path.c

   1 /*
   2  * Utilities for paths and pathnames
   3  */
   4 #include "cache.h"
   5 #include "strbuf.h"
   6 #include "string-list.h"
   7 #include "dir.h"
   8
   9 static int get_st_mode_bits(const char *path, int *mode)
  10 {
  11         struct stat st;
  12         if (lstat(path, &st) < 0)
  13                 return -1;
  14         *mode = st.st_mode;
  15         return 0;
  16 }
  17
  18 static char bad_path[] = "/bad-path/";
  19
  20 static struct strbuf *get_pathname(void)
  21 {
  22         static struct strbuf pathname_array[4] = {
  23                 STRBUF_INIT, STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
  24         };
  25         static int index;
  26         struct strbuf *sb = &pathname_array[3 & ++index];
  27         strbuf_reset(sb);
  28         return sb;
  29 }
  30
  31 static char *cleanup_path(char *path)
  32 {
  33         /* Clean it up */
  34         if (!memcmp(path, "./", 2)) {
  35                 path += 2;
  36                 while (*path == '/')
  37                         path++;
  38         }
  39         return path;
  40 }
  41
  42 static void strbuf_cleanup_path(struct strbuf *sb)
  43 {
  44         char *path = cleanup_path(sb->buf);
  45         if (path > sb->buf)
  46                 strbuf_remove(sb, 0, path - sb->buf);
  47 }
  48
  49 char *mksnpath(char *buf, size_t n, const char *fmt, ...)
  50 {
  51         va_list args;
  52         unsigned len;
  53
  54         va_start(args, fmt);
  55         len = vsnprintf(buf, n, fmt, args);
  56         va_end(args);
  57         if (len >= n) {
  58                 strlcpy(buf, bad_path, n);
  59                 return buf;
  60         }
  61         return cleanup_path(buf);
  62 }
  63
  64 static int dir_prefix(const char *buf, const char *dir)
  65 {
  66         int len = strlen(dir);
  67         return !strncmp(buf, dir, len) &&
  68                 (is_dir_sep(buf[len]) || buf[len] == '\0');
  69 }
  70
  71 /* $buf =~ m|$dir/+$file| but without regex */
  72 static int is_dir_file(const char *buf, const char *dir, const char *file)
  73 {
  74         int len = strlen(dir);
  75         if (strncmp(buf, dir, len) || !is_dir_sep(buf[len]))
  76                 return 0;
  77         while (is_dir_sep(buf[len]))
  78                 len++;
  79         return !strcmp(buf + len, file);
  80 }
  81
  82 static void replace_dir(struct strbuf *buf, int len, const char *newdir)
  83 {
  84         int newlen = strlen(newdir);
  85         int need_sep = (buf->buf[len] && !is_dir_sep(buf->buf[len])) &&
  86                 !is_dir_sep(newdir[newlen - 1]);
  87         if (need_sep)
  88                 len--;   /* keep one char, to be replaced with '/'  */
  89         strbuf_splice(buf, 0, len, newdir, newlen);
  90         if (need_sep)
  91                 buf->buf[newlen] = '/';
  92 }
  93
  94 static const char *common_list[] = {
  95         "/branches", "/hooks", "/info", "!/logs", "/lost-found",
  96         "/objects", "/refs", "/remotes", "/worktrees", "/rr-cache", "/svn",
  97         "config", "!gc.pid", "packed-refs", "shallow",
  98         NULL
  99 };
 100
 101 static void update_common_dir(struct strbuf *buf, int git_dir_len)
 102 {
 103         char *base = buf->buf + git_dir_len;
 104         const char **p;
 105
 106         if (is_dir_file(base, "logs", "HEAD") ||
 107             is_dir_file(base, "info", "sparse-checkout"))
 108                 return; /* keep this in $GIT_DIR */
 109         for (p = common_list; *p; p++) {
 110                 const char *path = *p;
 111                 int is_dir = 0;
 112                 if (*path == '!')
