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 struct common_dir {
  95         /* Not considered garbage for report_linked_checkout_garbage */
  96         unsigned ignore_garbage:1;
  97         unsigned is_dir:1;
  98         /* Not common even though its parent is */
  99         unsigned exclude:1;
 100         const char *dirname;
 101 };
 102
 103 static struct common_dir common_list[] = {
 104         { 0, 1, 0, "branches" },
 105         { 0, 1, 0, "hooks" },
 106         { 0, 1, 0, "info" },
 107         { 0, 0, 1, "info/sparse-checkout" },
 108         { 1, 1, 0, "logs" },
 109         { 1, 1, 1, "logs/HEAD" },
 110         { 0, 1, 0, "lost-found" },
 111         { 0, 1, 0, "objects" },
 112         { 0, 1, 0, "refs" },
 113         { 0, 1, 0, "remotes" },
 114         { 0, 1, 0, "worktrees" },
 115         { 0, 1, 0, "rr-cache" },
 116         { 0, 1, 0, "svn" },
 117         { 0, 0, 0, "config" },
 118         { 1, 0, 0, "gc.pid" },
 119         { 0, 0, 0, "packed-refs" },
 120         { 0, 0, 0, "shallow" },
 121         { 0, 0, 0, NULL }
 122 };
 123
 124 static void update_common_dir(struct strbuf *buf, int git_dir_len)
 125 {
 126         char *base = buf->buf + git_dir_len;
 127         const struct common_dir *p;
 128
 129         if (is_dir_file(base, "logs", "HEAD") ||
 130             is_dir_file(base, "info", "sparse-checkout"))
 131                 return; /* keep this in $GIT_DIR */
 132         for (p = common_list; p->dirname; p++) {
 133                 const char *path = p->dirname;
 134                 if (p->is_dir && dir_prefix(base, path)) {
 135                         replace_dir(buf, git_dir_len, get_git_common_dir());
 136                         return;
 137                 }
 138                 if (!p->is_dir && !strcmp(base, path)) {
 139                         replace_dir(buf, git_dir_len, get_git_common_dir());
 140                         return;
 141                 }
 142         }
 143 }
 144
 145 void report_linked_checkout_garbage(void)
 146 {
 147         struct strbuf sb = STRBUF_INIT;
 148         const struct common_dir *p;
 149         int len;
 150
 151         if (!git_common_dir_env)
 152                 return;
 153         strbuf_addf(&sb, "%s/", get_git_dir());
 154         len = sb.len;
 155         for (p = common_list; p->dirname; p++) {
 156                 const char *path = p->dirname;
 157                 if (p->ignore_garbage)
 158                         continue;
 159                 strbuf_setlen(&sb, len);
 160                 strbuf_addstr(&sb, path);
 161                 if (file_exists(sb.buf))
 162                         report_garbage("unused in linked checkout", sb.buf);
 163         }
 164         strbuf_release(&sb);
 165 }
 166
 167 static void adjust_git_path(struct strbuf *buf, int git_dir_len)
 168 {
 169         const char *base = buf->buf + git_dir_len;
 170         if (git_graft_env && is_dir_file(base, "info", "grafts"))
 171                 strbuf_splice(buf, 0, buf->len,
 172                               get_graft_file(), strlen(get_graft_file()));
 173         else if (git_index_env && !strcmp(base, "index"))
 174                 strbuf_splice(buf, 0, buf->len,
 175                               get_index_file(), strlen(get_index_file()));
 176         else if (git_db_env && dir_prefix(base, "objects"))
 177                 replace_dir(buf, git_dir_len + 7, get_object_directory());
 178         else if (git_common_dir_env)
 179                 update_common_dir(buf, git_dir_len);
 180 }
 181
 182 static void do_git_path(struct strbuf *buf, const char *fmt, va_list args)
 183 {
 184         int gitdir_len;
 185         strbuf_addstr(buf, get_git_dir());
 186         if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 187                 strbuf_addch(buf, '/');
 188         gitdir_len = buf->len;
 189         strbuf_vaddf(buf, fmt, args);
 190         adjust_git_path(buf, gitdir_len);
 191         strbuf_cleanup_path(buf);
 192 }
 193
 194 void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
 195 {
 196         va_list args;
 197         va_start(args, fmt);
 198         do_git_path(sb, fmt, args);
 199         va_end(args);
 200 }
 201
 202 const char *git_path(const char *fmt, ...)
