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 char *git_path_buf(struct strbuf *buf, const char *fmt, ...)
 179 {
 180         va_list args;
 181         strbuf_reset(buf);
 182         va_start(args, fmt);
 183         do_git_path(buf, fmt, args);
 184         va_end(args);
 185         return buf->buf;
 186 }
 187
 188 void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
 189 {
 190         va_list args;
 191         va_start(args, fmt);
 192         do_git_path(sb, fmt, args);
 193         va_end(args);
 194 }
 195
 196 const char *git_path(const char *fmt, ...)
 197 {
 198         struct strbuf *pathname = get_pathname();
 199         va_list args;
 200         va_start(args, fmt);
 201         do_git_path(pathname, fmt, args);
 202         va_end(args);
 203         return pathname->buf;
 204 }
 205
 206 char *git_pathdup(const char *fmt, ...)
 207 {
 208         struct strbuf path = STRBUF_INIT;
 209         va_list args;
 210         va_start(args, fmt);
 211         do_git_path(&path, fmt, args);
 212         va_end(args);
 213         return strbuf_detach(&path, NULL);
 214 }
 215
 216 char *mkpathdup(const char *fmt, ...)
 217 {
 218         struct strbuf sb = STRBUF_INIT;
 219         va_list args;
 220         va_start(args, fmt);
 221         strbuf_vaddf(&sb, fmt, args);
 222         va_end(args);
 223         strbuf_cleanup_path(&sb);
 224         return strbuf_detach(&sb, NULL);
 225 }
 226
 227 const char *mkpath(const char *fmt, ...)
 228 {
 229         va_list args;
 230         struct strbuf *pathname = get_pathname();
 231         va_start(args, fmt);
 232         strbuf_vaddf(pathname, fmt, args);
 233         va_end(args);
 234         return cleanup_path(pathname->buf);
 235 }
 236
 237 static void do_submodule_path(struct strbuf *buf, const char *path,
 238                               const char *fmt, va_list args)
 239 {
 240         const char *git_dir;
 241
 242         strbuf_addstr(buf, path);
 243         if (buf->len && buf->buf[buf->len - 1] != '/')
 244                 strbuf_addch(buf, '/');
 245         strbuf_addstr(buf, ".git");
 246
 247         git_dir = read_gitfile(buf->buf);
 248         if (git_dir) {
 249                 strbuf_reset(buf);
 250                 strbuf_addstr(buf, git_dir);
 251         }
 252         strbuf_addch(buf, '/');
 253
 254         strbuf_vaddf(buf, fmt, args);
 255         strbuf_cleanup_path(buf);
 256 }
 257
 258 char *git_pathdup_submodule(const char *path, const char *fmt, ...)
 259 {
 260         va_list args;
 261         struct strbuf buf = STRBUF_INIT;
 262         va_start(args, fmt);
 263         do_submodule_path(&buf, path, fmt, args);
 264         va_end(args);
 265         return strbuf_detach(&buf, NULL);
 266 }
 267
 268 void strbuf_git_path_submodule(struct strbuf *buf, const char *path,
 269                                const char *fmt, ...)
 270 {
 271         va_list args;
 272         va_start(args, fmt);
 273         do_submodule_path(buf, path, fmt, args);
 274         va_end(args);
 275 }
 276
 277 int validate_headref(const char *path)
 278 {
 279         struct stat st;
 280         char *buf, buffer[256];
 281         unsigned char sha1[20];
 282         int fd;
 283         ssize_t len;
 284
 285         if (lstat(path, &st) < 0)
 286                 return -1;
 287
 288         /* Make sure it is a "refs/.." symlink */
 289         if (S_ISLNK(st.st_mode)) {
 290                 len = readlink(path, buffer, sizeof(buffer)-1);
 291                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 292                         return 0;
 293                 return -1;
 294         }
 295
 296         /*
 297          * Anything else, just open it and try to see if it is a symbolic ref.
 298          */
 299         fd = open(path, O_RDONLY);
 300         if (fd < 0)
 301                 return -1;
 302         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 303         close(fd);
 304
 305         /*
 306          * Is it a symbolic ref?
 307          */
 308         if (len < 4)
 309                 return -1;
 310         if (!memcmp("ref:", buffer, 4)) {
 311                 buf = buffer + 4;
 312                 len -= 4;
 313                 while (len && isspace(*buf))
 314                         buf++, len--;
 315                 if (len >= 5 && !memcmp("refs/", buf, 5))
 316                         return 0;
 317         }
 318
 319         /*
 320          * Is this a detached HEAD?
