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, 1, "logs/refs/bisect" },
 111         { 0, 1, 0, "lost-found" },
 112         { 0, 1, 0, "objects" },
 113         { 0, 1, 0, "refs" },
 114         { 0, 1, 1, "refs/bisect" },
 115         { 0, 1, 0, "remotes" },
 116         { 0, 1, 0, "worktrees" },
 117         { 0, 1, 0, "rr-cache" },
 118         { 0, 1, 0, "svn" },
 119         { 0, 0, 0, "config" },
 120         { 1, 0, 0, "gc.pid" },
 121         { 0, 0, 0, "packed-refs" },
 122         { 0, 0, 0, "shallow" },
 123         { 0, 0, 0, NULL }
 124 };
 125
 126 /*
 127  * A compressed trie.  A trie node consists of zero or more characters that
 128  * are common to all elements with this prefix, optionally followed by some
 129  * children.  If value is not NULL, the trie node is a terminal node.
 130  *
 131  * For example, consider the following set of strings:
 132  * abc
 133  * def
 134  * definite
 135  * definition
 136  *
 137  * The trie would look look like:
 138  * root: len = 0, children a and d non-NULL, value = NULL.
 139  *    a: len = 2, contents = bc, value = (data for "abc")
 140  *    d: len = 2, contents = ef, children i non-NULL, value = (data for "def")
 141  *       i: len = 3, contents = nit, children e and i non-NULL, value = NULL
 142  *           e: len = 0, children all NULL, value = (data for "definite")
 143  *           i: len = 2, contents = on, children all NULL,
 144  *              value = (data for "definition")
 145  */
 146 struct trie {
 147         struct trie *children[256];
 148         int len;
 149         char *contents;
 150         void *value;
 151 };
 152
 153 static struct trie *make_trie_node(const char *key, void *value)
 154 {
 155         struct trie *new_node = xcalloc(1, sizeof(*new_node));
 156         new_node->len = strlen(key);
 157         if (new_node->len) {
 158                 new_node->contents = xmalloc(new_node->len);
 159                 memcpy(new_node->contents, key, new_node->len);
 160         }
 161         new_node->value = value;
 162         return new_node;
 163 }
 164
 165 /*
 166  * Add a key/value pair to a trie.  The key is assumed to be \0-terminated.
 167  * If there was an existing value for this key, return it.
 168  */
 169 static void *add_to_trie(struct trie *root, const char *key, void *value)
 170 {
 171         struct trie *child;
 172         void *old;
 173         int i;
 174
 175         if (!*key) {
 176                 /* we have reached the end of the key */
 177                 old = root->value;
 178                 root->value = value;
 179                 return old;
 180         }
 181
 182         for (i = 0; i < root->len; i++) {
 183                 if (root->contents[i] == key[i])
 184                         continue;
 185
 186                 /*
 187                  * Split this node: child will contain this node's
 188                  * existing children.
 189                  */
 190                 child = malloc(sizeof(*child));
 191                 memcpy(child->children, root->children, sizeof(root->children));
 192
 193                 child->len = root->len - i - 1;
 194                 if (child->len) {
 195                         child->contents = xstrndup(root->contents + i + 1,
 196                                                    child->len);
 197                 }
 198                 child->value = root->value;
 199                 root->value = NULL;
 200                 root->len = i;
 201
 202                 memset(root->children, 0, sizeof(root->children));
 203                 root->children[(unsigned char)root->contents[i]] = child;
 204
 205                 /* This is the newly-added child. */
 206                 root->children[(unsigned char)key[i]] =
 207                         make_trie_node(key + i + 1, value);
 208                 return NULL;
 209         }
 210
 211         /* We have matched the entire compressed section */
 212         if (key[i]) {
 213                 child = root->children[(unsigned char)key[root->len]];
 214                 if (child) {
 215                         return add_to_trie(child, key + root->len + 1, value);
 216                 } else {
 217                         child = make_trie_node(key + root->len + 1, value);
 218                         root->children[(unsigned char)key[root->len]] = child;
 219                         return NULL;
 220                 }
 221         }
 222
 223         old = root->value;
 224         root->value = value;
 225         return old;
 226 }
 227
 228 typedef int (*match_fn)(const char *unmatched, void *data, void *baton);
 229
 230 /*
 231  * Search a trie for some key.  Find the longest /-or-\0-terminated
 232  * prefix of the key for which the trie contains a value.  Call fn
 233  * with the unmatched portion of the key and the found value, and
 234  * return its return value.  If there is no such prefix, return -1.
