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