *buf, buffer[256];
 560         unsigned char sha1[20];
 561         int fd;
 562         ssize_t len;
 563
 564         if (lstat(path, &st) < 0)
 565                 return -1;
 566
 567         /* Make sure it is a "refs/.." symlink */
 568         if (S_ISLNK(st.st_mode)) {
 569                 len = readlink(path, buffer, sizeof(buffer)-1);
 570                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 571                         return 0;
 572                 return -1;
 573         }
 574
 575         /*
 576          * Anything else, just open it and try to see if it is a symbolic ref.
 577          */
 578         fd = open(path, O_RDONLY);
 579         if (fd < 0)
 580                 return -1;
 581         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 582         close(fd);
 583
 584         /*
 585          * Is it a symbolic ref?
 586          */
 587         if (len < 4)
 588                 return -1;
 589         if (!memcmp("ref:", buffer, 4)) {
 590                 buf = buffer + 4;
 591                 len -= 4;
 592                 while (len && isspace(*buf))
 593                         buf++, len--;
 594                 if (len >= 5 && !memcmp("refs/", buf, 5))
 595                         return 0;
 596         }
 597
 598         /*
 599          * Is this a detached HEAD?
 600          */
 601         if (!get_sha1_hex(buffer, sha1))
 602                 return 0;
 603
 604         return -1;
 605 }
 606
 607 static struct passwd *getpw_str(const char *username, size_t len)
 608 {
 609         struct passwd *pw;
 610         char *username_z = xmemdupz(username, len);
 611         pw = getpwnam(username_z);
 612         free(username_z);
 613         return pw;
 614 }
 615
 616 /*
 617  * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 618  * then it is a newly allocated string. Returns NULL on getpw failure or
 619  * if path is NULL.
 620  *
 621  * If real_home is true, real_path($HOME) is used in the expansion.
 622  */
 623 char *expand_user_path(const char *path, int real_home)
 624 {
 625         struct strbuf user_path = STRBUF_INIT;
 626         const char *to_copy = path;
 627
 628         if (path == NULL)
 629                 goto return_null;
 630         if (path[0] == '~') {
 631                 const char *first_slash = strchrnul(path, '/');
 632                 const char *username = path + 1;
 633                 size_t username_len = first_slash - username;
 634                 if (username_len == 0) {
 635                         const char *home = getenv("HOME");
 636                         if (!home)
 637                                 goto return_null;
 638                         if (real_home)
 639                                 strbuf_addstr(&user_path, real_path(home));
 640                         else
 641                                 strbuf_addstr(&user_path, home);
 642 #ifdef GIT_WINDOWS_NATIVE
 643                         convert_slashes(user_path.buf);
 644 #endif
 645                 } else {
 646                         struct passwd *pw = getpw_str(username, username_len);
 647                         if (!pw)
 648                                 goto return_null;
 649                         strbuf_addstr(&user_path, pw->pw_dir);
 650                 }
 651                 to_copy = first_slash;
 652         }
 653         strbuf_addstr(&user_path, to_copy);
 654         return strbuf_detach(&user_path, NULL);
 655 return_null:
 656         strbuf_release(&user_path);
 657         return NULL;
 658 }
 659
 660 /*
 661  * First, one directory to try is determined by the following algorithm.
 662  *
 663  * (0) If "strict" is given, the path is used as given and no DWIM is
 664  *     done. Otherwise:
 665  * (1) "~/path" to mean path under the running user's home directory;
 666  * (2) "~user/path" to mean path under named user's home directory;
 667  * (3) "relative/path" to mean cwd relative directory; or
 668  * (4) "/absolute/path" to mean absolute directory.
 669  *
 670  * Unless "strict" is given, we check "%s/.git", "%s", "%s.git/.git", "%s.git"
 671  * in this order. We select the first one that is a valid git repository, and
 672  * chdir() to it. If none match, or we fail to chdir, we return NULL.
 673  *
 674  * If all goes well, we return the directory we used to chdir() (but
 675  * before ~user is expanded), avoiding getcwd() resolving symbolic
 676  * links.  User relative paths are also returned as they are given,
 677  * except DWIM suffixing.