 321          */
 322         if (!get_sha1_hex(buffer, sha1))
 323                 return 0;
 324
 325         return -1;
 326 }
 327
 328 static struct passwd *getpw_str(const char *username, size_t len)
 329 {
 330         struct passwd *pw;
 331         char *username_z = xmemdupz(username, len);
 332         pw = getpwnam(username_z);
 333         free(username_z);
 334         return pw;
 335 }
 336
 337 /*
 338  * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 339  * then it is a newly allocated string. Returns NULL on getpw failure or
 340  * if path is NULL.
 341  */
 342 char *expand_user_path(const char *path)
 343 {
 344         struct strbuf user_path = STRBUF_INIT;
 345         const char *to_copy = path;
 346
 347         if (path == NULL)
 348                 goto return_null;
 349         if (path[0] == '~') {
 350                 const char *first_slash = strchrnul(path, '/');
 351                 const char *username = path + 1;
 352                 size_t username_len = first_slash - username;
 353                 if (username_len == 0) {
 354                         const char *home = getenv("HOME");
 355                         if (!home)
 356                                 goto return_null;
 357                         strbuf_addstr(&user_path, home);
 358                 } else {
 359                         struct passwd *pw = getpw_str(username, username_len);
 360                         if (!pw)
 361                                 goto return_null;
 362                         strbuf_addstr(&user_path, pw->pw_dir);
 363                 }
 364                 to_copy = first_slash;
 365         }
 366         strbuf_addstr(&user_path, to_copy);
 367         return strbuf_detach(&user_path, NULL);
 368 return_null:
 369         strbuf_release(&user_path);
 370         return NULL;
 371 }
 372
 373 /*
 374  * First, one directory to try is determined by the following algorithm.
 375  *
 376  * (0) If "strict" is given, the path is used as given and no DWIM is
 377  *     done. Otherwise:
 378  * (1) "~/path" to mean path under the running user's home directory;
 379  * (2) "~user/path" to mean path under named user's home directory;
 380  * (3) "relative/path" to mean cwd relative directory; or
 381  * (4) "/absolute/path" to mean absolute directory.
 382  *
 383  * Unless "strict" is given, we check "%s/.git", "%s", "%s.git/.git", "%s.git"
 384  * in this order. We select the first one that is a valid git repository, and
 385  * chdir() to it. If none match, or we fail to chdir, we return NULL.
 386  *
 387  * If all goes well, we return the directory we used to chdir() (but
 388  * before ~user is expanded), avoiding getcwd() resolving symbolic
 389  * links.  User relative paths are also returned as they are given,
 390  * except DWIM suffixing.
 391  */
 392 const char *enter_repo(const char *path, int strict)
 393 {
 394         static struct strbuf validated_path = STRBUF_INIT;
 395         static struct strbuf used_path = STRBUF_INIT;
 396
 397         if (!path)
 398                 return NULL;
 399
 400         if (!strict) {
 401                 static const char *suffix[] = {
 402                         "/.git", "", ".git/.git", ".git", NULL,
 403                 };
 404                 const char *gitfile;
 405                 int len = strlen(path);
 406                 int i;
 407                 while ((1 < len) && (path[len-1] == '/'))
 408                         len--;
 409
 410                 /*
 411                  * We can handle arbitrary-sized buffers, but this remains as a
 412                  * sanity check on untrusted input.
