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 (is_git_directory(".")) {
 445                 set_git_dir(".");
 446                 check_repository_format();
 447                 return path;
 448         }
 449
 450         return NULL;
 451 }
 452
 453 static int calc_shared_perm(int mode)
 454 {
 455         int tweak;
 456
 457         if (shared_repository < 0)
 458                 tweak = -shared_repository;
 459         else
 460                 tweak = shared_repository;
 461
 462         if (!(mode & S_IWUSR))
 463                 tweak &= ~0222;
 464         if (mode & S_IXUSR)
 465                 /* Copy read bits to execute bits */
 466                 tweak |= (tweak & 0444) >> 2;
 467         if (shared_repository < 0)
 468                 mode = (mode & ~0777) | tweak;
 469         else
 470                 mode |= tweak;
 471
 472         return mode;
 473 }
 474
 475
 476 int adjust_shared_perm(const char *path)
 477 {
 478         int old_mode, new_mode;
 479
 480         if (!shared_repository)
 481                 return 0;
 482         if (get_st_mode_bits(path, &old_mode) < 0)
 483                 return -1;
 484
 485         new_mode = calc_shared_perm(old_mode);
 486         if (S_ISDIR(old_mode)) {
 487                 /* Copy read bits to execute bits */
 488                 new_mode |= (new_mode & 0444) >> 2;
 489                 new_mode |= FORCE_DIR_SET_GID;
 490         }
 491
 492         if (((old_mode ^ new_mode) & ~S_IFMT) &&
 493                         chmod(path, (new_mode & ~S_IFMT)) < 0)
 494                 return -2;
 495         return 0;
 496 }
 497
 498 static int have_same_root(const char *path1, const char *path2)
 499 {
 500         int is_abs1, is_abs2;
 501
 502         is_abs1 = is_absolute_path(path1);
 503         is_abs2 = is_absolute_path(path2);
 504         return (is_abs1 && is_abs2 && tolower(path1[0]) == tolower(path2[0])) ||
 505                (!is_abs1 && !is_abs2);
 506 }
 507
 508 /*
 509  * Give path as relative to prefix.
 510  *
 511  * The strbuf may or may not be used, so do not assume it contains the
 512  * returned path.
 513  */
 514 const char *relative_path(const char *in, const char *prefix,
 515                           struct strbuf *sb)
 516 {
 517         int in_len = in ? strlen(in) : 0;
 518         int prefix_len = prefix ? strlen(prefix) : 0;
 519         int in_off = 0;
 520         int prefix_off = 0;
 521         int i = 0, j = 0;
 522
 523         if (!in_len)
 524                 return "./";
 525         else if (!prefix_len)
 526                 return in;
 527
 528         if (have_same_root(in, prefix)) {
 529                 /* bypass dos_drive, for "c:" is identical to "C:" */
 530                 if (has_dos_drive_prefix(in)) {
 531                         i = 2;
 532                         j = 2;
 533                 }
 534         } else {
 535                 return in;
 536         }
 537
 538         while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
 539                 if (is_dir_sep(prefix[i])) {
 540                         while (is_dir_sep(prefix[i]))
 541                                 i++;
 542                         while (is_dir_sep(in[j]))
 543                                 j++;
 544                         prefix_off = i;
 545                         in_off = j;
 546                 } else {
 547                         i++;
 548                         j++;
 549                 }
 550         }
 551
 552         if (
 553             /* "prefix" seems like prefix of "in" */
 554             i >= prefix_len &&
 555             /*
 556              * but "/foo" is not a prefix of "/foobar"
 557              * (i.e. prefix not end with '/')
 558              */
 559             prefix_off < prefix_len) {
 560                 if (j >= in_len) {
 561                         /* in="/a/b", prefix="/a/b" */
 562                         in_off = in_len;
 563                 } else if (is_dir_sep(in[j])) {
 564                         /* in="/a/b/c", prefix="/a/b" */
 565                         while (is_dir_sep(in[j]))
 566                                 j++;
 567                         in_off = j;
 568                 } else {
 569                         /* in="/a/bbb/c", prefix="/a/b" */
 570                         i = prefix_off;
 571                 }
 572         } else if (
 573                    /* "in" is short than "prefix" */
 574                    j >= in_len &&
 575                    /* "in" not end with '/' */
 576                    in_off < in_len) {
