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