 678  */
 679 const char *enter_repo(const char *path, int strict)
 680 {
 681         static struct strbuf validated_path = STRBUF_INIT;
 682         static struct strbuf used_path = STRBUF_INIT;
 683
 684         if (!path)
 685                 return NULL;
 686
 687         if (!strict) {
 688                 static const char *suffix[] = {
 689                         "/.git", "", ".git/.git", ".git", NULL,
 690                 };
 691                 const char *gitfile;
 692                 int len = strlen(path);
 693                 int i;
 694                 while ((1 < len) && (path[len-1] == '/'))
 695                         len--;
 696
 697                 /*
 698                  * We can handle arbitrary-sized buffers, but this remains as a
 699                  * sanity check on untrusted input.
 700                  */
 701                 if (PATH_MAX <= len)
 702                         return NULL;
 703
 704                 strbuf_reset(&used_path);
 705                 strbuf_reset(&validated_path);
 706                 strbuf_add(&used_path, path, len);
 707                 strbuf_add(&validated_path, path, len);
 708
 709                 if (used_path.buf[0] == '~') {
 710                         char *newpath = expand_user_path(used_path.buf, 0);
 711                         if (!newpath)
 712                                 return NULL;
 713                         strbuf_attach(&used_path, newpath, strlen(newpath),
 714                                       strlen(newpath));
 715                 }
 716                 for (i = 0; suffix[i]; i++) {
 717                         struct stat st;
 718                         size_t baselen = used_path.len;
 719                         strbuf_addstr(&used_path, suffix[i]);
 720                         if (!stat(used_path.buf, &st) &&
 721                             (S_ISREG(st.st_mode) ||
 722                             (S_ISDIR(st.st_mode) && is_git_directory(used_path.buf)))) {
 723                                 strbuf_addstr(&validated_path, suffix[i]);
 724                                 break;
 725                         }
 726                         strbuf_setlen(&used_path, baselen);
 727                 }
 728                 if (!suffix[i])
 729                         return NULL;
 730                 gitfile = read_gitfile(used_path.buf);
 731                 if (gitfile) {
 732                         strbuf_reset(&used_path);
 733                         strbuf_addstr(&used_path, gitfile);
 734                 }
 735                 if (chdir(used_path.buf))
 736                         return NULL;
 737                 path = validated_path.buf;
 738         }
 739         else {
 740                 const char *gitfile = read_gitfile(path);
 741                 if (gitfile)
 742                         path = gitfile;
 743                 if (chdir(path))
 744                         return NULL;
 745         }
 746
 747         if (is_git_directory(".")) {
 748                 set_git_dir(".");
 749                 check_repository_format();
 750                 return path;
 751         }
 752
 753         return NULL;
 754 }
 755
 756 static int calc_shared_perm(int mode)
 757 {
 758         int tweak;
 759
 760         if (get_shared_repository() < 0)
 761                 tweak = -get_shared_repository();
 762         else
 763                 tweak = get_shared_repository();
 764
 765         if (!(mode & S_IWUSR))
 766                 tweak &= ~0222;
 767         if (mode & S_IXUSR)
 768                 /* Copy read bits to execute bits */
 769                 tweak |= (tweak & 0444) >> 2;
 770         if (get_shared_repository() < 0)
 771                 mode = (mode & ~0777) | tweak;
 772         else
 773                 mode |= tweak;
 774
 775         return mode;
 776 }
 777
 778
 779 int adjust_shared_perm(const char *path)
 780 {
 781         int old_mode, new_mode;
 782
 783         if (!get_shared_repository())
 784                 return 0;
 785         if (get_st_mode_bits(path, &old_mode) < 0)
 786                 return -1;
 787
 788         new_mode = calc_shared_perm(old_mode);
 789         if (S_ISDIR(old_mode)) {
 790                 /* Copy read bits to execute bits */
 791                 new_mode |= (new_mode & 0444) >> 2;
 792                 new_mode |= FORCE_DIR_SET_GID;
 793         }
 794
 795         if (((old_mode ^ new_mode) & ~S_IFMT) &&
 796                         chmod(path, (new_mode & ~S_IFMT)) < 0)
 797                 return -2;
 798         return 0;
 799 }
 800
 801 void safe_create_dir(const char *dir, int share)
 802 {
 803         if (mkdir(dir, 0777) < 0) {
 804                 if (errno != EEXIST) {
 805                         perror(dir);
 806                         exit(1);
 807                 }
 808         }
 809         else if (share && adjust_shared_perm(dir))
 810                 die(_("Could not make %s writable by group"), dir);
 811 }
 812
 813 static int have_same_root(const char *path1, const char *path2)
 814 {
 815         int is_abs1, is_abs2;
 816
 817         is_abs1 = is_absolute_path(path1);
 818         is_abs2 = is_absolute_path(path2);
 819         return (is_abs1 && is_abs2 && tolower(path1[0]) == tolower(path2[0])) ||
 820                (!is_abs1 && !is_abs2);
 821 }
 822
 823 /*
 824  * Give path as relative to prefix.