 577                 if (is_dir_sep(prefix[i])) {
 578                         /* in="/a/b", prefix="/a/b/c/" */
 579                         while (is_dir_sep(prefix[i]))
 580                                 i++;
 581                         in_off = in_len;
 582                 }
 583         }
 584         in += in_off;
 585         in_len -= in_off;
 586
 587         if (i >= prefix_len) {
 588                 if (!in_len)
 589                         return "./";
 590                 else
 591                         return in;
 592         }
 593
 594         strbuf_reset(sb);
 595         strbuf_grow(sb, in_len);
 596
 597         while (i < prefix_len) {
 598                 if (is_dir_sep(prefix[i])) {
 599                         strbuf_addstr(sb, "../");
 600                         while (is_dir_sep(prefix[i]))
 601                                 i++;
 602                         continue;
 603                 }
 604                 i++;
 605         }
 606         if (!is_dir_sep(prefix[prefix_len - 1]))
 607                 strbuf_addstr(sb, "../");
 608
 609         strbuf_addstr(sb, in);
 610
 611         return sb->buf;
 612 }
 613
 614 /*
 615  * A simpler implementation of relative_path
 616  *
 617  * Get relative path by removing "prefix" from "in". This function
 618  * first appears in v1.5.6-1-g044bbbc, and makes git_dir shorter
 619  * to increase performance when traversing the path to work_tree.
 620  */
 621 const char *remove_leading_path(const char *in, const char *prefix)
 622 {
 623         static char buf[PATH_MAX + 1];
 624         int i = 0, j = 0;
 625
 626         if (!prefix || !prefix[0])
 627                 return in;
 628         while (prefix[i]) {
 629                 if (is_dir_sep(prefix[i])) {
 630                         if (!is_dir_sep(in[j]))
 631                                 return in;
 632                         while (is_dir_sep(prefix[i]))
 633                                 i++;
 634                         while (is_dir_sep(in[j]))
 635                                 j++;
 636                         continue;
 637                 } else if (in[j] != prefix[i]) {
 638                         return in;
 639                 }
 640                 i++;
 641                 j++;
 642         }
 643         if (
 644             /* "/foo" is a prefix of "/foo" */
 645             in[j] &&
 646             /* "/foo" is not a prefix of "/foobar" */
 647             !is_dir_sep(prefix[i-1]) && !is_dir_sep(in[j])
 648            )
 649                 return in;
 650         while (is_dir_sep(in[j]))
 651                 j++;
 652         if (!in[j])
 653                 strcpy(buf, ".");
 654         else
 655                 strcpy(buf, in + j);
 656         return buf;
 657 }
 658
 659 /*
 660  * It is okay if dst == src, but they should not overlap otherwise.
 661  *
 662  * Performs the following normalizations on src, storing the result in dst:
 663  * - Ensures that components are separated by '/' (Windows only)
 664  * - Squashes sequences of '/'.
 665  * - Removes "." components.
 666  * - Removes ".." components, and the components the precede them.
 667  * Returns failure (non-zero) if a ".." component appears as first path
 668  * component anytime during the normalization. Otherwise, returns success (0).
 669  *
 670  * Note that this function is purely textual.  It does not follow symlinks,
 671  * verify the existence of the path, or make any system calls.
 672  *
 673  * prefix_len != NULL is for a specific case of prefix_pathspec():
 674  * assume that src == dst and src[0..prefix_len-1] is already
 675  * normalized, any time "../" eats up to the prefix_len part,
 676  * prefix_len is reduced. In the end prefix_len is the remaining
 677  * prefix that has not been overridden by user pathspec.
 678  */
 679 int normalize_path_copy_len(char *dst, const char *src, int *prefix_len)
 680 {
 681         char *dst0;
 682
 683         if (has_dos_drive_prefix(src)) {
 684                 *dst++ = *src++;
 685                 *dst++ = *src++;
 686         }
 687         dst0 = dst;
 688
 689         if (is_dir_sep(*src)) {
 690                 *dst++ = '/';
 691                 while (is_dir_sep(*src))
 692                         src++;
 693         }
 694
 695         for (;;) {
 696                 char c = *src;
 697
 698                 /*
 699                  * A path component that begins with . could be
 700                  * special:
 701                  * (1) "." and ends   -- ignore and terminate.