 203 {
 204         struct strbuf *pathname = get_pathname();
 205         va_list args;
 206         va_start(args, fmt);
 207         do_git_path(pathname, fmt, args);
 208         va_end(args);
 209         return pathname->buf;
 210 }
 211
 212 char *git_pathdup(const char *fmt, ...)
 213 {
 214         struct strbuf path = STRBUF_INIT;
 215         va_list args;
 216         va_start(args, fmt);
 217         do_git_path(&path, fmt, args);
 218         va_end(args);
 219         return strbuf_detach(&path, NULL);
 220 }
 221
 222 char *mkpathdup(const char *fmt, ...)
 223 {
 224         struct strbuf sb = STRBUF_INIT;
 225         va_list args;
 226         va_start(args, fmt);
 227         strbuf_vaddf(&sb, fmt, args);
 228         va_end(args);
 229         strbuf_cleanup_path(&sb);
 230         return strbuf_detach(&sb, NULL);
 231 }
 232
 233 const char *mkpath(const char *fmt, ...)
 234 {
 235         va_list args;
 236         struct strbuf *pathname = get_pathname();
 237         va_start(args, fmt);
 238         strbuf_vaddf(pathname, fmt, args);
 239         va_end(args);
 240         return cleanup_path(pathname->buf);
 241 }
 242
 243 static void do_submodule_path(struct strbuf *buf, const char *path,
 244                               const char *fmt, va_list args)
 245 {
 246         const char *git_dir;
 247
 248         strbuf_addstr(buf, path);
 249         if (buf->len && buf->buf[buf->len - 1] != '/')
 250                 strbuf_addch(buf, '/');
 251         strbuf_addstr(buf, ".git");
 252
 253         git_dir = read_gitfile(buf->buf);
 254         if (git_dir) {
 255                 strbuf_reset(buf);
 256                 strbuf_addstr(buf, git_dir);
 257         }
 258         strbuf_addch(buf, '/');
 259
 260         strbuf_vaddf(buf, fmt, args);
 261         strbuf_cleanup_path(buf);
 262 }
 263
 264 char *git_pathdup_submodule(const char *path, const char *fmt, ...)
 265 {
 266         va_list args;
 267         struct strbuf buf = STRBUF_INIT;
 268         va_start(args, fmt);
 269         do_submodule_path(&buf, path, fmt, args);
 270         va_end(args);
 271         return strbuf_detach(&buf, NULL);
 272 }
 273
 274 void strbuf_git_path_submodule(struct strbuf *buf, const char *path,
 275                                const char *fmt, ...)
 276 {
 277         va_list args;
 278         va_start(args, fmt);
 279         do_submodule_path(buf, path, fmt, args);
 280         va_end(args);
 281 }
 282
 283 int validate_headref(const char *path)
 284 {
 285         struct stat st;
 286         char *buf, buffer[256];
 287         unsigned char sha1[20];
 288         int fd;
 289         ssize_t len;
 290
 291         if (lstat(path, &st) < 0)
 292                 return -1;
 293
 294         /* Make sure it is a "refs/.." symlink */
 295         if (S_ISLNK(st.st_mode)) {
 296                 len = readlink(path, buffer, sizeof(buffer)-1);
 297                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 298                         return 0;
 299                 return -1;
 300         }
 301
 302         /*
 303          * Anything else, just open it and try to see if it is a symbolic ref.
 304          */
 305         fd = open(path, O_RDONLY);
 306         if (fd < 0)
 307                 return -1;
 308         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 309         close(fd);
 310
 311         /*
 312          * Is it a symbolic ref?
 313          */
 314         if (len < 4)
 315                 return -1;
 316         if (!memcmp("ref:", buffer, 4)) {
 317                 buf = buffer + 4;
 318                 len -= 4;
 319                 while (len && isspace(*buf))
 320                         buf++, len--;
 321                 if (len >= 5 && !memcmp("refs/", buf, 5))
 322                         return 0;
 323         }
 324
 325         /*
 326          * Is this a detached HEAD?
