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 #include "submodule-config.h"
  10
  11 static int get_st_mode_bits(const char *path, int *mode)
  12 {
  13         struct stat st;
  14         if (lstat(path, &st) < 0)
  15                 return -1;
  16         *mode = st.st_mode;
  17         return 0;
  18 }
  19
  20 static char bad_path[] = "/bad-path/";
  21
  22 static struct strbuf *get_pathname(void)
  23 {
  24         static struct strbuf pathname_array[4] = {
  25                 STRBUF_INIT, STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
  26         };
  27         static int index;
  28         struct strbuf *sb = &pathname_array[3 & ++index];
  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 /* Returns 0 on success, negative on failure. */
 473 #define SUBMODULE_PATH_ERR_NOT_CONFIGURED -1
 474 static int do_submodule_path(struct strbuf *buf, const char *path,
 475                              const char *fmt, va_list args)
 476 {
 477         const char *git_dir;
 478         struct strbuf git_submodule_common_dir = STRBUF_INIT;
 479         struct strbuf git_submodule_dir = STRBUF_INIT;
 480         const struct submodule *sub;
 481         int err = 0;
 482
 483         strbuf_addstr(buf, path);
 484         strbuf_complete(buf, '/');
 485         strbuf_addstr(buf, ".git");
 486
 487         git_dir = read_gitfile(buf->buf);
 488         if (git_dir) {
 489                 strbuf_reset(buf);
 490                 strbuf_addstr(buf, git_dir);
 491         }
 492         if (!is_git_directory(buf->buf)) {
 493                 gitmodules_config();
 494                 sub = submodule_from_path(null_sha1, path);
 495                 if (!sub) {
 496                         err = SUBMODULE_PATH_ERR_NOT_CONFIGURED;
 497                         goto cleanup;
 498                 }
 499                 strbuf_reset(buf);
 500                 strbuf_git_path(buf, "%s/%s", "modules", sub->name);
 501         }
 502
 503         strbuf_addch(buf, '/');
 504         strbuf_addbuf(&git_submodule_dir, buf);
 505
 506         strbuf_vaddf(buf, fmt, args);
 507
 508         if (get_common_dir_noenv(&git_submodule_common_dir, git_submodule_dir.buf))
 509                 update_common_dir(buf, git_submodule_dir.len, git_submodule_common_dir.buf);
 510
 511         strbuf_cleanup_path(buf);
 512
 513 cleanup:
 514         strbuf_release(&git_submodule_dir);
 515         strbuf_release(&git_submodule_common_dir);
 516
 517         return err;
 518 }
 519
 520 char *git_pathdup_submodule(const char *path, const char *fmt, ...)
 521 {
 522         int err;
 523         va_list args;
 524         struct strbuf buf = STRBUF_INIT;
 525         va_start(args, fmt);
 526         err = do_submodule_path(&buf, path, fmt, args);
 527         va_end(args);
 528         if (err) {
 529                 strbuf_release(&buf);
 530                 return NULL;
 531         }
 532         return strbuf_detach(&buf, NULL);
 533 }
 534
 535 int strbuf_git_path_submodule(struct strbuf *buf, const char *path,
 536                               const char *fmt, ...)
 537 {
 538         int err;
 539         va_list args;
 540         va_start(args, fmt);
 541         err = do_submodule_path(buf, path, fmt, args);
 542         va_end(args);
 543
 544         return err;
 545 }
 546
 547 static void do_git_common_path(struct strbuf *buf,
 548                                const char *fmt,
 549                                va_list args)
 550 {
 551         strbuf_addstr(buf, get_git_common_dir());
 552         if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 553                 strbuf_addch(buf, '/');
 554         strbuf_vaddf(buf, fmt, args);
 555         strbuf_cleanup_path(buf);
 556 }
 557
 558 const char *git_common_path(const char *fmt, ...)
 559 {
 560         struct strbuf *pathname = get_pathname();
 561         va_list args;
 562         va_start(args, fmt);
 563         do_git_common_path(pathname, fmt, args);
 564         va_end(args);
 565         return pathname->buf;
 566 }
 567
 568 void strbuf_git_common_path(struct strbuf *sb, const char *fmt, ...)