 413                  */
 414                 if (PATH_MAX <= len)
 415                         return NULL;
 416
 417                 strbuf_reset(&used_path);
 418                 strbuf_reset(&validated_path);
 419                 strbuf_add(&used_path, path, len);
 420                 strbuf_add(&validated_path, path, len);
 421
 422                 if (used_path.buf[0] == '~') {
 423                         char *newpath = expand_user_path(used_path.buf);
 424                         if (!newpath)
 425                                 return NULL;
 426                         strbuf_attach(&used_path, newpath, strlen(newpath),
 427                                       strlen(newpath));
 428                 }
 429                 for (i = 0; suffix[i]; i++) {
 430                         struct stat st;
 431                         size_t baselen = used_path.len;
 432                         strbuf_addstr(&used_path, suffix[i]);
 433                         if (!stat(used_path.buf, &st) &&
 434                             (S_ISREG(st.st_mode) ||
 435                             (S_ISDIR(st.st_mode) && is_git_directory(used_path.buf)))) {
 436                                 strbuf_addstr(&validated_path, suffix[i]);
 437                                 break;
 438                         }
 439                         strbuf_setlen(&used_path, baselen);
 440                 }
 441                 if (!suffix[i])
 442                         return NULL;
 443                 gitfile = read_gitfile(used_path.buf) ;
 444                 if (gitfile) {
 445                         strbuf_reset(&used_path);
 446                         strbuf_addstr(&used_path, gitfile);
 447                 }
 448                 if (chdir(used_path.buf))
 449                         return NULL;
 450                 path = validated_path.buf;
 451         }
 452         else if (chdir(path))
 453                 return NULL;
 454
 455         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 456             validate_headref("HEAD") == 0) {
 457                 set_git_dir(".");
 458                 check_repository_format();
 459                 return path;
 460         }
 461
 462         return NULL;
 463 }
 464
 465 static int calc_shared_perm(int mode)
 466 {
 467         int tweak;
 468
 469         if (shared_repository < 0)
 470                 tweak = -shared_repository;
 471         else
 472                 tweak = shared_repository;
 473
 474         if (!(mode & S_IWUSR))
 475                 tweak &= ~0222;
 476         if (mode & S_IXUSR)
 477                 /* Copy read bits to execute bits */
 478                 tweak |= (tweak & 0444) >> 2;
 479         if (shared_repository < 0)
 480                 mode = (mode & ~0777) | tweak;
 481         else
 482                 mode |= tweak;
 483
 484         return mode;
 485 }
 486
 487
 488 int adjust_shared_perm(const char *path)
 489 {
 490         int old_mode, new_mode;
 491
 492         if (!shared_repository)
 493                 return 0;
 494         if (get_st_mode_bits(path, &old_mode) < 0)
 495                 return -1;
 496
 497         new_mode = calc_shared_perm(old_mode);
 498         if (S_ISDIR(old_mode)) {
 499                 /* Copy read bits to execute bits */
 500                 new_mode |= (new_mode & 0444) >> 2;
 501                 new_mode |= FORCE_DIR_SET_GID;
 502         }
 503
 504         if (((old_mode ^ new_mode) & ~S_IFMT) &&
 505                         chmod(path, (new_mode & ~S_IFMT)) < 0)
 506                 return -2;
 507         return 0;
 508 }
 509
 510 static int have_same_root(const char *path1, const char *path2)
 511 {
 512         int is_abs1, is_abs2;
 513
 514         is_abs1 = is_absolute_path(path1);
 515         is_abs2 = is_absolute_path(path2);
 516         return (is_abs1 && is_abs2 && tolower(path1[0]) == tolower(path2[0])) ||
 517                (!is_abs1 && !is_abs2);
 518 }
 519
 520 /*
 521  * Give path as relative to prefix.
 522  *
 523  * The strbuf may or may not be used, so do not assume it contains the
 524  * returned path.
 525  */
 526 const char *relative_path(const char *in, const char *prefix,
 527                           struct strbuf *sb)
 528 {
 529         int in_len = in ? strlen(in) : 0;
 530         int prefix_len = prefix ? strlen(prefix) : 0;
 531         int in_off = 0;
 532         int prefix_off = 0;
 533         int i = 0, j = 0;
 534
 535         if (!in_len)
 536                 return "./";
 537         else if (!prefix_len)
 538                 return in;
 539
 540         if (have_same_root(in, prefix)) {
 541                 /* bypass dos_drive, for "c:" is identical to "C:" */
 542                 if (has_dos_drive_prefix(in)) {
 543                         i = 2;
 544                         j = 2;
 545                 }
 546         } else {
 547                 return in;
 548         }
 549
 550         while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
 551                 if (is_dir_sep(prefix[i])) {
 552                         while (is_dir_sep(prefix[i]))
 553                                 i++;
 554                         while (is_dir_sep(in[j]))