 235  *
 236  * The key is partially normalized: consecutive slashes are skipped.
 237  *
 238  * For example, consider the trie containing only [refs,
 239  * refs/worktree] (both with values).
 240  *
 241  * | key             | unmatched  | val from node | return value |
 242  * |-----------------|------------|---------------|--------------|
 243  * | a               | not called | n/a           | -1           |
 244  * | refs            | \0         | refs          | as per fn    |
 245  * | refs/           | /          | refs          | as per fn    |
 246  * | refs/w          | /w         | refs          | as per fn    |
 247  * | refs/worktree   | \0         | refs/worktree | as per fn    |
 248  * | refs/worktree/  | /          | refs/worktree | as per fn    |
 249  * | refs/worktree/a | /a         | refs/worktree | as per fn    |
 250  * |-----------------|------------|---------------|--------------|
 251  *
 252  */
 253 static int trie_find(struct trie *root, const char *key, match_fn fn,
 254                      void *baton)
 255 {
 256         int i;
 257         int result;
 258         struct trie *child;
 259
 260         if (!*key) {
 261                 /* we have reached the end of the key */
 262                 if (root->value && !root->len)
 263                         return fn(key, root->value, baton);
 264                 else
 265                         return -1;
 266         }
 267
 268         for (i = 0; i < root->len; i++) {
 269                 /* Partial path normalization: skip consecutive slashes. */
 270                 if (key[i] == '/' && key[i+1] == '/') {
 271                         key++;
 272                         continue;
 273                 }
 274                 if (root->contents[i] != key[i])
 275                         return -1;
 276         }
 277
 278         /* Matched the entire compressed section */
 279         key += i;
 280         if (!*key)
 281                 /* End of key */
 282                 return fn(key, root->value, baton);
 283
 284         /* Partial path normalization: skip consecutive slashes */
 285         while (key[0] == '/' && key[1] == '/')
 286                 key++;
 287
 288         child = root->children[(unsigned char)*key];
 289         if (child)
 290                 result = trie_find(child, key + 1, fn, baton);
 291         else
 292                 result = -1;
 293
 294         if (result >= 0 || (*key != '/' && *key != 0))
 295                 return result;
 296         if (root->value)
 297                 return fn(key, root->value, baton);
 298         else
 299                 return -1;
 300 }
 301
 302 static struct trie common_trie;
 303 static int common_trie_done_setup;
 304
 305 static void init_common_trie(void)
 306 {
 307         struct common_dir *p;
 308
 309         if (common_trie_done_setup)
 310                 return;
 311
 312         for (p = common_list; p->dirname; p++)
 313                 add_to_trie(&common_trie, p->dirname, p);
 314
 315         common_trie_done_setup = 1;
 316 }
 317
 318 /*
 319  * Helper function for update_common_dir: returns 1 if the dir
 320  * prefix is common.
 321  */
 322 static int check_common(const char *unmatched, void *value, void *baton)
 323 {
 324         struct common_dir *dir = value;
 325
 326         if (!dir)
 327                 return 0;
 328
 329         if (dir->is_dir && (unmatched[0] == 0 || unmatched[0] == '/'))
 330                 return !dir->exclude;
 331
 332         if (!dir->is_dir && unmatched[0] == 0)
 333                 return !dir->exclude;
 334
 335         return 0;
 336 }
 337
 338 static void update_common_dir(struct strbuf *buf, int git_dir_len)
 339 {
 340         char *base = buf->buf + git_dir_len;
 341         init_common_trie();
 342         if (trie_find(&common_trie, base, check_common, NULL) > 0)
 343                 replace_dir(buf, git_dir_len, get_git_common_dir());
 344 }
 345
 346 void report_linked_checkout_garbage(void)
 347 {
 348         struct strbuf sb = STRBUF_INIT;
 349         const struct common_dir *p;
 350         int len;
 351
 352         if (!git_common_dir_env)
 353                 return;
 354         strbuf_addf(&sb, "%s/", get_git_dir());
 355         len = sb.len;
 356         for (p = common_list; p->dirname; p++) {
 357                 const char *path = p->dirname;
 358                 if (p->ignore_garbage)
 359                         continue;
 360                 strbuf_setlen(&sb, len);
 361                 strbuf_addstr(&sb, path);
 362                 if (file_exists(sb.buf))
 363                         report_garbage("unused in linked checkout", sb.buf);
 364         }
 365         strbuf_release(&sb);
 366 }
 367
 368 static void adjust_git_path(struct strbuf *buf, int git_dir_len)
 369 {
 370         const char *base = buf->buf + git_dir_len;
 371         if (git_graft_env && is_dir_file(base, "info", "grafts"))
 372                 strbuf_splice(buf, 0, buf->len,
 373                               get_graft_file(), strlen(get_graft_file()));
 374         else if (git_index_env && !strcmp(base, "index"))
 375                 strbuf_splice(buf, 0, buf->len,
 376                               get_index_file(), strlen(get_index_file()));
 377         else if (git_db_env && dir_prefix(base, "objects"))
 378                 replace_dir(buf, git_dir_len + 7, get_object_directory());
 379         else if (git_common_dir_env)
 380                 update_common_dir(buf, git_dir_len);
 381 }
 382
 383 static void do_git_path(struct strbuf *buf, const char *fmt, va_list args)
 384 {
 385         int gitdir_len;
 386         strbuf_addstr(buf, get_git_dir());
 387         if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 388                 strbuf_addch(buf, '/');
 389         gitdir_len = buf->len;
 390         strbuf_vaddf(buf, fmt, args);
 391         adjust_git_path(buf, gitdir_len);
 392         strbuf_cleanup_path(buf);
 393 }
 394
 395 void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
 396 {
 397         va_list args;
 398         va_start(args, fmt);
 399         do_git_path(sb, fmt, args);
 400         va_end(args);
 401 }
 402
 403 const char *git_path(const char *fmt, ...)