 569 {
 570         va_list args;
 571         va_start(args, fmt);
 572         do_git_common_path(sb, fmt, args);
 573         va_end(args);
 574 }
 575
 576 int validate_headref(const char *path)
 577 {
 578         struct stat st;
 579         char *buf, buffer[256];
 580         unsigned char sha1[20];
 581         int fd;
 582         ssize_t len;
 583
 584         if (lstat(path, &st) < 0)
 585                 return -1;
 586
 587         /* Make sure it is a "refs/.." symlink */
 588         if (S_ISLNK(st.st_mode)) {
 589                 len = readlink(path, buffer, sizeof(buffer)-1);
 590                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 591                         return 0;
 592                 return -1;
 593         }
 594
 595         /*
 596          * Anything else, just open it and try to see if it is a symbolic ref.
 597          */
 598         fd = open(path, O_RDONLY);
 599         if (fd < 0)
 600                 return -1;
 601         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 602         close(fd);
 603
 604         /*
 605          * Is it a symbolic ref?
 606          */
 607         if (len < 4)
 608                 return -1;
 609         if (!memcmp("ref:", buffer, 4)) {
 610                 buf = buffer + 4;
 611                 len -= 4;
 612                 while (len && isspace(*buf))
 613                         buf++, len--;
 614                 if (len >= 5 && !memcmp("refs/", buf, 5))
 615                         return 0;
 616         }
 617
 618         /*
 619          * Is this a detached HEAD?
 620          */
 621         if (!get_sha1_hex(buffer, sha1))
 622                 return 0;
 623
 624         return -1;
 625 }
 626
 627 static struct passwd *getpw_str(const char *username, size_t len)
 628 {
 629         struct passwd *pw;
 630         char *username_z = xmemdupz(username, len);
 631         pw = getpwnam(username_z);
 632         free(username_z);
 633         return pw;
 634 }
 635
 636 /*
 637  * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 638  * then it is a newly allocated string. Returns NULL on getpw failure or
 639  * if path is NULL.
 640  */
 641 char *expand_user_path(const char *path)
 642 {
 643         struct strbuf user_path = STRBUF_INIT;
 644         const char *to_copy = path;
 645
 646         if (path == NULL)
 647                 goto return_null;
 648         if (path[0] == '~') {
 649                 const char *first_slash = strchrnul(path, '/');
 650                 const char *username = path + 1;
 651                 size_t username_len = first_slash - username;
 652                 if (username_len == 0) {
 653                         const char *home = getenv("HOME");
 654                         if (!home)
 655                                 goto return_null;
 656                         strbuf_addstr(&user_path, home);
 657 #ifdef GIT_WINDOWS_NATIVE
 658                         convert_slashes(user_path.buf);
 659 #endif
 660                 } else {
 661                         struct passwd *pw = getpw_str(username, username_len);
 662                         if (!pw)
 663                                 goto return_null;
 664                         strbuf_addstr(&user_path, pw->pw_dir);
 665                 }
 666                 to_copy = first_slash;
 667         }
 668         strbuf_addstr(&user_path, to_copy);
 669         return strbuf_detach(&user_path, NULL);
 670 return_null:
 671         strbuf_release(&user_path);
 672         return NULL;
 673 }
 674
 675 /*
 676  * First, one directory to try is determined by the following algorithm.
 677  *
 678  * (0) If "strict" is given, the path is used as given and no DWIM is
 679  *     done. Otherwise:
 680  * (1) "~/path" to mean path under the running user's home directory;
 681  * (2) "~user/path" to mean path under named user's home directory;
 682  * (3) "relative/path" to mean cwd relative directory; or
 683  * (4) "/absolute/path" to mean absolute directory.
 684  *
 685  * Unless "strict" is given, we check "%s/.git", "%s", "%s.git/.git", "%s.git"
 686  * in this order. We select the first one that is a valid git repository, and
 687  * chdir() to it. If none match, or we fail to chdir, we return NULL.