 555                                 j++;
 556                         prefix_off = i;
 557                         in_off = j;
 558                 } else {
 559                         i++;
 560                         j++;
 561                 }
 562         }
 563
 564         if (
 565             /* "prefix" seems like prefix of "in" */
 566             i >= prefix_len &&
 567             /*
 568              * but "/foo" is not a prefix of "/foobar"
 569              * (i.e. prefix not end with '/')
 570              */
 571             prefix_off < prefix_len) {
 572                 if (j >= in_len) {
 573                         /* in="/a/b", prefix="/a/b" */
 574                         in_off = in_len;
 575                 } else if (is_dir_sep(in[j])) {
 576                         /* in="/a/b/c", prefix="/a/b" */
 577                         while (is_dir_sep(in[j]))
 578                                 j++;
 579                         in_off = j;
 580                 } else {
 581                         /* in="/a/bbb/c", prefix="/a/b" */
 582                         i = prefix_off;
 583                 }
 584         } else if (
 585                    /* "in" is short than "prefix" */
 586                    j >= in_len &&
 587                    /* "in" not end with '/' */
 588                    in_off < in_len) {
 589                 if (is_dir_sep(prefix[i])) {
 590                         /* in="/a/b", prefix="/a/b/c/" */
 591                         while (is_dir_sep(prefix[i]))
 592                                 i++;
 593                         in_off = in_len;
 594                 }
 595         }
 596         in += in_off;
 597         in_len -= in_off;
 598
 599         if (i >= prefix_len) {
 600                 if (!in_len)
 601                         return "./";
 602                 else
 603                         return in;
 604         }
 605
 606         strbuf_reset(sb);
 607         strbuf_grow(sb, in_len);
 608
 609         while (i < prefix_len) {
 610                 if (is_dir_sep(prefix[i])) {
 611                         strbuf_addstr(sb, "../");
 612                         while (is_dir_sep(prefix[i]))
 613                                 i++;
 614                         continue;
 615                 }
 616                 i++;
 617         }
 618         if (!is_dir_sep(prefix[prefix_len - 1]))
 619                 strbuf_addstr(sb, "../");
 620
 621         strbuf_addstr(sb, in);
 622
 623         return sb->buf;
 624 }
 625
 626 /*
 627  * A simpler implementation of relative_path
 628  *
 629  * Get relative path by removing "prefix" from "in". This function
 630  * first appears in v1.5.6-1-g044bbbc, and makes git_dir shorter
 631  * to increase performance when traversing the path to work_tree.
 632  */
 633 const char *remove_leading_path(const char *in, const char *prefix)
 634 {
 635         static char buf[PATH_MAX + 1];
 636         int i = 0, j = 0;
 637
 638         if (!prefix || !prefix[0])
 639                 return in;
 640         while (prefix[i]) {
 641                 if (is_dir_sep(prefix[i])) {
 642                         if (!is_dir_sep(in[j]))
 643                                 return in;
 644                         while (is_dir_sep(prefix[i]))
 645                                 i++;
 646                         while (is_dir_sep(in[j]))
 647                                 j++;
 648                         continue;
 649                 } else if (in[j] != prefix[i]) {
 650                         return in;
 651                 }
 652                 i++;
 653                 j++;
 654         }
 655         if (
 656             /* "/foo" is a prefix of "/foo" */
 657             in[j] &&
 658             /* "/foo" is not a prefix of "/foobar" */
 659             !is_dir_sep(prefix[i-1]) && !is_dir_sep(in[j])
 660            )
 661                 return in;
 662         while (is_dir_sep(in[j]))
 663                 j++;
 664         if (!in[j])
 665                 strcpy(buf, ".");
 666         else
 667                 strcpy(buf, in + j);
 668         return buf;
 669 }
 670
 671 /*
 672  * It is okay if dst == src, but they should not overlap otherwise.
 673  *
 674  * Performs the following normalizations on src, storing the result in dst:
 675  * - Ensures that components are separated by '/' (Windows only)
 676  * - Squashes sequences of '/'.
 677  * - Removes "." components.
 678  * - Removes ".." components, and the components the precede them.
 679  * Returns failure (non-zero) if a ".." component appears as first path
 680  * component anytime during the normalization. Otherwise, returns success (0).
 681  *
 682  * Note that this function is purely textual.  It does not follow symlinks,
 683  * verify the existence of the path, or make any system calls.
 684  *
 685  * prefix_len != NULL is for a specific case of prefix_pathspec():
 686  * assume that src == dst and src[0..prefix_len-1] is already
 687  * normalized, any time "../" eats up to the prefix_len part,
 688  * prefix_len is reduced. In the end prefix_len is the remaining
 689  * prefix that has not been overridden by user pathspec.
