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[index];
  29         index = (index + 1) % ARRAY_SIZE(pathname_array);
  30         strbuf_reset(sb);
  31         return sb;
  32 }
  33
  34 static char *cleanup_path(char *path)
  35 {
  36         /* Clean it up */
  37         if (!memcmp(path, "./", 2)) {
  38                 path += 2;
  39                 while (*path == '/')
  40                         path++;
  41         }
  42         return path;
  43 }
  44
  45 static void strbuf_cleanup_path(struct strbuf *sb)
  46 {
  47         char *path = cleanup_path(sb->buf);
  48         if (path > sb->buf)
  49                 strbuf_remove(sb, 0, path - sb->buf);
  50 }
  51
  52 char *mksnpath(char *buf, size_t n, const char *fmt, ...)
  53 {
  54         va_list args;
  55         unsigned len;
  56
  57         va_start(args, fmt);
  58         len = vsnprintf(buf, n, fmt, args);
  59         va_end(args);
  60         if (len >= n) {
  61                 strlcpy(buf, bad_path, n);
  62                 return buf;
  63         }
  64         return cleanup_path(buf);
  65 }
  66
  67 static int dir_prefix(const char *buf, const char *dir)
  68 {
  69         int len = strlen(dir);
  70         return !strncmp(buf, dir, len) &&
  71                 (is_dir_sep(buf[len]) || buf[len] == '\0');
  72 }
  73
  74 /* $buf =~ m|$dir/+$file| but without regex */
  75 static int is_dir_file(const char *buf, const char *dir, const char *file)
  76 {
  77         int len = strlen(dir);
  78         if (strncmp(buf, dir, len) || !is_dir_sep(buf[len]))
  79                 return 0;
  80         while (is_dir_sep(buf[len]))
  81                 len++;
  82         return !strcmp(buf + len, file);
  83 }
  84
  85 static void replace_dir(struct strbuf *buf, int len, const char *newdir)
  86 {
  87         int newlen = strlen(newdir);
  88         int need_sep = (buf->buf[len] && !is_dir_sep(buf->buf[len])) &&
  89                 !is_dir_sep(newdir[newlen - 1]);
  90         if (need_sep)
  91                 len--;   /* keep one char, to be replaced with '/'  */
  92         strbuf_splice(buf, 0, len, newdir, newlen);
  93         if (need_sep)
  94                 buf->buf[newlen] = '/';
  95 }
  96
  97 struct common_dir {
  98         /* Not considered garbage for report_linked_checkout_garbage */
  99         unsigned ignore_garbage:1;
 100         unsigned is_dir:1;
 101         /* Not common even though its parent is */
 102         unsigned exclude:1;
 103         const char *dirname;
 104 };
 105
 106 static struct common_dir common_list[] = {
 107         { 0, 1, 0, "branches" },
 108         { 0, 1, 0, "hooks" },
 109         { 0, 1, 0, "info" },
 110         { 0, 0, 1, "info/sparse-checkout" },
 111         { 1, 1, 0, "logs" },
 112         { 1, 1, 1, "logs/HEAD" },
 113         { 0, 1, 1, "logs/refs/bisect" },
 114         { 0, 1, 0, "lost-found" },
 115         { 0, 1, 0, "objects" },
 116         { 0, 1, 0, "refs" },
 117         { 0, 1, 1, "refs/bisect" },
 118         { 0, 1, 0, "remotes" },
 119         { 0, 1, 0, "worktrees" },
 120         { 0, 1, 0, "rr-cache" },
 121         { 0, 1, 0, "svn" },
 122         { 0, 0, 0, "config" },
 123         { 1, 0, 0, "gc.pid" },
 124         { 0, 0, 0, "packed-refs" },
 125         { 0, 0, 0, "shallow" },
 126         { 0, 0, 0, NULL }
 127 };
 128
 129 /*
 130  * A compressed trie.  A trie node consists of zero or more characters that
 131  * are common to all elements with this prefix, optionally followed by some
 132  * children.  If value is not NULL, the trie node is a terminal node.