 113                         path++;
 114                 if (*path == '/') {
 115                         path++;
 116                         is_dir = 1;
 117                 }
 118                 if (is_dir && dir_prefix(base, path)) {
 119                         replace_dir(buf, git_dir_len, get_git_common_dir());
 120                         return;
 121                 }
 122                 if (!is_dir && !strcmp(base, path)) {
 123                         replace_dir(buf, git_dir_len, get_git_common_dir());
 124                         return;
 125                 }
 126         }
 127 }
 128
 129 void report_linked_checkout_garbage(void)
 130 {
 131         struct strbuf sb = STRBUF_INIT;
 132         const char **p;
 133         int len;
 134
 135         if (!git_common_dir_env)
 136                 return;
 137         strbuf_addf(&sb, "%s/", get_git_dir());
 138         len = sb.len;
 139         for (p = common_list; *p; p++) {
 140                 const char *path = *p;
 141                 if (*path == '!')
 142                         continue;
 143                 strbuf_setlen(&sb, len);
 144                 strbuf_addstr(&sb, path);
 145                 if (file_exists(sb.buf))
 146                         report_garbage("unused in linked checkout", sb.buf);
 147         }
 148         strbuf_release(&sb);
 149 }
 150
 151 static void adjust_git_path(struct strbuf *buf, int git_dir_len)
 152 {
 153         const char *base = buf->buf + git_dir_len;
 154         if (git_graft_env && is_dir_file(base, "info", "grafts"))
 155                 strbuf_splice(buf, 0, buf->len,
 156                               get_graft_file(), strlen(get_graft_file()));
 157         else if (git_index_env && !strcmp(base, "index"))
 158                 strbuf_splice(buf, 0, buf->len,
 159                               get_index_file(), strlen(get_index_file()));
 160         else if (git_db_env && dir_prefix(base, "objects"))
 161                 replace_dir(buf, git_dir_len + 7, get_object_directory());
 162         else if (git_common_dir_env)
 163                 update_common_dir(buf, git_dir_len);
 164 }
 165
 166 static void do_git_path(struct strbuf *buf, const char *fmt, va_list args)
 167 {
 168         int gitdir_len;
 169         strbuf_addstr(buf, get_git_dir());
 170         if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 171                 strbuf_addch(buf, '/');
 172         gitdir_len = buf->len;
 173         strbuf_vaddf(buf, fmt, args);
 174         adjust_git_path(buf, gitdir_len);
 175         strbuf_cleanup_path(buf);
 176 }
 177
 178 void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
 179 {
 180         va_list args;
 181         va_start(args, fmt);
 182         do_git_path(sb, fmt, args);
 183         va_end(args);
 184 }
 185
 186 const char *git_path(const char *fmt, ...)
 187 {
 188         struct strbuf *pathname = get_pathname();
 189         va_list args;
 190         va_start(args, fmt);
 191         do_git_path(pathname, fmt, args);
 192         va_end(args);
 193         return pathname->buf;
 194 }
 195
 196 char *git_pathdup(const char *fmt, ...)
 197 {
 198         struct strbuf path = STRBUF_INIT;
 199         va_list args;
 200         va_start(args, fmt);
 201         do_git_path(&path, fmt, args);
 202         va_end(args);
 203         return strbuf_detach(&path, NULL);
 204 }
 205
 206 char *mkpathdup(const char *fmt, ...)
 207 {
 208         struct strbuf sb = STRBUF_INIT;
 209         va_list args;
 210         va_start(args, fmt);
 211         strbuf_vaddf(&sb, fmt, args);
 212         va_end(args);
 213         strbuf_cleanup_path(&sb);
 214         return strbuf_detach(&sb, NULL);
 215 }
 216
 217 const char *mkpath(const char *fmt, ...)
 218 {
 219         va_list args;
 220         struct strbuf *pathname = get_pathname();
 221         va_start(args, fmt);
 222         strbuf_vaddf(pathname, fmt, args);
 223         va_end(args);
 224         return cleanup_path(pathname->buf);
 225 }
 226
 227 void home_config_paths(char **global, char **xdg, char *file)
 228 {
 229         char *xdg_home = getenv("XDG_CONFIG_HOME");
 230         char *home = getenv("HOME");
 231         char *to_free = NULL;
 232
 233         if (!home) {
 234                 if (global)
 235                         *global = NULL;
 236         } else {
 237                 if (!xdg_home) {
 238                         to_free = mkpathdup("%s/.config", home);
 239                         xdg_home = to_free;
 240                 }
 241                 if (global)
 242                         *global = mkpathdup("%s/.gitconfig", home);
 243         }
 244
 245         if (xdg) {
 246                 if (!xdg_home)
 247                         *xdg = NULL;
 248                 else
 249                         *xdg = mkpathdup("%s/git/%s", xdg_home, file);
 250         }
 251
 252         free(to_free);
 253 }
 254
 255 const char *git_path_submodule(const char *path, const char *fmt, ...)
