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, const char *common_dir)
 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
 119                 if (!common_dir)
 120                         common_dir = get_git_common_dir();
 121
 122                 if (is_dir && dir_prefix(base, path)) {
 123                         replace_dir(buf, git_dir_len, common_dir);
 124                         return;
 125                 }
 126                 if (!is_dir && !strcmp(base, path)) {
 127                         replace_dir(buf, git_dir_len, common_dir);
 128                         return;
 129                 }
 130         }
 131 }
 132
 133 void report_linked_checkout_garbage(void)
 134 {
 135         struct strbuf sb = STRBUF_INIT;
 136         const char **p;
 137         int len;
 138
 139         if (!git_common_dir_env)
 140                 return;
 141         strbuf_addf(&sb, "%s/", get_git_dir());
 142         len = sb.len;
 143         for (p = common_list; *p; p++) {
 144                 const char *path = *p;
 145                 if (*path == '!')
 146                         continue;
 147                 strbuf_setlen(&sb, len);
 148                 strbuf_addstr(&sb, path);
 149                 if (file_exists(sb.buf))
 150                         report_garbage(PACKDIR_FILE_GARBAGE, sb.buf);
 151         }
 152         strbuf_release(&sb);
 153 }
 154
 155 static void adjust_git_path(struct strbuf *buf, int git_dir_len)
 156 {
 157         const char *base = buf->buf + git_dir_len;
 158         if (git_graft_env && is_dir_file(base, "info", "grafts"))
 159                 strbuf_splice(buf, 0, buf->len,
 160                               get_graft_file(), strlen(get_graft_file()));
 161         else if (git_index_env && !strcmp(base, "index"))
 162                 strbuf_splice(buf, 0, buf->len,
 163                               get_index_file(), strlen(get_index_file()));
 164         else if (git_db_env && dir_prefix(base, "objects"))
 165                 replace_dir(buf, git_dir_len + 7, get_object_directory());
 166         else if (git_common_dir_env)
 167                 update_common_dir(buf, git_dir_len, NULL);
 168 }
 169
 170 static void do_git_path(struct strbuf *buf, const char *fmt, va_list args)
 171 {
 172         int gitdir_len;
 173         strbuf_addstr(buf, get_git_dir());
 174         if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 175                 strbuf_addch(buf, '/');
 176         gitdir_len = buf->len;
 177         strbuf_vaddf(buf, fmt, args);
 178         adjust_git_path(buf, gitdir_len);
 179         strbuf_cleanup_path(buf);
 180 }
 181
 182 void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
 183 {
 184         va_list args;
 185         va_start(args, fmt);
 186         do_git_path(sb, fmt, args);
 187         va_end(args);
 188 }
 189
 190 const char *git_path(const char *fmt, ...)
 191 {
 192         struct strbuf *pathname = get_pathname();
 193         va_list args;
 194         va_start(args, fmt);
 195         do_git_path(pathname, fmt, args);
 196         va_end(args);
 197         return pathname->buf;
 198 }
 199
 200 char *git_pathdup(const char *fmt, ...)
 201 {
 202         struct strbuf path = STRBUF_INIT;
 203         va_list args;
 204         va_start(args, fmt);
 205         do_git_path(&path, fmt, args);
 206         va_end(args);
 207         return strbuf_detach(&path, NULL);
 208 }
 209
 210 char *mkpathdup(const char *fmt, ...)
 211 {
 212         struct strbuf sb = STRBUF_INIT;
 213         va_list args;
 214         va_start(args, fmt);
 215         strbuf_vaddf(&sb, fmt, args);
 216         va_end(args);
 217         strbuf_cleanup_path(&sb);
 218         return strbuf_detach(&sb, NULL);
 219 }
 220
 221 const char *mkpath(const char *fmt, ...)