 133  *
 134  * For example, consider the following set of strings:
 135  * abc
 136  * def
 137  * definite
 138  * definition
 139  *
 140  * The trie would look like:
 141  * root: len = 0, children a and d non-NULL, value = NULL.
 142  *    a: len = 2, contents = bc, value = (data for "abc")
 143  *    d: len = 2, contents = ef, children i non-NULL, value = (data for "def")
 144  *       i: len = 3, contents = nit, children e and i non-NULL, value = NULL
 145  *           e: len = 0, children all NULL, value = (data for "definite")
 146  *           i: len = 2, contents = on, children all NULL,
 147  *              value = (data for "definition")
 148  */
 149 struct trie {
 150         struct trie *children[256];
 151         int len;
 152         char *contents;
 153         void *value;
 154 };
 155
 156 static struct trie *make_trie_node(const char *key, void *value)
 157 {
 158         struct trie *new_node = xcalloc(1, sizeof(*new_node));
 159         new_node->len = strlen(key);
 160         if (new_node->len) {
 161                 new_node->contents = xmalloc(new_node->len);
 162                 memcpy(new_node->contents, key, new_node->len);
 163         }
 164         new_node->value = value;
 165         return new_node;
 166 }
 167
 168 /*
 169  * Add a key/value pair to a trie.  The key is assumed to be \0-terminated.
 170  * If there was an existing value for this key, return it.
 171  */
 172 static void *add_to_trie(struct trie *root, const char *key, void *value)
 173 {
 174         struct trie *child;
 175         void *old;
 176         int i;
 177
 178         if (!*key) {
 179                 /* we have reached the end of the key */
 180                 old = root->value;
 181                 root->value = value;
 182                 return old;
 183         }
 184
 185         for (i = 0; i < root->len; i++) {
 186                 if (root->contents[i] == key[i])
 187                         continue;
 188
 189                 /*
 190                  * Split this node: child will contain this node's
 191                  * existing children.
 192                  */
 193                 child = malloc(sizeof(*child));
 194                 memcpy(child->children, root->children, sizeof(root->children));
 195
 196                 child->len = root->len - i - 1;
 197                 if (child->len) {
 198                         child->contents = xstrndup(root->contents + i + 1,
 199                                                    child->len);
 200                 }
 201                 child->value = root->value;
 202                 root->value = NULL;
 203                 root->len = i;
 204
 205                 memset(root->children, 0, sizeof(root->children));
 206                 root->children[(unsigned char)root->contents[i]] = child;
 207
 208                 /* This is the newly-added child. */
 209                 root->children[(unsigned char)key[i]] =
 210                         make_trie_node(key + i + 1, value);
 211                 return NULL;
 212         }
 213
 214         /* We have matched the entire compressed section */
 215         if (key[i]) {
 216                 child = root->children[(unsigned char)key[root->len]];
 217                 if (child) {
 218                         return add_to_trie(child, key + root->len + 1, value);
 219                 } else {
 220                         child = make_trie_node(key + root->len + 1, value);
 221                         root->children[(unsigned char)key[root->len]] = child;
 222                         return NULL;
 223                 }
 224         }
 225
 226         old = root->value;
 227         root->value = value;
 228         return old;
 229 }
 230
 231 typedef int (*match_fn)(const char *unmatched, void *data, void *baton);
 232
 233 /*
 234  * Search a trie for some key.  Find the longest /-or-\0-terminated
 235  * prefix of the key for which the trie contains a value.  Call fn
 236  * with the unmatched portion of the key and the found value, and
 237  * return its return value.  If there is no such prefix, return -1.
 238  *
 239  * The key is partially normalized: consecutive slashes are skipped.
 240  *
 241  * For example, consider the trie containing only [refs,
 242  * refs/worktree] (both with values).