 690  */
 691 int normalize_path_copy_len(char *dst, const char *src, int *prefix_len)
 692 {
 693         char *dst0;
 694
 695         if (has_dos_drive_prefix(src)) {
 696                 *dst++ = *src++;
 697                 *dst++ = *src++;
 698         }
 699         dst0 = dst;
 700
 701         if (is_dir_sep(*src)) {
 702                 *dst++ = '/';
 703                 while (is_dir_sep(*src))
 704                         src++;
 705         }
 706
 707         for (;;) {
 708                 char c = *src;
 709
 710                 /*
 711                  * A path component that begins with . could be
 712                  * special:
 713                  * (1) "." and ends   -- ignore and terminate.
 714                  * (2) "./"           -- ignore them, eat slash and continue.
 715                  * (3) ".." and ends  -- strip one and terminate.
 716                  * (4) "../"          -- strip one, eat slash and continue.
 717                  */
 718                 if (c == '.') {
 719                         if (!src[1]) {
 720                                 /* (1) */
 721                                 src++;
 722                         } else if (is_dir_sep(src[1])) {
 723                                 /* (2) */
 724                                 src += 2;
 725                                 while (is_dir_sep(*src))
 726                                         src++;
 727                                 continue;
 728                         } else if (src[1] == '.') {
 729                                 if (!src[2]) {
 730                                         /* (3) */
 731                                         src += 2;
 732                                         goto up_one;
 733                                 } else if (is_dir_sep(src[2])) {
 734                                         /* (4) */
 735                                         src += 3;
 736                                         while (is_dir_sep(*src))
 737                                                 src++;
 738                                         goto up_one;
 739                                 }
 740                         }
 741                 }
 742
 743                 /* copy up to the next '/', and eat all '/' */
 744                 while ((c = *src++) != '\0' && !is_dir_sep(c))
 745                         *dst++ = c;
 746                 if (is_dir_sep(c)) {
 747                         *dst++ = '/';
 748                         while (is_dir_sep(c))
 749                                 c = *src++;
 750                         src--;
 751                 } else if (!c)
 752                         break;
 753                 continue;
 754
 755         up_one:
 756                 /*
 757                  * dst0..dst is prefix portion, and dst[-1] is '/';
 758                  * go up one level.
 759                  */
 760                 dst--;  /* go to trailing '/' */
 761                 if (dst <= dst0)
 762                         return -1;
 763                 /* Windows: dst[-1] cannot be backslash anymore */
 764                 while (dst0 < dst && dst[-1] != '/')
 765                         dst--;
 766                 if (prefix_len && *prefix_len > dst - dst0)
 767                         *prefix_len = dst - dst0;
 768         }
 769         *dst = '\0';
 770         return 0;
 771 }
 772
 773 int normalize_path_copy(char *dst, const char *src)
 774 {
 775         return normalize_path_copy_len(dst, src, NULL);
 776 }
 777
 778 /*
 779  * path = Canonical absolute path
 780  * prefixes = string_list containing normalized, absolute paths without
 781  * trailing slashes (except for the root directory, which is denoted by "/").
 782  *
 783  * Determines, for each path in prefixes, whether the "prefix"
 784  * is an ancestor directory of path.  Returns the length of the longest
 785  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 786  * is an ancestor.  (Note that this means 0 is returned if prefixes is
 787  * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
 788  * are not considered to be their own ancestors.  path must be in a
 789  * canonical form: empty components, or "." or ".." components are not
 790  * allowed.
 791  */
 792 int longest_ancestor_length(const char *path, struct string_list *prefixes)
 793 {
 794         int i, max_len = -1;
 795
 796         if (!strcmp(path, "/"))
 797                 return -1;
 798
 799         for (i = 0; i < prefixes->nr; i++) {
 800                 const char *ceil = prefixes->items[i].string;
 801                 int len = strlen(ceil);
 802
 803                 if (len == 1 && ceil[0] == '/')
 804                         len = 0; /* root matches anything, with length 0 */
 805                 else if (!strncmp(path, ceil, len) && path[len] == '/')
 806                         ; /* match of length len */
 807                 else
 808                         continue; /* no match */
 809
 810                 if (len > max_len)
 811                         max_len = len;
 812         }
 813
 814         return max_len;
 815 }
 816
 817 /* strip arbitrary amount of directory separators at end of path */
 818 static inline int chomp_trailing_dir_sep(const char *path, int len)
 819 {
 820         while (len && is_dir_sep(path[len - 1]))
 821                 len--;
 822         return len;
 823 }
 824
 825 /*
 826  * If path ends with suffix (complete path components), returns the
 827  * part before suffix (sans trailing directory separators).
 828  * Otherwise returns NULL.