 256 {
 257         struct strbuf *buf = get_pathname();
 258         const char *git_dir;
 259         va_list args;
 260
 261         strbuf_addstr(buf, path);
 262         if (buf->len && buf->buf[buf->len - 1] != '/')
 263                 strbuf_addch(buf, '/');
 264         strbuf_addstr(buf, ".git");
 265
 266         git_dir = read_gitfile(buf->buf);
 267         if (git_dir) {
 268                 strbuf_reset(buf);
 269                 strbuf_addstr(buf, git_dir);
 270         }
 271         strbuf_addch(buf, '/');
 272
 273         va_start(args, fmt);
 274         strbuf_vaddf(buf, fmt, args);
 275         va_end(args);
 276         strbuf_cleanup_path(buf);
 277         return buf->buf;
 278 }
 279
 280 int validate_headref(const char *path)
 281 {
 282         struct stat st;
 283         char *buf, buffer[256];
 284         unsigned char sha1[20];
 285         int fd;
 286         ssize_t len;
 287
 288         if (lstat(path, &st) < 0)
 289                 return -1;
 290
 291         /* Make sure it is a "refs/.." symlink */
 292         if (S_ISLNK(st.st_mode)) {
 293                 len = readlink(path, buffer, sizeof(buffer)-1);
 294                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 295                         return 0;
 296                 return -1;
 297         }
 298
 299         /*
 300          * Anything else, just open it and try to see if it is a symbolic ref.
 301          */
 302         fd = open(path, O_RDONLY);
 303         if (fd < 0)
 304                 return -1;
 305         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 306         close(fd);
 307
 308         /*
 309          * Is it a symbolic ref?
 310          */
 311         if (len < 4)
 312                 return -1;
 313         if (!memcmp("ref:", buffer, 4)) {
 314                 buf = buffer + 4;
 315                 len -= 4;
 316                 while (len && isspace(*buf))
 317                         buf++, len--;
 318                 if (len >= 5 && !memcmp("refs/", buf, 5))
 319                         return 0;
 320         }
 321
 322         /*
 323          * Is this a detached HEAD?
 324          */
 325         if (!get_sha1_hex(buffer, sha1))
 326                 return 0;
 327
 328         return -1;
 329 }
 330
 331 static struct passwd *getpw_str(const char *username, size_t len)
 332 {
 333         struct passwd *pw;
 334         char *username_z = xmemdupz(username, len);
 335         pw = getpwnam(username_z);
 336         free(username_z);
 337         return pw;
 338 }
 339
 340 /*
 341  * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 342  * then it is a newly allocated string. Returns NULL on getpw failure or
 343  * if path is NULL.
 344  */
 345 char *expand_user_path(const char *path)
 346 {
 347         struct strbuf user_path = STRBUF_INIT;
 348         const char *to_copy = path;
 349
 350         if (path == NULL)
 351                 goto return_null;
 352         if (path[0] == '~') {
 353                 const char *first_slash = strchrnul(path, '/');
 354                 const char *username = path + 1;
 355                 size_t username_len = first_slash - username;
 356                 if (username_len == 0) {
 357                         const char *home = getenv("HOME");
 358                         if (!home)
 359                                 goto return_null;
 360                         strbuf_addstr(&user_path, home);
 361                 } else {
 362                         struct passwd *pw = getpw_str(username, username_len);
 363                         if (!pw)
 364                                 goto return_null;
 365                         strbuf_addstr(&user_path, pw->pw_dir);
 366                 }
 367                 to_copy = first_slash;
 368         }
 369         strbuf_addstr(&user_path, to_copy);
 370         return strbuf_detach(&user_path, NULL);
 371 return_null:
 372         strbuf_release(&user_path);
 373         return NULL;
 374 }
 375
 376 /*
 377  * First, one directory to try is determined by the following algorithm.
 378  *
 379  * (0) If "strict" is given, the path is used as given and no DWIM is
 380  *     done. Otherwise:
 381  * (1) "~/path" to mean path under the running user's home directory;
 382  * (2) "~user/path" to mean path under named user's home directory;
 383  * (3) "relative/path" to mean cwd relative directory; or
 384  * (4) "/absolute/path" to mean absolute directory.
 385  *
 386  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 387  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 388  * what we try.