 243  *
 244  * | key             | unmatched  | val from node | return value |
 245  * |-----------------|------------|---------------|--------------|
 246  * | a               | not called | n/a           | -1           |
 247  * | refs            | \0         | refs          | as per fn    |
 248  * | refs/           | /          | refs          | as per fn    |
 249  * | refs/w          | /w         | refs          | as per fn    |
 250  * | refs/worktree   | \0         | refs/worktree | as per fn    |
 251  * | refs/worktree/  | /          | refs/worktree | as per fn    |
 252  * | refs/worktree/a | /a         | refs/worktree | as per fn    |
 253  * |-----------------|------------|---------------|--------------|
 254  *
 255  */
 256 static int trie_find(struct trie *root, const char *key, match_fn fn,
 257                      void *baton)
 258 {
 259         int i;
 260         int result;
 261         struct trie *child;
 262
 263         if (!*key) {
 264                 /* we have reached the end of the key */
 265                 if (root->value && !root->len)
 266                         return fn(key, root->value, baton);
 267                 else
 268                         return -1;
 269         }
 270
 271         for (i = 0; i < root->len; i++) {
 272                 /* Partial path normalization: skip consecutive slashes. */
 273                 if (key[i] == '/' && key[i+1] == '/') {
 274                         key++;
 275                         continue;
 276                 }
 277                 if (root->contents[i] != key[i])
 278                         return -1;
 279         }
 280
 281         /* Matched the entire compressed section */
 282         key += i;
 283         if (!*key)
 284                 /* End of key */
 285                 return fn(key, root->value, baton);
 286
 287         /* Partial path normalization: skip consecutive slashes */
 288         while (key[0] == '/' && key[1] == '/')
 289                 key++;
 290
 291         child = root->children[(unsigned char)*key];
 292         if (child)
 293                 result = trie_find(child, key + 1, fn, baton);
 294         else
 295                 result = -1;
 296
 297         if (result >= 0 || (*key != '/' && *key != 0))
 298                 return result;
 299         if (root->value)
 300                 return fn(key, root->value, baton);
 301         else
 302                 return -1;
 303 }
 304
 305 static struct trie common_trie;
 306 static int common_trie_done_setup;
 307
 308 static void init_common_trie(void)
 309 {
 310         struct common_dir *p;
 311
 312         if (common_trie_done_setup)
 313                 return;
 314
 315         for (p = common_list; p->dirname; p++)
 316                 add_to_trie(&common_trie, p->dirname, p);
 317
 318         common_trie_done_setup = 1;
 319 }
 320
 321 /*
 322  * Helper function for update_common_dir: returns 1 if the dir
 323  * prefix is common.
 324  */
 325 static int check_common(const char *unmatched, void *value, void *baton)
 326 {
 327         struct common_dir *dir = value;
 328
 329         if (!dir)
 330                 return 0;
 331
 332         if (dir->is_dir && (unmatched[0] == 0 || unmatched[0] == '/'))
 333                 return !dir->exclude;
 334
 335         if (!dir->is_dir && unmatched[0] == 0)
 336                 return !dir->exclude;
 337
 338         return 0;
 339 }
 340
 341 static void update_common_dir(struct strbuf *buf, int git_dir_len,
 342                               const char *common_dir)
 343 {
 344         char *base = buf->buf + git_dir_len;
 345         init_common_trie();
 346         if (!common_dir)
 347                 common_dir = get_git_common_dir();
 348         if (trie_find(&common_trie, base, check_common, NULL) > 0)
 349                 replace_dir(buf, git_dir_len, common_dir);
 350 }
 351
 352 void report_linked_checkout_garbage(void)
 353 {