 327          */
 328         if (!get_sha1_hex(buffer, sha1))
 329                 return 0;
 330
 331         return -1;
 332 }
 333
 334 static struct passwd *getpw_str(const char *username, size_t len)
 335 {
 336         struct passwd *pw;
 337         char *username_z = xmemdupz(username, len);
 338         pw = getpwnam(username_z);
 339         free(username_z);
 340         return pw;
 341 }
 342
 343 /*
 344  * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 345  * then it is a newly allocated string. Returns NULL on getpw failure or
 346  * if path is NULL.
 347  */
 348 char *expand_user_path(const char *path)
 349 {
 350         struct strbuf user_path = STRBUF_INIT;
 351         const char *to_copy = path;
 352
 353         if (path == NULL)
 354                 goto return_null;
 355         if (path[0] == '~') {
 356                 const char *first_slash = strchrnul(path, '/');
 357                 const char *username = path + 1;
 358                 size_t username_len = first_slash - username;
 359                 if (username_len == 0) {
 360                         const char *home = getenv("HOME");
 361                         if (!home)
 362                                 goto return_null;
 363                         strbuf_addstr(&user_path, home);
 364                 } else {
 365                         struct passwd *pw = getpw_str(username, username_len);
 366                         if (!pw)
 367                                 goto return_null;
 368                         strbuf_addstr(&user_path, pw->pw_dir);
 369                 }
 370                 to_copy = first_slash;
 371         }
 372         strbuf_addstr(&user_path, to_copy);
 373         return strbuf_detach(&user_path, NULL);
 374 return_null:
 375         strbuf_release(&user_path);
 376         return NULL;
 377 }
 378
 379 /*
 380  * First, one directory to try is determined by the following algorithm.
 381  *
 382  * (0) If "strict" is given, the path is used as given and no DWIM is
 383  *     done. Otherwise:
 384  * (1) "~/path" to mean path under the running user's home directory;
 385  * (2) "~user/path" to mean path under named user's home directory;
 386  * (3) "relative/path" to mean cwd relative directory; or
 387  * (4) "/absolute/path" to mean absolute directory.
 388  *
 389  * Unless "strict" is given, we check "%s/.git", "%s", "%s.git/.git", "%s.git"
 390  * in this order. We select the first one that is a valid git repository, and
 391  * chdir() to it. If none match, or we fail to chdir, we return NULL.
 392  *
 393  * If all goes well, we return the directory we used to chdir() (but
 394  * before ~user is expanded), avoiding getcwd() resolving symbolic
 395  * links.  User relative paths are also returned as they are given,
 396  * except DWIM suffixing.
 397  */
 398 const char *enter_repo(const char *path, int strict)
 399 {
 400         static char used_path[PATH_MAX];
 401         static char validated_path[PATH_MAX];
 402
 403         if (!path)
 404                 return NULL;
 405
 406         if (!strict) {
 407                 static const char *suffix[] = {
 408                         "/.git", "", ".git/.git", ".git", NULL,
 409                 };
 410                 const char *gitfile;
 411                 int len = strlen(path);
 412                 int i;
 413                 while ((1 < len) && (path[len-1] == '/'))
 414                         len--;
 415
 416                 if (PATH_MAX <= len)
 417                         return NULL;
 418                 strncpy(used_path, path, len); used_path[len] = 0 ;
 419                 strcpy(validated_path, used_path);
 420
 421                 if (used_path[0] == '~') {
 422                         char *newpath = expand_user_path(used_path);
 423                         if (!newpath || (PATH_MAX - 10 < strlen(newpath))) {
 424                                 free(newpath);
 425                                 return NULL;
 426                         }
 427                         /*
 428                          * Copy back into the static buffer. A pity
 429                          * since newpath was not bounded, but other
 430                          * branches of the if are limited by PATH_MAX
 431                          * anyway.