 389  *
 390  * Second, we try chdir() to that.  Upon failure, we return NULL.
 391  *
 392  * Then, we try if the current directory is a valid git repository.
 393  * Upon failure, we return NULL.
 394  *
 395  * If all goes well, we return the directory we used to chdir() (but
 396  * before ~user is expanded), avoiding getcwd() resolving symbolic
 397  * links.  User relative paths are also returned as they are given,
 398  * except DWIM suffixing.
 399  */
 400 const char *enter_repo(const char *path, int strict)
 401 {
 402         static char used_path[PATH_MAX];
 403         static char validated_path[PATH_MAX];
 404
 405         if (!path)
 406                 return NULL;
 407
 408         if (!strict) {
 409                 static const char *suffix[] = {
 410                         "/.git", "", ".git/.git", ".git", NULL,
 411                 };
 412                 const char *gitfile;
 413                 int len = strlen(path);
 414                 int i;
 415                 while ((1 < len) && (path[len-1] == '/'))
 416                         len--;
 417
 418                 if (PATH_MAX <= len)
 419                         return NULL;
 420                 strncpy(used_path, path, len); used_path[len] = 0 ;
 421                 strcpy(validated_path, used_path);
 422
 423                 if (used_path[0] == '~') {
 424                         char *newpath = expand_user_path(used_path);
 425                         if (!newpath || (PATH_MAX - 10 < strlen(newpath))) {
 426                                 free(newpath);
 427                                 return NULL;
 428                         }
 429                         /*
 430                          * Copy back into the static buffer. A pity
 431                          * since newpath was not bounded, but other
 432                          * branches of the if are limited by PATH_MAX
 433                          * anyway.
 434                          */
 435                         strcpy(used_path, newpath); free(newpath);
 436                 }
 437                 else if (PATH_MAX - 10 < len)
 438                         return NULL;
 439                 len = strlen(used_path);
 440                 for (i = 0; suffix[i]; i++) {
 441                         struct stat st;
 442                         strcpy(used_path + len, suffix[i]);
 443                         if (!stat(used_path, &st) &&
 444                             (S_ISREG(st.st_mode) ||
 445                             (S_ISDIR(st.st_mode) && is_git_directory(used_path)))) {
 446                                 strcat(validated_path, suffix[i]);
 447                                 break;
 448                         }
 449                 }
 450                 if (!suffix[i])
 451                         return NULL;
 452                 gitfile = read_gitfile(used_path) ;
 453                 if (gitfile)
 454                         strcpy(used_path, gitfile);
 455                 if (chdir(used_path))
 456                         return NULL;
 457                 path = validated_path;
 458         }
 459         else if (chdir(path))
 460                 return NULL;
 461
 462         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 463             validate_headref("HEAD") == 0) {
 464                 set_git_dir(".");
 465                 check_repository_format();
 466                 return path;
 467         }
 468
 469         return NULL;
 470 }
 471
 472 static int calc_shared_perm(int mode)
 473 {
 474         int tweak;
 475
 476         if (shared_repository < 0)
 477                 tweak = -shared_repository;
 478         else
 479                 tweak = shared_repository;
 480
 481         if (!(mode & S_IWUSR))
 482                 tweak &= ~0222;
 483         if (mode & S_IXUSR)
 484                 /* Copy read bits to execute bits */
 485                 tweak |= (tweak & 0444) >> 2;
 486         if (shared_repository < 0)
 487                 mode = (mode & ~0777) | tweak;
 488         else
 489                 mode |= tweak;
 490
 491         return mode;
 492 }
 493
 494
 495 int adjust_shared_perm(const char *path)
 496 {
 497         int old_mode, new_mode;
 498
 499         if (!shared_repository)
 500                 return 0;
 501         if (get_st_mode_bits(path, &old_mode) < 0)
 502                 return -1;
 503
 504         new_mode = calc_shared_perm(old_mode);
 505         if (S_ISDIR(old_mode)) {
 506                 /* Copy read bits to execute bits */
 507                 new_mode |= (new_mode & 0444) >> 2;
 508                 new_mode |= FORCE_DIR_SET_GID;
 509         }
 510
 511         if (((old_mode ^ new_mode) & ~S_IFMT) &&
 512                         chmod(path, (new_mode & ~S_IFMT)) < 0)
 513                 return -2;
 514         return 0;
 515 }
 516
 517 static int have_same_root(const char *path1, const char *path2)
 518 {
 519         int is_abs1, is_abs2;
 520
 521         is_abs1 = is_absolute_path(path1);
 522         is_abs2 = is_absolute_path(path2);
 523         return (is_abs1 && is_abs2 && tolower(path1[0]) == tolower(path2[0])) ||
 524                (!is_abs1 && !is_abs2);
 525 }
 526
 527 /*
 528  * Give path as relative to prefix.
