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 static void do_submodule_path(struct strbuf *buf, const char *path,
 228                               const char *fmt, va_list args)
 229 {
 230         const char *git_dir;
 231
 232         strbuf_addstr(buf, path);
 233         if (buf->len && buf->buf[buf->len - 1] != '/')
 234                 strbuf_addch(buf, '/');
 235         strbuf_addstr(buf, ".git");
 236
 237         git_dir = read_gitfile(buf->buf);
 238         if (git_dir) {
 239                 strbuf_reset(buf);
 240                 strbuf_addstr(buf, git_dir);
 241         }
 242         strbuf_addch(buf, '/');
 243
 244         strbuf_vaddf(buf, fmt, args);
 245         strbuf_cleanup_path(buf);
 246 }
 247
 248 char *git_pathdup_submodule(const char *path, const char *fmt, ...)
 249 {
 250         va_list args;
 251         struct strbuf buf = STRBUF_INIT;
 252         va_start(args, fmt);
 253         do_submodule_path(&buf, path, fmt, args);
 254         va_end(args);
 255         return strbuf_detach(&buf, NULL);
 256 }
 257
 258 void strbuf_git_path_submodule(struct strbuf *buf, const char *path,
 259                                const char *fmt, ...)
 260 {
 261         va_list args;
 262         va_start(args, fmt);
 263         do_submodule_path(buf, path, fmt, args);
 264         va_end(args);
 265 }
 266
 267 int validate_headref(const char *path)
 268 {
 269         struct stat st;
 270         char *buf, buffer[256];
 271         unsigned char sha1[20];
 272         int fd;
 273         ssize_t len;
 274
 275         if (lstat(path, &st) < 0)
 276                 return -1;
 277
 278         /* Make sure it is a "refs/.." symlink */
 279         if (S_ISLNK(st.st_mode)) {
 280                 len = readlink(path, buffer, sizeof(buffer)-1);
 281                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 282                         return 0;
 283                 return -1;
 284         }
 285
 286         /*
 287          * Anything else, just open it and try to see if it is a symbolic ref.
 288          */
 289         fd = open(path, O_RDONLY);
 290         if (fd < 0)
 291                 return -1;
 292         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 293         close(fd);
 294
 295         /*
 296          * Is it a symbolic ref?
 297          */
 298         if (len < 4)
 299                 return -1;
 300         if (!memcmp("ref:", buffer, 4)) {
 301                 buf = buffer + 4;
 302                 len -= 4;
 303                 while (len && isspace(*buf))
 304                         buf++, len--;
 305                 if (len >= 5 && !memcmp("refs/", buf, 5))
 306                         return 0;
 307         }
 308
 309         /*
 310          * Is this a detached HEAD?
 311          */
 312         if (!get_sha1_hex(buffer, sha1))
 313                 return 0;
 314
 315         return -1;
 316 }
 317
 318 static struct passwd *getpw_str(const char *username, size_t len)
 319 {
 320         struct passwd *pw;
 321         char *username_z = xmemdupz(username, len);
 322         pw = getpwnam(username_z);
 323         free(username_z);
 324         return pw;
 325 }
 326
 327 /*
 328  * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 329  * then it is a newly allocated string. Returns NULL on getpw failure or
 330  * if path is NULL.
 331  */
 332 char *expand_user_path(const char *path)
 333 {
 334         struct strbuf user_path = STRBUF_INIT;
 335         const char *to_copy = path;
 336
 337         if (path == NULL)
 338                 goto return_null;
 339         if (path[0] == '~') {
 340                 const char *first_slash = strchrnul(path, '/');
 341                 const char *username = path + 1;
 342                 size_t username_len = first_slash - username;
 343                 if (username_len == 0) {
 344                         const char *home = getenv("HOME");
 345                         if (!home)
 346                                 goto return_null;
 347                         strbuf_addstr(&user_path, home);
 348                 } else {
 349                         struct passwd *pw = getpw_str(username, username_len);
 350                         if (!pw)
 351                                 goto return_null;
 352                         strbuf_addstr(&user_path, pw->pw_dir);
 353                 }
 354                 to_copy = first_slash;
 355         }
 356         strbuf_addstr(&user_path, to_copy);
 357         return strbuf_detach(&user_path, NULL);
 358 return_null:
 359         strbuf_release(&user_path);
 360         return NULL;
 361 }
 362
 363 /*
 364  * First, one directory to try is determined by the following algorithm.