 404 {
 405         struct strbuf *pathname = get_pathname();
 406         va_list args;
 407         va_start(args, fmt);
 408         do_git_path(pathname, fmt, args);
 409         va_end(args);
 410         return pathname->buf;
 411 }
 412
 413 char *git_pathdup(const char *fmt, ...)
 414 {
 415         struct strbuf path = STRBUF_INIT;
 416         va_list args;
 417         va_start(args, fmt);
 418         do_git_path(&path, fmt, args);
 419         va_end(args);
 420         return strbuf_detach(&path, NULL);
 421 }
 422
 423 char *mkpathdup(const char *fmt, ...)
 424 {
 425         struct strbuf sb = STRBUF_INIT;
 426         va_list args;
 427         va_start(args, fmt);
 428         strbuf_vaddf(&sb, fmt, args);
 429         va_end(args);
 430         strbuf_cleanup_path(&sb);
 431         return strbuf_detach(&sb, NULL);
 432 }
 433
 434 const char *mkpath(const char *fmt, ...)
 435 {
 436         va_list args;
 437         struct strbuf *pathname = get_pathname();
 438         va_start(args, fmt);
 439         strbuf_vaddf(pathname, fmt, args);
 440         va_end(args);
 441         return cleanup_path(pathname->buf);
 442 }
 443
 444 static void do_submodule_path(struct strbuf *buf, const char *path,
 445                               const char *fmt, va_list args)
 446 {
 447         const char *git_dir;
 448
 449         strbuf_addstr(buf, path);
 450         if (buf->len && buf->buf[buf->len - 1] != '/')
 451                 strbuf_addch(buf, '/');
 452         strbuf_addstr(buf, ".git");
 453
 454         git_dir = read_gitfile(buf->buf);
 455         if (git_dir) {
 456                 strbuf_reset(buf);
 457                 strbuf_addstr(buf, git_dir);
 458         }
 459         strbuf_addch(buf, '/');
 460
 461         strbuf_vaddf(buf, fmt, args);
 462         strbuf_cleanup_path(buf);
 463 }
 464
 465 char *git_pathdup_submodule(const char *path, const char *fmt, ...)
 466 {
 467         va_list args;
 468         struct strbuf buf = STRBUF_INIT;
 469         va_start(args, fmt);
 470         do_submodule_path(&buf, path, fmt, args);
 471         va_end(args);
 472         return strbuf_detach(&buf, NULL);
 473 }
 474
 475 void strbuf_git_path_submodule(struct strbuf *buf, const char *path,
 476                                const char *fmt, ...)
 477 {
 478         va_list args;
 479         va_start(args, fmt);
 480         do_submodule_path(buf, path, fmt, args);
 481         va_end(args);
 482 }
 483
 484 int validate_headref(const char *path)
 485 {
 486         struct stat st;
 487         char *buf, buffer[256];
 488         unsigned char sha1[20];
 489         int fd;
 490         ssize_t len;
 491
 492         if (lstat(path, &st) < 0)
 493                 return -1;
 494
 495         /* Make sure it is a "refs/.." symlink */
 496         if (S_ISLNK(st.st_mode)) {
 497                 len = readlink(path, buffer, sizeof(buffer)-1);
 498                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 499                         return 0;
 500                 return -1;
 501         }
 502
 503         /*
 504          * Anything else, just open it and try to see if it is a symbolic ref.