 829  */
 830 char *strip_path_suffix(const char *path, const char *suffix)
 831 {
 832         int path_len = strlen(path), suffix_len = strlen(suffix);
 833
 834         while (suffix_len) {
 835                 if (!path_len)
 836                         return NULL;
 837
 838                 if (is_dir_sep(path[path_len - 1])) {
 839                         if (!is_dir_sep(suffix[suffix_len - 1]))
 840                                 return NULL;
 841                         path_len = chomp_trailing_dir_sep(path, path_len);
 842                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
 843                 }
 844                 else if (path[--path_len] != suffix[--suffix_len])
 845                         return NULL;
 846         }
 847
 848         if (path_len && !is_dir_sep(path[path_len - 1]))
 849                 return NULL;
 850         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
 851 }
 852
 853 int daemon_avoid_alias(const char *p)
 854 {
 855         int sl, ndot;
 856
 857         /*
 858          * This resurrects the belts and suspenders paranoia check by HPA
 859          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
 860          * does not do getcwd() based path canonicalization.
 861          *
 862          * sl becomes true immediately after seeing '/' and continues to
 863          * be true as long as dots continue after that without intervening
 864          * non-dot character.
 865          */
 866         if (!p || (*p != '/' && *p != '~'))
 867                 return -1;
 868         sl = 1; ndot = 0;
 869         p++;
 870
 871         while (1) {
 872                 char ch = *p++;
 873                 if (sl) {
 874                         if (ch == '.')
 875                                 ndot++;
 876                         else if (ch == '/') {
 877                                 if (ndot < 3)
 878                                         /* reject //, /./ and /../ */
 879                                         return -1;
 880                                 ndot = 0;
 881                         }
 882                         else if (ch == 0) {
 883                                 if (0 < ndot && ndot < 3)
 884                                         /* reject /.$ and /..$ */
 885                                         return -1;
 886                                 return 0;
 887                         }
 888                         else
 889                                 sl = ndot = 0;
 890                 }
 891                 else if (ch == 0)
 892                         return 0;
 893                 else if (ch == '/') {
 894                         sl = 1;
 895                         ndot = 0;
 896                 }
 897         }
 898 }
 899
 900 static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
 901 {
 902         if (len < skip)
 903                 return 0;
 904         len -= skip;
 905         path += skip;
 906         while (len-- > 0) {
 907                 char c = *(path++);
 908                 if (c != ' ' && c != '.')
 909                         return 0;
 910         }
 911         return 1;
 912 }
 913
 914 int is_ntfs_dotgit(const char *name)
 915 {
 916         int len;
 917
 918         for (len = 0; ; len++)
 919                 if (!name[len] || name[len] == '\\' || is_dir_sep(name[len])) {
 920                         if (only_spaces_and_periods(name, len, 4) &&
 921                                         !strncasecmp(name, ".git", 4))
 922                                 return 1;
 923                         if (only_spaces_and_periods(name, len, 5) &&
 924                                         !strncasecmp(name, "git~1", 5))
 925                                 return 1;
 926                         if (name[len] != '\\')
 927                                 return 0;
 928                         name += len + 1;
 929                         len = -1;
 930                 }
 931 }
 932
 933 char *xdg_config_home(const char *filename)
 934 {
 935         const char *home, *config_home;
 936
 937         assert(filename);
 938         config_home = getenv("XDG_CONFIG_HOME");
 939         if (config_home && *config_home)
 940                 return mkpathdup("%s/git/%s", config_home, filename);
 941
 942         home = getenv("HOME");
 943         if (home)
 944                 return mkpathdup("%s/.config/git/%s", home, filename);
 945         return NULL;
 946 }
 947
 948 GIT_PATH_FUNC(git_path_cherry_pick_head, "CHERRY_PICK_HEAD")
 949 GIT_PATH_FUNC(git_path_revert_head, "REVERT_HEAD")
 950 GIT_PATH_FUNC(git_path_squash_msg, "SQUASH_MSG")
 951 GIT_PATH_FUNC(git_path_merge_msg, "MERGE_MSG")
 952 GIT_PATH_FUNC(git_path_merge_rr, "MERGE_RR")
 953 GIT_PATH_FUNC(git_path_merge_mode, "MERGE_MODE")
 954 GIT_PATH_FUNC(git_path_merge_head, "MERGE_HEAD")
 955 GIT_PATH_FUNC(git_path_fetch_head, "FETCH_HEAD")
 956 GIT_PATH_FUNC(git_path_shallow, "shallow")