 222 {
 223         va_list args;
 224         struct strbuf *pathname = get_pathname();
 225         va_start(args, fmt);
 226         strbuf_vaddf(pathname, fmt, args);
 227         va_end(args);
 228         return cleanup_path(pathname->buf);
 229 }
 230
 231 static void do_submodule_path(struct strbuf *buf, const char *path,
 232                               const char *fmt, va_list args)
 233 {
 234         const char *git_dir;
 235         struct strbuf git_submodule_common_dir = STRBUF_INIT;
 236         struct strbuf git_submodule_dir = STRBUF_INIT;
 237
 238         strbuf_addstr(buf, path);
 239         if (buf->len && buf->buf[buf->len - 1] != '/')
 240                 strbuf_addch(buf, '/');
 241         strbuf_addstr(buf, ".git");
 242
 243         git_dir = read_gitfile(buf->buf);
 244         if (git_dir) {
 245                 strbuf_reset(buf);
 246                 strbuf_addstr(buf, git_dir);
 247         }
 248         strbuf_addch(buf, '/');
 249         strbuf_addstr(&git_submodule_dir, buf->buf);
 250
 251         strbuf_vaddf(buf, fmt, args);
 252
 253         if (get_common_dir_noenv(&git_submodule_common_dir, git_submodule_dir.buf))
 254                 update_common_dir(buf, git_submodule_dir.len, git_submodule_common_dir.buf);
 255
 256         strbuf_cleanup_path(buf);
 257
 258         strbuf_release(&git_submodule_dir);
 259         strbuf_release(&git_submodule_common_dir);
 260 }
 261
 262 char *git_pathdup_submodule(const char *path, const char *fmt, ...)
 263 {
 264         va_list args;
 265         struct strbuf buf = STRBUF_INIT;
 266         va_start(args, fmt);
 267         do_submodule_path(&buf, path, fmt, args);
 268         va_end(args);
 269         return strbuf_detach(&buf, NULL);
 270 }
 271
 272 void strbuf_git_path_submodule(struct strbuf *buf, const char *path,
 273                                const char *fmt, ...)
 274 {
 275         va_list args;
 276         va_start(args, fmt);
 277         do_submodule_path(buf, path, fmt, args);
 278         va_end(args);
 279 }
 280
 281 int validate_headref(const char *path)
 282 {
 283         struct stat st;
 284         char *buf, buffer[256];
 285         unsigned char sha1[20];
 286         int fd;
 287         ssize_t len;
 288
 289         if (lstat(path, &st) < 0)
 290                 return -1;
 291
 292         /* Make sure it is a "refs/.." symlink */
 293         if (S_ISLNK(st.st_mode)) {
 294                 len = readlink(path, buffer, sizeof(buffer)-1);
 295                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 296                         return 0;
 297                 return -1;
 298         }
 299
 300         /*
 301          * Anything else, just open it and try to see if it is a symbolic ref.
 302          */
 303         fd = open(path, O_RDONLY);
 304         if (fd < 0)
 305                 return -1;
 306         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 307         close(fd);
 308
 309         /*
 310          * Is it a symbolic ref?
 311          */
 312         if (len < 4)
 313                 return -1;
 314         if (!memcmp("ref:", buffer, 4)) {
 315                 buf = buffer + 4;
 316                 len -= 4;
 317                 while (len && isspace(*buf))
 318                         buf++, len--;
 319                 if (len >= 5 && !memcmp("refs/", buf, 5))
 320                         return 0;
 321         }
 322
 323         /*
 324          * Is this a detached HEAD?
 325          */
 326         if (!get_sha1_hex(buffer, sha1))
 327                 return 0;
 328
 329         return -1;
 330 }
 331
 332 static struct passwd *getpw_str(const char *username, size_t len)
 333 {
 334         struct passwd *pw;
 335         char *username_z = xmemdupz(username, len);
 336         pw = getpwnam(username_z);
 337         free(username_z);
 338         return pw;
 339 }
 340
 341 /*
 342  * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 343  * then it is a newly allocated string. Returns NULL on getpw failure or
 344  * if path is NULL.
 345  */
 346 char *expand_user_path(const char *path)
 347 {
 348         struct strbuf user_path = STRBUF_INIT;
 349         const char *to_copy = path;
 350
 351         if (path == NULL)
 352                 goto return_null;
 353         if (path[0] == '~') {
 354                 const char *first_slash = strchrnul(path, '/');
 355                 const char *username = path + 1;
 356                 size_t username_len = first_slash - username;
 357                 if (username_len == 0) {
 358                         const char *home = getenv("HOME");
 359                         if (!home)
 360                                 goto return_null;
 361                         strbuf_addstr(&user_path, home);
 362                 } else {
 363                         struct passwd *pw = getpw_str(username, username_len);
 364                         if (!pw)
 365                                 goto return_null;
 366                         strbuf_addstr(&user_path, pw->pw_dir);
 367                 }
 368                 to_copy = first_slash;
 369         }
 370         strbuf_addstr(&user_path, to_copy);
 371         return strbuf_detach(&user_path, NULL);
 372 return_null:
 373         strbuf_release(&user_path);
 374         return NULL;
 375 }
 376
 377 /*
 378  * First, one directory to try is determined by the following algorithm.