 688  *
 689  * If all goes well, we return the directory we used to chdir() (but
 690  * before ~user is expanded), avoiding getcwd() resolving symbolic
 691  * links.  User relative paths are also returned as they are given,
 692  * except DWIM suffixing.
 693  */
 694 const char *enter_repo(const char *path, int strict)
 695 {
 696         static struct strbuf validated_path = STRBUF_INIT;
 697         static struct strbuf used_path = STRBUF_INIT;
 698
 699         if (!path)
 700                 return NULL;
 701
 702         if (!strict) {
 703                 static const char *suffix[] = {
 704                         "/.git", "", ".git/.git", ".git", NULL,
 705                 };
 706                 const char *gitfile;
 707                 int len = strlen(path);
 708                 int i;
 709                 while ((1 < len) && (path[len-1] == '/'))
 710                         len--;
 711
 712                 /*
 713                  * We can handle arbitrary-sized buffers, but this remains as a
 714                  * sanity check on untrusted input.
 715                  */
 716                 if (PATH_MAX <= len)
 717                         return NULL;
 718
 719                 strbuf_reset(&used_path);
 720                 strbuf_reset(&validated_path);
 721                 strbuf_add(&used_path, path, len);
 722                 strbuf_add(&validated_path, path, len);
 723
 724                 if (used_path.buf[0] == '~') {
 725                         char *newpath = expand_user_path(used_path.buf);
 726                         if (!newpath)
 727                                 return NULL;
 728                         strbuf_attach(&used_path, newpath, strlen(newpath),
 729                                       strlen(newpath));
 730                 }
 731                 for (i = 0; suffix[i]; i++) {
 732                         struct stat st;
 733                         size_t baselen = used_path.len;
 734                         strbuf_addstr(&used_path, suffix[i]);
 735                         if (!stat(used_path.buf, &st) &&
 736                             (S_ISREG(st.st_mode) ||
 737                             (S_ISDIR(st.st_mode) && is_git_directory(used_path.buf)))) {
 738                                 strbuf_addstr(&validated_path, suffix[i]);
 739                                 break;
 740                         }
 741                         strbuf_setlen(&used_path, baselen);
 742                 }
 743                 if (!suffix[i])
 744                         return NULL;
 745                 gitfile = read_gitfile(used_path.buf);
 746                 if (gitfile) {
 747                         strbuf_reset(&used_path);
 748                         strbuf_addstr(&used_path, gitfile);
 749                 }
 750                 if (chdir(used_path.buf))
 751                         return NULL;
 752                 path = validated_path.buf;
 753         }
 754         else {
 755                 const char *gitfile = read_gitfile(path);
 756                 if (gitfile)
 757                         path = gitfile;
 758                 if (chdir(path))
 759                         return NULL;
 760         }
 761
 762         if (is_git_directory(".")) {
 763                 set_git_dir(".");
 764                 check_repository_format();
 765                 return path;
 766         }
 767
 768         return NULL;
 769 }
 770
 771 static int calc_shared_perm(int mode)
 772 {
 773         int tweak;
 774
 775         if (get_shared_repository() < 0)
 776                 tweak = -get_shared_repository();
 777         else
 778                 tweak = get_shared_repository();
 779
 780         if (!(mode & S_IWUSR))
 781                 tweak &= ~0222;
 782         if (mode & S_IXUSR)
 783                 /* Copy read bits to execute bits */
 784                 tweak |= (tweak & 0444) >> 2;
 785         if (get_shared_repository() < 0)
 786                 mode = (mode & ~0777) | tweak;
 787         else
 788                 mode |= tweak;
 789
 790         return mode;
 791 }
 792
 793
 794 int adjust_shared_perm(const char *path)
 795 {
 796         int old_mode, new_mode;
 797
 798         if (!get_shared_repository())
 799                 return 0;
 800         if (get_st_mode_bits(path, &old_mode) < 0)
 801                 return -1;
 802
 803         new_mode = calc_shared_perm(old_mode);
 804         if (S_ISDIR(old_mode)) {
 805                 /* Copy read bits to execute bits */
 806                 new_mode |= (new_mode & 0444) >> 2;
 807                 new_mode |= FORCE_DIR_SET_GID;
 808         }
 809
 810         if (((old_mode ^ new_mode) & ~S_IFMT) &&
 811                         chmod(path, (new_mode & ~S_IFMT)) < 0)
 812                 return -2;
 813         return 0;
 814 }
 815
 816 void safe_create_dir(const char *dir, int share)
 817 {
 818         if (mkdir(dir, 0777) < 0) {
 819                 if (errno != EEXIST) {
 820                         perror(dir);
 821                         exit(1);
 822                 }
 823         }
 824         else if (share && adjust_shared_perm(dir))
 825                 die(_("Could not make %s writable by group"), dir);
 826 }
 827
 828 static int have_same_root(const char *path1, const char *path2)
 829 {
 830         int is_abs1, is_abs2;
 831
 832         is_abs1 = is_absolute_path(path1);
 833         is_abs2 = is_absolute_path(path2);
 834         return (is_abs1 && is_abs2 && tolower(path1[0]) == tolower(path2[0])) ||
 835                (!is_abs1 && !is_abs2);
 836 }
 837
 838 /*
 839  * Give path as relative to prefix.
