path.c

   1 /*
   2  * Utilities for paths and pathnames
   3  */
   4 #include "cache.h"
   5 #include "strbuf.h"
   6 #include "string-list.h"
   7
   8 static int get_st_mode_bits(const char *path, int *mode)
   9 {
  10         struct stat st;
  11         if (lstat(path, &st) < 0)
  12                 return -1;
  13         *mode = st.st_mode;
  14         return 0;
  15 }
  16
  17 static char bad_path[] = "/bad-path/";
  18
  19 static char *get_pathname(void)
  20 {
  21         static char pathname_array[4][PATH_MAX];
  22         static int index;
  23         return pathname_array[3 & ++index];
  24 }
  25
  26 static char *cleanup_path(char *path)
  27 {
  28         /* Clean it up */
  29         if (!memcmp(path, "./", 2)) {
  30                 path += 2;
  31                 while (*path == '/')
  32                         path++;
  33         }
  34         return path;
  35 }
  36
  37 char *mksnpath(char *buf, size_t n, const char *fmt, ...)
  38 {
  39         va_list args;
  40         unsigned len;
  41
  42         va_start(args, fmt);
  43         len = vsnprintf(buf, n, fmt, args);
  44         va_end(args);
  45         if (len >= n) {
  46                 strlcpy(buf, bad_path, n);
  47                 return buf;
  48         }
  49         return cleanup_path(buf);
  50 }
  51
  52 static char *vsnpath(char *buf, size_t n, const char *fmt, va_list args)
  53 {
  54         const char *git_dir = get_git_dir();
  55         size_t len;
  56
  57         len = strlen(git_dir);
  58         if (n < len + 1)
  59                 goto bad;
  60         memcpy(buf, git_dir, len);
  61         if (len && !is_dir_sep(git_dir[len-1]))
  62                 buf[len++] = '/';
  63         len += vsnprintf(buf + len, n - len, fmt, args);
  64         if (len >= n)
  65                 goto bad;
  66         return cleanup_path(buf);
  67 bad:
  68         strlcpy(buf, bad_path, n);
  69         return buf;
  70 }
  71
  72 char *git_snpath(char *buf, size_t n, const char *fmt, ...)
  73 {
  74         char *ret;
  75         va_list args;
  76         va_start(args, fmt);
  77         ret = vsnpath(buf, n, fmt, args);
  78         va_end(args);
  79         return ret;
  80 }
  81
  82 char *git_pathdup(const char *fmt, ...)
  83 {
  84         char path[PATH_MAX], *ret;
  85         va_list args;
  86         va_start(args, fmt);
  87         ret = vsnpath(path, sizeof(path), fmt, args);
  88         va_end(args);
  89         return xstrdup(ret);
  90 }
  91
  92 char *mkpathdup(const char *fmt, ...)
  93 {
  94         char *path;
  95         struct strbuf sb = STRBUF_INIT;
  96         va_list args;
  97
  98         va_start(args, fmt);
  99         strbuf_vaddf(&sb, fmt, args);
 100         va_end(args);
 101         path = xstrdup(cleanup_path(sb.buf));
 102
 103         strbuf_release(&sb);
 104         return path;
 105 }
 106
 107 char *mkpath(const char *fmt, ...)
 108 {
 109         va_list args;
 110         unsigned len;
 111         char *pathname = get_pathname();
 112
 113         va_start(args, fmt);
 114         len = vsnprintf(pathname, PATH_MAX, fmt, args);
 115         va_end(args);
 116         if (len >= PATH_MAX)
 117                 return bad_path;
 118         return cleanup_path(pathname);
 119 }
 120
 121 char *git_path(const char *fmt, ...)
