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