 840  *
 841  * The strbuf may or may not be used, so do not assume it contains the
 842  * returned path.
 843  */
 844 const char *relative_path(const char *in, const char *prefix,
 845                           struct strbuf *sb)
 846 {
 847         int in_len = in ? strlen(in) : 0;
 848         int prefix_len = prefix ? strlen(prefix) : 0;
 849         int in_off = 0;
 850         int prefix_off = 0;
 851         int i = 0, j = 0;
 852
 853         if (!in_len)
 854                 return "./";
 855         else if (!prefix_len)
 856                 return in;
 857
 858         if (have_same_root(in, prefix))
 859                 /* bypass dos_drive, for "c:" is identical to "C:" */
 860                 i = j = has_dos_drive_prefix(in);
 861         else {
 862                 return in;
 863         }
 864
 865         while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
 866                 if (is_dir_sep(prefix[i])) {
 867                         while (is_dir_sep(prefix[i]))
 868                                 i++;
 869                         while (is_dir_sep(in[j]))
 870                                 j++;
 871                         prefix_off = i;
 872                         in_off = j;
 873                 } else {
 874                         i++;
 875                         j++;
 876                 }
 877         }
 878
 879         if (
 880             /* "prefix" seems like prefix of "in" */
 881             i >= prefix_len &&
 882             /*
 883              * but "/foo" is not a prefix of "/foobar"
 884              * (i.e. prefix not end with '/')
 885              */
 886             prefix_off < prefix_len) {
 887                 if (j >= in_len) {
 888                         /* in="/a/b", prefix="/a/b" */
 889                         in_off = in_len;
 890                 } else if (is_dir_sep(in[j])) {
 891                         /* in="/a/b/c", prefix="/a/b" */
 892                         while (is_dir_sep(in[j]))
 893                                 j++;
 894                         in_off = j;
 895                 } else {
 896                         /* in="/a/bbb/c", prefix="/a/b" */
 897                         i = prefix_off;
 898                 }
 899         } else if (
 900                    /* "in" is short than "prefix" */
 901                    j >= in_len &&
 902                    /* "in" not end with '/' */
 903                    in_off < in_len) {
 904                 if (is_dir_sep(prefix[i])) {
 905                         /* in="/a/b", prefix="/a/b/c/" */
 906                         while (is_dir_sep(prefix[i]))
 907                                 i++;
 908                         in_off = in_len;
 909                 }
 910         }
 911         in += in_off;
 912         in_len -= in_off;
 913
 914         if (i >= prefix_len) {
 915                 if (!in_len)
 916                         return "./";
 917                 else
 918                         return in;
 919         }
 920
 921         strbuf_reset(sb);
 922         strbuf_grow(sb, in_len);
 923
 924         while (i < prefix_len) {
 925                 if (is_dir_sep(prefix[i])) {
 926                         strbuf_addstr(sb, "../");
 927                         while (is_dir_sep(prefix[i]))
 928                                 i++;
 929                         continue;
 930                 }
 931                 i++;
 932         }
 933         if (!is_dir_sep(prefix[prefix_len - 1]))
 934                 strbuf_addstr(sb, "../");
 935
 936         strbuf_addstr(sb, in);
 937
 938         return sb->buf;
 939 }
 940
 941 /*
 942  * A simpler implementation of relative_path
 943  *
 944  * Get relative path by removing "prefix" from "in". This function
 945  * first appears in v1.5.6-1-g044bbbc, and makes git_dir shorter
 946  * to increase performance when traversing the path to work_tree.