 122 {
 123         char *pathname = get_pathname();
 124         va_list args;
 125         char *ret;
 126
 127         va_start(args, fmt);
 128         ret = vsnpath(pathname, PATH_MAX, fmt, args);
 129         va_end(args);
 130         return ret;
 131 }
 132
 133 void home_config_paths(char **global, char **xdg, char *file)
 134 {
 135         char *xdg_home = getenv("XDG_CONFIG_HOME");
 136         char *home = getenv("HOME");
 137         char *to_free = NULL;
 138
 139         if (!home) {
 140                 if (global)
 141                         *global = NULL;
 142         } else {
 143                 if (!xdg_home) {
 144                         to_free = mkpathdup("%s/.config", home);
 145                         xdg_home = to_free;
 146                 }
 147                 if (global)
 148                         *global = mkpathdup("%s/.gitconfig", home);
 149         }
 150
 151         if (!xdg_home)
 152                 *xdg = NULL;
 153         else
 154                 *xdg = mkpathdup("%s/git/%s", xdg_home, file);
 155
 156         free(to_free);
 157 }
 158
 159 char *git_path_submodule(const char *path, const char *fmt, ...)
 160 {
 161         char *pathname = get_pathname();
 162         struct strbuf buf = STRBUF_INIT;
 163         const char *git_dir;
 164         va_list args;
 165         unsigned len;
 166
 167         len = strlen(path);
 168         if (len > PATH_MAX-100)
 169                 return bad_path;
 170
 171         strbuf_addstr(&buf, path);
 172         if (len && path[len-1] != '/')
 173                 strbuf_addch(&buf, '/');
 174         strbuf_addstr(&buf, ".git");
 175
 176         git_dir = read_gitfile(buf.buf);
 177         if (git_dir) {
 178                 strbuf_reset(&buf);
 179                 strbuf_addstr(&buf, git_dir);
 180         }
 181         strbuf_addch(&buf, '/');
 182
 183         if (buf.len >= PATH_MAX)
 184                 return bad_path;
 185         memcpy(pathname, buf.buf, buf.len + 1);
 186
 187         strbuf_release(&buf);
 188         len = strlen(pathname);
 189
 190         va_start(args, fmt);
 191         len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
 192         va_end(args);
 193         if (len >= PATH_MAX)
 194                 return bad_path;
 195         return cleanup_path(pathname);
 196 }
 197
 198 int validate_headref(const char *path)
 199 {
 200         struct stat st;
 201         char *buf, buffer[256];
 202         unsigned char sha1[20];
 203         int fd;
 204         ssize_t len;
 205
 206         if (lstat(path, &st) < 0)
 207                 return -1;
 208
 209         /* Make sure it is a "refs/.." symlink */
 210         if (S_ISLNK(st.st_mode)) {
 211                 len = readlink(path, buffer, sizeof(buffer)-1);
 212                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 213                         return 0;
 214                 return -1;
 215         }
 216
 217         /*
 218          * Anything else, just open it and try to see if it is a symbolic ref.
 219          */
 220         fd = open(path, O_RDONLY);
 221         if (fd < 0)
 222                 return -1;
 223         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 224         close(fd);
 225
 226         /*
 227          * Is it a symbolic ref?
 228          */
 229         if (len < 4)
 230                 return -1;
 231         if (!memcmp("ref:", buffer, 4)) {
 232                 buf = buffer + 4;
 233                 len -= 4;
 234                 while (len && isspace(*buf))
 235                         buf++, len--;
 236                 if (len >= 5 && !memcmp("refs/", buf, 5))
 237                         return 0;
 238         }
 239
 240         /*
 241          * Is this a detached HEAD?
 242          */
 243         if (!get_sha1_hex(buffer, sha1))
 244                 return 0;
 245
 246         return -1;
 247 }
 248
 249 static struct passwd *getpw_str(const char *username, size_t len)
 250 {
 251         struct passwd *pw;
 252         char *username_z = xmemdupz(username, len);
 253         pw = getpwnam(username_z);
 254         free(username_z);
 255         return pw;
 256 }
 257
 258 /*
 259  * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 260  * then it is a newly allocated string. Returns NULL on getpw failure or
 261  * if path is NULL.