 379  *
 380  * (0) If "strict" is given, the path is used as given and no DWIM is
 381  *     done. Otherwise:
 382  * (1) "~/path" to mean path under the running user's home directory;
 383  * (2) "~user/path" to mean path under named user's home directory;
 384  * (3) "relative/path" to mean cwd relative directory; or
 385  * (4) "/absolute/path" to mean absolute directory.
 386  *
 387  * Unless "strict" is given, we check "%s/.git", "%s", "%s.git/.git", "%s.git"
 388  * in this order. We select the first one that is a valid git repository, and
 389  * chdir() to it. If none match, or we fail to chdir, we return NULL.
 390  *
 391  * If all goes well, we return the directory we used to chdir() (but
 392  * before ~user is expanded), avoiding getcwd() resolving symbolic
 393  * links.  User relative paths are also returned as they are given,
 394  * except DWIM suffixing.
 395  */
 396 const char *enter_repo(const char *path, int strict)
 397 {
 398         static char used_path[PATH_MAX];
 399         static char validated_path[PATH_MAX];
 400
 401         if (!path)
 402                 return NULL;
 403
 404         if (!strict) {
 405                 static const char *suffix[] = {
 406                         "/.git", "", ".git/.git", ".git", NULL,
 407                 };
 408                 const char *gitfile;
 409                 int len = strlen(path);
 410                 int i;
 411                 while ((1 < len) && (path[len-1] == '/'))
 412                         len--;
 413
 414                 if (PATH_MAX <= len)
 415                         return NULL;
 416                 strncpy(used_path, path, len); used_path[len] = 0 ;
 417                 strcpy(validated_path, used_path);
 418
 419                 if (used_path[0] == '~') {
 420                         char *newpath = expand_user_path(used_path);
 421                         if (!newpath || (PATH_MAX - 10 < strlen(newpath))) {
 422                                 free(newpath);
 423                                 return NULL;
 424                         }
 425                         /*
 426                          * Copy back into the static buffer. A pity
 427                          * since newpath was not bounded, but other
 428                          * branches of the if are limited by PATH_MAX
 429                          * anyway.
 430                          */
 431                         strcpy(used_path, newpath); free(newpath);
 432                 }
 433                 else if (PATH_MAX - 10 < len)
 434                         return NULL;
 435                 len = strlen(used_path);
 436                 for (i = 0; suffix[i]; i++) {
 437                         struct stat st;
 438                         strcpy(used_path + len, suffix[i]);
 439                         if (!stat(used_path, &st) &&
 440                             (S_ISREG(st.st_mode) ||
 441                             (S_ISDIR(st.st_mode) && is_git_directory(used_path)))) {
 442                                 strcat(validated_path, suffix[i]);
 443                                 break;
 444                         }
 445                 }
 446                 if (!suffix[i])
 447                         return NULL;
 448                 gitfile = read_gitfile(used_path);
 449                 if (gitfile)
 450                         strcpy(used_path, gitfile);
 451                 if (chdir(used_path))
 452                         return NULL;
 453                 path = validated_path;
 454         }
 455         else {
 456                 const char *gitfile = read_gitfile(path);
 457                 if (gitfile)
 458                         path = gitfile;
 459                 if (chdir(path))
 460                         return NULL;
 461         }
 462
 463         if (is_git_directory(".")) {
 464                 set_git_dir(".");
 465                 check_repository_format();
 466                 return path;
 467         }
 468
 469         return NULL;
 470 }
 471
 472 static int calc_shared_perm(int mode)
 473 {
 474         int tweak;
 475
 476         if (shared_repository < 0)
 477                 tweak = -shared_repository;
 478         else
 479                 tweak = shared_repository;
 480
 481         if (!(mode & S_IWUSR))
 482                 tweak &= ~0222;
 483         if (mode & S_IXUSR)
 484                 /* Copy read bits to execute bits */
 485                 tweak |= (tweak & 0444) >> 2;
 486         if (shared_repository < 0)
 487                 mode = (mode & ~0777) | tweak;
 488         else
 489                 mode |= tweak;
 490
 491         return mode;
 492 }
 493
 494
 495 int adjust_shared_perm(const char *path)
 496 {
 497         int old_mode, new_mode;
 498
 499         if (!shared_repository)
 500                 return 0;
 501         if (get_st_mode_bits(path, &old_mode) < 0)