 432                          */
 433                         strcpy(used_path, newpath); free(newpath);
 434                 }
 435                 else if (PATH_MAX - 10 < len)
 436                         return NULL;
 437                 len = strlen(used_path);
 438                 for (i = 0; suffix[i]; i++) {
 439                         struct stat st;
 440                         strcpy(used_path + len, suffix[i]);
 441                         if (!stat(used_path, &st) &&
 442                             (S_ISREG(st.st_mode) ||
 443                             (S_ISDIR(st.st_mode) && is_git_directory(used_path)))) {
 444                                 strcat(validated_path, suffix[i]);
 445                                 break;
 446                         }
 447                 }
 448                 if (!suffix[i])
 449                         return NULL;
 450                 gitfile = read_gitfile(used_path) ;
 451                 if (gitfile)
 452                         strcpy(used_path, gitfile);
 453                 if (chdir(used_path))
 454                         return NULL;
 455                 path = validated_path;
 456         }
 457         else if (chdir(path))
 458                 return NULL;
 459
 460         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 461             validate_headref("HEAD") == 0) {
 462                 set_git_dir(".");
 463                 check_repository_format();
 464                 return path;
 465         }
 466
 467         return NULL;
 468 }
 469
 470 static int calc_shared_perm(int mode)
 471 {
 472         int tweak;
 473
 474         if (shared_repository < 0)
 475                 tweak = -shared_repository;
 476         else
 477                 tweak = shared_repository;
 478
 479         if (!(mode & S_IWUSR))
 480                 tweak &= ~0222;
 481         if (mode & S_IXUSR)
 482                 /* Copy read bits to execute bits */
 483                 tweak |= (tweak & 0444) >> 2;
 484         if (shared_repository < 0)
 485                 mode = (mode & ~0777) | tweak;
 486         else
 487                 mode |= tweak;
 488
 489         return mode;
 490 }
 491
 492
 493 int adjust_shared_perm(const char *path)
 494 {
 495         int old_mode, new_mode;
 496
 497         if (!shared_repository)
 498                 return 0;
 499         if (get_st_mode_bits(path, &old_mode) < 0)
 500                 return -1;
 501
 502         new_mode = calc_shared_perm(old_mode);
 503         if (S_ISDIR(old_mode)) {
 504                 /* Copy read bits to execute bits */
 505                 new_mode |= (new_mode & 0444) >> 2;
 506                 new_mode |= FORCE_DIR_SET_GID;
 507         }
 508
 509         if (((old_mode ^ new_mode) & ~S_IFMT) &&
 510                         chmod(path, (new_mode & ~S_IFMT)) < 0)
 511                 return -2;
 512         return 0;
 513 }
 514
 515 static int have_same_root(const char *path1, const char *path2)
 516 {
 517         int is_abs1, is_abs2;
 518
 519         is_abs1 = is_absolute_path(path1);
 520         is_abs2 = is_absolute_path(path2);
 521         return (is_abs1 && is_abs2 && tolower(path1[0]) == tolower(path2[0])) ||
 522                (!is_abs1 && !is_abs2);
 523 }
 524
 525 /*
 526  * Give path as relative to prefix.
 527  *
 528  * The strbuf may or may not be used, so do not assume it contains the
 529  * returned path.
 530  */
 531 const char *relative_path(const char *in, const char *prefix,
 532                           struct strbuf *sb)
 533 {
 534         int in_len = in ? strlen(in) : 0;
 535         int prefix_len = prefix ? strlen(prefix) : 0;
 536         int in_off = 0;
 537         int prefix_off = 0;
 538         int i = 0, j = 0;
 539
 540         if (!in_len)
 541                 return "./";
 542         else if (!prefix_len)
 543                 return in;
 544
 545         if (have_same_root(in, prefix)) {
 546                 /* bypass dos_drive, for "c:" is identical to "C:" */
 547                 if (has_dos_drive_prefix(in)) {
 548                         i = 2;
 549                         j = 2;
 550                 }
 551         } else {
 552                 return in;
 553         }
 554
 555         while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
 556                 if (is_dir_sep(prefix[i])) {
 557                         while (is_dir_sep(prefix[i]))
 558                                 i++;
 559                         while (is_dir_sep(in[j]))
 560                                 j++;
 561                         prefix_off = i;
 562                         in_off = j;
 563                 } else {
 564                         i++;
 565                         j++;
 566                 }
 567         }
 568
 569         if (
 570             /* "prefix" seems like prefix of "in" */
 571             i >= prefix_len &&
 572             /*
 573              * but "/foo" is not a prefix of "/foobar"
 574              * (i.e. prefix not end with '/')
 575              */
 576             prefix_off < prefix_len) {
 577                 if (j >= in_len) {
 578                         /* in="/a/b", prefix="/a/b" */