 262  */
 263 char *expand_user_path(const char *path)
 264 {
 265         struct strbuf user_path = STRBUF_INIT;
 266         const char *to_copy = path;
 267
 268         if (path == NULL)
 269                 goto return_null;
 270         if (path[0] == '~') {
 271                 const char *first_slash = strchrnul(path, '/');
 272                 const char *username = path + 1;
 273                 size_t username_len = first_slash - username;
 274                 if (username_len == 0) {
 275                         const char *home = getenv("HOME");
 276                         if (!home)
 277                                 goto return_null;
 278                         strbuf_add(&user_path, home, strlen(home));
 279                 } else {
 280                         struct passwd *pw = getpw_str(username, username_len);
 281                         if (!pw)
 282                                 goto return_null;
 283                         strbuf_add(&user_path, pw->pw_dir, strlen(pw->pw_dir));
 284                 }
 285                 to_copy = first_slash;
 286         }
 287         strbuf_add(&user_path, to_copy, strlen(to_copy));
 288         return strbuf_detach(&user_path, NULL);
 289 return_null:
 290         strbuf_release(&user_path);
 291         return NULL;
 292 }
 293
 294 /*
 295  * First, one directory to try is determined by the following algorithm.
 296  *
 297  * (0) If "strict" is given, the path is used as given and no DWIM is
 298  *     done. Otherwise:
 299  * (1) "~/path" to mean path under the running user's home directory;
 300  * (2) "~user/path" to mean path under named user's home directory;
 301  * (3) "relative/path" to mean cwd relative directory; or
 302  * (4) "/absolute/path" to mean absolute directory.
 303  *
 304  * Unless "strict" is given, we check "%s/.git", "%s", "%s.git/.git", "%s.git"
 305  * in this order. We select the first one that is a valid git repository, and
 306  * chdir() to it. If none match, or we fail to chdir, we return NULL.
 307  *
 308  * If all goes well, we return the directory we used to chdir() (but
 309  * before ~user is expanded), avoiding getcwd() resolving symbolic
 310  * links.  User relative paths are also returned as they are given,
 311  * except DWIM suffixing.
 312  */
 313 const char *enter_repo(const char *path, int strict)
 314 {
 315         static char used_path[PATH_MAX];
 316         static char validated_path[PATH_MAX];
 317
 318         if (!path)
 319                 return NULL;
 320
 321         if (!strict) {
 322                 static const char *suffix[] = {
 323                         "/.git", "", ".git/.git", ".git", NULL,
 324                 };
 325                 const char *gitfile;
 326                 int len = strlen(path);
 327                 int i;
 328                 while ((1 < len) && (path[len-1] == '/'))
 329                         len--;
 330
 331                 if (PATH_MAX <= len)
 332                         return NULL;
 333                 strncpy(used_path, path, len); used_path[len] = 0 ;
 334                 strcpy(validated_path, used_path);
 335
 336                 if (used_path[0] == '~') {
 337                         char *newpath = expand_user_path(used_path);
 338                         if (!newpath || (PATH_MAX - 10 < strlen(newpath))) {
 339                                 free(newpath);
 340                                 return NULL;
 341                         }
 342                         /*
 343                          * Copy back into the static buffer. A pity
 344                          * since newpath was not bounded, but other
 345                          * branches of the if are limited by PATH_MAX
 346                          * anyway.