 947  */
 948 const char *remove_leading_path(const char *in, const char *prefix)
 949 {
 950         static struct strbuf buf = STRBUF_INIT;
 951         int i = 0, j = 0;
 952
 953         if (!prefix || !prefix[0])
 954                 return in;
 955         while (prefix[i]) {
 956                 if (is_dir_sep(prefix[i])) {
 957                         if (!is_dir_sep(in[j]))
 958                                 return in;
 959                         while (is_dir_sep(prefix[i]))
 960                                 i++;
 961                         while (is_dir_sep(in[j]))
 962                                 j++;
 963                         continue;
 964                 } else if (in[j] != prefix[i]) {
 965                         return in;
 966                 }
 967                 i++;
 968                 j++;
 969         }
 970         if (
 971             /* "/foo" is a prefix of "/foo" */
 972             in[j] &&
 973             /* "/foo" is not a prefix of "/foobar" */
 974             !is_dir_sep(prefix[i-1]) && !is_dir_sep(in[j])
 975            )
 976                 return in;
 977         while (is_dir_sep(in[j]))
 978                 j++;
 979
 980         strbuf_reset(&buf);
 981         if (!in[j])
 982                 strbuf_addstr(&buf, ".");
 983         else
 984                 strbuf_addstr(&buf, in + j);
 985         return buf.buf;
 986 }
 987
 988 /*
 989  * It is okay if dst == src, but they should not overlap otherwise.
 990  *
 991  * Performs the following normalizations on src, storing the result in dst:
 992  * - Ensures that components are separated by '/' (Windows only)
 993  * - Squashes sequences of '/'.
 994  * - Removes "." components.
 995  * - Removes ".." components, and the components the precede them.
 996  * Returns failure (non-zero) if a ".." component appears as first path
 997  * component anytime during the normalization. Otherwise, returns success (0).
 998  *
 999  * Note that this function is purely textual.  It does not follow symlinks,
1000  * verify the existence of the path, or make any system calls.
1001  *
1002  * prefix_len != NULL is for a specific case of prefix_pathspec():
1003  * assume that src == dst and src[0..prefix_len-1] is already
1004  * normalized, any time "../" eats up to the prefix_len part,
1005  * prefix_len is reduced. In the end prefix_len is the remaining
1006  * prefix that has not been overridden by user pathspec.
1007  *
1008  * NEEDSWORK: This function doesn't perform normalization w.r.t. trailing '/'.
1009  * For everything but the root folder itself, the normalized path should not
1010  * end with a '/', then the callers need to be fixed up accordingly.
1011  *
1012  */
1013 int normalize_path_copy_len(char *dst, const char *src, int *prefix_len)
1014 {
1015         char *dst0;
1016         int i;
1017
1018         for (i = has_dos_drive_prefix(src); i > 0; i--)
1019                 *dst++ = *src++;
1020         dst0 = dst;
1021
1022         if (is_dir_sep(*src)) {
1023                 *dst++ = '/';
1024                 while (is_dir_sep(*src))
1025                         src++;
1026         }
1027
1028         for (;;) {
1029                 char c = *src;
1030
1031                 /*
1032                  * A path component that begins with . could be
1033                  * special:
1034                  * (1) "." and ends   -- ignore and terminate.
1035                  * (2) "./"           -- ignore them, eat slash and continue.
1036                  * (3) ".." and ends  -- strip one and terminate.
1037                  * (4) "../"          -- strip one, eat slash and continue.