 579                         in_off = in_len;
 580                 } else if (is_dir_sep(in[j])) {
 581                         /* in="/a/b/c", prefix="/a/b" */
 582                         while (is_dir_sep(in[j]))
 583                                 j++;
 584                         in_off = j;
 585                 } else {
 586                         /* in="/a/bbb/c", prefix="/a/b" */
 587                         i = prefix_off;
 588                 }
 589         } else if (
 590                    /* "in" is short than "prefix" */
 591                    j >= in_len &&
 592                    /* "in" not end with '/' */
 593                    in_off < in_len) {
 594                 if (is_dir_sep(prefix[i])) {
 595                         /* in="/a/b", prefix="/a/b/c/" */
 596                         while (is_dir_sep(prefix[i]))
 597                                 i++;
 598                         in_off = in_len;
 599                 }
 600         }
 601         in += in_off;
 602         in_len -= in_off;
 603
 604         if (i >= prefix_len) {
 605                 if (!in_len)
 606                         return "./";
 607                 else
 608                         return in;
 609         }
 610
 611         strbuf_reset(sb);
 612         strbuf_grow(sb, in_len);
 613
 614         while (i < prefix_len) {
 615                 if (is_dir_sep(prefix[i])) {
 616                         strbuf_addstr(sb, "../");
 617                         while (is_dir_sep(prefix[i]))
 618                                 i++;
 619                         continue;
 620                 }
 621                 i++;
 622         }
 623         if (!is_dir_sep(prefix[prefix_len - 1]))
 624                 strbuf_addstr(sb, "../");
 625
 626         strbuf_addstr(sb, in);
 627
 628         return sb->buf;
 629 }
 630
 631 /*
 632  * A simpler implementation of relative_path
 633  *
 634  * Get relative path by removing "prefix" from "in". This function
 635  * first appears in v1.5.6-1-g044bbbc, and makes git_dir shorter
 636  * to increase performance when traversing the path to work_tree.
 637  */
 638 const char *remove_leading_path(const char *in, const char *prefix)
 639 {
 640         static char buf[PATH_MAX + 1];
 641         int i = 0, j = 0;
 642
 643         if (!prefix || !prefix[0])
 644                 return in;
 645         while (prefix[i]) {
 646                 if (is_dir_sep(prefix[i])) {
 647                         if (!is_dir_sep(in[j]))
 648                                 return in;
 649                         while (is_dir_sep(prefix[i]))
 650                                 i++;
 651                         while (is_dir_sep(in[j]))
 652                                 j++;
 653                         continue;
 654                 } else if (in[j] != prefix[i]) {
 655                         return in;
 656                 }
 657                 i++;
 658                 j++;
 659         }
 660         if (
 661             /* "/foo" is a prefix of "/foo" */
 662             in[j] &&
 663             /* "/foo" is not a prefix of "/foobar" */
 664             !is_dir_sep(prefix[i-1]) && !is_dir_sep(in[j])
 665            )
 666                 return in;
 667         while (is_dir_sep(in[j]))
 668                 j++;
 669         if (!in[j])
 670                 strcpy(buf, ".");
 671         else
 672                 strcpy(buf, in + j);
 673         return buf;
 674 }
 675
 676 /*
 677  * It is okay if dst == src, but they should not overlap otherwise.
 678  *
 679  * Performs the following normalizations on src, storing the result in dst:
 680  * - Ensures that components are separated by '/' (Windows only)
 681  * - Squashes sequences of '/'.
 682  * - Removes "." components.
 683  * - Removes ".." components, and the components the precede them.
 684  * Returns failure (non-zero) if a ".." component appears as first path
 685  * component anytime during the normalization. Otherwise, returns success (0).
 686  *
 687  * Note that this function is purely textual.  It does not follow symlinks,
 688  * verify the existence of the path, or make any system calls.
 689  *
 690  * prefix_len != NULL is for a specific case of prefix_pathspec():
 691  * assume that src == dst and src[0..prefix_len-1] is already
 692  * normalized, any time "../" eats up to the prefix_len part,
 693  * prefix_len is reduced. In the end prefix_len is the remaining
 694  * prefix that has not been overridden by user pathspec.
 695  */
 696 int normalize_path_copy_len(char *dst, const char *src, int *prefix_len)
 697 {
 698         char *dst0;
 699
 700         if (has_dos_drive_prefix(src)) {
 701                 *dst++ = *src++;
 702                 *dst++ = *src++;
 703         }
 704         dst0 = dst;
 705
 706         if (is_dir_sep(*src)) {
 707                 *dst++ = '/';
 708                 while (is_dir_sep(*src))
 709                         src++;
 710         }
 711
 712         for (;;) {
 713                 char c = *src;
 714
 715                 /*
 716                  * A path component that begins with . could be
 717                  * special:
 718                  * (1) "." and ends   -- ignore and terminate.