 825  *
 826  * The strbuf may or may not be used, so do not assume it contains the
 827  * returned path.
 828  */
 829 const char *relative_path(const char *in, const char *prefix,
 830                           struct strbuf *sb)
 831 {
 832         int in_len = in ? strlen(in) : 0;
 833         int prefix_len = prefix ? strlen(prefix) : 0;
 834         int in_off = 0;
 835         int prefix_off = 0;
 836         int i = 0, j = 0;
 837
 838         if (!in_len)
 839                 return "./";
 840         else if (!prefix_len)
 841                 return in;
 842
 843         if (have_same_root(in, prefix))
 844                 /* bypass dos_drive, for "c:" is identical to "C:" */
 845                 i = j = has_dos_drive_prefix(in);
 846         else {
 847                 return in;
 848         }
 849
 850         while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
 851                 if (is_dir_sep(prefix[i])) {
 852                         while (is_dir_sep(prefix[i]))
 853                                 i++;
 854                         while (is_dir_sep(in[j]))
 855                                 j++;
 856                         prefix_off = i;
 857                         in_off = j;
 858                 } else {
 859                         i++;
 860                         j++;
 861                 }
 862         }
 863
 864         if (
 865             /* "prefix" seems like prefix of "in" */
 866             i >= prefix_len &&
 867             /*
 868              * but "/foo" is not a prefix of "/foobar"
 869              * (i.e. prefix not end with '/')
 870              */
 871             prefix_off < prefix_len) {
 872                 if (j >= in_len) {
 873                         /* in="/a/b", prefix="/a/b" */
 874                         in_off = in_len;
 875                 } else if (is_dir_sep(in[j])) {
 876                         /* in="/a/b/c", prefix="/a/b" */
 877                         while (is_dir_sep(in[j]))
 878                                 j++;
 879                         in_off = j;
 880                 } else {
 881                         /* in="/a/bbb/c", prefix="/a/b" */
 882                         i = prefix_off;
 883                 }
 884         } else if (
 885                    /* "in" is short than "prefix" */
 886                    j >= in_len &&
 887                    /* "in" not end with '/' */
 888                    in_off < in_len) {
 889                 if (is_dir_sep(prefix[i])) {
 890                         /* in="/a/b", prefix="/a/b/c/" */
 891                         while (is_dir_sep(prefix[i]))
 892                                 i++;
 893                         in_off = in_len;
 894                 }
 895         }
 896         in += in_off;
 897         in_len -= in_off;
 898
 899         if (i >= prefix_len) {
 900                 if (!in_len)
 901                         return "./";
 902                 else
 903                         return in;
 904         }
 905
 906         strbuf_reset(sb);
 907         strbuf_grow(sb, in_len);
 908
 909         while (i < prefix_len) {
 910                 if (is_dir_sep(prefix[i])) {
 911                         strbuf_addstr(sb, "../");
 912                         while (is_dir_sep(prefix[i]))
 913                                 i++;
 914                         continue;
 915                 }
 916                 i++;
 917         }
 918         if (!is_dir_sep(prefix[prefix_len - 1]))
 919                 strbuf_addstr(sb, "../");
 920
 921         strbuf_addstr(sb, in);
 922
 923         return sb->buf;
 924 }
 925
 926 /*
 927  * A simpler implementation of relative_path
 928  *
 929  * Get relative path by removing "prefix" from "in". This function
 930  * first appears in v1.5.6-1-g044bbbc, and makes git_dir shorter
 931  * to increase performance when traversing the path to work_tree.