 702                  * (2) "./"           -- ignore them, eat slash and continue.
 703                  * (3) ".." and ends  -- strip one and terminate.
 704                  * (4) "../"          -- strip one, eat slash and continue.
 705                  */
 706                 if (c == '.') {
 707                         if (!src[1]) {
 708                                 /* (1) */
 709                                 src++;
 710                         } else if (is_dir_sep(src[1])) {
 711                                 /* (2) */
 712                                 src += 2;
 713                                 while (is_dir_sep(*src))
 714                                         src++;
 715                                 continue;
 716                         } else if (src[1] == '.') {
 717                                 if (!src[2]) {
 718                                         /* (3) */
 719                                         src += 2;
 720                                         goto up_one;
 721                                 } else if (is_dir_sep(src[2])) {
 722                                         /* (4) */
 723                                         src += 3;
 724                                         while (is_dir_sep(*src))
 725                                                 src++;
 726                                         goto up_one;
 727                                 }
 728                         }
 729                 }
 730
 731                 /* copy up to the next '/', and eat all '/' */
 732                 while ((c = *src++) != '\0' && !is_dir_sep(c))
 733                         *dst++ = c;
 734                 if (is_dir_sep(c)) {
 735                         *dst++ = '/';
 736                         while (is_dir_sep(c))
 737                                 c = *src++;
 738                         src--;
 739                 } else if (!c)
 740                         break;
 741                 continue;
 742
 743         up_one:
 744                 /*
 745                  * dst0..dst is prefix portion, and dst[-1] is '/';
 746                  * go up one level.
 747                  */
 748                 dst--;  /* go to trailing '/' */
 749                 if (dst <= dst0)
 750                         return -1;
 751                 /* Windows: dst[-1] cannot be backslash anymore */
 752                 while (dst0 < dst && dst[-1] != '/')
 753                         dst--;
 754                 if (prefix_len && *prefix_len > dst - dst0)
 755                         *prefix_len = dst - dst0;
 756         }
 757         *dst = '\0';
 758         return 0;
 759 }
 760
 761 int normalize_path_copy(char *dst, const char *src)
 762 {
 763         return normalize_path_copy_len(dst, src, NULL);
 764 }
 765
 766 /*
 767  * path = Canonical absolute path
 768  * prefixes = string_list containing normalized, absolute paths without
 769  * trailing slashes (except for the root directory, which is denoted by "/").
 770  *
 771  * Determines, for each path in prefixes, whether the "prefix"
 772  * is an ancestor directory of path.  Returns the length of the longest
 773  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 774  * is an ancestor.  (Note that this means 0 is returned if prefixes is
 775  * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
 776  * are not considered to be their own ancestors.  path must be in a
 777  * canonical form: empty components, or "." or ".." components are not
 778  * allowed.
 779  */
 780 int longest_ancestor_length(const char *path, struct string_list *prefixes)
 781 {
 782         int i, max_len = -1;
 783
 784         if (!strcmp(path, "/"))
 785                 return -1;
 786
 787         for (i = 0; i < prefixes->nr; i++) {
 788                 const char *ceil = prefixes->items[i].string;
 789                 int len = strlen(ceil);
 790
 791                 if (len == 1 && ceil[0] == '/')
 792                         len = 0; /* root matches anything, with length 0 */
 793                 else if (!strncmp(path, ceil, len) && path[len] == '/')
 794                         ; /* match of length len */
 795                 else
 796                         continue; /* no match */
 797
 798                 if (len > max_len)
 799                         max_len = len;
 800         }
 801
 802         return max_len;
 803 }
 804
 805 /* strip arbitrary amount of directory separators at end of path */
 806 static inline int chomp_trailing_dir_sep(const char *path, int len)
 807 {
 808         while (len && is_dir_sep(path[len - 1]))
 809                 len--;
 810         return len;
 811 }
 812
 813 /*
 814  * If path ends with suffix (complete path components), returns the
 815  * part before suffix (sans trailing directory separators).
 816  * Otherwise returns NULL.
