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 try access() for existence of "%s.git/.git",
 305  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 306  * what we try.
 307  *
 308  * Second, we try chdir() to that.  Upon failure, we return NULL.
 309  *
 310  * Then, we try if the current directory is a valid git repository.
 311  * Upon failure, we return NULL.
 312  *
 313  * If all goes well, we return the directory we used to chdir() (but
 314  * before ~user is expanded), avoiding getcwd() resolving symbolic
 315  * links.  User relative paths are also returned as they are given,
 316  * except DWIM suffixing.
 317  */
 318 const char *enter_repo(const char *path, int strict)
 319 {
 320         static char used_path[PATH_MAX];
 321         static char validated_path[PATH_MAX];
 322
 323         if (!path)
 324                 return NULL;
 325
 326         if (!strict) {
 327                 static const char *suffix[] = {
 328                         "/.git", "", ".git/.git", ".git", NULL,
 329                 };
 330                 const char *gitfile;
 331                 int len = strlen(path);
 332                 int i;
 333                 while ((1 < len) && (path[len-1] == '/'))
 334                         len--;
 335
 336                 if (PATH_MAX <= len)
 337                         return NULL;
 338                 strncpy(used_path, path, len); used_path[len] = 0 ;
 339                 strcpy(validated_path, used_path);
 340
 341                 if (used_path[0] == '~') {
 342                         char *newpath = expand_user_path(used_path);
 343                         if (!newpath || (PATH_MAX - 10 < strlen(newpath))) {
 344                                 free(newpath);
 345                                 return NULL;
 346                         }
 347                         /*
 348                          * Copy back into the static buffer. A pity
 349                          * since newpath was not bounded, but other
 350                          * branches of the if are limited by PATH_MAX
 351                          * anyway.
 352                          */
 353                         strcpy(used_path, newpath); free(newpath);
 354                 }
 355                 else if (PATH_MAX - 10 < len)
 356                         return NULL;
 357                 len = strlen(used_path);
 358                 for (i = 0; suffix[i]; i++) {
 359                         struct stat st;
 360                         strcpy(used_path + len, suffix[i]);
 361                         if (!stat(used_path, &st) &&
 362                             (S_ISREG(st.st_mode) ||
 363                             (S_ISDIR(st.st_mode) && is_git_directory(used_path)))) {
 364                                 strcat(validated_path, suffix[i]);
 365                                 break;
 366                         }
 367                 }
 368                 if (!suffix[i])
 369                         return NULL;
 370                 gitfile = read_gitfile(used_path) ;
 371                 if (gitfile)
 372                         strcpy(used_path, gitfile);
 373                 if (chdir(used_path))
 374                         return NULL;
 375                 path = validated_path;
 376         }
 377         else if (chdir(path))
 378                 return NULL;
 379
 380         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 381             validate_headref("HEAD") == 0) {
 382                 set_git_dir(".");
 383                 check_repository_format();
 384                 return path;
 385         }
 386
 387         return NULL;
 388 }
 389
 390 static int calc_shared_perm(int mode)
 391 {
 392         int tweak;
 393
 394         if (shared_repository < 0)
 395                 tweak = -shared_repository;
 396         else
 397                 tweak = shared_repository;
 398
 399         if (!(mode & S_IWUSR))
 400                 tweak &= ~0222;
 401         if (mode & S_IXUSR)
 402                 /* Copy read bits to execute bits */
 403                 tweak |= (tweak & 0444) >> 2;
 404         if (shared_repository < 0)
 405                 mode = (mode & ~0777) | tweak;
 406         else
 407                 mode |= tweak;
 408
 409         return mode;
 410 }
 411
 412
 413 int adjust_shared_perm(const char *path)
 414 {
 415         int old_mode, new_mode;
 416
 417         if (!shared_repository)
 418                 return 0;
 419         if (get_st_mode_bits(path, &old_mode) < 0)
 420                 return -1;
 421
 422         new_mode = calc_shared_perm(old_mode);
 423         if (S_ISDIR(old_mode)) {
 424                 /* Copy read bits to execute bits */
 425                 new_mode |= (new_mode & 0444) >> 2;
 426                 new_mode |= FORCE_DIR_SET_GID;
 427         }
 428
 429         if (((old_mode ^ new_mode) & ~S_IFMT) &&
 430                         chmod(path, (new_mode & ~S_IFMT)) < 0)
 431                 return -2;
 432         return 0;
 433 }
 434
 435 static int have_same_root(const char *path1, const char *path2)
 436 {
 437         int is_abs1, is_abs2;
 438
 439         is_abs1 = is_absolute_path(path1);
 440         is_abs2 = is_absolute_path(path2);
 441         return (is_abs1 && is_abs2 && tolower(path1[0]) == tolower(path2[0])) ||
 442                (!is_abs1 && !is_abs2);
 443 }
 444
 445 /*
 446  * Give path as relative to prefix.