 505          */
 506         fd = open(path, O_RDONLY);
 507         if (fd < 0)
 508                 return -1;
 509         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 510         close(fd);
 511
 512         /*
 513          * Is it a symbolic ref?
 514          */
 515         if (len < 4)
 516                 return -1;
 517         if (!memcmp("ref:", buffer, 4)) {
 518                 buf = buffer + 4;
 519                 len -= 4;
 520                 while (len && isspace(*buf))
 521                         buf++, len--;
 522                 if (len >= 5 && !memcmp("refs/", buf, 5))
 523                         return 0;
 524         }
 525
 526         /*
 527          * Is this a detached HEAD?
 528          */
 529         if (!get_sha1_hex(buffer, sha1))
 530                 return 0;
 531
 532         return -1;
 533 }
 534
 535 static struct passwd *getpw_str(const char *username, size_t len)
 536 {
 537         struct passwd *pw;
 538         char *username_z = xmemdupz(username, len);
 539         pw = getpwnam(username_z);
 540         free(username_z);
 541         return pw;
 542 }
 543
 544 /*
 545  * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 546  * then it is a newly allocated string. Returns NULL on getpw failure or
 547  * if path is NULL.
 548  */
 549 char *expand_user_path(const char *path)
 550 {
 551         struct strbuf user_path = STRBUF_INIT;
 552         const char *to_copy = path;
 553
 554         if (path == NULL)
 555                 goto return_null;
 556         if (path[0] == '~') {
 557                 const char *first_slash = strchrnul(path, '/');
 558                 const char *username = path + 1;
 559                 size_t username_len = first_slash - username;
 560                 if (username_len == 0) {
 561                         const char *home = getenv("HOME");
 562                         if (!home)
 563                                 goto return_null;
 564                         strbuf_addstr(&user_path, home);
 565                 } else {
 566                         struct passwd *pw = getpw_str(username, username_len);
 567                         if (!pw)
 568                                 goto return_null;
 569                         strbuf_addstr(&user_path, pw->pw_dir);
 570                 }
 571                 to_copy = first_slash;
 572         }
 573         strbuf_addstr(&user_path, to_copy);
 574         return strbuf_detach(&user_path, NULL);
 575 return_null:
 576         strbuf_release(&user_path);
 577         return NULL;
 578 }
 579
 580 /*
 581  * First, one directory to try is determined by the following algorithm.
 582  *
 583  * (0) If "strict" is given, the path is used as given and no DWIM is
 584  *     done. Otherwise:
 585  * (1) "~/path" to mean path under the running user's home directory;
 586  * (2) "~user/path" to mean path under named user's home directory;
 587  * (3) "relative/path" to mean cwd relative directory; or
 588  * (4) "/absolute/path" to mean absolute directory.
 589  *
 590  * Unless "strict" is given, we check "%s/.git", "%s", "%s.git/.git", "%s.git"
 591  * in this order. We select the first one that is a valid git repository, and
 592  * chdir() to it. If none match, or we fail to chdir, we return NULL.
 593  *
 594  * If all goes well, we return the directory we used to chdir() (but
 595  * before ~user is expanded), avoiding getcwd() resolving symbolic
 596  * links.  User relative paths are also returned as they are given,
 597  * except DWIM suffixing.
 598  */
 599 const char *enter_repo(const char *path, int strict)
 600 {
 601         static char used_path[PATH_MAX];
 602         static char validated_path[PATH_MAX];
 603
 604         if (!path)
 605                 return NULL;
 606
 607         if (!strict) {
 608                 static const char *suffix[] = {
 609                         "/.git", "", ".git/.git", ".git", NULL,
 610                 };
 611                 const char *gitfile;
 612                 int len = strlen(path);
 613                 int i;
 614                 while ((1 < len) && (path[len-1] == '/'))
 615                         len--;
 616
 617                 if (PATH_MAX <= len)
 618                         return NULL;
 619                 strncpy(used_path, path, len); used_path[len] = 0 ;
 620                 strcpy(validated_path, used_path);
 621
 622                 if (used_path[0] == '~') {
 623                         char *newpath = expand_user_path(used_path);
 624                         if (!newpath || (PATH_MAX - 10 < strlen(newpath))) {
 625                                 free(newpath);
 626                                 return NULL;
 627                         }
 628                         /*
 629                          * Copy back into the static buffer. A pity
 630                          * since newpath was not bounded, but other
 631                          * branches of the if are limited by PATH_MAX
 632                          * anyway.