 354         struct strbuf sb = STRBUF_INIT;
 355         const struct common_dir *p;
 356         int len;
 357
 358         if (!git_common_dir_env)
 359                 return;
 360         strbuf_addf(&sb, "%s/", get_git_dir());
 361         len = sb.len;
 362         for (p = common_list; p->dirname; p++) {
 363                 const char *path = p->dirname;
 364                 if (p->ignore_garbage)
 365                         continue;
 366                 strbuf_setlen(&sb, len);
 367                 strbuf_addstr(&sb, path);
 368                 if (file_exists(sb.buf))
 369                         report_garbage(PACKDIR_FILE_GARBAGE, sb.buf);
 370         }
 371         strbuf_release(&sb);
 372 }
 373
 374 static void adjust_git_path(struct strbuf *buf, int git_dir_len)
 375 {
 376         const char *base = buf->buf + git_dir_len;
 377         if (git_graft_env && is_dir_file(base, "info", "grafts"))
 378                 strbuf_splice(buf, 0, buf->len,
 379                               get_graft_file(), strlen(get_graft_file()));
 380         else if (git_index_env && !strcmp(base, "index"))
 381                 strbuf_splice(buf, 0, buf->len,
 382                               get_index_file(), strlen(get_index_file()));
 383         else if (git_db_env && dir_prefix(base, "objects"))
 384                 replace_dir(buf, git_dir_len + 7, get_object_directory());
 385         else if (git_hooks_path && dir_prefix(base, "hooks"))
 386                 replace_dir(buf, git_dir_len + 5, git_hooks_path);
 387         else if (git_common_dir_env)
 388                 update_common_dir(buf, git_dir_len, NULL);
 389 }
 390
 391 static void do_git_path(const struct worktree *wt, struct strbuf *buf,
 392                         const char *fmt, va_list args)
 393 {
 394         int gitdir_len;
 395         strbuf_addstr(buf, get_worktree_git_dir(wt));
 396         if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 397                 strbuf_addch(buf, '/');
 398         gitdir_len = buf->len;
 399         strbuf_vaddf(buf, fmt, args);
 400         adjust_git_path(buf, gitdir_len);
 401         strbuf_cleanup_path(buf);
 402 }
 403
 404 char *git_path_buf(struct strbuf *buf, const char *fmt, ...)
 405 {
 406         va_list args;
 407         strbuf_reset(buf);
 408         va_start(args, fmt);
 409         do_git_path(NULL, buf, fmt, args);
 410         va_end(args);
 411         return buf->buf;
 412 }
 413
 414 void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
 415 {
 416         va_list args;
 417         va_start(args, fmt);
 418         do_git_path(NULL, sb, fmt, args);
 419         va_end(args);
 420 }
 421
 422 const char *git_path(const char *fmt, ...)
 423 {
 424         struct strbuf *pathname = get_pathname();
 425         va_list args;
 426         va_start(args, fmt);
 427         do_git_path(NULL, pathname, fmt, args);
 428         va_end(args);
 429         return pathname->buf;
 430 }
 431
 432 char *git_pathdup(const char *fmt, ...)
 433 {
 434         struct strbuf path = STRBUF_INIT;
 435         va_list args;
 436         va_start(args, fmt);
 437         do_git_path(NULL, &path, fmt, args);
 438         va_end(args);
 439         return strbuf_detach(&path, NULL);
 440 }
 441
 442 char *mkpathdup(const char *fmt, ...)
 443 {
 444         struct strbuf sb = STRBUF_INIT;
 445         va_list args;
 446         va_start(args, fmt);
 447         strbuf_vaddf(&sb, fmt, args);
 448         va_end(args);
 449         strbuf_cleanup_path(&sb);
 450         return strbuf_detach(&sb, NULL);
 451 }
 452
 453 const char *mkpath(const char *fmt, ...)
 454 {
 455         va_list args;
 456         struct strbuf *pathname = get_pathname();
 457         va_start(args, fmt);
 458         strbuf_vaddf(pathname, fmt, args);
 459         va_end(args);
 460         return cleanup_path(pathname->buf);
 461 }
 462
 463 const char *worktree_git_path(const struct worktree *wt, const char *fmt, ...)