 447  *
 448  * The strbuf may or may not be used, so do not assume it contains the
 449  * returned path.
 450  */
 451 const char *relative_path(const char *in, const char *prefix,
 452                           struct strbuf *sb)
 453 {
 454         int in_len = in ? strlen(in) : 0;
 455         int prefix_len = prefix ? strlen(prefix) : 0;
 456         int in_off = 0;
 457         int prefix_off = 0;
 458         int i = 0, j = 0;
 459
 460         if (!in_len)
 461                 return "./";
 462         else if (!prefix_len)
 463                 return in;
 464
 465         if (have_same_root(in, prefix)) {
 466                 /* bypass dos_drive, for "c:" is identical to "C:" */
 467                 if (has_dos_drive_prefix(in)) {
 468                         i = 2;
 469                         j = 2;
 470                 }
 471         } else {
 472                 return in;
 473         }
 474
 475         while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
 476                 if (is_dir_sep(prefix[i])) {
 477                         while (is_dir_sep(prefix[i]))
 478                                 i++;
 479                         while (is_dir_sep(in[j]))
 480                                 j++;
 481                         prefix_off = i;
 482                         in_off = j;
 483                 } else {
 484                         i++;
 485                         j++;
 486                 }
 487         }
 488
 489         if (
 490             /* "prefix" seems like prefix of "in" */
 491             i >= prefix_len &&
 492             /*
 493              * but "/foo" is not a prefix of "/foobar"
 494              * (i.e. prefix not end with '/')
 495              */
 496             prefix_off < prefix_len) {
 497                 if (j >= in_len) {
 498                         /* in="/a/b", prefix="/a/b" */
 499                         in_off = in_len;
 500                 } else if (is_dir_sep(in[j])) {
 501                         /* in="/a/b/c", prefix="/a/b" */
 502                         while (is_dir_sep(in[j]))
 503                                 j++;
 504                         in_off = j;
 505                 } else {
 506                         /* in="/a/bbb/c", prefix="/a/b" */
 507                         i = prefix_off;
 508                 }
 509         } else if (
 510                    /* "in" is short than "prefix" */
 511                    j >= in_len &&
 512                    /* "in" not end with '/' */
 513                    in_off < in_len) {
 514                 if (is_dir_sep(prefix[i])) {
 515                         /* in="/a/b", prefix="/a/b/c/" */
 516                         while (is_dir_sep(prefix[i]))
 517                                 i++;
 518                         in_off = in_len;
 519                 }
 520         }
 521         in += in_off;
 522         in_len -= in_off;
 523
 524         if (i >= prefix_len) {
 525                 if (!in_len)
 526                         return "./";
 527                 else
 528                         return in;
 529         }
 530
 531         strbuf_reset(sb);
 532         strbuf_grow(sb, in_len);
 533
 534         while (i < prefix_len) {
 535                 if (is_dir_sep(prefix[i])) {
 536                         strbuf_addstr(sb, "../");
 537                         while (is_dir_sep(prefix[i]))
 538                                 i++;
 539                         continue;
 540                 }
 541                 i++;
 542         }
 543         if (!is_dir_sep(prefix[prefix_len - 1]))
 544                 strbuf_addstr(sb, "../");
 545
 546         strbuf_addstr(sb, in);
 547
 548         return sb->buf;
 549 }
 550
 551 /*
 552  * A simpler implementation of relative_path
 553  *
 554  * Get relative path by removing "prefix" from "in". This function
 555  * first appears in v1.5.6-1-g044bbbc, and makes git_dir shorter
 556  * to increase performance when traversing the path to work_tree.
 557  */
 558 const char *remove_leading_path(const char *in, const char *prefix)
 559 {
 560         static char buf[PATH_MAX + 1];
 561         int i = 0, j = 0;
 562
 563         if (!prefix || !prefix[0])
 564                 return in;
 565         while (prefix[i]) {
 566                 if (is_dir_sep(prefix[i])) {
 567                         if (!is_dir_sep(in[j]))
 568                                 return in;
 569                         while (is_dir_sep(prefix[i]))
 570                                 i++;
 571                         while (is_dir_sep(in[j]))
 572                                 j++;
 573                         continue;
 574                 } else if (in[j] != prefix[i]) {
 575                         return in;
 576                 }
 577                 i++;
 578                 j++;
 579         }
 580         if (
 581             /* "/foo" is a prefix of "/foo" */
 582             in[j] &&
 583             /* "/foo" is not a prefix of "/foobar" */
 584             !is_dir_sep(prefix[i-1]) && !is_dir_sep(in[j])
 585            )
 586                 return in;
 587         while (is_dir_sep(in[j]))
 588                 j++;
 589         if (!in[j])
 590                 strcpy(buf, ".");
 591         else
 592                 strcpy(buf, in + j);
 593         return buf;
 594 }
 595
 596 /*
 597  * It is okay if dst == src, but they should not overlap otherwise.