 502                 return -1;
 503
 504         new_mode = calc_shared_perm(old_mode);
 505         if (S_ISDIR(old_mode)) {
 506                 /* Copy read bits to execute bits */
 507                 new_mode |= (new_mode & 0444) >> 2;
 508                 new_mode |= FORCE_DIR_SET_GID;
 509         }
 510
 511         if (((old_mode ^ new_mode) & ~S_IFMT) &&
 512                         chmod(path, (new_mode & ~S_IFMT)) < 0)
 513                 return -2;
 514         return 0;
 515 }
 516
 517 static int have_same_root(const char *path1, const char *path2)
 518 {
 519         int is_abs1, is_abs2;
 520
 521         is_abs1 = is_absolute_path(path1);
 522         is_abs2 = is_absolute_path(path2);
 523         return (is_abs1 && is_abs2 && tolower(path1[0]) == tolower(path2[0])) ||
 524                (!is_abs1 && !is_abs2);
 525 }
 526
 527 /*
 528  * Give path as relative to prefix.
 529  *
 530  * The strbuf may or may not be used, so do not assume it contains the
 531  * returned path.
 532  */
 533 const char *relative_path(const char *in, const char *prefix,
 534                           struct strbuf *sb)
 535 {
 536         int in_len = in ? strlen(in) : 0;
 537         int prefix_len = prefix ? strlen(prefix) : 0;
 538         int in_off = 0;
 539         int prefix_off = 0;
 540         int i = 0, j = 0;
 541
 542         if (!in_len)
 543                 return "./";
 544         else if (!prefix_len)
 545                 return in;
 546
 547         if (have_same_root(in, prefix)) {
 548                 /* bypass dos_drive, for "c:" is identical to "C:" */
 549                 if (has_dos_drive_prefix(in)) {
 550                         i = 2;
 551                         j = 2;
 552                 }
 553         } else {
 554                 return in;
 555         }
 556
 557         while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
 558                 if (is_dir_sep(prefix[i])) {
 559                         while (is_dir_sep(prefix[i]))
 560                                 i++;
 561                         while (is_dir_sep(in[j]))
 562                                 j++;
 563                         prefix_off = i;
 564                         in_off = j;
 565                 } else {
 566                         i++;
 567                         j++;
 568                 }
 569         }
 570
 571         if (
 572             /* "prefix" seems like prefix of "in" */
 573             i >= prefix_len &&
 574             /*
 575              * but "/foo" is not a prefix of "/foobar"
 576              * (i.e. prefix not end with '/')
 577              */
 578             prefix_off < prefix_len) {
 579                 if (j >= in_len) {
 580                         /* in="/a/b", prefix="/a/b" */
 581                         in_off = in_len;
 582                 } else if (is_dir_sep(in[j])) {
 583                         /* in="/a/b/c", prefix="/a/b" */
 584                         while (is_dir_sep(in[j]))
 585                                 j++;
 586                         in_off = j;
 587                 } else {
 588                         /* in="/a/bbb/c", prefix="/a/b" */
 589                         i = prefix_off;
 590                 }
 591         } else if (
 592                    /* "in" is short than "prefix" */
 593                    j >= in_len &&
 594                    /* "in" not end with '/' */
 595                    in_off < in_len) {
 596                 if (is_dir_sep(prefix[i])) {
 597                         /* in="/a/b", prefix="/a/b/c/" */
 598                         while (is_dir_sep(prefix[i]))
 599                                 i++;
 600                         in_off = in_len;
 601                 }
 602         }
 603         in += in_off;
 604         in_len -= in_off;
 605
 606         if (i >= prefix_len) {
 607                 if (!in_len)
 608                         return "./";
 609                 else
 610                         return in;
 611         }
 612
 613         strbuf_reset(sb);
 614         strbuf_grow(sb, in_len);
 615
 616         while (i < prefix_len) {
 617                 if (is_dir_sep(prefix[i])) {
 618                         strbuf_addstr(sb, "../");
 619                         while (is_dir_sep(prefix[i]))
 620                                 i++;
 621                         continue;
 622                 }
 623                 i++;
 624         }
 625         if (!is_dir_sep(prefix[prefix_len - 1]))
 626                 strbuf_addstr(sb, "../");
 627
 628         strbuf_addstr(sb, in);
 629
 630         return sb->buf;
 631 }
 632
 633 /*
 634  * A simpler implementation of relative_path
 635  *
 636  * Get relative path by removing "prefix" from "in". This function
 637  * first appears in v1.5.6-1-g044bbbc, and makes git_dir shorter
 638  * to increase performance when traversing the path to work_tree.
