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