 598  *
 599  * Performs the following normalizations on src, storing the result in dst:
 600  * - Ensures that components are separated by '/' (Windows only)
 601  * - Squashes sequences of '/'.
 602  * - Removes "." components.
 603  * - Removes ".." components, and the components the precede them.
 604  * Returns failure (non-zero) if a ".." component appears as first path
 605  * component anytime during the normalization. Otherwise, returns success (0).
 606  *
 607  * Note that this function is purely textual.  It does not follow symlinks,
 608  * verify the existence of the path, or make any system calls.
 609  *
 610  * prefix_len != NULL is for a specific case of prefix_pathspec():
 611  * assume that src == dst and src[0..prefix_len-1] is already
 612  * normalized, any time "../" eats up to the prefix_len part,
 613  * prefix_len is reduced. In the end prefix_len is the remaining
 614  * prefix that has not been overridden by user pathspec.
 615  */
 616 int normalize_path_copy_len(char *dst, const char *src, int *prefix_len)
 617 {
 618         char *dst0;
 619
 620         if (has_dos_drive_prefix(src)) {
 621                 *dst++ = *src++;
 622                 *dst++ = *src++;
 623         }
 624         dst0 = dst;
 625
 626         if (is_dir_sep(*src)) {
 627                 *dst++ = '/';
 628                 while (is_dir_sep(*src))
 629                         src++;
 630         }
 631
 632         for (;;) {
 633                 char c = *src;
 634
 635                 /*
 636                  * A path component that begins with . could be
 637                  * special:
 638                  * (1) "." and ends   -- ignore and terminate.
 639                  * (2) "./"           -- ignore them, eat slash and continue.
 640                  * (3) ".." and ends  -- strip one and terminate.
 641                  * (4) "../"          -- strip one, eat slash and continue.
 642                  */
 643                 if (c == '.') {
 644                         if (!src[1]) {
 645                                 /* (1) */
 646                                 src++;
 647                         } else if (is_dir_sep(src[1])) {
 648                                 /* (2) */
 649                                 src += 2;
 650                                 while (is_dir_sep(*src))
 651                                         src++;
 652                                 continue;
 653                         } else if (src[1] == '.') {
 654                                 if (!src[2]) {
 655                                         /* (3) */
 656                                         src += 2;
 657                                         goto up_one;
 658                                 } else if (is_dir_sep(src[2])) {
 659                                         /* (4) */
 660                                         src += 3;
 661                                         while (is_dir_sep(*src))
 662                                                 src++;
 663                                         goto up_one;
 664                                 }
 665                         }
 666                 }
 667
 668                 /* copy up to the next '/', and eat all '/' */
 669                 while ((c = *src++) != '\0' && !is_dir_sep(c))
 670                         *dst++ = c;
 671                 if (is_dir_sep(c)) {
 672                         *dst++ = '/';
 673                         while (is_dir_sep(c))
 674                                 c = *src++;
 675                         src--;
 676                 } else if (!c)
 677                         break;
 678                 continue;
 679
 680         up_one:
 681                 /*
 682                  * dst0..dst is prefix portion, and dst[-1] is '/';
 683                  * go up one level.
 684                  */
 685                 dst--;  /* go to trailing '/' */
 686                 if (dst <= dst0)
 687                         return -1;
 688                 /* Windows: dst[-1] cannot be backslash anymore */
 689                 while (dst0 < dst && dst[-1] != '/')
 690                         dst--;
 691                 if (prefix_len && *prefix_len > dst - dst0)
 692                         *prefix_len = dst - dst0;
 693         }
 694         *dst = '\0';
 695         return 0;
 696 }
 697
 698 int normalize_path_copy(char *dst, const char *src)
 699 {
 700         return normalize_path_copy_len(dst, src, NULL);
 701 }
 702
 703 /*
 704  * path = Canonical absolute path
 705  * prefixes = string_list containing normalized, absolute paths without
 706  * trailing slashes (except for the root directory, which is denoted by "/").
 707  *
 708  * Determines, for each path in prefixes, whether the "prefix"
 709  * is an ancestor directory of path.  Returns the length of the longest
 710  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 711  * is an ancestor.  (Note that this means 0 is returned if prefixes is
 712  * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
 713  * are not considered to be their own ancestors.  path must be in a
 714  * canonical form: empty components, or "." or ".." components are not
 715  * allowed.