 932  */
 933 const char *remove_leading_path(const char *in, const char *prefix)
 934 {
 935         static struct strbuf buf = STRBUF_INIT;
 936         int i = 0, j = 0;
 937
 938         if (!prefix || !prefix[0])
 939                 return in;
 940         while (prefix[i]) {
 941                 if (is_dir_sep(prefix[i])) {
 942                         if (!is_dir_sep(in[j]))
 943                                 return in;
 944                         while (is_dir_sep(prefix[i]))
 945                                 i++;
 946                         while (is_dir_sep(in[j]))
 947                                 j++;
 948                         continue;
 949                 } else if (in[j] != prefix[i]) {
 950                         return in;
 951                 }
 952                 i++;
 953                 j++;
 954         }
 955         if (
 956             /* "/foo" is a prefix of "/foo" */
 957             in[j] &&
 958             /* "/foo" is not a prefix of "/foobar" */
 959             !is_dir_sep(prefix[i-1]) && !is_dir_sep(in[j])
 960            )
 961                 return in;
 962         while (is_dir_sep(in[j]))
 963                 j++;
 964
 965         strbuf_reset(&buf);
 966         if (!in[j])
 967                 strbuf_addstr(&buf, ".");
 968         else
 969                 strbuf_addstr(&buf, in + j);
 970         return buf.buf;
 971 }
 972
 973 /*
 974  * It is okay if dst == src, but they should not overlap otherwise.
 975  *
 976  * Performs the following normalizations on src, storing the result in dst:
 977  * - Ensures that components are separated by '/' (Windows only)
 978  * - Squashes sequences of '/' except "//server/share" on Windows
 979  * - Removes "." components.
 980  * - Removes ".." components, and the components the precede them.
 981  * Returns failure (non-zero) if a ".." component appears as first path
 982  * component anytime during the normalization. Otherwise, returns success (0).
 983  *
 984  * Note that this function is purely textual.  It does not follow symlinks,
 985  * verify the existence of the path, or make any system calls.
 986  *
 987  * prefix_len != NULL is for a specific case of prefix_pathspec():
 988  * assume that src == dst and src[0..prefix_len-1] is already
 989  * normalized, any time "../" eats up to the prefix_len part,
 990  * prefix_len is reduced. In the end prefix_len is the remaining
 991  * prefix that has not been overridden by user pathspec.
 992  *
 993  * NEEDSWORK: This function doesn't perform normalization w.r.t. trailing '/'.
 994  * For everything but the root folder itself, the normalized path should not
 995  * end with a '/', then the callers need to be fixed up accordingly.
 996  *
 997  */
 998 int normalize_path_copy_len(char *dst, const char *src, int *prefix_len)
 999 {
1000         char *dst0;
1001         const char *end;
1002
1003         /*
1004          * Copy initial part of absolute path: "/", "C:/", "//server/share/".
1005          */
1006         end = src + offset_1st_component(src);
1007         while (src < end) {
1008                 char c = *src++;
1009                 if (is_dir_sep(c))
1010                         c = '/';
1011                 *dst++ = c;
1012         }
1013         dst0 = dst;
1014
1015         while (is_dir_sep(*src))
1016                 src++;
1017
1018         for (;;) {
1019                 char c = *src;
1020
1021                 /*
1022                  * A path component that begins with . could be
1023                  * special:
1024                  * (1) "." and ends   -- ignore and terminate.
1025                  * (2) "./"           -- ignore them, eat slash and continue.
1026                  * (3) ".." and ends  -- strip one and terminate.
1027                  * (4) "../"          -- strip one, eat slash and continue.