 639  */
 640 const char *remove_leading_path(const char *in, const char *prefix)
 641 {
 642         static char buf[PATH_MAX + 1];
 643         int i = 0, j = 0;
 644
 645         if (!prefix || !prefix[0])
 646                 return in;
 647         while (prefix[i]) {
 648                 if (is_dir_sep(prefix[i])) {
 649                         if (!is_dir_sep(in[j]))
 650                                 return in;
 651                         while (is_dir_sep(prefix[i]))
 652                                 i++;
 653                         while (is_dir_sep(in[j]))
 654                                 j++;
 655                         continue;
 656                 } else if (in[j] != prefix[i]) {
 657                         return in;
 658                 }
 659                 i++;
 660                 j++;
 661         }
 662         if (
 663             /* "/foo" is a prefix of "/foo" */
 664             in[j] &&
 665             /* "/foo" is not a prefix of "/foobar" */
 666             !is_dir_sep(prefix[i-1]) && !is_dir_sep(in[j])
 667            )
 668                 return in;
 669         while (is_dir_sep(in[j]))
 670                 j++;
 671         if (!in[j])
 672                 strcpy(buf, ".");
 673         else
 674                 strcpy(buf, in + j);
 675         return buf;
 676 }
 677
 678 /*
 679  * It is okay if dst == src, but they should not overlap otherwise.
 680  *
 681  * Performs the following normalizations on src, storing the result in dst:
 682  * - Ensures that components are separated by '/' (Windows only)
 683  * - Squashes sequences of '/'.
 684  * - Removes "." components.
 685  * - Removes ".." components, and the components the precede them.
 686  * Returns failure (non-zero) if a ".." component appears as first path
 687  * component anytime during the normalization. Otherwise, returns success (0).
 688  *
 689  * Note that this function is purely textual.  It does not follow symlinks,
 690  * verify the existence of the path, or make any system calls.
 691  *
 692  * prefix_len != NULL is for a specific case of prefix_pathspec():
 693  * assume that src == dst and src[0..prefix_len-1] is already
 694  * normalized, any time "../" eats up to the prefix_len part,
 695  * prefix_len is reduced. In the end prefix_len is the remaining
 696  * prefix that has not been overridden by user pathspec.
 697  *
 698  * NEEDSWORK: This function doesn't perform normalization w.r.t. trailing '/'.
 699  * For everything but the root folder itself, the normalized path should not
 700  * end with a '/', then the callers need to be fixed up accordingly.
 701  *
 702  */
 703 int normalize_path_copy_len(char *dst, const char *src, int *prefix_len)
 704 {
 705         char *dst0;
 706
 707         if (has_dos_drive_prefix(src)) {
 708                 *dst++ = *src++;
 709                 *dst++ = *src++;
 710         }
 711         dst0 = dst;
 712
 713         if (is_dir_sep(*src)) {
 714                 *dst++ = '/';
 715                 while (is_dir_sep(*src))
 716                         src++;
 717         }
 718
 719         for (;;) {
 720                 char c = *src;
 721
 722                 /*
 723                  * A path component that begins with . could be
 724                  * special:
 725                  * (1) "." and ends   -- ignore and terminate.