 365  *
 366  * (0) If "strict" is given, the path is used as given and no DWIM is
 367  *     done. Otherwise:
 368  * (1) "~/path" to mean path under the running user's home directory;
 369  * (2) "~user/path" to mean path under named user's home directory;
 370  * (3) "relative/path" to mean cwd relative directory; or
 371  * (4) "/absolute/path" to mean absolute directory.
 372  *
 373  * Unless "strict" is given, we check "%s/.git", "%s", "%s.git/.git", "%s.git"
 374  * in this order. We select the first one that is a valid git repository, and
 375  * chdir() to it. If none match, or we fail to chdir, we return NULL.
 376  *
 377  * If all goes well, we return the directory we used to chdir() (but
 378  * before ~user is expanded), avoiding getcwd() resolving symbolic
 379  * links.  User relative paths are also returned as they are given,
 380  * except DWIM suffixing.
 381  */
 382 const char *enter_repo(const char *path, int strict)
 383 {
 384         static char used_path[PATH_MAX];
 385         static char validated_path[PATH_MAX];
 386
 387         if (!path)
 388                 return NULL;
 389
 390         if (!strict) {
 391                 static const char *suffix[] = {
 392                         "/.git", "", ".git/.git", ".git", NULL,
 393                 };
 394                 const char *gitfile;
 395                 int len = strlen(path);
 396                 int i;
 397                 while ((1 < len) && (path[len-1] == '/'))
 398                         len--;
 399
 400                 if (PATH_MAX <= len)
 401                         return NULL;
 402                 strncpy(used_path, path, len); used_path[len] = 0 ;
 403                 strcpy(validated_path, used_path);
 404
 405                 if (used_path[0] == '~') {
 406                         char *newpath = expand_user_path(used_path);
 407                         if (!newpath || (PATH_MAX - 10 < strlen(newpath))) {
 408                                 free(newpath);
 409                                 return NULL;
 410                         }
 411                         /*
 412                          * Copy back into the static buffer. A pity
 413                          * since newpath was not bounded, but other
 414                          * branches of the if are limited by PATH_MAX
 415                          * anyway.
 416                          */
 417                         strcpy(used_path, newpath); free(newpath);
 418                 }
 419                 else if (PATH_MAX - 10 < len)
 420                         return NULL;
 421                 len = strlen(used_path);
 422                 for (i = 0; suffix[i]; i++) {
 423                         struct stat st;
 424                         strcpy(used_path + len, suffix[i]);
 425                         if (!stat(used_path, &st) &&
 426                             (S_ISREG(st.st_mode) ||
 427                             (S_ISDIR(st.st_mode) && is_git_directory(used_path)))) {
 428                                 strcat(validated_path, suffix[i]);
 429                                 break;
 430                         }
 431                 }
 432                 if (!suffix[i])
 433                         return NULL;
 434                 gitfile = read_gitfile(used_path) ;
 435                 if (gitfile)
 436                         strcpy(used_path, gitfile);
 437                 if (chdir(used_path))
 438                         return NULL;
 439                 path = validated_path;
 440         }
 441         else if (chdir(path))
 442                 return NULL;
 443
 444         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 445             validate_headref("HEAD") == 0) {
 446                 set_git_dir(".");
 447                 check_repository_format();
 448                 return path;
 449         }
 450
 451         return NULL;
 452 }
 453
 454 static int calc_shared_perm(int mode)
 455 {
 456         int tweak;
 457
 458         if (shared_repository < 0)
 459                 tweak = -shared_repository;
 460         else
 461                 tweak = shared_repository;
 462
 463         if (!(mode & S_IWUSR))
 464                 tweak &= ~0222;
 465         if (mode & S_IXUSR)
