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 #include "worktree.h"
   9
  10 static int get_st_mode_bits(const char *path, int *mode)
  11 {
  12         struct stat st;
  13         if (lstat(path, &st) < 0)
  14                 return -1;
  15         *mode = st.st_mode;
  16         return 0;
  17 }
  18
  19 static char bad_path[] = "/bad-path/";
  20
  21 static struct strbuf *get_pathname(void)
  22 {
  23         static struct strbuf pathname_array[4] = {
  24                 STRBUF_INIT, STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
  25         };
  26         static int index;
  27         struct strbuf *sb = &pathname_array[index];
  28         index = (index + 1) % ARRAY_SIZE(pathname_array);
  29         strbuf_reset(sb);
  30         return sb;
  31 }
  32
  33 static char *cleanup_path(char *path)
  34 {
  35         /* Clean it up */
  36         if (!memcmp(path, "./", 2)) {
  37                 path += 2;
  38                 while (*path == '/')
  39                         path++;
  40         }
  41         return path;
  42 }
  43
  44 static void strbuf_cleanup_path(struct strbuf *sb)
  45 {
  46         char *path = cleanup_path(sb->buf);
  47         if (path > sb->buf)
  48                 strbuf_remove(sb, 0, path - sb->buf);
  49 }
  50
  51 char *mksnpath(char *buf, size_t n, const char *fmt, ...)
  52 {
  53         va_list args;
  54         unsigned len;
  55
  56         va_start(args, fmt);
  57         len = vsnprintf(buf, n, fmt, args);
  58         va_end(args);
  59         if (len >= n) {
  60                 strlcpy(buf, bad_path, n);
  61                 return buf;
  62         }
  63         return cleanup_path(buf);
  64 }
  65
  66 static int dir_prefix(const char *buf, const char *dir)
  67 {
  68         int len = strlen(dir);
  69         return !strncmp(buf, dir, len) &&
  70                 (is_dir_sep(buf[len]) || buf[len] == '\0');
  71 }
  72
  73 /* $buf =~ m|$dir/+$file| but without regex */
  74 static int is_dir_file(const char *buf, const char *dir, const char *file)
  75 {
  76         int len = strlen(dir);
  77         if (strncmp(buf, dir, len) || !is_dir_sep(buf[len]))
  78                 return 0;
  79         while (is_dir_sep(buf[len]))
  80                 len++;
  81         return !strcmp(buf + len, file);
  82 }
  83
  84 static void replace_dir(struct strbuf *buf, int len, const char *newdir)
  85 {
  86         int newlen = strlen(newdir);
  87         int need_sep = (buf->buf[len] && !is_dir_sep(buf->buf[len])) &&
  88                 !is_dir_sep(newdir[newlen - 1]);
  89         if (need_sep)
  90                 len--;   /* keep one char, to be replaced with '/'  */
  91         strbuf_splice(buf, 0, len, newdir, newlen);
  92         if (need_sep)
  93                 buf->buf[newlen] = '/';
  94 }
  95
  96 struct common_dir {
  97         /* Not considered garbage for report_linked_checkout_garbage */
  98         unsigned ignore_garbage:1;
  99         unsigned is_dir:1;
 100         /* Not common even though its parent is */
 101         unsigned exclude:1;
 102         const char *dirname;
 103 };
 104
 105 static struct common_dir common_list[] = {
 106         { 0, 1, 0, "branches" },
 107         { 0, 1, 0, "hooks" },
 108         { 0, 1, 0, "info" },
 109         { 0, 0, 1, "info/sparse-checkout" },
 110         { 1, 1, 0, "logs" },
 111         { 1, 1, 1, "logs/HEAD" },
 112         { 0, 1, 1, "logs/refs/bisect" },
 113         { 0, 1, 0, "lost-found" },
 114         { 0, 1, 0, "objects" },
 115         { 0, 1, 0, "refs" },
 116         { 0, 1, 1, "refs/bisect" },
 117         { 0, 1, 0, "remotes" },
 118         { 0, 1, 0, "worktrees" },
 119         { 0, 1, 0, "rr-cache" },
 120         { 0, 1, 0, "svn" },
 121         { 0, 0, 0, "config" },
 122         { 1, 0, 0, "gc.pid" },
 123         { 0, 0, 0, "packed-refs" },
 124         { 0, 0, 0, "shallow" },
 125         { 0, 0, 0, NULL }
 126 };
 127
 128 /*
 129  * A compressed trie.  A trie node consists of zero or more characters that
 130  * are common to all elements with this prefix, optionally followed by some
 131  * children.  If value is not NULL, the trie node is a terminal node.
 132  *
 133  * For example, consider the following set of strings:
 134  * abc
 135  * def
 136  * definite
 137  * definition
 138  *
 139  * The trie would look like:
 140  * root: len = 0, children a and d non-NULL, value = NULL.
 141  *    a: len = 2, contents = bc, value = (data for "abc")
 142  *    d: len = 2, contents = ef, children i non-NULL, value = (data for "def")
 143  *       i: len = 3, contents = nit, children e and i non-NULL, value = NULL
 144  *           e: len = 0, children all NULL, value = (data for "definite")
 145  *           i: len = 2, contents = on, children all NULL,
 146  *              value = (data for "definition")
 147  */
 148 struct trie {
 149         struct trie *children[256];
 150         int len;
 151         char *contents;
 152         void *value;
 153 };
 154
 155 static struct trie *make_trie_node(const char *key, void *value)
 156 {
 157         struct trie *new_node = xcalloc(1, sizeof(*new_node));
 158         new_node->len = strlen(key);
 159         if (new_node->len) {
 160                 new_node->contents = xmalloc(new_node->len);
 161                 memcpy(new_node->contents, key, new_node->len);
 162         }
 163         new_node->value = value;
 164         return new_node;
 165 }
 166
 167 /*
 168  * Add a key/value pair to a trie.  The key is assumed to be \0-terminated.