 347                          */
 348                         strcpy(used_path, newpath); free(newpath);
 349                 }
 350                 else if (PATH_MAX - 10 < len)
 351                         return NULL;
 352                 len = strlen(used_path);
 353                 for (i = 0; suffix[i]; i++) {
 354                         struct stat st;
 355                         strcpy(used_path + len, suffix[i]);
 356                         if (!stat(used_path, &st) &&
 357                             (S_ISREG(st.st_mode) ||
 358                             (S_ISDIR(st.st_mode) && is_git_directory(used_path)))) {
 359                                 strcat(validated_path, suffix[i]);
 360                                 break;
 361                         }
 362                 }
 363                 if (!suffix[i])
 364                         return NULL;
 365                 gitfile = read_gitfile(used_path) ;
 366                 if (gitfile)
 367                         strcpy(used_path, gitfile);
 368                 if (chdir(used_path))
 369                         return NULL;
 370                 path = validated_path;
 371         }
 372         else if (chdir(path))
 373                 return NULL;
 374
 375         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 376             validate_headref("HEAD") == 0) {
 377                 set_git_dir(".");
 378                 check_repository_format();
 379                 return path;
 380         }
 381
 382         return NULL;
 383 }
 384
 385 static int calc_shared_perm(int mode)
 386 {
 387         int tweak;
 388
 389         if (shared_repository < 0)
 390                 tweak = -shared_repository;
 391         else
 392                 tweak = shared_repository;
 393
 394         if (!(mode & S_IWUSR))
 395                 tweak &= ~0222;
 396         if (mode & S_IXUSR)
 397                 /* Copy read bits to execute bits */
 398                 tweak |= (tweak & 0444) >> 2;
 399         if (shared_repository < 0)
 400                 mode = (mode & ~0777) | tweak;
 401         else
 402                 mode |= tweak;
 403
 404         return mode;
 405 }
 406
 407
 408 int adjust_shared_perm(const char *path)
 409 {
 410         int old_mode, new_mode;
 411
 412         if (!shared_repository)
 413                 return 0;
 414         if (get_st_mode_bits(path, &old_mode) < 0)
 415                 return -1;
 416
 417         new_mode = calc_shared_perm(old_mode);
 418         if (S_ISDIR(old_mode)) {
 419                 /* Copy read bits to execute bits */
 420                 new_mode |= (new_mode & 0444) >> 2;
 421                 new_mode |= FORCE_DIR_SET_GID;
 422         }
 423
 424         if (((old_mode ^ new_mode) & ~S_IFMT) &&
 425                         chmod(path, (new_mode & ~S_IFMT)) < 0)
 426                 return -2;
 427         return 0;
 428 }
 429
 430 static int have_same_root(const char *path1, const char *path2)
 431 {
 432         int is_abs1, is_abs2;
 433
 434         is_abs1 = is_absolute_path(path1);
 435         is_abs2 = is_absolute_path(path2);
 436         return (is_abs1 && is_abs2 && tolower(path1[0]) == tolower(path2[0])) ||
 437                (!is_abs1 && !is_abs2);
 438 }
 439
 440 /*
 441  * Give path as relative to prefix.
 442  *
 443  * The strbuf may or may not be used, so do not assume it contains the
 444  * returned path.
 445  */
 446 const char *relative_path(const char *in, const char *prefix,
 447                           struct strbuf *sb)
 448 {
 449         int in_len = in ? strlen(in) : 0;
 450         int prefix_len = prefix ? strlen(prefix) : 0;
 451         int in_off = 0;
 452         int prefix_off = 0;
 453         int i = 0, j = 0;
 454
 455         if (!in_len)
 456                 return "./";
 457         else if (!prefix_len)
 458                 return in;
 459
 460         if (have_same_root(in, prefix)) {
 461                 /* bypass dos_drive, for "c:" is identical to "C:" */
 462                 if (has_dos_drive_prefix(in)) {
 463                         i = 2;
 464                         j = 2;
 465                 }
 466         } else {
 467                 return in;
 468         }
 469
 470         while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
 471                 if (is_dir_sep(prefix[i])) {
 472                         while (is_dir_sep(prefix[i]))
 473                                 i++;
 474                         while (is_dir_sep(in[j]))
 475                                 j++;
 476                         prefix_off = i;
 477                         in_off = j;
 478                 } else {
 479                         i++;
 480                         j++;
 481                 }
 482         }
 483
 484         if (
 485             /* "prefix" seems like prefix of "in" */