 817  */
 818 char *strip_path_suffix(const char *path, const char *suffix)
 819 {
 820         int path_len = strlen(path), suffix_len = strlen(suffix);
 821
 822         while (suffix_len) {
 823                 if (!path_len)
 824                         return NULL;
 825
 826                 if (is_dir_sep(path[path_len - 1])) {
 827                         if (!is_dir_sep(suffix[suffix_len - 1]))
 828                                 return NULL;
 829                         path_len = chomp_trailing_dir_sep(path, path_len);
 830                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
 831                 }
 832                 else if (path[--path_len] != suffix[--suffix_len])
 833                         return NULL;
 834         }
 835
 836         if (path_len && !is_dir_sep(path[path_len - 1]))
 837                 return NULL;
 838         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
 839 }
 840
 841 int daemon_avoid_alias(const char *p)
 842 {
 843         int sl, ndot;
 844
 845         /*
 846          * This resurrects the belts and suspenders paranoia check by HPA
 847          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
 848          * does not do getcwd() based path canonicalization.
 849          *
 850          * sl becomes true immediately after seeing '/' and continues to
 851          * be true as long as dots continue after that without intervening
 852          * non-dot character.
 853          */
 854         if (!p || (*p != '/' && *p != '~'))
 855                 return -1;
 856         sl = 1; ndot = 0;
 857         p++;
 858
 859         while (1) {
 860                 char ch = *p++;
 861                 if (sl) {
 862                         if (ch == '.')
 863                                 ndot++;
 864                         else if (ch == '/') {
 865                                 if (ndot < 3)
 866                                         /* reject //, /./ and /../ */
 867                                         return -1;
 868                                 ndot = 0;
 869                         }
 870                         else if (ch == 0) {
 871                                 if (0 < ndot && ndot < 3)
 872                                         /* reject /.$ and /..$ */
 873                                         return -1;
 874                                 return 0;
 875                         }
 876                         else
 877                                 sl = ndot = 0;
 878                 }
 879                 else if (ch == 0)
 880                         return 0;
 881                 else if (ch == '/') {
 882                         sl = 1;
 883                         ndot = 0;
 884                 }
 885         }
 886 }
 887
 888 static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
 889 {
 890         if (len < skip)
 891                 return 0;
 892         len -= skip;
 893         path += skip;
 894         while (len-- > 0) {
 895                 char c = *(path++);
 896                 if (c != ' ' && c != '.')
 897                         return 0;
 898         }
 899         return 1;
 900 }
 901
 902 int is_ntfs_dotgit(const char *name)
 903 {
 904         int len;
 905
 906         for (len = 0; ; len++)
 907                 if (!name[len] || name[len] == '\\' || is_dir_sep(name[len])) {
 908                         if (only_spaces_and_periods(name, len, 4) &&
 909                                         !strncasecmp(name, ".git", 4))
 910                                 return 1;
 911                         if (only_spaces_and_periods(name, len, 5) &&
 912                                         !strncasecmp(name, "git~1", 5))
 913                                 return 1;
 914                         if (name[len] != '\\')
 915                                 return 0;
 916                         name += len + 1;
 917                         len = -1;
 918                 }
 919 }
 920
 921 char *xdg_config_home(const char *filename)
 922 {
 923         const char *home, *config_home;
 924
 925         assert(filename);
 926         config_home = getenv("XDG_CONFIG_HOME");
 927         if (config_home && *config_home)
 928                 return mkpathdup("%s/git/%s", config_home, filename);
 929
 930         home = getenv("HOME");
 931         if (home)
 932                 return mkpathdup("%s/.config/git/%s", home, filename);
 933         return NULL;
 934 }
 935
 936 GIT_PATH_FUNC(git_path_cherry_pick_head, "CHERRY_PICK_HEAD")
 937 GIT_PATH_FUNC(git_path_revert_head, "REVERT_HEAD")
 938 GIT_PATH_FUNC(git_path_squash_msg, "SQUASH_MSG")
 939 GIT_PATH_FUNC(git_path_merge_msg, "MERGE_MSG")
 940 GIT_PATH_FUNC(git_path_merge_rr, "MERGE_RR")
 941 GIT_PATH_FUNC(git_path_merge_mode, "MERGE_MODE")
 942 GIT_PATH_FUNC(git_path_merge_head, "MERGE_HEAD")
 943 GIT_PATH_FUNC(git_path_fetch_head, "FETCH_HEAD")
 944 GIT_PATH_FUNC(git_path_shallow, "shallow")