 169  * If there was an existing value for this key, return it.
 170  */
 171 static void *add_to_trie(struct trie *root, const char *key, void *value)
 172 {
 173         struct trie *child;
 174         void *old;
 175         int i;
 176
 177         if (!*key) {
 178                 /* we have reached the end of the key */
 179                 old = root->value;
 180                 root->value = value;
 181                 return old;
 182         }
 183
 184         for (i = 0; i < root->len; i++) {
 185                 if (root->contents[i] == key[i])
 186                         continue;
 187
 188                 /*
 189                  * Split this node: child will contain this node's
 190                  * existing children.
 191                  */
 192                 child = malloc(sizeof(*child));
 193                 memcpy(child->children, root->children, sizeof(root->children));
 194
 195                 child->len = root->len - i - 1;
 196                 if (child->len) {
 197                         child->contents = xstrndup(root->contents + i + 1,
 198                                                    child->len);
 199                 }
 200                 child->value = root->value;
 201                 root->value = NULL;
 202                 root->len = i;
 203
 204                 memset(root->children, 0, sizeof(root->children));
 205                 root->children[(unsigned char)root->contents[i]] = child;
 206
 207                 /* This is the newly-added child. */
 208                 root->children[(unsigned char)key[i]] =
 209                         make_trie_node(key + i + 1, value);
 210                 return NULL;
 211         }
 212
 213         /* We have matched the entire compressed section */
 214         if (key[i]) {
 215                 child = root->children[(unsigned char)key[root->len]];
 216                 if (child) {
 217                         return add_to_trie(child, key + root->len + 1, value);
 218                 } else {
 219                         child = make_trie_node(key + root->len + 1, value);
 220                         root->children[(unsigned char)key[root->len]] = child;
 221                         return NULL;
 222                 }
 223         }
 224
 225         old = root->value;
 226         root->value = value;
 227         return old;
 228 }
 229
 230 typedef int (*match_fn)(const char *unmatched, void *data, void *baton);
 231
 232 /*
 233  * Search a trie for some key.  Find the longest /-or-\0-terminated
 234  * prefix of the key for which the trie contains a value.  Call fn
 235  * with the unmatched portion of the key and the found value, and
 236  * return its return value.  If there is no such prefix, return -1.
 237  *
 238  * The key is partially normalized: consecutive slashes are skipped.
 239  *
 240  * For example, consider the trie containing only [refs,
 241  * refs/worktree] (both with values).
 242  *
 243  * | key             | unmatched  | val from node | return value |
 244  * |-----------------|------------|---------------|--------------|
 245  * | a               | not called | n/a           | -1           |
 246  * | refs            | \0         | refs          | as per fn    |
 247  * | refs/           | /          | refs          | as per fn    |
 248  * | refs/w          | /w         | refs          | as per fn    |
 249  * | refs/worktree   | \0         | refs/worktree | as per fn    |
 250  * | refs/worktree/  | /          | refs/worktree | as per fn    |
 251  * | refs/worktree/a | /a         | refs/worktree | as per fn    |
 252  * |-----------------|------------|---------------|--------------|
 253  *
 254  */
 255 static int trie_find(struct trie *root, const char *key, match_fn fn,
 256                      void *baton)
 257 {
 258         int i;
 259         int result;
 260         struct trie *child;
 261
 262         if (!*key) {
 263                 /* we have reached the end of the key */
 264                 if (root->value && !root->len)
 265                         return fn(key, root->value, baton);
 266                 else
 267                         return -1;
 268         }
 269
 270         for (i = 0; i < root->len; i++) {
 271                 /* Partial path normalization: skip consecutive slashes. */
 272                 if (key[i] == '/' && key[i+1] == '/') {
 273                         key++;
 274                         continue;
 275                 }
 276                 if (root->contents[i] != key[i])
 277                         return -1;
 278         }
 279
 280         /* Matched the entire compressed section */
 281         key += i;
 282         if (!*key)
 283                 /* End of key */
 284                 return fn(key, root->value, baton);
 285
 286         /* Partial path normalization: skip consecutive slashes */
 287         while (key[0] == '/' && key[1] == '/')
 288                 key++;
 289
 290         child = root->children[(unsigned char)*key];
 291         if (child)
 292                 result = trie_find(child, key + 1, fn, baton);
 293         else
 294                 result = -1;
 295
 296         if (result >= 0 || (*key != '/' && *key != 0))
 297                 return result;
 298         if (root->value)
 299                 return fn(key, root->value, baton);
 300         else
 301                 return -1;
 302 }
 303
 304 static struct trie common_trie;
 305 static int common_trie_done_setup;
 306
 307 static void init_common_trie(void)
 308 {
 309         struct common_dir *p;
 310
 311         if (common_trie_done_setup)
 312                 return;
 313
 314         for (p = common_list; p->dirname; p++)
 315                 add_to_trie(&common_trie, p->dirname, p);
 316
 317         common_trie_done_setup = 1;
 318 }
 319
 320 /*
 321  * Helper function for update_common_dir: returns 1 if the dir
 322  * prefix is common.