1028                  */
1029                 if (c == '.') {
1030                         if (!src[1]) {
1031                                 /* (1) */
1032                                 src++;
1033                         } else if (is_dir_sep(src[1])) {
1034                                 /* (2) */
1035                                 src += 2;
1036                                 while (is_dir_sep(*src))
1037                                         src++;
1038                                 continue;
1039                         } else if (src[1] == '.') {
1040                                 if (!src[2]) {
1041                                         /* (3) */
1042                                         src += 2;
1043                                         goto up_one;
1044                                 } else if (is_dir_sep(src[2])) {
1045                                         /* (4) */
1046                                         src += 3;
1047                                         while (is_dir_sep(*src))
1048                                                 src++;
1049                                         goto up_one;
1050                                 }
1051                         }
1052                 }
1053
1054                 /* copy up to the next '/', and eat all '/' */
1055                 while ((c = *src++) != '\0' && !is_dir_sep(c))
1056                         *dst++ = c;
1057                 if (is_dir_sep(c)) {
1058                         *dst++ = '/';
1059                         while (is_dir_sep(c))
1060                                 c = *src++;
1061                         src--;
1062                 } else if (!c)
1063                         break;
1064                 continue;
1065
1066         up_one:
1067                 /*
1068                  * dst0..dst is prefix portion, and dst[-1] is '/';
1069                  * go up one level.
1070                  */
1071                 dst--;  /* go to trailing '/' */
1072                 if (dst <= dst0)
1073                         return -1;
1074                 /* Windows: dst[-1] cannot be backslash anymore */
1075                 while (dst0 < dst && dst[-1] != '/')
1076                         dst--;
1077                 if (prefix_len && *prefix_len > dst - dst0)
1078                         *prefix_len = dst - dst0;
1079         }
1080         *dst = '\0';
1081         return 0;
1082 }
1083
1084 int normalize_path_copy(char *dst, const char *src)
1085 {
1086         return normalize_path_copy_len(dst, src, NULL);
1087 }
1088
1089 /*
1090  * path = Canonical absolute path
1091  * prefixes = string_list containing normalized, absolute paths without
1092  * trailing slashes (except for the root directory, which is denoted by "/").
1093  *
1094  * Determines, for each path in prefixes, whether the "prefix"
1095  * is an ancestor directory of path.  Returns the length of the longest
1096  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
1097  * is an ancestor.  (Note that this means 0 is returned if prefixes is
1098  * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
1099  * are not considered to be their own ancestors.  path must be in a
1100  * canonical form: empty components, or "." or ".." components are not
1101  * allowed.
1102  */
1103 int longest_ancestor_length(const char *path, struct string_list *prefixes)
1104 {
1105         int i, max_len = -1;
1106
1107         if (!strcmp(path, "/"))
1108                 return -1;
1109
1110         for (i = 0; i < prefixes->nr; i++) {
1111                 const char *ceil = prefixes->items[i].string;
1112                 int len = strlen(ceil);
1113
1114                 if (len == 1 && ceil[0] == '/')
1115                         len = 0; /* root matches anything, with length 0 */
1116                 else if (!strncmp(path, ceil, len) && path[len] == '/')
1117                         ; /* match of length len */
1118                 else
1119                         continue; /* no match */
1120
1121                 if (len > max_len)
1122                         max_len = len;
1123         }
1124
1125         return max_len;
1126 }
1127
1128 /* strip arbitrary amount of directory separators at end of path */
1129 static inline int chomp_trailing_dir_sep(const char *path, int len)
1130 {
1131         while (len && is_dir_sep(path[len - 1]))
1132                 len--;
1133         return len;
1134 }
1135
1136 /*
1137  * If path ends with suffix (complete path components), returns the
1138  * part before suffix (sans trailing directory separators).
1139  * Otherwise returns NULL.
1140  */
1141 char *strip_path_suffix(const char *path, const char *suffix)
1142 {
1143         int path_len = strlen(path), suffix_len = strlen(suffix);
1144
1145         while (suffix_len) {
1146                 if (!path_len)
1147                         return NULL;
1148
1149                 if (is_dir_sep(path[path_len - 1])) {
1150                         if (!is_dir_sep(suffix[suffix_len - 1]))
1151                                 return NULL;
1152                         path_len = chomp_trailing_dir_sep(path, path_len);
1153                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
1154                 }
1155                 else if (path[--path_len] != suffix[--suffix_len])
1156                         return NULL;
1157         }
1158
1159         if (path_len && !is_dir_sep(path[path_len - 1]))
1160                 return NULL;
1161         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
1162 }
1163
1164 int daemon_avoid_alias(const char *p)
1165 {
1166         int sl, ndot;
1167
1168         /*
1169          * This resurrects the belts and suspenders paranoia check by HPA
1170          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
1171          * does not do getcwd() based path canonicalization.