 633                          */
 634                         strcpy(used_path, newpath); free(newpath);
 635                 }
 636                 else if (PATH_MAX - 10 < len)
 637                         return NULL;
 638                 len = strlen(used_path);
 639                 for (i = 0; suffix[i]; i++) {
 640                         struct stat st;
 641                         strcpy(used_path + len, suffix[i]);
 642                         if (!stat(used_path, &st) &&
 643                             (S_ISREG(st.st_mode) ||
 644                             (S_ISDIR(st.st_mode) && is_git_directory(used_path)))) {
 645                                 strcat(validated_path, suffix[i]);
 646                                 break;
 647                         }
 648                 }
 649                 if (!suffix[i])
 650                         return NULL;
 651                 gitfile = read_gitfile(used_path) ;
 652                 if (gitfile)
 653                         strcpy(used_path, gitfile);
 654                 if (chdir(used_path))
 655                         return NULL;
 656                 path = validated_path;
 657         }
 658         else if (chdir(path))
 659                 return NULL;
 660
 661         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 662             validate_headref("HEAD") == 0) {
 663                 set_git_dir(".");
 664                 check_repository_format();
 665                 return path;
 666         }
 667
 668         return NULL;
 669 }
 670
 671 static int calc_shared_perm(int mode)
 672 {
 673         int tweak;
 674
 675         if (shared_repository < 0)
 676                 tweak = -shared_repository;
 677         else
 678                 tweak = shared_repository;
 679
 680         if (!(mode & S_IWUSR))
 681                 tweak &= ~0222;
 682         if (mode & S_IXUSR)
 683                 /* Copy read bits to execute bits */
 684                 tweak |= (tweak & 0444) >> 2;
 685         if (shared_repository < 0)
 686                 mode = (mode & ~0777) | tweak;
 687         else
 688                 mode |= tweak;
 689
 690         return mode;
 691 }
 692
 693
 694 int adjust_shared_perm(const char *path)
 695 {
 696         int old_mode, new_mode;
 697
 698         if (!shared_repository)
 699                 return 0;
 700         if (get_st_mode_bits(path, &old_mode) < 0)
 701                 return -1;
 702
 703         new_mode = calc_shared_perm(old_mode);
 704         if (S_ISDIR(old_mode)) {
 705                 /* Copy read bits to execute bits */
 706                 new_mode |= (new_mode & 0444) >> 2;
 707                 new_mode |= FORCE_DIR_SET_GID;
 708         }
 709
 710         if (((old_mode ^ new_mode) & ~S_IFMT) &&
 711                         chmod(path, (new_mode & ~S_IFMT)) < 0)
 712                 return -2;
 713         return 0;
 714 }
 715
 716 static int have_same_root(const char *path1, const char *path2)
 717 {
 718         int is_abs1, is_abs2;
 719
 720         is_abs1 = is_absolute_path(path1);
 721         is_abs2 = is_absolute_path(path2);
 722         return (is_abs1 && is_abs2 && tolower(path1[0]) == tolower(path2[0])) ||
 723                (!is_abs1 && !is_abs2);
 724 }
 725
 726 /*
 727  * Give path as relative to prefix.
 728  *
 729  * The strbuf may or may not be used, so do not assume it contains the
 730  * returned path.