 323  */
 324 static int check_common(const char *unmatched, void *value, void *baton)
 325 {
 326         struct common_dir *dir = value;
 327
 328         if (!dir)
 329                 return 0;
 330
 331         if (dir->is_dir && (unmatched[0] == 0 || unmatched[0] == '/'))
 332                 return !dir->exclude;
 333
 334         if (!dir->is_dir && unmatched[0] == 0)
 335                 return !dir->exclude;
 336
 337         return 0;
 338 }
 339
 340 static void update_common_dir(struct strbuf *buf, int git_dir_len,
 341                               const char *common_dir)
 342 {
 343         char *base = buf->buf + git_dir_len;
 344         init_common_trie();
 345         if (!common_dir)
 346                 common_dir = get_git_common_dir();
 347         if (trie_find(&common_trie, base, check_common, NULL) > 0)
 348                 replace_dir(buf, git_dir_len, common_dir);
 349 }
 350
 351 void report_linked_checkout_garbage(void)
 352 {
 353         struct strbuf sb = STRBUF_INIT;
 354         const struct common_dir *p;
 355         int len;
 356
 357         if (!git_common_dir_env)
 358                 return;
 359         strbuf_addf(&sb, "%s/", get_git_dir());
 360         len = sb.len;
 361         for (p = common_list; p->dirname; p++) {
 362                 const char *path = p->dirname;
 363                 if (p->ignore_garbage)
 364                         continue;
 365                 strbuf_setlen(&sb, len);
 366                 strbuf_addstr(&sb, path);
 367                 if (file_exists(sb.buf))
 368                         report_garbage(PACKDIR_FILE_GARBAGE, sb.buf);
 369         }
 370         strbuf_release(&sb);
 371 }
 372
 373 static void adjust_git_path(struct strbuf *buf, int git_dir_len)
 374 {
 375         const char *base = buf->buf + git_dir_len;
 376         if (git_graft_env && is_dir_file(base, "info", "grafts"))
 377                 strbuf_splice(buf, 0, buf->len,
 378                               get_graft_file(), strlen(get_graft_file()));
 379         else if (git_index_env && !strcmp(base, "index"))
 380                 strbuf_splice(buf, 0, buf->len,
 381                               get_index_file(), strlen(get_index_file()));
 382         else if (git_db_env && dir_prefix(base, "objects"))
 383                 replace_dir(buf, git_dir_len + 7, get_object_directory());
 384         else if (git_hooks_path && dir_prefix(base, "hooks"))
 385                 replace_dir(buf, git_dir_len + 5, git_hooks_path);
 386         else if (git_common_dir_env)
 387                 update_common_dir(buf, git_dir_len, NULL);
 388 }
 389
 390 static void do_git_path(const struct worktree *wt, struct strbuf *buf,
 391                         const char *fmt, va_list args)
 392 {
 393         int gitdir_len;
 394         strbuf_addstr(buf, get_worktree_git_dir(wt));
 395         if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 396                 strbuf_addch(buf, '/');
 397         gitdir_len = buf->len;
 398         strbuf_vaddf(buf, fmt, args);
 399         adjust_git_path(buf, gitdir_len);
 400         strbuf_cleanup_path(buf);
 401 }
 402
 403 char *git_path_buf(struct strbuf *buf, const char *fmt, ...)
 404 {
 405         va_list args;
 406         strbuf_reset(buf);
 407         va_start(args, fmt);
 408         do_git_path(NULL, buf, fmt, args);
 409         va_end(args);
 410         return buf->buf;
 411 }
 412
 413 void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
 414 {
 415         va_list args;
 416         va_start(args, fmt);
 417         do_git_path(NULL, sb, fmt, args);
 418         va_end(args);
 419 }
 420
 421 const char *git_path(const char *fmt, ...)
 422 {
 423         struct strbuf *pathname = get_pathname();
 424         va_list args;
 425         va_start(args, fmt);
 426         do_git_path(NULL, pathname, fmt, args);
 427         va_end(args);
 428         return pathname->buf;
 429 }
 430
 431 char *git_pathdup(const char *fmt, ...)
 432 {
 433         struct strbuf path = STRBUF_INIT;
 434         va_list args;
 435         va_start(args, fmt);
 436         do_git_path(NULL, &path, fmt, args);
 437         va_end(args);
 438         return strbuf_detach(&path, NULL);
 439 }
 440
 441 char *mkpathdup(const char *fmt, ...)
 442 {
 443         struct strbuf sb = STRBUF_INIT;
 444         va_list args;
 445         va_start(args, fmt);
 446         strbuf_vaddf(&sb, fmt, args);
 447         va_end(args);
 448         strbuf_cleanup_path(&sb);
 449         return strbuf_detach(&sb, NULL);
 450 }
 451
 452 const char *mkpath(const char *fmt, ...)
 453 {
 454         va_list args;
 455         struct strbuf *pathname = get_pathname();
 456         va_start(args, fmt);
 457         strbuf_vaddf(pathname, fmt, args);
 458         va_end(args);
 459         return cleanup_path(pathname->buf);
 460 }
 461
 462 const char *worktree_git_path(const struct worktree *wt, const char *fmt, ...)