1172          *
1173          * sl becomes true immediately after seeing '/' and continues to
1174          * be true as long as dots continue after that without intervening
1175          * non-dot character.
1176          */
1177         if (!p || (*p != '/' && *p != '~'))
1178                 return -1;
1179         sl = 1; ndot = 0;
1180         p++;
1181
1182         while (1) {
1183                 char ch = *p++;
1184                 if (sl) {
1185                         if (ch == '.')
1186                                 ndot++;
1187                         else if (ch == '/') {
1188                                 if (ndot < 3)
1189                                         /* reject //, /./ and /../ */
1190                                         return -1;
1191                                 ndot = 0;
1192                         }
1193                         else if (ch == 0) {
1194                                 if (0 < ndot && ndot < 3)
1195                                         /* reject /.$ and /..$ */
1196                                         return -1;
1197                                 return 0;
1198                         }
1199                         else
1200                                 sl = ndot = 0;
1201                 }
1202                 else if (ch == 0)
1203                         return 0;
1204                 else if (ch == '/') {
1205                         sl = 1;
1206                         ndot = 0;
1207                 }
1208         }
1209 }
1210
1211 static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
1212 {
1213         if (len < skip)
1214                 return 0;
1215         len -= skip;
1216         path += skip;
1217         while (len-- > 0) {
1218                 char c = *(path++);
1219                 if (c != ' ' && c != '.')
1220                         return 0;
1221         }
1222         return 1;
1223 }
1224
1225 int is_ntfs_dotgit(const char *name)
1226 {
1227         int len;
1228
1229         for (len = 0; ; len++)
1230                 if (!name[len] || name[len] == '\\' || is_dir_sep(name[len])) {
1231                         if (only_spaces_and_periods(name, len, 4) &&
1232                                         !strncasecmp(name, ".git", 4))
1233                                 return 1;
1234                         if (only_spaces_and_periods(name, len, 5) &&
1235                                         !strncasecmp(name, "git~1", 5))
1236                                 return 1;
1237                         if (name[len] != '\\')
1238                                 return 0;
1239                         name += len + 1;
1240                         len = -1;
1241                 }
1242 }
1243
1244 char *xdg_config_home(const char *filename)
1245 {
1246         const char *home, *config_home;
1247
1248         assert(filename);
1249         config_home = getenv("XDG_CONFIG_HOME");
1250         if (config_home && *config_home)
1251                 return mkpathdup("%s/git/%s", config_home, filename);
1252
1253         home = getenv("HOME");
1254         if (home)
1255                 return mkpathdup("%s/.config/git/%s", home, filename);
1256         return NULL;
1257 }
1258
1259 char *xdg_cache_home(const char *filename)
1260 {
1261         const char *home, *cache_home;
1262
1263         assert(filename);
1264         cache_home = getenv("XDG_CACHE_HOME");
1265         if (cache_home && *cache_home)
1266                 return mkpathdup("%s/git/%s", cache_home, filename);
1267
1268         home = getenv("HOME");
1269         if (home)
1270                 return mkpathdup("%s/.cache/git/%s", home, filename);
1271         return NULL;
1272 }
1273
1274 GIT_PATH_FUNC(git_path_cherry_pick_head, "CHERRY_PICK_HEAD")
1275 GIT_PATH_FUNC(git_path_revert_head, "REVERT_HEAD")
1276 GIT_PATH_FUNC(git_path_squash_msg, "SQUASH_MSG")
1277 GIT_PATH_FUNC(git_path_merge_msg, "MERGE_MSG")
1278 GIT_PATH_FUNC(git_path_merge_rr, "MERGE_RR")
1279 GIT_PATH_FUNC(git_path_merge_mode, "MERGE_MODE")
1280 GIT_PATH_FUNC(git_path_merge_head, "MERGE_HEAD")
1281 GIT_PATH_FUNC(git_path_fetch_head, "FETCH_HEAD")
1282 GIT_PATH_FUNC(git_path_shallow, "shallow")