1038                  */
1039                 if (c == '.') {
1040                         if (!src[1]) {
1041                                 /* (1) */
1042                                 src++;
1043                         } else if (is_dir_sep(src[1])) {
1044                                 /* (2) */
1045                                 src += 2;
1046                                 while (is_dir_sep(*src))
1047                                         src++;
1048                                 continue;
1049                         } else if (src[1] == '.') {
1050                                 if (!src[2]) {
1051                                         /* (3) */
1052                                         src += 2;
1053                                         goto up_one;
1054                                 } else if (is_dir_sep(src[2])) {
1055                                         /* (4) */
1056                                         src += 3;
1057                                         while (is_dir_sep(*src))
1058                                                 src++;
1059                                         goto up_one;
1060                                 }
1061                         }
1062                 }
1063
1064                 /* copy up to the next '/', and eat all '/' */
1065                 while ((c = *src++) != '\0' && !is_dir_sep(c))
1066                         *dst++ = c;
1067                 if (is_dir_sep(c)) {
1068                         *dst++ = '/';
1069                         while (is_dir_sep(c))
1070                                 c = *src++;
1071                         src--;
1072                 } else if (!c)
1073                         break;
1074                 continue;
1075
1076         up_one:
1077                 /*
1078                  * dst0..dst is prefix portion, and dst[-1] is '/';
1079                  * go up one level.
1080                  */
1081                 dst--;  /* go to trailing '/' */
1082                 if (dst <= dst0)
1083                         return -1;
1084                 /* Windows: dst[-1] cannot be backslash anymore */
1085                 while (dst0 < dst && dst[-1] != '/')
1086                         dst--;
1087                 if (prefix_len && *prefix_len > dst - dst0)
1088                         *prefix_len = dst - dst0;
1089         }
1090         *dst = '\0';
1091         return 0;
1092 }
1093
1094 int normalize_path_copy(char *dst, const char *src)
1095 {
1096         return normalize_path_copy_len(dst, src, NULL);
1097 }
1098
1099 /*
1100  * path = Canonical absolute path
1101  * prefixes = string_list containing normalized, absolute paths without
1102  * trailing slashes (except for the root directory, which is denoted by "/").
1103  *
1104  * Determines, for each path in prefixes, whether the "prefix"
1105  * is an ancestor directory of path.  Returns the length of the longest
1106  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
1107  * is an ancestor.  (Note that this means 0 is returned if prefixes is
1108  * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
1109  * are not considered to be their own ancestors.  path must be in a
1110  * canonical form: empty components, or "." or ".." components are not
1111  * allowed.
1112  */
1113 int longest_ancestor_length(const char *path, struct string_list *prefixes)
1114 {
1115         int i, max_len = -1;
1116
1117         if (!strcmp(path, "/"))
1118                 return -1;
1119
1120         for (i = 0; i < prefixes->nr; i++) {
1121                 const char *ceil = prefixes->items[i].string;
1122                 int len = strlen(ceil);
1123
1124                 if (len == 1 && ceil[0] == '/')
1125                         len = 0; /* root matches anything, with length 0 */
1126                 else if (!strncmp(path, ceil, len) && path[len] == '/')
1127                         ; /* match of length len */
1128                 else
1129                         continue; /* no match */
1130
1131                 if (len > max_len)
1132                         max_len = len;
1133         }
1134
1135         return max_len;
1136 }
1137
1138 /* strip arbitrary amount of directory separators at end of path */
1139 static inline int chomp_trailing_dir_sep(const char *path, int len)
1140 {
1141         while (len && is_dir_sep(path[len - 1]))
1142                 len--;
1143         return len;
1144 }
1145
1146 /*
1147  * If path ends with suffix (complete path components), returns the
1148  * part before suffix (sans trailing directory separators).
1149  * Otherwise returns NULL.