 463 {
 464         struct strbuf *pathname = get_pathname();
 465         va_list args;
 466         va_start(args, fmt);
 467         do_git_path(wt, pathname, fmt, args);
 468         va_end(args);
 469         return pathname->buf;
 470 }
 471
 472 static void do_submodule_path(struct strbuf *buf, const char *path,
 473                               const char *fmt, va_list args)
 474 {
 475         const char *git_dir;
 476         struct strbuf git_submodule_common_dir = STRBUF_INIT;
 477         struct strbuf git_submodule_dir = STRBUF_INIT;
 478
 479         strbuf_addstr(buf, path);
 480         strbuf_complete(buf, '/');
 481         strbuf_addstr(buf, ".git");
 482
 483         git_dir = read_gitfile(buf->buf);
 484         if (git_dir) {
 485                 strbuf_reset(buf);
 486                 strbuf_addstr(buf, git_dir);
 487         }
 488         strbuf_addch(buf, '/');
 489         strbuf_addbuf(&git_submodule_dir, buf);
 490
 491         strbuf_vaddf(buf, fmt, args);
 492
 493         if (get_common_dir_noenv(&git_submodule_common_dir, git_submodule_dir.buf))
 494                 update_common_dir(buf, git_submodule_dir.len, git_submodule_common_dir.buf);
 495
 496         strbuf_cleanup_path(buf);
 497
 498         strbuf_release(&git_submodule_dir);
 499         strbuf_release(&git_submodule_common_dir);
 500 }
 501
 502 char *git_pathdup_submodule(const char *path, const char *fmt, ...)
 503 {
 504         va_list args;
 505         struct strbuf buf = STRBUF_INIT;
 506         va_start(args, fmt);
 507         do_submodule_path(&buf, path, fmt, args);
 508         va_end(args);
 509         return strbuf_detach(&buf, NULL);
 510 }
 511
 512 void strbuf_git_path_submodule(struct strbuf *buf, const char *path,
 513                                const char *fmt, ...)
 514 {
 515         va_list args;
 516         va_start(args, fmt);
 517         do_submodule_path(buf, path, fmt, args);
 518         va_end(args);
 519 }
 520
 521 static void do_git_common_path(struct strbuf *buf,
 522                                const char *fmt,
 523                                va_list args)
 524 {
 525         strbuf_addstr(buf, get_git_common_dir());
 526         if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 527                 strbuf_addch(buf, '/');
 528         strbuf_vaddf(buf, fmt, args);
 529         strbuf_cleanup_path(buf);
 530 }
 531
 532 const char *git_common_path(const char *fmt, ...)
 533 {
 534         struct strbuf *pathname = get_pathname();
 535         va_list args;
 536         va_start(args, fmt);
 537         do_git_common_path(pathname, fmt, args);
 538         va_end(args);
 539         return pathname->buf;
 540 }
 541
 542 void strbuf_git_common_path(struct strbuf *sb, const char *fmt, ...)
 543 {
 544         va_list args;
 545         va_start(args, fmt);
 546         do_git_common_path(sb, fmt, args);
 547         va_end(args);
 548 }
 549
 550 int validate_headref(const char *path)
 551 {
 552         struct stat st;
 553         char *buf, buffer[256];
 554         unsigned char sha1[20];
 555         int fd;
 556         ssize_t len;
 557
 558         if (lstat(path, &st) < 0)
 559                 return -1;
 560
 561         /* Make sure it is a "refs/.." symlink */
 562         if (S_ISLNK(st.st_mode)) {
 563                 len = readlink(path, buffer, sizeof(buffer)-1);
 564                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 565                         return 0;
 566                 return -1;
 567         }
 568
 569         /*
 570          * Anything else, just open it and try to see if it is a symbolic ref.
 571          */
 572         fd = open(path, O_RDONLY);
 573         if (fd < 0)
 574                 return -1;
 575         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 576         close(fd);
 577
 578         /*
 579          * Is it a symbolic ref?
 580          */
 581         if (len < 4)
 582                 return -1;
 583         if (!memcmp("ref:", buffer, 4)) {
 584                 buf = buffer + 4;
 585                 len -= 4;
 586                 while (len && isspace(*buf))
 587                         buf++, len--;
 588                 if (len >= 5 && !memcmp("refs/", buf, 5))
 589                         return 0;
 590         }
 591
 592         /*
 593          * Is this a detached HEAD?
 594          */
 595         if (!get_sha1_hex(buffer, sha1))
 596                 return 0;
 597
 598         return -1;
 599 }
 600
 601 static struct passwd *getpw_str(const char *username, size_t len)
 602 {
 603         struct passwd *pw;
 604         char *username_z = xmemdupz(username, len);
 605         pw = getpwnam(username_z);
 606         free(username_z);
 607         return pw;
 608 }
 609
 610 /*
 611  * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 612  * then it is a newly allocated string. Returns NULL on getpw failure or
 613  * if path is NULL.
 614  */
 615 char *expand_user_path(const char *path)
 616 {
 617         struct strbuf user_path = STRBUF_INIT;
 618         const char *to_copy = path;
 619
 620         if (path == NULL)
 621                 goto return_null;
 622         if (path[0] == '~') {
 623                 const char *first_slash = strchrnul(path, '/');
 624                 const char *username = path + 1;
 625                 size_t username_len = first_slash - username;
 626                 if (username_len == 0) {
 627                         const char *home = getenv("HOME");
 628                         if (!home)
 629                                 goto return_null;
 630                         strbuf_addstr(&user_path, home);
 631 #ifdef GIT_WINDOWS_NATIVE
 632                         convert_slashes(user_path.buf);
 633 #endif
 634                 } else {
 635                         struct passwd *pw = getpw_str(username, username_len);
 636                         if (!pw)
 637                                 goto return_null;
 638                         strbuf_addstr(&user_path, pw->pw_dir);
 639                 }
 640                 to_copy = first_slash;
 641         }
 642         strbuf_addstr(&user_path, to_copy);
 643         return strbuf_detach(&user_path, NULL);
 644 return_null:
 645         strbuf_release(&user_path);
 646         return NULL;
 647 }
 648
 649 /*
 650  * First, one directory to try is determined by the following algorithm.