 464 {
 465         struct strbuf *pathname = get_pathname();
 466         va_list args;
 467         va_start(args, fmt);
 468         do_git_path(wt, pathname, fmt, args);
 469         va_end(args);
 470         return pathname->buf;
 471 }
 472
 473 /* Returns 0 on success, negative on failure. */
 474 #define SUBMODULE_PATH_ERR_NOT_CONFIGURED -1
 475 static int do_submodule_path(struct strbuf *buf, const char *path,
 476                              const char *fmt, va_list args)
 477 {
 478         const char *git_dir;
 479         struct strbuf git_submodule_common_dir = STRBUF_INIT;
 480         struct strbuf git_submodule_dir = STRBUF_INIT;
 481         const struct submodule *sub;
 482         int err = 0;
 483
 484         strbuf_addstr(buf, path);
 485         strbuf_complete(buf, '/');
 486         strbuf_addstr(buf, ".git");
 487
 488         git_dir = read_gitfile(buf->buf);
 489         if (git_dir) {
 490                 strbuf_reset(buf);
 491                 strbuf_addstr(buf, git_dir);
 492         }
 493         if (!is_git_directory(buf->buf)) {
 494                 gitmodules_config();
 495                 sub = submodule_from_path(null_sha1, path);
 496                 if (!sub) {
 497                         err = SUBMODULE_PATH_ERR_NOT_CONFIGURED;
 498                         goto cleanup;
 499                 }
 500                 strbuf_reset(buf);
 501                 strbuf_git_path(buf, "%s/%s", "modules", sub->name);
 502         }
 503
 504         strbuf_addch(buf, '/');
 505         strbuf_addbuf(&git_submodule_dir, buf);
 506
 507         strbuf_vaddf(buf, fmt, args);
 508
 509         if (get_common_dir_noenv(&git_submodule_common_dir, git_submodule_dir.buf))
 510                 update_common_dir(buf, git_submodule_dir.len, git_submodule_common_dir.buf);
 511
 512         strbuf_cleanup_path(buf);
 513
 514 cleanup:
 515         strbuf_release(&git_submodule_dir);
 516         strbuf_release(&git_submodule_common_dir);
 517
 518         return err;
 519 }
 520
 521 char *git_pathdup_submodule(const char *path, const char *fmt, ...)
 522 {
 523         int err;
 524         va_list args;
 525         struct strbuf buf = STRBUF_INIT;
 526         va_start(args, fmt);
 527         err = do_submodule_path(&buf, path, fmt, args);
 528         va_end(args);
 529         if (err) {
 530                 strbuf_release(&buf);
 531                 return NULL;
 532         }
 533         return strbuf_detach(&buf, NULL);
 534 }
 535
 536 int strbuf_git_path_submodule(struct strbuf *buf, const char *path,
 537                               const char *fmt, ...)
 538 {
 539         int err;
 540         va_list args;
 541         va_start(args, fmt);
 542         err = do_submodule_path(buf, path, fmt, args);
 543         va_end(args);
 544
 545         return err;
 546 }
 547
 548 static void do_git_common_path(struct strbuf *buf,
 549                                const char *fmt,
 550                                va_list args)
 551 {
 552         strbuf_addstr(buf, get_git_common_dir());
 553         if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 554                 strbuf_addch(buf, '/');
 555         strbuf_vaddf(buf, fmt, args);
 556         strbuf_cleanup_path(buf);
 557 }
 558
 559 const char *git_common_path(const char *fmt, ...)
 560 {
 561         struct strbuf *pathname = get_pathname();
 562         va_list args;
 563         va_start(args, fmt);
 564         do_git_common_path(pathname, fmt, args);
 565         va_end(args);
 566         return pathname->buf;
 567 }
 568
 569 void strbuf_git_common_path(struct strbuf *sb, const char *fmt, ...)
 570 {
 571         va_list args;
 572         va_start(args, fmt);
 573         do_git_common_path(sb, fmt, args);
 574         va_end(args);
 575 }
 576
 577 int validate_headref(const char *path)
 578 {
 579         struct stat st;
 580         char *buf, buffer[256];
 581         unsigned char sha1[20];
 582         int fd;
 583         ssize_t len;
 584
 585         if (lstat(path, &st) < 0)
 586                 return -1;
 587
 588         /* Make sure it is a "refs/.." symlink */
 589         if (S_ISLNK(st.st_mode)) {
 590                 len = readlink(path, buffer, sizeof(buffer)-1);
 591                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 592                         return 0;
 593                 return -1;
 594         }
 595
 596         /*
 597          * Anything else, just open it and try to see if it is a symbolic ref.