 466                 /* Copy read bits to execute bits */
 467                 tweak |= (tweak & 0444) >> 2;
 468         if (shared_repository < 0)
 469                 mode = (mode & ~0777) | tweak;
 470         else
 471                 mode |= tweak;
 472
 473         return mode;
 474 }
 475
 476
 477 int adjust_shared_perm(const char *path)
 478 {
 479         int old_mode, new_mode;
 480
 481         if (!shared_repository)
 482                 return 0;
 483         if (get_st_mode_bits(path, &old_mode) < 0)
 484                 return -1;
 485
 486         new_mode = calc_shared_perm(old_mode);
 487         if (S_ISDIR(old_mode)) {
 488                 /* Copy read bits to execute bits */
 489                 new_mode |= (new_mode & 0444) >> 2;
 490                 new_mode |= FORCE_DIR_SET_GID;
 491         }
 492
 493         if (((old_mode ^ new_mode) & ~S_IFMT) &&
 494                         chmod(path, (new_mode & ~S_IFMT)) < 0)
 495                 return -2;
 496         return 0;
 497 }
 498
 499 static int have_same_root(const char *path1, const char *path2)
 500 {
 501         int is_abs1, is_abs2;
 502
 503         is_abs1 = is_absolute_path(path1);
 504         is_abs2 = is_absolute_path(path2);
 505         return (is_abs1 && is_abs2 && tolower(path1[0]) == tolower(path2[0])) ||
 506                (!is_abs1 && !is_abs2);
 507 }
 508
 509 /*
 510  * Give path as relative to prefix.
 511  *
 512  * The strbuf may or may not be used, so do not assume it contains the
 513  * returned path.
 514  */
 515 const char *relative_path(const char *in, const char *prefix,
 516                           struct strbuf *sb)
 517 {
 518         int in_len = in ? strlen(in) : 0;
 519         int prefix_len = prefix ? strlen(prefix) : 0;
 520         int in_off = 0;
 521         int prefix_off = 0;
 522         int i = 0, j = 0;
 523
 524         if (!in_len)
 525                 return "./";
 526         else if (!prefix_len)
 527                 return in;
 528
 529         if (have_same_root(in, prefix)) {
 530                 /* bypass dos_drive, for "c:" is identical to "C:" */
 531                 if (has_dos_drive_prefix(in)) {
 532                         i = 2;
 533                         j = 2;
 534                 }
 535         } else {
 536                 return in;
 537         }
 538
 539         while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
 540                 if (is_dir_sep(prefix[i])) {
 541                         while (is_dir_sep(prefix[i]))
 542                                 i++;
 543                         while (is_dir_sep(in[j]))
 544                                 j++;
 545                         prefix_off = i;
 546                         in_off = j;
 547                 } else {
 548                         i++;
 549                         j++;
 550                 }
 551         }
 552
 553         if (
 554             /* "prefix" seems like prefix of "in" */
 555             i >= prefix_len &&
 556             /*
 557              * but "/foo" is not a prefix of "/foobar"
 558              * (i.e. prefix not end with '/')
 559              */
 560             prefix_off < prefix_len) {
 561                 if (j >= in_len) {
 562                         /* in="/a/b", prefix="/a/b" */
 563                         in_off = in_len;
 564                 } else if (is_dir_sep(in[j])) {
 565                         /* in="/a/b/c", prefix="/a/b" */
 566                         while (is_dir_sep(in[j]))
 567                                 j++;
 568                         in_off = j;
 569                 } else {
 570                         /* in="/a/bbb/c", prefix="/a/b" */
 571                         i = prefix_off;
 572                 }
 573         } else if (
 574                    /* "in" is short than "prefix" */
 575                    j >= in_len &&
 576                    /* "in" not end with '/' */
 577                    in_off < in_len) {
 578                 if (is_dir_sep(prefix[i])) {
 579                         /* in="/a/b", prefix="/a/b/c/" */
 580                         while (is_dir_sep(prefix[i]))
 581                                 i++;
 582                         in_off = in_len;
 583                 }
 584         }