 529  *
 530  * The strbuf may or may not be used, so do not assume it contains the
 531  * returned path.
 532  */
 533 const char *relative_path(const char *in, const char *prefix,
 534                           struct strbuf *sb)
 535 {
 536         int in_len = in ? strlen(in) : 0;
 537         int prefix_len = prefix ? strlen(prefix) : 0;
 538         int in_off = 0;
 539         int prefix_off = 0;
 540         int i = 0, j = 0;
 541
 542         if (!in_len)
 543                 return "./";
 544         else if (!prefix_len)
 545                 return in;
 546
 547         if (have_same_root(in, prefix)) {
 548                 /* bypass dos_drive, for "c:" is identical to "C:" */
 549                 if (has_dos_drive_prefix(in)) {
 550                         i = 2;
 551                         j = 2;
 552                 }
 553         } else {
 554                 return in;
 555         }
 556
 557         while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
 558                 if (is_dir_sep(prefix[i])) {
 559                         while (is_dir_sep(prefix[i]))
 560                                 i++;
 561                         while (is_dir_sep(in[j]))
 562                                 j++;
 563                         prefix_off = i;
 564                         in_off = j;
 565                 } else {
 566                         i++;
 567                         j++;
 568                 }
 569         }
 570
 571         if (
 572             /* "prefix" seems like prefix of "in" */
 573             i >= prefix_len &&
 574             /*
 575              * but "/foo" is not a prefix of "/foobar"
 576              * (i.e. prefix not end with '/')
 577              */
 578             prefix_off < prefix_len) {
 579                 if (j >= in_len) {
 580                         /* in="/a/b", prefix="/a/b" */
 581                         in_off = in_len;
 582                 } else if (is_dir_sep(in[j])) {
 583                         /* in="/a/b/c", prefix="/a/b" */
 584                         while (is_dir_sep(in[j]))
 585                                 j++;
 586                         in_off = j;
 587                 } else {
 588                         /* in="/a/bbb/c", prefix="/a/b" */
 589                         i = prefix_off;
 590                 }
 591         } else if (
 592                    /* "in" is short than "prefix" */
 593                    j >= in_len &&
 594                    /* "in" not end with '/' */
 595                    in_off < in_len) {
 596                 if (is_dir_sep(prefix[i])) {
 597                         /* in="/a/b", prefix="/a/b/c/" */
 598                         while (is_dir_sep(prefix[i]))
 599                                 i++;
 600                         in_off = in_len;
 601                 }
 602         }
 603         in += in_off;
 604         in_len -= in_off;
 605
 606         if (i >= prefix_len) {
 607                 if (!in_len)
 608                         return "./";
 609                 else
 610                         return in;
 611         }
 612
 613         strbuf_reset(sb);
 614         strbuf_grow(sb, in_len);
 615
 616         while (i < prefix_len) {
 617                 if (is_dir_sep(prefix[i])) {
 618                         strbuf_addstr(sb, "../");
 619                         while (is_dir_sep(prefix[i]))
 620                                 i++;
 621                         continue;
 622                 }
 623                 i++;
 624         }
 625         if (!is_dir_sep(prefix[prefix_len - 1]))
 626                 strbuf_addstr(sb, "../");
 627
 628         strbuf_addstr(sb, in);
 629
 630         return sb->buf;
 631 }
 632
 633 /*
 634  * A simpler implementation of relative_path
 635  *
 636  * Get relative path by removing "prefix" from "in". This function
 637  * first appears in v1.5.6-1-g044bbbc, and makes git_dir shorter
 638  * to increase performance when traversing the path to work_tree.