 486             i >= prefix_len &&
 487             /*
 488              * but "/foo" is not a prefix of "/foobar"
 489              * (i.e. prefix not end with '/')
 490              */
 491             prefix_off < prefix_len) {
 492                 if (j >= in_len) {
 493                         /* in="/a/b", prefix="/a/b" */
 494                         in_off = in_len;
 495                 } else if (is_dir_sep(in[j])) {
 496                         /* in="/a/b/c", prefix="/a/b" */
 497                         while (is_dir_sep(in[j]))
 498                                 j++;
 499                         in_off = j;
 500                 } else {
 501                         /* in="/a/bbb/c", prefix="/a/b" */
 502                         i = prefix_off;
 503                 }
 504         } else if (
 505                    /* "in" is short than "prefix" */
 506                    j >= in_len &&
 507                    /* "in" not end with '/' */
 508                    in_off < in_len) {
 509                 if (is_dir_sep(prefix[i])) {
 510                         /* in="/a/b", prefix="/a/b/c/" */
 511                         while (is_dir_sep(prefix[i]))
 512                                 i++;
 513                         in_off = in_len;
 514                 }
 515         }
 516         in += in_off;
 517         in_len -= in_off;
 518
 519         if (i >= prefix_len) {
 520                 if (!in_len)
 521                         return "./";
 522                 else
 523                         return in;
 524         }
 525
 526         strbuf_reset(sb);
 527         strbuf_grow(sb, in_len);
 528
 529         while (i < prefix_len) {
 530                 if (is_dir_sep(prefix[i])) {
 531                         strbuf_addstr(sb, "../");
 532                         while (is_dir_sep(prefix[i]))
 533                                 i++;
 534                         continue;
 535                 }
 536                 i++;
 537         }
 538         if (!is_dir_sep(prefix[prefix_len - 1]))
 539                 strbuf_addstr(sb, "../");
 540
 541         strbuf_addstr(sb, in);
 542
 543         return sb->buf;
 544 }
 545
 546 /*
 547  * A simpler implementation of relative_path
 548  *
 549  * Get relative path by removing "prefix" from "in". This function
 550  * first appears in v1.5.6-1-g044bbbc, and makes git_dir shorter
 551  * to increase performance when traversing the path to work_tree.
 552  */
 553 const char *remove_leading_path(const char *in, const char *prefix)
 554 {
 555         static char buf[PATH_MAX + 1];
 556         int i = 0, j = 0;
 557
 558         if (!prefix || !prefix[0])
 559                 return in;
 560         while (prefix[i]) {
 561                 if (is_dir_sep(prefix[i])) {
 562                         if (!is_dir_sep(in[j]))
 563                                 return in;
 564                         while (is_dir_sep(prefix[i]))
 565                                 i++;
 566                         while (is_dir_sep(in[j]))
 567                                 j++;
 568                         continue;
 569                 } else if (in[j] != prefix[i]) {
 570                         return in;
 571                 }
 572                 i++;
 573                 j++;
 574         }
 575         if (
 576             /* "/foo" is a prefix of "/foo" */
 577             in[j] &&
 578             /* "/foo" is not a prefix of "/foobar" */
 579             !is_dir_sep(prefix[i-1]) && !is_dir_sep(in[j])
 580            )
 581                 return in;
 582         while (is_dir_sep(in[j]))
 583                 j++;
 584         if (!in[j])
 585                 strcpy(buf, ".");
 586         else
 587                 strcpy(buf, in + j);
 588         return buf;
 589 }
 590
 591 /*
 592  * It is okay if dst == src, but they should not overlap otherwise.
 593  *
 594  * Performs the following normalizations on src, storing the result in dst:
 595  * - Ensures that components are separated by '/' (Windows only)
 596  * - Squashes sequences of '/'.
 597  * - Removes "." components.
 598  * - Removes ".." components, and the components the precede them.
 599  * Returns failure (non-zero) if a ".." component appears as first path
 600  * component anytime during the normalization. Otherwise, returns success (0).
 601  *
 602  * Note that this function is purely textual.  It does not follow symlinks,
 603  * verify the existence of the path, or make any system calls.
 604  *
 605  * prefix_len != NULL is for a specific case of prefix_pathspec():
 606  * assume that src == dst and src[0..prefix_len-1] is already
 607  * normalized, any time "../" eats up to the prefix_len part,
 608  * prefix_len is reduced. In the end prefix_len is the remaining
 609  * prefix that has not been overridden by user pathspec.