 585         in += in_off;
 586         in_len -= in_off;
 587
 588         if (i >= prefix_len) {
 589                 if (!in_len)
 590                         return "./";
 591                 else
 592                         return in;
 593         }
 594
 595         strbuf_reset(sb);
 596         strbuf_grow(sb, in_len);
 597
 598         while (i < prefix_len) {
 599                 if (is_dir_sep(prefix[i])) {
 600                         strbuf_addstr(sb, "../");
 601                         while (is_dir_sep(prefix[i]))
 602                                 i++;
 603                         continue;
 604                 }
 605                 i++;
 606         }
 607         if (!is_dir_sep(prefix[prefix_len - 1]))
 608                 strbuf_addstr(sb, "../");
 609
 610         strbuf_addstr(sb, in);
 611
 612         return sb->buf;
 613 }
 614
 615 /*
 616  * A simpler implementation of relative_path
 617  *
 618  * Get relative path by removing "prefix" from "in". This function
 619  * first appears in v1.5.6-1-g044bbbc, and makes git_dir shorter
 620  * to increase performance when traversing the path to work_tree.
 621  */
 622 const char *remove_leading_path(const char *in, const char *prefix)
 623 {
 624         static char buf[PATH_MAX + 1];
 625         int i = 0, j = 0;
 626
 627         if (!prefix || !prefix[0])
 628                 return in;
 629         while (prefix[i]) {
 630                 if (is_dir_sep(prefix[i])) {
 631                         if (!is_dir_sep(in[j]))
 632                                 return in;
 633                         while (is_dir_sep(prefix[i]))
 634                                 i++;
 635                         while (is_dir_sep(in[j]))
 636                                 j++;
 637                         continue;
 638                 } else if (in[j] != prefix[i]) {
 639                         return in;
 640                 }
 641                 i++;
 642                 j++;
 643         }
 644         if (
 645             /* "/foo" is a prefix of "/foo" */
 646             in[j] &&
 647             /* "/foo" is not a prefix of "/foobar" */
 648             !is_dir_sep(prefix[i-1]) && !is_dir_sep(in[j])
 649            )
 650                 return in;
 651         while (is_dir_sep(in[j]))
 652                 j++;
 653         if (!in[j])
 654                 strcpy(buf, ".");
 655         else
 656                 strcpy(buf, in + j);
 657         return buf;
 658 }
 659
 660 /*
 661  * It is okay if dst == src, but they should not overlap otherwise.
 662  *
 663  * Performs the following normalizations on src, storing the result in dst:
 664  * - Ensures that components are separated by '/' (Windows only)
 665  * - Squashes sequences of '/'.
 666  * - Removes "." components.
 667  * - Removes ".." components, and the components the precede them.
 668  * Returns failure (non-zero) if a ".." component appears as first path
 669  * component anytime during the normalization. Otherwise, returns success (0).
 670  *
 671  * Note that this function is purely textual.  It does not follow symlinks,
 672  * verify the existence of the path, or make any system calls.
 673  *
 674  * prefix_len != NULL is for a specific case of prefix_pathspec():
 675  * assume that src == dst and src[0..prefix_len-1] is already
 676  * normalized, any time "../" eats up to the prefix_len part,
 677  * prefix_len is reduced. In the end prefix_len is the remaining
 678  * prefix that has not been overridden by user pathspec.
 679  */
 680 int normalize_path_copy_len(char *dst, const char *src, int *prefix_len)
 681 {
 682         char *dst0;
 683
 684         if (has_dos_drive_prefix(src)) {
 685                 *dst++ = *src++;
 686                 *dst++ = *src++;
 687         }
 688         dst0 = dst;
 689
 690         if (is_dir_sep(*src)) {
 691                 *dst++ = '/';
 692                 while (is_dir_sep(*src))
 693                         src++;
 694         }
 695
 696         for (;;) {
 697                 char c = *src;
 698
 699                 /*
 700                  * A path component that begins with . could be
 701                  * special:
 702                  * (1) "." and ends   -- ignore and terminate.