 726                  * (2) "./"           -- ignore them, eat slash and continue.
 727                  * (3) ".." and ends  -- strip one and terminate.
 728                  * (4) "../"          -- strip one, eat slash and continue.
 729                  */
 730                 if (c == '.') {
 731                         if (!src[1]) {
 732                                 /* (1) */
 733                                 src++;
 734                         } else if (is_dir_sep(src[1])) {
 735                                 /* (2) */
 736                                 src += 2;
 737                                 while (is_dir_sep(*src))
 738                                         src++;
 739                                 continue;
 740                         } else if (src[1] == '.') {
 741                                 if (!src[2]) {
 742                                         /* (3) */
 743                                         src += 2;
 744                                         goto up_one;
 745                                 } else if (is_dir_sep(src[2])) {
 746                                         /* (4) */
 747                                         src += 3;
 748                                         while (is_dir_sep(*src))
 749                                                 src++;
 750                                         goto up_one;
 751                                 }
 752                         }
 753                 }
 754
 755                 /* copy up to the next '/', and eat all '/' */
 756                 while ((c = *src++) != '\0' && !is_dir_sep(c))
 757                         *dst++ = c;
 758                 if (is_dir_sep(c)) {
 759                         *dst++ = '/';
 760                         while (is_dir_sep(c))
 761                                 c = *src++;
 762                         src--;
 763                 } else if (!c)
 764                         break;
 765                 continue;
 766
 767         up_one:
 768                 /*
 769                  * dst0..dst is prefix portion, and dst[-1] is '/';
 770                  * go up one level.
 771                  */
 772                 dst--;  /* go to trailing '/' */
 773                 if (dst <= dst0)
 774                         return -1;
 775                 /* Windows: dst[-1] cannot be backslash anymore */
 776                 while (dst0 < dst && dst[-1] != '/')
 777                         dst--;
 778                 if (prefix_len && *prefix_len > dst - dst0)
 779                         *prefix_len = dst - dst0;
 780         }
 781         *dst = '\0';
 782         return 0;
 783 }
 784
 785 int normalize_path_copy(char *dst, const char *src)
 786 {
 787         return normalize_path_copy_len(dst, src, NULL);
 788 }
 789
 790 /*
 791  * path = Canonical absolute path
 792  * prefixes = string_list containing normalized, absolute paths without
 793  * trailing slashes (except for the root directory, which is denoted by "/").
 794  *
 795  * Determines, for each path in prefixes, whether the "prefix"
 796  * is an ancestor directory of path.  Returns the length of the longest
 797  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 798  * is an ancestor.  (Note that this means 0 is returned if prefixes is
 799  * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
 800  * are not considered to be their own ancestors.  path must be in a
 801  * canonical form: empty components, or "." or ".." components are not
 802  * allowed.
 803  */
 804 int longest_ancestor_length(const char *path, struct string_list *prefixes)
 805 {
 806         int i, max_len = -1;
 807
 808         if (!strcmp(path, "/"))
 809                 return -1;
 810
 811         for (i = 0; i < prefixes->nr; i++) {
 812                 const char *ceil = prefixes->items[i].string;
 813                 int len = strlen(ceil);
 814
 815                 if (len == 1 && ceil[0] == '/')
 816                         len = 0; /* root matches anything, with length 0 */
 817                 else if (!strncmp(path, ceil, len) && path[len] == '/')
 818                         ; /* match of length len */
 819                 else
 820                         continue; /* no match */
 821
 822                 if (len > max_len)
 823                         max_len = len;
 824         }
 825
 826         return max_len;
 827 }
 828
 829 /* strip arbitrary amount of directory separators at end of path */
 830 static inline int chomp_trailing_dir_sep(const char *path, int len)
 831 {
 832         while (len && is_dir_sep(path[len - 1]))
 833                 len--;
 834         return len;
 835 }
 836
 837 /*
 838  * If path ends with suffix (complete path components), returns the
 839  * part before suffix (sans trailing directory separators).
 840  * Otherwise returns NULL.