 651  *
 652  * (0) If "strict" is given, the path is used as given and no DWIM is
 653  *     done. Otherwise:
 654  * (1) "~/path" to mean path under the running user's home directory;
 655  * (2) "~user/path" to mean path under named user's home directory;
 656  * (3) "relative/path" to mean cwd relative directory; or
 657  * (4) "/absolute/path" to mean absolute directory.
 658  *
 659  * Unless "strict" is given, we check "%s/.git", "%s", "%s.git/.git", "%s.git"
 660  * in this order. We select the first one that is a valid git repository, and
 661  * chdir() to it. If none match, or we fail to chdir, we return NULL.
 662  *
 663  * If all goes well, we return the directory we used to chdir() (but
 664  * before ~user is expanded), avoiding getcwd() resolving symbolic
 665  * links.  User relative paths are also returned as they are given,
 666  * except DWIM suffixing.
 667  */
 668 const char *enter_repo(const char *path, int strict)
 669 {
 670         static struct strbuf validated_path = STRBUF_INIT;
 671         static struct strbuf used_path = STRBUF_INIT;
 672
 673         if (!path)
 674                 return NULL;
 675
 676         if (!strict) {
 677                 static const char *suffix[] = {
 678                         "/.git", "", ".git/.git", ".git", NULL,
 679                 };
 680                 const char *gitfile;
 681                 int len = strlen(path);
 682                 int i;
 683                 while ((1 < len) && (path[len-1] == '/'))
 684                         len--;
 685
 686                 /*
 687                  * We can handle arbitrary-sized buffers, but this remains as a
 688                  * sanity check on untrusted input.
 689                  */
 690                 if (PATH_MAX <= len)
 691                         return NULL;
 692
 693                 strbuf_reset(&used_path);
 694                 strbuf_reset(&validated_path);
 695                 strbuf_add(&used_path, path, len);
 696                 strbuf_add(&validated_path, path, len);
 697
 698                 if (used_path.buf[0] == '~') {
 699                         char *newpath = expand_user_path(used_path.buf);
 700                         if (!newpath)
 701                                 return NULL;
 702                         strbuf_attach(&used_path, newpath, strlen(newpath),
 703                                       strlen(newpath));
 704                 }
 705                 for (i = 0; suffix[i]; i++) {
 706                         struct stat st;
 707                         size_t baselen = used_path.len;
 708                         strbuf_addstr(&used_path, suffix[i]);
 709                         if (!stat(used_path.buf, &st) &&
 710                             (S_ISREG(st.st_mode) ||
 711                             (S_ISDIR(st.st_mode) && is_git_directory(used_path.buf)))) {
 712                                 strbuf_addstr(&validated_path, suffix[i]);
 713                                 break;
 714                         }
 715                         strbuf_setlen(&used_path, baselen);
 716                 }
 717                 if (!suffix[i])
 718                         return NULL;
 719                 gitfile = read_gitfile(used_path.buf);
 720                 if (gitfile) {
 721                         strbuf_reset(&used_path);
 722                         strbuf_addstr(&used_path, gitfile);
 723                 }
 724                 if (chdir(used_path.buf))
 725                         return NULL;
 726                 path = validated_path.buf;
 727         }
 728         else {
 729                 const char *gitfile = read_gitfile(path);
 730                 if (gitfile)
 731                         path = gitfile;
 732                 if (chdir(path))
 733                         return NULL;
 734         }
 735
 736         if (is_git_directory(".")) {
 737                 set_git_dir(".");
 738                 check_repository_format();
 739                 return path;
 740         }
 741
 742         return NULL;
 743 }
 744
 745 static int calc_shared_perm(int mode)
 746 {
 747         int tweak;
 748
 749         if (get_shared_repository() < 0)
 750                 tweak = -get_shared_repository();
 751         else
 752                 tweak = get_shared_repository();
 753
 754         if (!(mode & S_IWUSR))
 755                 tweak &= ~0222;
 756         if (mode & S_IXUSR)
 757                 /* Copy read bits to execute bits */
 758                 tweak |= (tweak & 0444) >> 2;
 759         if (get_shared_repository() < 0)
 760                 mode = (mode & ~0777) | tweak;
 761         else
 762                 mode |= tweak;
 763
 764         return mode;
 765 }
 766
 767
 768 int adjust_shared_perm(const char *path)
 769 {
 770         int old_mode, new_mode;
 771
 772         if (!get_shared_repository())
 773                 return 0;
 774         if (get_st_mode_bits(path, &old_mode) < 0)
 775                 return -1;
 776
 777         new_mode = calc_shared_perm(old_mode);
 778         if (S_ISDIR(old_mode)) {
 779                 /* Copy read bits to execute bits */
 780                 new_mode |= (new_mode & 0444) >> 2;
 781                 new_mode |= FORCE_DIR_SET_GID;
 782         }
 783
 784         if (((old_mode ^ new_mode) & ~S_IFMT) &&
 785                         chmod(path, (new_mode & ~S_IFMT)) < 0)
 786                 return -2;
 787         return 0;
 788 }
 789
 790 void safe_create_dir(const char *dir, int share)
 791 {
 792         if (mkdir(dir, 0777) < 0) {
 793                 if (errno != EEXIST) {
 794                         perror(dir);
 795                         exit(1);
 796                 }
 797         }
 798         else if (share && adjust_shared_perm(dir))
 799                 die(_("Could not make %s writable by group"), dir);
 800 }
 801
 802 static int have_same_root(const char *path1, const char *path2)
 803 {
 804         int is_abs1, is_abs2;
 805
 806         is_abs1 = is_absolute_path(path1);
 807         is_abs2 = is_absolute_path(path2);
 808         return (is_abs1 && is_abs2 && tolower(path1[0]) == tolower(path2[0])) ||
 809                (!is_abs1 && !is_abs2);
 810 }
 811
 812 /*
 813  * Give path as relative to prefix.