 703                  * (2) "./"           -- ignore them, eat slash and continue.
 704                  * (3) ".." and ends  -- strip one and terminate.
 705                  * (4) "../"          -- strip one, eat slash and continue.
 706                  */
 707                 if (c == '.') {
 708                         if (!src[1]) {
 709                                 /* (1) */
 710                                 src++;
 711                         } else if (is_dir_sep(src[1])) {
 712                                 /* (2) */
 713                                 src += 2;
 714                                 while (is_dir_sep(*src))
 715                                         src++;
 716                                 continue;
 717                         } else if (src[1] == '.') {
 718                                 if (!src[2]) {
 719                                         /* (3) */
 720                                         src += 2;
 721                                         goto up_one;
 722                                 } else if (is_dir_sep(src[2])) {
 723                                         /* (4) */
 724                                         src += 3;
 725                                         while (is_dir_sep(*src))
 726                                                 src++;
 727                                         goto up_one;
 728                                 }
 729                         }
 730                 }
 731
 732                 /* copy up to the next '/', and eat all '/' */
 733                 while ((c = *src++) != '\0' && !is_dir_sep(c))
 734                         *dst++ = c;
 735                 if (is_dir_sep(c)) {
 736                         *dst++ = '/';
 737                         while (is_dir_sep(c))
 738                                 c = *src++;
 739                         src--;
 740                 } else if (!c)
 741                         break;
 742                 continue;
 743
 744         up_one:
 745                 /*
 746                  * dst0..dst is prefix portion, and dst[-1] is '/';
 747                  * go up one level.
 748                  */
 749                 dst--;  /* go to trailing '/' */
 750                 if (dst <= dst0)
 751                         return -1;
 752                 /* Windows: dst[-1] cannot be backslash anymore */
 753                 while (dst0 < dst && dst[-1] != '/')
 754                         dst--;
 755                 if (prefix_len && *prefix_len > dst - dst0)
 756                         *prefix_len = dst - dst0;
 757         }
 758         *dst = '\0';
 759         return 0;
 760 }
 761
 762 int normalize_path_copy(char *dst, const char *src)
 763 {
 764         return normalize_path_copy_len(dst, src, NULL);
 765 }
 766
 767 /*
 768  * path = Canonical absolute path
 769  * prefixes = string_list containing normalized, absolute paths without
 770  * trailing slashes (except for the root directory, which is denoted by "/").
 771  *
 772  * Determines, for each path in prefixes, whether the "prefix"
 773  * is an ancestor directory of path.  Returns the length of the longest
 774  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 775  * is an ancestor.  (Note that this means 0 is returned if prefixes is
 776  * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
 777  * are not considered to be their own ancestors.  path must be in a
 778  * canonical form: empty components, or "." or ".." components are not
 779  * allowed.
 780  */
 781 int longest_ancestor_length(const char *path, struct string_list *prefixes)
 782 {
 783         int i, max_len = -1;
 784
 785         if (!strcmp(path, "/"))
 786                 return -1;
 787
 788         for (i = 0; i < prefixes->nr; i++) {
 789                 const char *ceil = prefixes->items[i].string;
 790                 int len = strlen(ceil);
 791
 792                 if (len == 1 && ceil[0] == '/')
 793                         len = 0; /* root matches anything, with length 0 */
 794                 else if (!strncmp(path, ceil, len) && path[len] == '/')
 795                         ; /* match of length len */
 796                 else
 797                         continue; /* no match */
 798
 799                 if (len > max_len)
 800                         max_len = len;
 801         }
 802
 803         return max_len;
 804 }
 805
 806 /* strip arbitrary amount of directory separators at end of path */
 807 static inline int chomp_trailing_dir_sep(const char *path, int len)
 808 {
 809         while (len && is_dir_sep(path[len - 1]))
 810                 len--;
 811         return len;
 812 }
 813
 814 /*
 815  * If path ends with suffix (complete path components), returns the
 816  * part before suffix (sans trailing directory separators).