 731  */
 732 const char *relative_path(const char *in, const char *prefix,
 733                           struct strbuf *sb)
 734 {
 735         int in_len = in ? strlen(in) : 0;
 736         int prefix_len = prefix ? strlen(prefix) : 0;
 737         int in_off = 0;
 738         int prefix_off = 0;
 739         int i = 0, j = 0;
 740
 741         if (!in_len)
 742                 return "./";
 743         else if (!prefix_len)
 744                 return in;
 745
 746         if (have_same_root(in, prefix)) {
 747                 /* bypass dos_drive, for "c:" is identical to "C:" */
 748                 if (has_dos_drive_prefix(in)) {
 749                         i = 2;
 750                         j = 2;
 751                 }
 752         } else {
 753                 return in;
 754         }
 755
 756         while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
 757                 if (is_dir_sep(prefix[i])) {
 758                         while (is_dir_sep(prefix[i]))
 759                                 i++;
 760                         while (is_dir_sep(in[j]))
 761                                 j++;
 762                         prefix_off = i;
 763                         in_off = j;
 764                 } else {
 765                         i++;
 766                         j++;
 767                 }
 768         }
 769
 770         if (
 771             /* "prefix" seems like prefix of "in" */
 772             i >= prefix_len &&
 773             /*
 774              * but "/foo" is not a prefix of "/foobar"
 775              * (i.e. prefix not end with '/')
 776              */
 777             prefix_off < prefix_len) {
 778                 if (j >= in_len) {
 779                         /* in="/a/b", prefix="/a/b" */
 780                         in_off = in_len;
 781                 } else if (is_dir_sep(in[j])) {
 782                         /* in="/a/b/c", prefix="/a/b" */
 783                         while (is_dir_sep(in[j]))
 784                                 j++;
 785                         in_off = j;
 786                 } else {
 787                         /* in="/a/bbb/c", prefix="/a/b" */
 788                         i = prefix_off;
 789                 }
 790         } else if (
 791                    /* "in" is short than "prefix" */
 792                    j >= in_len &&
 793                    /* "in" not end with '/' */
 794                    in_off < in_len) {
 795                 if (is_dir_sep(prefix[i])) {
 796                         /* in="/a/b", prefix="/a/b/c/" */
 797                         while (is_dir_sep(prefix[i]))
 798                                 i++;
 799                         in_off = in_len;
 800                 }
 801         }
 802         in += in_off;
 803         in_len -= in_off;
 804
 805         if (i >= prefix_len) {
 806                 if (!in_len)
 807                         return "./";
 808                 else
 809                         return in;
 810         }
 811
 812         strbuf_reset(sb);
 813         strbuf_grow(sb, in_len);
 814
 815         while (i < prefix_len) {
 816                 if (is_dir_sep(prefix[i])) {
 817                         strbuf_addstr(sb, "../");
 818                         while (is_dir_sep(prefix[i]))
 819                                 i++;
 820                         continue;
 821                 }
 822                 i++;
 823         }
 824         if (!is_dir_sep(prefix[prefix_len - 1]))
 825                 strbuf_addstr(sb, "../");
 826
 827         strbuf_addstr(sb, in);
 828
 829         return sb->buf;
 830 }
 831
 832 /*
 833  * A simpler implementation of relative_path
 834  *
 835  * Get relative path by removing "prefix" from "in". This function
 836  * first appears in v1.5.6-1-g044bbbc, and makes git_dir shorter
 837  * to increase performance when traversing the path to work_tree.
 838  */
 839 const char *remove_leading_path(const char *in, const char *prefix)
 840 {
 841         static char buf[PATH_MAX + 1];
 842         int i = 0, j = 0;
 843
 844         if (!prefix || !prefix[0])
 845                 return in;
 846         while (prefix[i]) {
 847                 if (is_dir_sep(prefix[i])) {
 848                         if (!is_dir_sep(in[j]))
 849                                 return in;
 850                         while (is_dir_sep(prefix[i]))
 851                                 i++;
 852                         while (is_dir_sep(in[j]))
 853                                 j++;
 854                         continue;
 855                 } else if (in[j] != prefix[i]) {
 856                         return in;
 857                 }
 858                 i++;
 859                 j++;
 860         }
 861         if (
 862             /* "/foo" is a prefix of "/foo" */
 863             in[j] &&
 864             /* "/foo" is not a prefix of "/foobar" */
 865             !is_dir_sep(prefix[i-1]) && !is_dir_sep(in[j])
 866            )
 867                 return in;
 868         while (is_dir_sep(in[j]))
 869                 j++;
 870         if (!in[j])
 871                 strcpy(buf, ".");
 872         else
 873                 strcpy(buf, in + j);
 874         return buf;
 875 }
 876
 877 /*
 878  * It is okay if dst == src, but they should not overlap otherwise.
 879  *
 880  * Performs the following normalizations on src, storing the result in dst:
 881  * - Ensures that components are separated by '/' (Windows only)
 882  * - Squashes sequences of '/'.
 883  * - Removes "." components.
 884  * - Removes ".." components, and the components the precede them.
 885  * Returns failure (non-zero) if a ".." component appears as first path
 886  * component anytime during the normalization. Otherwise, returns success (0).
 887  *
 888  * Note that this function is purely textual.  It does not follow symlinks,
 889  * verify the existence of the path, or make any system calls.
 890  *
 891  * prefix_len != NULL is for a specific case of prefix_pathspec():
 892  * assume that src == dst and src[0..prefix_len-1] is already
 893  * normalized, any time "../" eats up to the prefix_len part,
 894  * prefix_len is reduced. In the end prefix_len is the remaining
 895  * prefix that has not been overridden by user pathspec.