 814  *
 815  * The strbuf may or may not be used, so do not assume it contains the
 816  * returned path.
 817  */
 818 const char *relative_path(const char *in, const char *prefix,
 819                           struct strbuf *sb)
 820 {
 821         int in_len = in ? strlen(in) : 0;
 822         int prefix_len = prefix ? strlen(prefix) : 0;
 823         int in_off = 0;
 824         int prefix_off = 0;
 825         int i = 0, j = 0;
 826
 827         if (!in_len)
 828                 return "./";
 829         else if (!prefix_len)
 830                 return in;
 831
 832         if (have_same_root(in, prefix))
 833                 /* bypass dos_drive, for "c:" is identical to "C:" */
 834                 i = j = has_dos_drive_prefix(in);
 835         else {
 836                 return in;
 837         }
 838
 839         while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
 840                 if (is_dir_sep(prefix[i])) {
 841                         while (is_dir_sep(prefix[i]))
 842                                 i++;
 843                         while (is_dir_sep(in[j]))
 844                                 j++;
 845                         prefix_off = i;
 846                         in_off = j;
 847                 } else {
 848                         i++;
 849                         j++;
 850                 }
 851         }
 852
 853         if (
 854             /* "prefix" seems like prefix of "in" */
 855             i >= prefix_len &&
 856             /*
 857              * but "/foo" is not a prefix of "/foobar"
 858              * (i.e. prefix not end with '/')
 859              */
 860             prefix_off < prefix_len) {
 861                 if (j >= in_len) {
 862                         /* in="/a/b", prefix="/a/b" */
 863                         in_off = in_len;
 864                 } else if (is_dir_sep(in[j])) {
 865                         /* in="/a/b/c", prefix="/a/b" */
 866                         while (is_dir_sep(in[j]))
 867                                 j++;
 868                         in_off = j;
 869                 } else {
 870                         /* in="/a/bbb/c", prefix="/a/b" */
 871                         i = prefix_off;
 872                 }
 873         } else if (
 874                    /* "in" is short than "prefix" */
 875                    j >= in_len &&
 876                    /* "in" not end with '/' */
 877                    in_off < in_len) {
 878                 if (is_dir_sep(prefix[i])) {
 879                         /* in="/a/b", prefix="/a/b/c/" */
 880                         while (is_dir_sep(prefix[i]))
 881                                 i++;
 882                         in_off = in_len;
 883                 }
 884         }
 885         in += in_off;
 886         in_len -= in_off;
 887
 888         if (i >= prefix_len) {
 889                 if (!in_len)
 890                         return "./";
 891                 else
 892                         return in;
 893         }
 894
 895         strbuf_reset(sb);
 896         strbuf_grow(sb, in_len);
 897
 898         while (i < prefix_len) {
 899                 if (is_dir_sep(prefix[i])) {
 900                         strbuf_addstr(sb, "../");
 901                         while (is_dir_sep(prefix[i]))
 902                                 i++;
 903                         continue;
 904                 }
 905                 i++;
 906         }
 907         if (!is_dir_sep(prefix[prefix_len - 1]))
 908                 strbuf_addstr(sb, "../");
 909
 910         strbuf_addstr(sb, in);
 911
 912         return sb->buf;
 913 }
 914
 915 /*
 916  * A simpler implementation of relative_path
 917  *
 918  * Get relative path by removing "prefix" from "in". This function
 919  * first appears in v1.5.6-1-g044bbbc, and makes git_dir shorter
 920  * to increase performance when traversing the path to work_tree.
 921  */
 922 const char *remove_leading_path(const char *in, const char *prefix)
 923 {
 924         static struct strbuf buf = STRBUF_INIT;
 925         int i = 0, j = 0;
 926
 927         if (!prefix || !prefix[0])
 928                 return in;
 929         while (prefix[i]) {
 930                 if (is_dir_sep(prefix[i])) {
 931                         if (!is_dir_sep(in[j]))
 932                                 return in;
 933                         while (is_dir_sep(prefix[i]))
 934                                 i++;
 935                         while (is_dir_sep(in[j]))
 936                                 j++;
 937                         continue;
 938                 } else if (in[j] != prefix[i]) {
 939                         return in;
 940                 }
 941                 i++;
 942                 j++;
 943         }
 944         if (
 945             /* "/foo" is a prefix of "/foo" */
 946             in[j] &&
 947             /* "/foo" is not a prefix of "/foobar" */
 948             !is_dir_sep(prefix[i-1]) && !is_dir_sep(in[j])
 949            )
 950                 return in;
 951         while (is_dir_sep(in[j]))
 952                 j++;
 953
 954         strbuf_reset(&buf);
 955         if (!in[j])
 956                 strbuf_addstr(&buf, ".");
 957         else
 958                 strbuf_addstr(&buf, in + j);
 959         return buf.buf;
 960 }
 961
 962 /*
 963  * It is okay if dst == src, but they should not overlap otherwise.