 817  * Otherwise returns NULL.
 818  */
 819 char *strip_path_suffix(const char *path, const char *suffix)
 820 {
 821         int path_len = strlen(path), suffix_len = strlen(suffix);
 822
 823         while (suffix_len) {
 824                 if (!path_len)
 825                         return NULL;
 826
 827                 if (is_dir_sep(path[path_len - 1])) {
 828                         if (!is_dir_sep(suffix[suffix_len - 1]))
 829                                 return NULL;
 830                         path_len = chomp_trailing_dir_sep(path, path_len);
 831                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
 832                 }
 833                 else if (path[--path_len] != suffix[--suffix_len])
 834                         return NULL;
 835         }
 836
 837         if (path_len && !is_dir_sep(path[path_len - 1]))
 838                 return NULL;
 839         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
 840 }
 841
 842 int daemon_avoid_alias(const char *p)
 843 {
 844         int sl, ndot;
 845
 846         /*
 847          * This resurrects the belts and suspenders paranoia check by HPA
 848          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
 849          * does not do getcwd() based path canonicalization.
 850          *
 851          * sl becomes true immediately after seeing '/' and continues to
 852          * be true as long as dots continue after that without intervening
 853          * non-dot character.
 854          */
 855         if (!p || (*p != '/' && *p != '~'))
 856                 return -1;
 857         sl = 1; ndot = 0;
 858         p++;
 859
 860         while (1) {
 861                 char ch = *p++;
 862                 if (sl) {
 863                         if (ch == '.')
 864                                 ndot++;
 865                         else if (ch == '/') {
 866                                 if (ndot < 3)
 867                                         /* reject //, /./ and /../ */
 868                                         return -1;
 869                                 ndot = 0;
 870                         }
 871                         else if (ch == 0) {
 872                                 if (0 < ndot && ndot < 3)
 873                                         /* reject /.$ and /..$ */
 874                                         return -1;
 875                                 return 0;
 876                         }
 877                         else
 878                                 sl = ndot = 0;
 879                 }
 880                 else if (ch == 0)
 881                         return 0;
 882                 else if (ch == '/') {
 883                         sl = 1;
 884                         ndot = 0;
 885                 }
 886         }
 887 }
 888
 889 static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
 890 {
 891         if (len < skip)
 892                 return 0;
 893         len -= skip;
 894         path += skip;
 895         while (len-- > 0) {
 896                 char c = *(path++);
 897                 if (c != ' ' && c != '.')
 898                         return 0;
 899         }
 900         return 1;
 901 }
 902
 903 int is_ntfs_dotgit(const char *name)
 904 {
 905         int len;
 906
 907         for (len = 0; ; len++)
 908                 if (!name[len] || name[len] == '\\' || is_dir_sep(name[len])) {
 909                         if (only_spaces_and_periods(name, len, 4) &&
 910                                         !strncasecmp(name, ".git", 4))
 911                                 return 1;
 912                         if (only_spaces_and_periods(name, len, 5) &&
 913                                         !strncasecmp(name, "git~1", 5))
 914                                 return 1;
 915                         if (name[len] != '\\')
 916                                 return 0;
 917                         name += len + 1;
 918                         len = -1;
 919                 }
 920 }
 921
 922 char *xdg_config_home(const char *filename)
 923 {
 924         const char *home, *config_home;
 925
 926         assert(filename);
 927         config_home = getenv("XDG_CONFIG_HOME");
 928         if (config_home && *config_home)
 929                 return mkpathdup("%s/git/%s", config_home, filename);
 930
 931         home = getenv("HOME");
 932         if (home)
 933                 return mkpathdup("%s/.config/git/%s", home, filename);
 934         return NULL;
 935 }