 610  */
 611 int normalize_path_copy_len(char *dst, const char *src, int *prefix_len)
 612 {
 613         char *dst0;
 614
 615         if (has_dos_drive_prefix(src)) {
 616                 *dst++ = *src++;
 617                 *dst++ = *src++;
 618         }
 619         dst0 = dst;
 620
 621         if (is_dir_sep(*src)) {
 622                 *dst++ = '/';
 623                 while (is_dir_sep(*src))
 624                         src++;
 625         }
 626
 627         for (;;) {
 628                 char c = *src;
 629
 630                 /*
 631                  * A path component that begins with . could be
 632                  * special:
 633                  * (1) "." and ends   -- ignore and terminate.
 634                  * (2) "./"           -- ignore them, eat slash and continue.
 635                  * (3) ".." and ends  -- strip one and terminate.
 636                  * (4) "../"          -- strip one, eat slash and continue.
 637                  */
 638                 if (c == '.') {
 639                         if (!src[1]) {
 640                                 /* (1) */
 641                                 src++;
 642                         } else if (is_dir_sep(src[1])) {
 643                                 /* (2) */
 644                                 src += 2;
 645                                 while (is_dir_sep(*src))
 646                                         src++;
 647                                 continue;
 648                         } else if (src[1] == '.') {
 649                                 if (!src[2]) {
 650                                         /* (3) */
 651                                         src += 2;
 652                                         goto up_one;
 653                                 } else if (is_dir_sep(src[2])) {
 654                                         /* (4) */
 655                                         src += 3;
 656                                         while (is_dir_sep(*src))
 657                                                 src++;
 658                                         goto up_one;
 659                                 }
 660                         }
 661                 }
 662
 663                 /* copy up to the next '/', and eat all '/' */
 664                 while ((c = *src++) != '\0' && !is_dir_sep(c))
 665                         *dst++ = c;
 666                 if (is_dir_sep(c)) {
 667                         *dst++ = '/';
 668                         while (is_dir_sep(c))
 669                                 c = *src++;
 670                         src--;
 671                 } else if (!c)
 672                         break;
 673                 continue;
 674
 675         up_one:
 676                 /*
 677                  * dst0..dst is prefix portion, and dst[-1] is '/';
 678                  * go up one level.
 679                  */
 680                 dst--;  /* go to trailing '/' */
 681                 if (dst <= dst0)
 682                         return -1;
 683                 /* Windows: dst[-1] cannot be backslash anymore */
 684                 while (dst0 < dst && dst[-1] != '/')
 685                         dst--;
 686                 if (prefix_len && *prefix_len > dst - dst0)
 687                         *prefix_len = dst - dst0;
 688         }
 689         *dst = '\0';
 690         return 0;
 691 }
 692
 693 int normalize_path_copy(char *dst, const char *src)
 694 {
 695         return normalize_path_copy_len(dst, src, NULL);
 696 }
 697
 698 /*
 699  * path = Canonical absolute path
 700  * prefixes = string_list containing normalized, absolute paths without
 701  * trailing slashes (except for the root directory, which is denoted by "/").
 702  *
 703  * Determines, for each path in prefixes, whether the "prefix"
 704  * is an ancestor directory of path.  Returns the length of the longest
 705  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 706  * is an ancestor.  (Note that this means 0 is returned if prefixes is
 707  * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
 708  * are not considered to be their own ancestors.  path must be in a
 709  * canonical form: empty components, or "." or ".." components are not
 710  * allowed.