 896  */
 897 int normalize_path_copy_len(char *dst, const char *src, int *prefix_len)
 898 {
 899         char *dst0;
 900
 901         if (has_dos_drive_prefix(src)) {
 902                 *dst++ = *src++;
 903                 *dst++ = *src++;
 904         }
 905         dst0 = dst;
 906
 907         if (is_dir_sep(*src)) {
 908                 *dst++ = '/';
 909                 while (is_dir_sep(*src))
 910                         src++;
 911         }
 912
 913         for (;;) {
 914                 char c = *src;
 915
 916                 /*
 917                  * A path component that begins with . could be
 918                  * special:
 919                  * (1) "." and ends   -- ignore and terminate.
 920                  * (2) "./"           -- ignore them, eat slash and continue.
 921                  * (3) ".." and ends  -- strip one and terminate.
 922                  * (4) "../"          -- strip one, eat slash and continue.
 923                  */
 924                 if (c == '.') {
 925                         if (!src[1]) {
 926                                 /* (1) */
 927                                 src++;
 928                         } else if (is_dir_sep(src[1])) {
 929                                 /* (2) */
 930                                 src += 2;
 931                                 while (is_dir_sep(*src))
 932                                         src++;
 933                                 continue;
 934                         } else if (src[1] == '.') {
 935                                 if (!src[2]) {
 936                                         /* (3) */
 937                                         src += 2;
 938                                         goto up_one;
 939                                 } else if (is_dir_sep(src[2])) {
 940                                         /* (4) */
 941                                         src += 3;
 942                                         while (is_dir_sep(*src))
 943                                                 src++;
 944                                         goto up_one;
 945                                 }
 946                         }
 947                 }
 948
 949                 /* copy up to the next '/', and eat all '/' */
 950                 while ((c = *src++) != '\0' && !is_dir_sep(c))
 951                         *dst++ = c;
 952                 if (is_dir_sep(c)) {
 953                         *dst++ = '/';
 954                         while (is_dir_sep(c))
 955                                 c = *src++;
 956                         src--;
 957                 } else if (!c)
 958                         break;
 959                 continue;
 960
 961         up_one:
 962                 /*
 963                  * dst0..dst is prefix portion, and dst[-1] is '/';
 964                  * go up one level.
 965                  */
 966                 dst--;  /* go to trailing '/' */
 967                 if (dst <= dst0)
 968                         return -1;
 969                 /* Windows: dst[-1] cannot be backslash anymore */
 970                 while (dst0 < dst && dst[-1] != '/')
 971                         dst--;
 972                 if (prefix_len && *prefix_len > dst - dst0)
 973                         *prefix_len = dst - dst0;
 974         }
 975         *dst = '\0';
 976         return 0;
 977 }
 978
 979 int normalize_path_copy(char *dst, const char *src)
 980 {
 981         return normalize_path_copy_len(dst, src, NULL);
 982 }
 983
 984 /*
 985  * path = Canonical absolute path
 986  * prefixes = string_list containing normalized, absolute paths without
 987  * trailing slashes (except for the root directory, which is denoted by "/").
 988  *
 989  * Determines, for each path in prefixes, whether the "prefix"
 990  * is an ancestor directory of path.  Returns the length of the longest
 991  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 992  * is an ancestor.  (Note that this means 0 is returned if prefixes is
 993  * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
 994  * are not considered to be their own ancestors.  path must be in a
 995  * canonical form: empty components, or "." or ".." components are not
 996  * allowed.
 997  */
 998 int longest_ancestor_length(const char *path, struct string_list *prefixes)
 999 {
1000         int i, max_len = -1;
1001
1002         if (!strcmp(path, "/"))
1003                 return -1;
1004
1005         for (i = 0; i < prefixes->nr; i++) {
1006                 const char *ceil = prefixes->items[i].string;
1007                 int len = strlen(ceil);
1008
1009                 if (len == 1 && ceil[0] == '/')
1010                         len = 0; /* root matches anything, with length 0 */
1011                 else if (!strncmp(path, ceil, len) && path[len] == '/')
1012                         ; /* match of length len */
1013                 else
1014                         continue; /* no match */
1015
1016                 if (len > max_len)
1017                         max_len = len;
1018         }
1019
1020         return max_len;
1021 }
1022
1023 /* strip arbitrary amount of directory separators at end of path */
1024 static inline int chomp_trailing_dir_sep(const char *path, int len)
1025 {
1026         while (len && is_dir_sep(path[len - 1]))
1027                 len--;
1028         return len;
1029 }
1030
1031 /*
1032  * If path ends with suffix (complete path components), returns the
1033  * part before suffix (sans trailing directory separators).