 964  *
 965  * Performs the following normalizations on src, storing the result in dst:
 966  * - Ensures that components are separated by '/' (Windows only)
 967  * - Squashes sequences of '/'.
 968  * - Removes "." components.
 969  * - Removes ".." components, and the components the precede them.
 970  * Returns failure (non-zero) if a ".." component appears as first path
 971  * component anytime during the normalization. Otherwise, returns success (0).
 972  *
 973  * Note that this function is purely textual.  It does not follow symlinks,
 974  * verify the existence of the path, or make any system calls.
 975  *
 976  * prefix_len != NULL is for a specific case of prefix_pathspec():
 977  * assume that src == dst and src[0..prefix_len-1] is already
 978  * normalized, any time "../" eats up to the prefix_len part,
 979  * prefix_len is reduced. In the end prefix_len is the remaining
 980  * prefix that has not been overridden by user pathspec.
 981  *
 982  * NEEDSWORK: This function doesn't perform normalization w.r.t. trailing '/'.
 983  * For everything but the root folder itself, the normalized path should not
 984  * end with a '/', then the callers need to be fixed up accordingly.
 985  *
 986  */
 987 int normalize_path_copy_len(char *dst, const char *src, int *prefix_len)
 988 {
 989         char *dst0;
 990         int i;
 991
 992         for (i = has_dos_drive_prefix(src); i > 0; i--)
 993                 *dst++ = *src++;
 994         dst0 = dst;
 995
 996         if (is_dir_sep(*src)) {
 997                 *dst++ = '/';
 998                 while (is_dir_sep(*src))
 999                         src++;
1000         }
1001
1002         for (;;) {
1003                 char c = *src;
1004
1005                 /*
1006                  * A path component that begins with . could be
1007                  * special:
1008                  * (1) "." and ends   -- ignore and terminate.
1009                  * (2) "./"           -- ignore them, eat slash and continue.
1010                  * (3) ".." and ends  -- strip one and terminate.
1011                  * (4) "../"          -- strip one, eat slash and continue.
1012                  */
1013                 if (c == '.') {
1014                         if (!src[1]) {
1015                                 /* (1) */
1016                                 src++;
1017                         } else if (is_dir_sep(src[1])) {
1018                                 /* (2) */
1019                                 src += 2;
1020                                 while (is_dir_sep(*src))
1021                                         src++;
1022                                 continue;
1023                         } else if (src[1] == '.') {
1024                                 if (!src[2]) {
1025                                         /* (3) */
1026                                         src += 2;
1027                                         goto up_one;
1028                                 } else if (is_dir_sep(src[2])) {
1029                                         /* (4) */
1030                                         src += 3;
1031                                         while (is_dir_sep(*src))
1032                                                 src++;
1033                                         goto up_one;
1034                                 }
1035                         }
1036                 }
1037
1038                 /* copy up to the next '/', and eat all '/' */
1039                 while ((c = *src++) != '\0' && !is_dir_sep(c))
1040                         *dst++ = c;
1041                 if (is_dir_sep(c)) {
1042                         *dst++ = '/';
1043                         while (is_dir_sep(c))
1044                                 c = *src++;
1045                         src--;
1046                 } else if (!c)
1047                         break;
1048                 continue;
1049
1050         up_one:
1051                 /*
1052                  * dst0..dst is prefix portion, and dst[-1] is '/';
1053                  * go up one level.
1054                  */
1055                 dst--;  /* go to trailing '/' */
1056                 if (dst <= dst0)
1057                         return -1;
1058                 /* Windows: dst[-1] cannot be backslash anymore */
1059                 while (dst0 < dst && dst[-1] != '/')
1060                         dst--;
1061                 if (prefix_len && *prefix_len > dst - dst0)
1062                         *prefix_len = dst - dst0;
1063         }
1064         *dst = '\0';
1065         return 0;
1066 }
1067
1068 int normalize_path_copy(char *dst, const char *src)
1069 {
1070         return normalize_path_copy_len(dst, src, NULL);
1071 }
1072
1073 /*
1074  * path = Canonical absolute path
1075  * prefixes = string_list containing normalized, absolute paths without
1076  * trailing slashes (except for the root directory, which is denoted by "/").
1077  *
1078  * Determines, for each path in prefixes, whether the "prefix"
1079  * is an ancestor directory of path.  Returns the length of the longest
1080  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
1081  * is an ancestor.  (Note that this means 0 is returned if prefixes is
1082  * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
1083  * are not considered to be their own ancestors.  path must be in a
1084  * canonical form: empty components, or "." or ".." components are not
1085  * allowed.