 639  */
 640 const char *remove_leading_path(const char *in, const char *prefix)
 641 {
 642         static char buf[PATH_MAX + 1];
 643         int i = 0, j = 0;
 644
 645         if (!prefix || !prefix[0])
 646                 return in;
 647         while (prefix[i]) {
 648                 if (is_dir_sep(prefix[i])) {
 649                         if (!is_dir_sep(in[j]))
 650                                 return in;
 651                         while (is_dir_sep(prefix[i]))
 652                                 i++;
 653                         while (is_dir_sep(in[j]))
 654                                 j++;
 655                         continue;
 656                 } else if (in[j] != prefix[i]) {
 657                         return in;
 658                 }
 659                 i++;
 660                 j++;
 661         }
 662         if (
 663             /* "/foo" is a prefix of "/foo" */
 664             in[j] &&
 665             /* "/foo" is not a prefix of "/foobar" */
 666             !is_dir_sep(prefix[i-1]) && !is_dir_sep(in[j])
 667            )
 668                 return in;
 669         while (is_dir_sep(in[j]))
 670                 j++;
 671         if (!in[j])
 672                 strcpy(buf, ".");
 673         else
 674                 strcpy(buf, in + j);
 675         return buf;
 676 }
 677
 678 /*
 679  * It is okay if dst == src, but they should not overlap otherwise.
 680  *
 681  * Performs the following normalizations on src, storing the result in dst:
 682  * - Ensures that components are separated by '/' (Windows only)
 683  * - Squashes sequences of '/'.
 684  * - Removes "." components.
 685  * - Removes ".." components, and the components the precede them.
 686  * Returns failure (non-zero) if a ".." component appears as first path
 687  * component anytime during the normalization. Otherwise, returns success (0).
 688  *
 689  * Note that this function is purely textual.  It does not follow symlinks,
 690  * verify the existence of the path, or make any system calls.
 691  *
 692  * prefix_len != NULL is for a specific case of prefix_pathspec():
 693  * assume that src == dst and src[0..prefix_len-1] is already
 694  * normalized, any time "../" eats up to the prefix_len part,
 695  * prefix_len is reduced. In the end prefix_len is the remaining
 696  * prefix that has not been overridden by user pathspec.
 697  */
 698 int normalize_path_copy_len(char *dst, const char *src, int *prefix_len)
 699 {
 700         char *dst0;
 701
 702         if (has_dos_drive_prefix(src)) {
 703                 *dst++ = *src++;
 704                 *dst++ = *src++;
 705         }
 706         dst0 = dst;
 707
 708         if (is_dir_sep(*src)) {
 709                 *dst++ = '/';
 710                 while (is_dir_sep(*src))
 711                         src++;
 712         }
 713
 714         for (;;) {
 715                 char c = *src;
 716
 717                 /*
 718                  * A path component that begins with . could be
 719                  * special:
 720                  * (1) "." and ends   -- ignore and terminate.
 721                  * (2) "./"           -- ignore them, eat slash and continue.
 722                  * (3) ".." and ends  -- strip one and terminate.
 723                  * (4) "../"          -- strip one, eat slash and continue.
 724                  */
 725                 if (c == '.') {
 726                         if (!src[1]) {
 727                                 /* (1) */
 728                                 src++;
 729                         } else if (is_dir_sep(src[1])) {
 730                                 /* (2) */
 731                                 src += 2;
 732                                 while (is_dir_sep(*src))
 733                                         src++;
 734                                 continue;
 735                         } else if (src[1] == '.') {
 736                                 if (!src[2]) {
 737                                         /* (3) */
 738                                         src += 2;
 739                                         goto up_one;
 740                                 } else if (is_dir_sep(src[2])) {
 741                                         /* (4) */
 742                                         src += 3;
 743                                         while (is_dir_sep(*src))
 744                                                 src++;
 745                                         goto up_one;
 746                                 }
 747                         }
 748                 }
 749
 750                 /* copy up to the next '/', and eat all '/' */
 751                 while ((c = *src++) != '\0' && !is_dir_sep(c))
 752                         *dst++ = c;
 753                 if (is_dir_sep(c)) {
 754                         *dst++ = '/';
 755                         while (is_dir_sep(c))
 756                                 c = *src++;
 757                         src--;
 758                 } else if (!c)
 759                         break;
 760                 continue;
 761
 762         up_one:
 763                 /*
 764                  * dst0..dst is prefix portion, and dst[-1] is '/';
 765                  * go up one level.