1150  */
1151 char *strip_path_suffix(const char *path, const char *suffix)
1152 {
1153         int path_len = strlen(path), suffix_len = strlen(suffix);
1154
1155         while (suffix_len) {
1156                 if (!path_len)
1157                         return NULL;
1158
1159                 if (is_dir_sep(path[path_len - 1])) {
1160                         if (!is_dir_sep(suffix[suffix_len - 1]))
1161                                 return NULL;
1162                         path_len = chomp_trailing_dir_sep(path, path_len);
1163                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
1164                 }
1165                 else if (path[--path_len] != suffix[--suffix_len])
1166                         return NULL;
1167         }
1168
1169         if (path_len && !is_dir_sep(path[path_len - 1]))
1170                 return NULL;
1171         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
1172 }
1173
1174 int daemon_avoid_alias(const char *p)
1175 {
1176         int sl, ndot;
1177
1178         /*
1179          * This resurrects the belts and suspenders paranoia check by HPA
1180          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
1181          * does not do getcwd() based path canonicalization.
1182          *
1183          * sl becomes true immediately after seeing '/' and continues to
1184          * be true as long as dots continue after that without intervening
1185          * non-dot character.
1186          */
1187         if (!p || (*p != '/' && *p != '~'))
1188                 return -1;
1189         sl = 1; ndot = 0;
1190         p++;
1191
1192         while (1) {
1193                 char ch = *p++;
1194                 if (sl) {
1195                         if (ch == '.')
1196                                 ndot++;
1197                         else if (ch == '/') {
1198                                 if (ndot < 3)
1199                                         /* reject //, /./ and /../ */
1200                                         return -1;
1201                                 ndot = 0;
1202                         }
1203                         else if (ch == 0) {
1204                                 if (0 < ndot && ndot < 3)
1205                                         /* reject /.$ and /..$ */
1206                                         return -1;
1207                                 return 0;
1208                         }
1209                         else
1210                                 sl = ndot = 0;
1211                 }
1212                 else if (ch == 0)
1213                         return 0;
1214                 else if (ch == '/') {
1215                         sl = 1;
1216                         ndot = 0;
1217                 }
1218         }
1219 }
1220
1221 static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
1222 {
1223         if (len < skip)
1224                 return 0;
1225         len -= skip;
1226         path += skip;
1227         while (len-- > 0) {
1228                 char c = *(path++);
1229                 if (c != ' ' && c != '.')
1230                         return 0;
1231         }
1232         return 1;
1233 }
1234
1235 int is_ntfs_dotgit(const char *name)
1236 {
1237         int len;
1238
1239         for (len = 0; ; len++)
1240                 if (!name[len] || name[len] == '\\' || is_dir_sep(name[len])) {
1241                         if (only_spaces_and_periods(name, len, 4) &&
1242                                         !strncasecmp(name, ".git", 4))
1243                                 return 1;
1244                         if (only_spaces_and_periods(name, len, 5) &&
1245                                         !strncasecmp(name, "git~1", 5))
1246                                 return 1;
1247                         if (name[len] != '\\')
1248                                 return 0;
1249                         name += len + 1;
1250                         len = -1;
1251                 }
1252 }
1253
1254 char *xdg_config_home(const char *filename)
1255 {
1256         const char *home, *config_home;
1257
1258         assert(filename);
1259         config_home = getenv("XDG_CONFIG_HOME");
1260         if (config_home && *config_home)
1261                 return mkpathdup("%s/git/%s", config_home, filename);
1262
1263         home = getenv("HOME");
1264         if (home)
1265                 return mkpathdup("%s/.config/git/%s", home, filename);
1266         return NULL;
1267 }
1268
1269 GIT_PATH_FUNC(git_path_cherry_pick_head, "CHERRY_PICK_HEAD")
1270 GIT_PATH_FUNC(git_path_revert_head, "REVERT_HEAD")
1271 GIT_PATH_FUNC(git_path_squash_msg, "SQUASH_MSG")
1272 GIT_PATH_FUNC(git_path_merge_msg, "MERGE_MSG")
1273 GIT_PATH_FUNC(git_path_merge_rr, "MERGE_RR")
1274 GIT_PATH_FUNC(git_path_merge_mode, "MERGE_MODE")
1275 GIT_PATH_FUNC(git_path_merge_head, "MERGE_HEAD")
1276 GIT_PATH_FUNC(git_path_fetch_head, "FETCH_HEAD")
1277 GIT_PATH_FUNC(git_path_shallow, "shallow")