 711  */
 712 int longest_ancestor_length(const char *path, struct string_list *prefixes)
 713 {
 714         int i, max_len = -1;
 715
 716         if (!strcmp(path, "/"))
 717                 return -1;
 718
 719         for (i = 0; i < prefixes->nr; i++) {
 720                 const char *ceil = prefixes->items[i].string;
 721                 int len = strlen(ceil);
 722
 723                 if (len == 1 && ceil[0] == '/')
 724                         len = 0; /* root matches anything, with length 0 */
 725                 else if (!strncmp(path, ceil, len) && path[len] == '/')
 726                         ; /* match of length len */
 727                 else
 728                         continue; /* no match */
 729
 730                 if (len > max_len)
 731                         max_len = len;
 732         }
 733
 734         return max_len;
 735 }
 736
 737 /* strip arbitrary amount of directory separators at end of path */
 738 static inline int chomp_trailing_dir_sep(const char *path, int len)
 739 {
 740         while (len && is_dir_sep(path[len - 1]))
 741                 len--;
 742         return len;
 743 }
 744
 745 /*
 746  * If path ends with suffix (complete path components), returns the
 747  * part before suffix (sans trailing directory separators).
 748  * Otherwise returns NULL.
 749  */
 750 char *strip_path_suffix(const char *path, const char *suffix)
 751 {
 752         int path_len = strlen(path), suffix_len = strlen(suffix);
 753
 754         while (suffix_len) {
 755                 if (!path_len)
 756                         return NULL;
 757
 758                 if (is_dir_sep(path[path_len - 1])) {
 759                         if (!is_dir_sep(suffix[suffix_len - 1]))
 760                                 return NULL;
 761                         path_len = chomp_trailing_dir_sep(path, path_len);
 762                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
 763                 }
 764                 else if (path[--path_len] != suffix[--suffix_len])
 765                         return NULL;
 766         }
 767
 768         if (path_len && !is_dir_sep(path[path_len - 1]))
 769                 return NULL;
 770         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
 771 }
 772
 773 int daemon_avoid_alias(const char *p)
 774 {
 775         int sl, ndot;
 776
 777         /*
 778          * This resurrects the belts and suspenders paranoia check by HPA
 779          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
 780          * does not do getcwd() based path canonicalization.
 781          *
 782          * sl becomes true immediately after seeing '/' and continues to
 783          * be true as long as dots continue after that without intervening
 784          * non-dot character.
 785          */
 786         if (!p || (*p != '/' && *p != '~'))
 787                 return -1;
 788         sl = 1; ndot = 0;
 789         p++;
 790
 791         while (1) {
 792                 char ch = *p++;
 793                 if (sl) {
 794                         if (ch == '.')
 795                                 ndot++;
 796                         else if (ch == '/') {
 797                                 if (ndot < 3)
 798                                         /* reject //, /./ and /../ */
 799                                         return -1;
 800                                 ndot = 0;
 801                         }
 802                         else if (ch == 0) {
 803                                 if (0 < ndot && ndot < 3)
 804                                         /* reject /.$ and /..$ */
 805                                         return -1;
 806                                 return 0;
 807                         }
 808                         else
 809                                 sl = ndot = 0;
 810                 }
 811                 else if (ch == 0)
 812                         return 0;
 813                 else if (ch == '/') {
 814                         sl = 1;
 815                         ndot = 0;
 816                 }
 817         }
 818 }
 819
 820 int offset_1st_component(const char *path)
 821 {
 822         if (has_dos_drive_prefix(path))
 823                 return 2 + is_dir_sep(path[2]);
 824         return is_dir_sep(path[0]);
 825 }
 826
 827 static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
 828 {
 829         if (len < skip)
 830                 return 0;
 831         len -= skip;
 832         path += skip;
 833         while (len-- > 0) {
 834                 char c = *(path++);
 835                 if (c != ' ' && c != '.')
 836                         return 0;
 837         }
 838         return 1;
 839 }
 840
 841 int is_ntfs_dotgit(const char *name)
 842 {
 843         int len;
 844
 845         for (len = 0; ; len++)
 846                 if (!name[len] || name[len] == '\\' || is_dir_sep(name[len])) {
 847                         if (only_spaces_and_periods(name, len, 4) &&
 848                                         !strncasecmp(name, ".git", 4))
 849                                 return 1;
 850                         if (only_spaces_and_periods(name, len, 5) &&
 851                                         !strncasecmp(name, "git~1", 5))
 852                                 return 1;
 853                         if (name[len] != '\\')
 854                                 return 0;
 855                         name += len + 1;
 856                         len = -1;
 857                 }
 858 }