 766                  */
 767                 dst--;  /* go to trailing '/' */
 768                 if (dst <= dst0)
 769                         return -1;
 770                 /* Windows: dst[-1] cannot be backslash anymore */
 771                 while (dst0 < dst && dst[-1] != '/')
 772                         dst--;
 773                 if (prefix_len && *prefix_len > dst - dst0)
 774                         *prefix_len = dst - dst0;
 775         }
 776         *dst = '\0';
 777         return 0;
 778 }
 779
 780 int normalize_path_copy(char *dst, const char *src)
 781 {
 782         return normalize_path_copy_len(dst, src, NULL);
 783 }
 784
 785 /*
 786  * path = Canonical absolute path
 787  * prefixes = string_list containing normalized, absolute paths without
 788  * trailing slashes (except for the root directory, which is denoted by "/").
 789  *
 790  * Determines, for each path in prefixes, whether the "prefix"
 791  * is an ancestor directory of path.  Returns the length of the longest
 792  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 793  * is an ancestor.  (Note that this means 0 is returned if prefixes is
 794  * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
 795  * are not considered to be their own ancestors.  path must be in a
 796  * canonical form: empty components, or "." or ".." components are not
 797  * allowed.
 798  */
 799 int longest_ancestor_length(const char *path, struct string_list *prefixes)
 800 {
 801         int i, max_len = -1;
 802
 803         if (!strcmp(path, "/"))
 804                 return -1;
 805
 806         for (i = 0; i < prefixes->nr; i++) {
 807                 const char *ceil = prefixes->items[i].string;
 808                 int len = strlen(ceil);
 809
 810                 if (len == 1 && ceil[0] == '/')
 811                         len = 0; /* root matches anything, with length 0 */
 812                 else if (!strncmp(path, ceil, len) && path[len] == '/')
 813                         ; /* match of length len */
 814                 else
 815                         continue; /* no match */
 816
 817                 if (len > max_len)
 818                         max_len = len;
 819         }
 820
 821         return max_len;
 822 }
 823
 824 /* strip arbitrary amount of directory separators at end of path */
 825 static inline int chomp_trailing_dir_sep(const char *path, int len)
 826 {
 827         while (len && is_dir_sep(path[len - 1]))
 828                 len--;
 829         return len;
 830 }
 831
 832 /*
 833  * If path ends with suffix (complete path components), returns the
 834  * part before suffix (sans trailing directory separators).
 835  * Otherwise returns NULL.
 836  */
 837 char *strip_path_suffix(const char *path, const char *suffix)
 838 {
 839         int path_len = strlen(path), suffix_len = strlen(suffix);
 840
 841         while (suffix_len) {
 842                 if (!path_len)
 843                         return NULL;
 844
 845                 if (is_dir_sep(path[path_len - 1])) {
 846                         if (!is_dir_sep(suffix[suffix_len - 1]))
 847                                 return NULL;
 848                         path_len = chomp_trailing_dir_sep(path, path_len);
 849                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
 850                 }
 851                 else if (path[--path_len] != suffix[--suffix_len])
 852                         return NULL;
 853         }
 854
 855         if (path_len && !is_dir_sep(path[path_len - 1]))
 856                 return NULL;
 857         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
 858 }
 859
 860 int daemon_avoid_alias(const char *p)
 861 {
 862         int sl, ndot;
 863
 864         /*
 865          * This resurrects the belts and suspenders paranoia check by HPA
 866          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
 867          * does not do getcwd() based path canonicalization.
 868          *
 869          * sl becomes true immediately after seeing '/' and continues to
 870          * be true as long as dots continue after that without intervening
 871          * non-dot character.
 872          */
 873         if (!p || (*p != '/' && *p != '~'))
 874                 return -1;
 875         sl = 1; ndot = 0;
 876         p++;
 877
 878         while (1) {
 879                 char ch = *p++;
 880                 if (sl) {
 881                         if (ch == '.')
 882                                 ndot++;
 883                         else if (ch == '/') {
 884                                 if (ndot < 3)
 885                                         /* reject //, /./ and /../ */
 886                                         return -1;
 887                                 ndot = 0;
 888                         }
 889                         else if (ch == 0) {
 890                                 if (0 < ndot && ndot < 3)
 891                                         /* reject /.$ and /..$ */
 892                                         return -1;
 893                                 return 0;
 894                         }
 895                         else
 896                                 sl = ndot = 0;
 897                 }
 898                 else if (ch == 0)
 899                         return 0;
 900                 else if (ch == '/') {
 901                         sl = 1;
 902                         ndot = 0;
 903                 }
 904         }
 905 }