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