 598          */
 599         fd = open(path, O_RDONLY);
 600         if (fd < 0)
 601                 return -1;
 602         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 603         close(fd);
 604
 605         /*
 606          * Is it a symbolic ref?
 607          */
 608         if (len < 4)
 609                 return -1;
 610         if (!memcmp("ref:", buffer, 4)) {
 611                 buf = buffer + 4;
 612                 len -= 4;
 613                 while (len && isspace(*buf))
 614                         buf++, len--;
 615                 if (len >= 5 && !memcmp("refs/", buf, 5))
 616                         return 0;
 617         }
 618
 619         /*
 620          * Is this a detached HEAD?
 621          */
 622         if (!get_sha1_hex(buffer, sha1))
 623                 return 0;
 624
 625         return -1;
 626 }
 627
 628 static struct passwd *getpw_str(const char *username, size_t len)
 629 {
 630         struct passwd *pw;
 631         char *username_z = xmemdupz(username, len);
 632         pw = getpwnam(username_z);
 633         free(username_z);
 634         return pw;
 635 }
 636
 637 /*
 638  * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 639  * then it is a newly allocated string. Returns NULL on getpw failure or
 640  * if path is NULL.
 641  */
 642 char *expand_user_path(const char *path)
 643 {
 644         struct strbuf user_path = STRBUF_INIT;
 645         const char *to_copy = path;
 646
 647         if (path == NULL)
 648                 goto return_null;
 649         if (path[0] == '~') {
 650                 const char *first_slash = strchrnul(path, '/');
 651                 const char *username = path + 1;
 652                 size_t username_len = first_slash - username;
 653                 if (username_len == 0) {
 654                         const char *home = getenv("HOME");
 655                         if (!home)
 656                                 goto return_null;
 657                         strbuf_addstr(&user_path, home);
 658 #ifdef GIT_WINDOWS_NATIVE
 659                         convert_slashes(user_path.buf);
 660 #endif
 661                 } else {
 662                         struct passwd *pw = getpw_str(username, username_len);
 663                         if (!pw)
 664                                 goto return_null;
 665                         strbuf_addstr(&user_path, pw->pw_dir);
 666                 }
 667                 to_copy = first_slash;
 668         }
 669         strbuf_addstr(&user_path, to_copy);
 670         return strbuf_detach(&user_path, NULL);
 671 return_null:
 672         strbuf_release(&user_path);
 673         return NULL;
 674 }
 675
 676 /*
 677  * First, one directory to try is determined by the following algorithm.
 678  *
 679  * (0) If "strict" is given, the path is used as given and no DWIM is
 680  *     done. Otherwise:
 681  * (1) "~/path" to mean path under the running user's home directory;
 682  * (2) "~user/path" to mean path under named user's home directory;
 683  * (3) "relative/path" to mean cwd relative directory; or
 684  * (4) "/absolute/path" to mean absolute directory.
 685  *
 686  * Unless "strict" is given, we check "%s/.git", "%s", "%s.git/.git", "%s.git"
 687  * in this order. We select the first one that is a valid git repository, and
 688  * chdir() to it. If none match, or we fail to chdir, we return NULL.
 689  *
 690  * If all goes well, we return the directory we used to chdir() (but
 691  * before ~user is expanded), avoiding getcwd() resolving symbolic
 692  * links.  User relative paths are also returned as they are given,
 693  * except DWIM suffixing.
 694  */
 695 const char *enter_repo(const char *path, int strict)
 696 {
 697         static struct strbuf validated_path = STRBUF_INIT;
 698         static struct strbuf used_path = STRBUF_INIT;
 699
 700         if (!path)
 701                 return NULL;
 702
 703         if (!strict) {
 704                 static const char *suffix[] = {
 705                         "/.git", "", ".git/.git", ".git", NULL,
 706                 };
 707                 const char *gitfile;
 708                 int len = strlen(path);
 709                 int i;
 710                 while ((1 < len) && (path[len-1] == '/'))
 711                         len--;
 712
 713                 /*
 714                  * We can handle arbitrary-sized buffers, but this remains as a
 715                  * sanity check on untrusted input.