 716  */
 717 int longest_ancestor_length(const char *path, struct string_list *prefixes)
 718 {
 719         int i, max_len = -1;
 720
 721         if (!strcmp(path, "/"))
 722                 return -1;
 723
 724         for (i = 0; i < prefixes->nr; i++) {
 725                 const char *ceil = prefixes->items[i].string;
 726                 int len = strlen(ceil);
 727
 728                 if (len == 1 && ceil[0] == '/')
 729                         len = 0; /* root matches anything, with length 0 */
 730                 else if (!strncmp(path, ceil, len) && path[len] == '/')
 731                         ; /* match of length len */
 732                 else
 733                         continue; /* no match */
 734
 735                 if (len > max_len)
 736                         max_len = len;
 737         }
 738
 739         return max_len;
 740 }
 741
 742 /* strip arbitrary amount of directory separators at end of path */
 743 static inline int chomp_trailing_dir_sep(const char *path, int len)
 744 {
 745         while (len && is_dir_sep(path[len - 1]))
 746                 len--;
 747         return len;
 748 }
 749
 750 /*
 751  * If path ends with suffix (complete path components), returns the
 752  * part before suffix (sans trailing directory separators).
 753  * Otherwise returns NULL.
 754  */
 755 char *strip_path_suffix(const char *path, const char *suffix)
 756 {
 757         int path_len = strlen(path), suffix_len = strlen(suffix);
 758
 759         while (suffix_len) {
 760                 if (!path_len)
 761                         return NULL;
 762
 763                 if (is_dir_sep(path[path_len - 1])) {
 764                         if (!is_dir_sep(suffix[suffix_len - 1]))
 765                                 return NULL;
 766                         path_len = chomp_trailing_dir_sep(path, path_len);
 767                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
 768                 }
 769                 else if (path[--path_len] != suffix[--suffix_len])
 770                         return NULL;
 771         }
 772
 773         if (path_len && !is_dir_sep(path[path_len - 1]))
 774                 return NULL;
 775         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
 776 }
 777
 778 int daemon_avoid_alias(const char *p)
 779 {
 780         int sl, ndot;
 781
 782         /*
 783          * This resurrects the belts and suspenders paranoia check by HPA
 784          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
 785          * does not do getcwd() based path canonicalization.
 786          *
 787          * sl becomes true immediately after seeing '/' and continues to
 788          * be true as long as dots continue after that without intervening
 789          * non-dot character.
 790          */
 791         if (!p || (*p != '/' && *p != '~'))
 792                 return -1;
 793         sl = 1; ndot = 0;
 794         p++;
 795
 796         while (1) {
 797                 char ch = *p++;
 798                 if (sl) {
 799                         if (ch == '.')
 800                                 ndot++;
 801                         else if (ch == '/') {
 802                                 if (ndot < 3)
 803                                         /* reject //, /./ and /../ */
 804                                         return -1;
 805                                 ndot = 0;
 806                         }
 807                         else if (ch == 0) {
 808                                 if (0 < ndot && ndot < 3)
 809                                         /* reject /.$ and /..$ */
 810                                         return -1;
 811                                 return 0;
 812                         }
 813                         else
 814                                 sl = ndot = 0;
 815                 }
 816                 else if (ch == 0)
 817                         return 0;
 818                 else if (ch == '/') {
 819                         sl = 1;
 820                         ndot = 0;
 821                 }
 822         }
 823 }
 824
 825 int offset_1st_component(const char *path)
 826 {
 827         if (has_dos_drive_prefix(path))
 828                 return 2 + is_dir_sep(path[2]);
 829         return is_dir_sep(path[0]);
 830 }
 831
 832 static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
 833 {
 834         if (len < skip)
 835                 return 0;
 836         len -= skip;
 837         path += skip;
 838         while (len-- > 0) {
 839                 char c = *(path++);
 840                 if (c != ' ' && c != '.')
 841                         return 0;
 842         }
 843         return 1;
 844 }
 845
 846 int is_ntfs_dotgit(const char *name)
 847 {
 848         int len;
 849
 850         for (len = 0; ; len++)
 851                 if (!name[len] || name[len] == '\\' || is_dir_sep(name[len])) {
 852                         if (only_spaces_and_periods(name, len, 4) &&
 853                                         !strncasecmp(name, ".git", 4))
 854                                 return 1;
 855                         if (only_spaces_and_periods(name, len, 5) &&
 856                                         !strncasecmp(name, "git~1", 5))
 857                                 return 1;
 858                         if (name[len] != '\\')
 859                                 return 0;
 860                         name += len + 1;
 861                         len = -1;
 862                 }
 863 }