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