 716                  */
 717                 if (PATH_MAX <= len)
 718                         return NULL;
 719
 720                 strbuf_reset(&used_path);
 721                 strbuf_reset(&validated_path);
 722                 strbuf_add(&used_path, path, len);
 723                 strbuf_add(&validated_path, path, len);
 724
 725                 if (used_path.buf[0] == '~') {
 726                         char *newpath = expand_user_path(used_path.buf);
 727                         if (!newpath)
 728                                 return NULL;
 729                         strbuf_attach(&used_path, newpath, strlen(newpath),
 730                                       strlen(newpath));
 731                 }
 732                 for (i = 0; suffix[i]; i++) {
 733                         struct stat st;
 734                         size_t baselen = used_path.len;
 735                         strbuf_addstr(&used_path, suffix[i]);
 736                         if (!stat(used_path.buf, &st) &&
 737                             (S_ISREG(st.st_mode) ||
 738                             (S_ISDIR(st.st_mode) && is_git_directory(used_path.buf)))) {
 739                                 strbuf_addstr(&validated_path, suffix[i]);
 740                                 break;
 741                         }
 742                         strbuf_setlen(&used_path, baselen);
 743                 }
 744                 if (!suffix[i])
 745                         return NULL;
 746                 gitfile = read_gitfile(used_path.buf);
 747                 if (gitfile) {
 748                         strbuf_reset(&used_path);
 749                         strbuf_addstr(&used_path, gitfile);
 750                 }
 751                 if (chdir(used_path.buf))
 752                         return NULL;
 753                 path = validated_path.buf;
 754         }
 755         else {
 756                 const char *gitfile = read_gitfile(path);
 757                 if (gitfile)
 758                         path = gitfile;
 759                 if (chdir(path))
 760                         return NULL;
 761         }
 762
 763         if (is_git_directory(".")) {
 764                 set_git_dir(".");
 765                 check_repository_format();
 766                 return path;
 767         }
 768
 769         return NULL;
 770 }
 771
 772 static int calc_shared_perm(int mode)
 773 {
 774         int tweak;
 775
 776         if (get_shared_repository() < 0)
 777                 tweak = -get_shared_repository();
 778         else
 779                 tweak = get_shared_repository();
 780
 781         if (!(mode & S_IWUSR))
 782                 tweak &= ~0222;
 783         if (mode & S_IXUSR)
 784                 /* Copy read bits to execute bits */
 785                 tweak |= (tweak & 0444) >> 2;
 786         if (get_shared_repository() < 0)
 787                 mode = (mode & ~0777) | tweak;
 788         else
 789                 mode |= tweak;
 790
 791         return mode;
 792 }
 793
 794
 795 int adjust_shared_perm(const char *path)
 796 {
 797         int old_mode, new_mode;
 798
 799         if (!get_shared_repository())
 800                 return 0;
 801         if (get_st_mode_bits(path, &old_mode) < 0)
 802                 return -1;
 803
 804         new_mode = calc_shared_perm(old_mode);
 805         if (S_ISDIR(old_mode)) {
 806                 /* Copy read bits to execute bits */
 807                 new_mode |= (new_mode & 0444) >> 2;
 808                 new_mode |= FORCE_DIR_SET_GID;
 809         }
 810
 811         if (((old_mode ^ new_mode) & ~S_IFMT) &&
 812                         chmod(path, (new_mode & ~S_IFMT)) < 0)
 813                 return -2;
 814         return 0;
 815 }
 816
 817 void safe_create_dir(const char *dir, int share)
 818 {
 819         if (mkdir(dir, 0777) < 0) {
 820                 if (errno != EEXIST) {
 821                         perror(dir);
 822                         exit(1);
 823                 }
 824         }
 825         else if (share && adjust_shared_perm(dir))
 826                 die(_("Could not make %s writable by group"), dir);
 827 }
 828
 829 static int have_same_root(const char *path1, const char *path2)
 830 {
 831         int is_abs1, is_abs2;
 832
 833         is_abs1 = is_absolute_path(path1);
 834         is_abs2 = is_absolute_path(path2);
 835         return (is_abs1 && is_abs2 && tolower(path1[0]) == tolower(path2[0])) ||
 836                (!is_abs1 && !is_abs2);
 837 }
 838
 839 /*
 840  * Give path as relative to prefix.