 719                  * (2) "./"           -- ignore them, eat slash and continue.
 720                  * (3) ".." and ends  -- strip one and terminate.
 721                  * (4) "../"          -- strip one, eat slash and continue.
 722                  */
 723                 if (c == '.') {
 724                         if (!src[1]) {
 725                                 /* (1) */
 726                                 src++;
 727                         } else if (is_dir_sep(src[1])) {
 728                                 /* (2) */
 729                                 src += 2;
 730                                 while (is_dir_sep(*src))
 731                                         src++;
 732                                 continue;
 733                         } else if (src[1] == '.') {
 734                                 if (!src[2]) {
 735                                         /* (3) */
 736                                         src += 2;
 737                                         goto up_one;
 738                                 } else if (is_dir_sep(src[2])) {
 739                                         /* (4) */
 740                                         src += 3;
 741                                         while (is_dir_sep(*src))
 742                                                 src++;
 743                                         goto up_one;
 744                                 }
 745                         }
 746                 }
 747
 748                 /* copy up to the next '/', and eat all '/' */
 749                 while ((c = *src++) != '\0' && !is_dir_sep(c))
 750                         *dst++ = c;
 751                 if (is_dir_sep(c)) {
 752                         *dst++ = '/';
 753                         while (is_dir_sep(c))
 754                                 c = *src++;
 755                         src--;
 756                 } else if (!c)
 757                         break;
 758                 continue;
 759
 760         up_one:
 761                 /*
 762                  * dst0..dst is prefix portion, and dst[-1] is '/';
 763                  * go up one level.
 764                  */
 765                 dst--;  /* go to trailing '/' */
 766                 if (dst <= dst0)
 767                         return -1;
 768                 /* Windows: dst[-1] cannot be backslash anymore */
 769                 while (dst0 < dst && dst[-1] != '/')
 770                         dst--;
 771                 if (prefix_len && *prefix_len > dst - dst0)
 772                         *prefix_len = dst - dst0;
 773         }
 774         *dst = '\0';
 775         return 0;
 776 }
 777
 778 int normalize_path_copy(char *dst, const char *src)
 779 {
 780         return normalize_path_copy_len(dst, src, NULL);
 781 }
 782
 783 /*
 784  * path = Canonical absolute path
 785  * prefixes = string_list containing normalized, absolute paths without
 786  * trailing slashes (except for the root directory, which is denoted by "/").
 787  *
 788  * Determines, for each path in prefixes, whether the "prefix"
 789  * is an ancestor directory of path.  Returns the length of the longest
 790  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 791  * is an ancestor.  (Note that this means 0 is returned if prefixes is
 792  * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
 793  * are not considered to be their own ancestors.  path must be in a
 794  * canonical form: empty components, or "." or ".." components are not
 795  * allowed.
 796  */
 797 int longest_ancestor_length(const char *path, struct string_list *prefixes)
 798 {
 799         int i, max_len = -1;
 800
 801         if (!strcmp(path, "/"))
 802                 return -1;
 803
 804         for (i = 0; i < prefixes->nr; i++) {
 805                 const char *ceil = prefixes->items[i].string;
 806                 int len = strlen(ceil);
 807
 808                 if (len == 1 && ceil[0] == '/')
 809                         len = 0; /* root matches anything, with length 0 */
 810                 else if (!strncmp(path, ceil, len) && path[len] == '/')
 811                         ; /* match of length len */
 812                 else
 813                         continue; /* no match */
 814
 815                 if (len > max_len)
 816                         max_len = len;
 817         }
 818
 819         return max_len;
 820 }
 821
 822 /* strip arbitrary amount of directory separators at end of path */
 823 static inline int chomp_trailing_dir_sep(const char *path, int len)
 824 {
 825         while (len && is_dir_sep(path[len - 1]))
 826                 len--;
 827         return len;
 828 }
 829
 830 /*
 831  * If path ends with suffix (complete path components), returns the
 832  * part before suffix (sans trailing directory separators).
 833  * Otherwise returns NULL.