1034  * Otherwise returns NULL.
1035  */
1036 char *strip_path_suffix(const char *path, const char *suffix)
1037 {
1038         int path_len = strlen(path), suffix_len = strlen(suffix);
1039
1040         while (suffix_len) {
1041                 if (!path_len)
1042                         return NULL;
1043
1044                 if (is_dir_sep(path[path_len - 1])) {
1045                         if (!is_dir_sep(suffix[suffix_len - 1]))
1046                                 return NULL;
1047                         path_len = chomp_trailing_dir_sep(path, path_len);
1048                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
1049                 }
1050                 else if (path[--path_len] != suffix[--suffix_len])
1051                         return NULL;
1052         }
1053
1054         if (path_len && !is_dir_sep(path[path_len - 1]))
1055                 return NULL;
1056         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
1057 }
1058
1059 int daemon_avoid_alias(const char *p)
1060 {
1061         int sl, ndot;
1062
1063         /*
1064          * This resurrects the belts and suspenders paranoia check by HPA
1065          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
1066          * does not do getcwd() based path canonicalization.
1067          *
1068          * sl becomes true immediately after seeing '/' and continues to
1069          * be true as long as dots continue after that without intervening
1070          * non-dot character.
1071          */
1072         if (!p || (*p != '/' && *p != '~'))
1073                 return -1;
1074         sl = 1; ndot = 0;
1075         p++;
1076
1077         while (1) {
1078                 char ch = *p++;
1079                 if (sl) {
1080                         if (ch == '.')
1081                                 ndot++;
1082                         else if (ch == '/') {
1083                                 if (ndot < 3)
1084                                         /* reject //, /./ and /../ */
1085                                         return -1;
1086                                 ndot = 0;
1087                         }
1088                         else if (ch == 0) {
1089                                 if (0 < ndot && ndot < 3)
1090                                         /* reject /.$ and /..$ */
1091                                         return -1;
1092                                 return 0;
1093                         }
1094                         else
1095                                 sl = ndot = 0;
1096                 }
1097                 else if (ch == 0)
1098                         return 0;
1099                 else if (ch == '/') {
1100                         sl = 1;
1101                         ndot = 0;
1102                 }
1103         }
1104 }
1105
1106 static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
1107 {
1108         if (len < skip)
1109                 return 0;
1110         len -= skip;
1111         path += skip;
1112         while (len-- > 0) {
1113                 char c = *(path++);
1114                 if (c != ' ' && c != '.')
1115                         return 0;
1116         }
1117         return 1;
1118 }
1119
1120 int is_ntfs_dotgit(const char *name)
1121 {
1122         int len;
1123
1124         for (len = 0; ; len++)
1125                 if (!name[len] || name[len] == '\\' || is_dir_sep(name[len])) {
1126                         if (only_spaces_and_periods(name, len, 4) &&
1127                                         !strncasecmp(name, ".git", 4))
1128                                 return 1;
1129                         if (only_spaces_and_periods(name, len, 5) &&
1130                                         !strncasecmp(name, "git~1", 5))
1131                                 return 1;
1132                         if (name[len] != '\\')
1133                                 return 0;
1134                         name += len + 1;
1135                         len = -1;
1136                 }
1137 }
1138
1139 char *xdg_config_home(const char *filename)
1140 {
1141         const char *home, *config_home;
1142
1143         assert(filename);
1144         config_home = getenv("XDG_CONFIG_HOME");
1145         if (config_home && *config_home)
1146                 return mkpathdup("%s/git/%s", config_home, filename);
1147
1148         home = getenv("HOME");
1149         if (home)
1150                 return mkpathdup("%s/.config/git/%s", home, filename);
1151         return NULL;
1152 }
1153
1154 GIT_PATH_FUNC(git_path_cherry_pick_head, "CHERRY_PICK_HEAD")
1155 GIT_PATH_FUNC(git_path_revert_head, "REVERT_HEAD")
1156 GIT_PATH_FUNC(git_path_squash_msg, "SQUASH_MSG")
1157 GIT_PATH_FUNC(git_path_merge_msg, "MERGE_MSG")
1158 GIT_PATH_FUNC(git_path_merge_rr, "MERGE_RR")
1159 GIT_PATH_FUNC(git_path_merge_mode, "MERGE_MODE")
1160 GIT_PATH_FUNC(git_path_merge_head, "MERGE_HEAD")
1161 GIT_PATH_FUNC(git_path_fetch_head, "FETCH_HEAD")
1162 GIT_PATH_FUNC(git_path_shallow, "shallow")