1086  */
1087 int longest_ancestor_length(const char *path, struct string_list *prefixes)
1088 {
1089         int i, max_len = -1;
1090
1091         if (!strcmp(path, "/"))
1092                 return -1;
1093
1094         for (i = 0; i < prefixes->nr; i++) {
1095                 const char *ceil = prefixes->items[i].string;
1096                 int len = strlen(ceil);
1097
1098                 if (len == 1 && ceil[0] == '/')
1099                         len = 0; /* root matches anything, with length 0 */
1100                 else if (!strncmp(path, ceil, len) && path[len] == '/')
1101                         ; /* match of length len */
1102                 else
1103                         continue; /* no match */
1104
1105                 if (len > max_len)
1106                         max_len = len;
1107         }
1108
1109         return max_len;
1110 }
1111
1112 /* strip arbitrary amount of directory separators at end of path */
1113 static inline int chomp_trailing_dir_sep(const char *path, int len)
1114 {
1115         while (len && is_dir_sep(path[len - 1]))
1116                 len--;
1117         return len;
1118 }
1119
1120 /*
1121  * If path ends with suffix (complete path components), returns the
1122  * part before suffix (sans trailing directory separators).
1123  * Otherwise returns NULL.
1124  */
1125 char *strip_path_suffix(const char *path, const char *suffix)
1126 {
1127         int path_len = strlen(path), suffix_len = strlen(suffix);
1128
1129         while (suffix_len) {
1130                 if (!path_len)
1131                         return NULL;
1132
1133                 if (is_dir_sep(path[path_len - 1])) {
1134                         if (!is_dir_sep(suffix[suffix_len - 1]))
1135                                 return NULL;
1136                         path_len = chomp_trailing_dir_sep(path, path_len);
1137                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
1138                 }
1139                 else if (path[--path_len] != suffix[--suffix_len])
1140                         return NULL;
1141         }
1142
1143         if (path_len && !is_dir_sep(path[path_len - 1]))
1144                 return NULL;
1145         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
1146 }
1147
1148 int daemon_avoid_alias(const char *p)
1149 {
1150         int sl, ndot;
1151
1152         /*
1153          * This resurrects the belts and suspenders paranoia check by HPA
1154          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
1155          * does not do getcwd() based path canonicalization.
1156          *
1157          * sl becomes true immediately after seeing '/' and continues to
1158          * be true as long as dots continue after that without intervening
1159          * non-dot character.
1160          */
1161         if (!p || (*p != '/' && *p != '~'))
1162                 return -1;
1163         sl = 1; ndot = 0;
1164         p++;
1165
1166         while (1) {
1167                 char ch = *p++;
1168                 if (sl) {
1169                         if (ch == '.')
1170                                 ndot++;
1171                         else if (ch == '/') {
1172                                 if (ndot < 3)
1173                                         /* reject //, /./ and /../ */
1174                                         return -1;
1175                                 ndot = 0;
1176                         }
1177                         else if (ch == 0) {
1178                                 if (0 < ndot && ndot < 3)
1179                                         /* reject /.$ and /..$ */
1180                                         return -1;
1181                                 return 0;
1182                         }
1183                         else
1184                                 sl = ndot = 0;
1185                 }
1186                 else if (ch == 0)
1187                         return 0;
1188                 else if (ch == '/') {
1189                         sl = 1;
1190                         ndot = 0;
1191                 }
1192         }
1193 }
1194
1195 static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
1196 {
1197         if (len < skip)
1198                 return 0;
1199         len -= skip;
1200         path += skip;
1201         while (len-- > 0) {
1202                 char c = *(path++);
1203                 if (c != ' ' && c != '.')
1204                         return 0;
1205         }
1206         return 1;
1207 }
1208
1209 int is_ntfs_dotgit(const char *name)
1210 {
1211         int len;
1212
1213         for (len = 0; ; len++)
1214                 if (!name[len] || name[len] == '\\' || is_dir_sep(name[len])) {
1215                         if (only_spaces_and_periods(name, len, 4) &&
1216                                         !strncasecmp(name, ".git", 4))
1217                                 return 1;
1218                         if (only_spaces_and_periods(name, len, 5) &&
1219                                         !strncasecmp(name, "git~1", 5))
1220                                 return 1;
1221                         if (name[len] != '\\')
1222                                 return 0;
1223                         name += len + 1;
1224                         len = -1;
1225                 }
1226 }
1227
1228 char *xdg_config_home(const char *filename)
1229 {
1230         const char *home, *config_home;
1231
1232         assert(filename);
1233         config_home = getenv("XDG_CONFIG_HOME");
1234         if (config_home && *config_home)
1235                 return mkpathdup("%s/git/%s", config_home, filename);
1236
1237         home = getenv("HOME");
1238         if (home)
1239                 return mkpathdup("%s/.config/git/%s", home, filename);
1240         return NULL;
1241 }
1242
1243 GIT_PATH_FUNC(git_path_cherry_pick_head, "CHERRY_PICK_HEAD")
1244 GIT_PATH_FUNC(git_path_revert_head, "REVERT_HEAD")
1245 GIT_PATH_FUNC(git_path_squash_msg, "SQUASH_MSG")
1246 GIT_PATH_FUNC(git_path_merge_msg, "MERGE_MSG")
1247 GIT_PATH_FUNC(git_path_merge_rr, "MERGE_RR")
1248 GIT_PATH_FUNC(git_path_merge_mode, "MERGE_MODE")
1249 GIT_PATH_FUNC(git_path_merge_head, "MERGE_HEAD")
1250 GIT_PATH_FUNC(git_path_fetch_head, "FETCH_HEAD")
1251 GIT_PATH_FUNC(git_path_shallow, "shallow")