 834  */
 835 char *strip_path_suffix(const char *path, const char *suffix)
 836 {
 837         int path_len = strlen(path), suffix_len = strlen(suffix);
 838
 839         while (suffix_len) {
 840                 if (!path_len)
 841                         return NULL;
 842
 843                 if (is_dir_sep(path[path_len - 1])) {
 844                         if (!is_dir_sep(suffix[suffix_len - 1]))
 845                                 return NULL;
 846                         path_len = chomp_trailing_dir_sep(path, path_len);
 847                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
 848                 }
 849                 else if (path[--path_len] != suffix[--suffix_len])
 850                         return NULL;
 851         }
 852
 853         if (path_len && !is_dir_sep(path[path_len - 1]))
 854                 return NULL;
 855         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
 856 }
 857
 858 int daemon_avoid_alias(const char *p)
 859 {
 860         int sl, ndot;
 861
 862         /*
 863          * This resurrects the belts and suspenders paranoia check by HPA
 864          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
 865          * does not do getcwd() based path canonicalization.
 866          *
 867          * sl becomes true immediately after seeing '/' and continues to
 868          * be true as long as dots continue after that without intervening
 869          * non-dot character.
 870          */
 871         if (!p || (*p != '/' && *p != '~'))
 872                 return -1;
 873         sl = 1; ndot = 0;
 874         p++;
 875
 876         while (1) {
 877                 char ch = *p++;
 878                 if (sl) {
 879                         if (ch == '.')
 880                                 ndot++;
 881                         else if (ch == '/') {
 882                                 if (ndot < 3)
 883                                         /* reject //, /./ and /../ */
 884                                         return -1;
 885                                 ndot = 0;
 886                         }
 887                         else if (ch == 0) {
 888                                 if (0 < ndot && ndot < 3)
 889                                         /* reject /.$ and /..$ */
 890                                         return -1;
 891                                 return 0;
 892                         }
 893                         else
 894                                 sl = ndot = 0;
 895                 }
 896                 else if (ch == 0)
 897                         return 0;
 898                 else if (ch == '/') {
 899                         sl = 1;
 900                         ndot = 0;
 901                 }
 902         }
 903 }
 904
 905 static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
 906 {
 907         if (len < skip)
 908                 return 0;
 909         len -= skip;
 910         path += skip;
 911         while (len-- > 0) {
 912                 char c = *(path++);
 913                 if (c != ' ' && c != '.')
 914                         return 0;
 915         }
 916         return 1;
 917 }
 918
 919 int is_ntfs_dotgit(const char *name)
 920 {
 921         int len;
 922
 923         for (len = 0; ; len++)
 924                 if (!name[len] || name[len] == '\\' || is_dir_sep(name[len])) {
 925                         if (only_spaces_and_periods(name, len, 4) &&
 926                                         !strncasecmp(name, ".git", 4))
 927                                 return 1;
 928                         if (only_spaces_and_periods(name, len, 5) &&
 929                                         !strncasecmp(name, "git~1", 5))
 930                                 return 1;
 931                         if (name[len] != '\\')
 932                                 return 0;
 933                         name += len + 1;
 934                         len = -1;
 935                 }
 936 }
 937
 938 char *xdg_config_home(const char *filename)
 939 {
 940         const char *home, *config_home;
 941
 942         assert(filename);
 943         config_home = getenv("XDG_CONFIG_HOME");
 944         if (config_home && *config_home)
 945                 return mkpathdup("%s/git/%s", config_home, filename);
 946
 947         home = getenv("HOME");
 948         if (home)
 949                 return mkpathdup("%s/.config/git/%s", home, filename);
 950         return NULL;
 951 }
 952
 953 GIT_PATH_FUNC(git_path_cherry_pick_head, "CHERRY_PICK_HEAD")
 954 GIT_PATH_FUNC(git_path_revert_head, "REVERT_HEAD")
 955 GIT_PATH_FUNC(git_path_squash_msg, "SQUASH_MSG")
 956 GIT_PATH_FUNC(git_path_merge_msg, "MERGE_MSG")
 957 GIT_PATH_FUNC(git_path_merge_rr, "MERGE_RR")
 958 GIT_PATH_FUNC(git_path_merge_mode, "MERGE_MODE")
 959 GIT_PATH_FUNC(git_path_merge_head, "MERGE_HEAD")
 960 GIT_PATH_FUNC(git_path_fetch_head, "FETCH_HEAD")
 961 GIT_PATH_FUNC(git_path_shallow, "shallow")