 841  */
 842 char *strip_path_suffix(const char *path, const char *suffix)
 843 {
 844         int path_len = strlen(path), suffix_len = strlen(suffix);
 845
 846         while (suffix_len) {
 847                 if (!path_len)
 848                         return NULL;
 849
 850                 if (is_dir_sep(path[path_len - 1])) {
 851                         if (!is_dir_sep(suffix[suffix_len - 1]))
 852                                 return NULL;
 853                         path_len = chomp_trailing_dir_sep(path, path_len);
 854                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
 855                 }
 856                 else if (path[--path_len] != suffix[--suffix_len])
 857                         return NULL;
 858         }
 859
 860         if (path_len && !is_dir_sep(path[path_len - 1]))
 861                 return NULL;
 862         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
 863 }
 864
 865 int daemon_avoid_alias(const char *p)
 866 {
 867         int sl, ndot;
 868
 869         /*
 870          * This resurrects the belts and suspenders paranoia check by HPA
 871          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
 872          * does not do getcwd() based path canonicalization.
 873          *
 874          * sl becomes true immediately after seeing '/' and continues to
 875          * be true as long as dots continue after that without intervening
 876          * non-dot character.
 877          */
 878         if (!p || (*p != '/' && *p != '~'))
 879                 return -1;
 880         sl = 1; ndot = 0;
 881         p++;
 882
 883         while (1) {
 884                 char ch = *p++;
 885                 if (sl) {
 886                         if (ch == '.')
 887                                 ndot++;
 888                         else if (ch == '/') {
 889                                 if (ndot < 3)
 890                                         /* reject //, /./ and /../ */
 891                                         return -1;
 892                                 ndot = 0;
 893                         }
 894                         else if (ch == 0) {
 895                                 if (0 < ndot && ndot < 3)
 896                                         /* reject /.$ and /..$ */
 897                                         return -1;
 898                                 return 0;
 899                         }
 900                         else
 901                                 sl = ndot = 0;
 902                 }
 903                 else if (ch == 0)
 904                         return 0;
 905                 else if (ch == '/') {
 906                         sl = 1;
 907                         ndot = 0;
 908                 }
 909         }
 910 }
 911
 912 static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
 913 {
 914         if (len < skip)
 915                 return 0;
 916         len -= skip;
 917         path += skip;
 918         while (len-- > 0) {
 919                 char c = *(path++);
 920                 if (c != ' ' && c != '.')
 921                         return 0;
 922         }
 923         return 1;
 924 }
 925
 926 int is_ntfs_dotgit(const char *name)
 927 {
 928         int len;
 929
 930         for (len = 0; ; len++)
 931                 if (!name[len] || name[len] == '\\' || is_dir_sep(name[len])) {
 932                         if (only_spaces_and_periods(name, len, 4) &&
 933                                         !strncasecmp(name, ".git", 4))
 934                                 return 1;
 935                         if (only_spaces_and_periods(name, len, 5) &&
 936                                         !strncasecmp(name, "git~1", 5))
 937                                 return 1;
 938                         if (name[len] != '\\')
 939                                 return 0;
 940                         name += len + 1;
 941                         len = -1;
 942                 }
 943 }
 944
 945 char *xdg_config_home(const char *filename)
 946 {
 947         const char *home, *config_home;
 948
 949         assert(filename);
 950         config_home = getenv("XDG_CONFIG_HOME");
 951         if (config_home && *config_home)
 952                 return mkpathdup("%s/git/%s", config_home, filename);
 953
 954         home = getenv("HOME");
 955         if (home)
 956                 return mkpathdup("%s/.config/git/%s", home, filename);
 957         return NULL;
 958 }
 959
 960 GIT_PATH_FUNC(git_path_cherry_pick_head, "CHERRY_PICK_HEAD")
 961 GIT_PATH_FUNC(git_path_revert_head, "REVERT_HEAD")
 962 GIT_PATH_FUNC(git_path_squash_msg, "SQUASH_MSG")
 963 GIT_PATH_FUNC(git_path_merge_msg, "MERGE_MSG")
 964 GIT_PATH_FUNC(git_path_merge_rr, "MERGE_RR")
 965 GIT_PATH_FUNC(git_path_merge_mode, "MERGE_MODE")
 966 GIT_PATH_FUNC(git_path_merge_head, "MERGE_HEAD")
 967 GIT_PATH_FUNC(git_path_fetch_head, "FETCH_HEAD")
 968 GIT_PATH_FUNC(git_path_shallow, "shallow")