 841  *
 842  * The strbuf may or may not be used, so do not assume it contains the
 843  * returned path.
 844  */
 845 const char *relative_path(const char *in, const char *prefix,
 846                           struct strbuf *sb)
 847 {
 848         int in_len = in ? strlen(in) : 0;
 849         int prefix_len = prefix ? strlen(prefix) : 0;
 850         int in_off = 0;
 851         int prefix_off = 0;
 852         int i = 0, j = 0;
 853
 854         if (!in_len)
 855                 return "./";
 856         else if (!prefix_len)
 857                 return in;
 858
 859         if (have_same_root(in, prefix))
 860                 /* bypass dos_drive, for "c:" is identical to "C:" */
 861                 i = j = has_dos_drive_prefix(in);
 862         else {
 863                 return in;
 864         }
 865
 866         while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
 867                 if (is_dir_sep(prefix[i])) {
 868                         while (is_dir_sep(prefix[i]))
 869                                 i++;
 870                         while (is_dir_sep(in[j]))
 871                                 j++;
 872                         prefix_off = i;
 873                         in_off = j;
 874                 } else {
 875                         i++;
 876                         j++;
 877                 }
 878         }
 879
 880         if (
 881             /* "prefix" seems like prefix of "in" */
 882             i >= prefix_len &&
 883             /*
 884              * but "/foo" is not a prefix of "/foobar"
 885              * (i.e. prefix not end with '/')
 886              */
 887             prefix_off < prefix_len) {
 888                 if (j >= in_len) {
 889                         /* in="/a/b", prefix="/a/b" */
 890                         in_off = in_len;
 891                 } else if (is_dir_sep(in[j])) {
 892                         /* in="/a/b/c", prefix="/a/b" */
 893                         while (is_dir_sep(in[j]))
 894                                 j++;
 895                         in_off = j;
 896                 } else {
 897                         /* in="/a/bbb/c", prefix="/a/b" */
 898                         i = prefix_off;
 899                 }
 900         } else if (
 901                    /* "in" is short than "prefix" */
 902                    j >= in_len &&
 903                    /* "in" not end with '/' */
 904                    in_off < in_len) {
 905                 if (is_dir_sep(prefix[i])) {
 906                         /* in="/a/b", prefix="/a/b/c/" */
 907                         while (is_dir_sep(prefix[i]))
 908                                 i++;
 909                         in_off = in_len;
 910                 }
 911         }
 912         in += in_off;
 913         in_len -= in_off;
 914
 915         if (i >= prefix_len) {
 916                 if (!in_len)
 917                         return "./";
 918                 else
 919                         return in;
 920         }
 921
 922         strbuf_reset(sb);
 923         strbuf_grow(sb, in_len);
 924
 925         while (i < prefix_len) {
 926                 if (is_dir_sep(prefix[i])) {
 927                         strbuf_addstr(sb, "../");
 928                         while (is_dir_sep(prefix[i]))
 929                                 i++;
 930                         continue;
 931                 }
 932                 i++;
 933         }
 934         if (!is_dir_sep(prefix[prefix_len - 1]))
 935                 strbuf_addstr(sb, "../");
 936
 937         strbuf_addstr(sb, in);
 938
 939         return sb->buf;
 940 }
 941
 942 /*
 943  * A simpler implementation of relative_path
 944  *
 945  * Get relative path by removing "prefix" from "in". This function
 946  * first appears in v1.5.6-1-g044bbbc, and makes git_dir shorter
 947  * to increase performance when traversing the path to work_tree.
 948  */
 949 const char *remove_leading_path(const char *in, const char *prefix)
 950 {
 951         static struct strbuf buf = STRBUF_INIT;
 952         int i = 0, j = 0;
 953
 954         if (!prefix || !prefix[0])
 955                 return in;
 956         while (prefix[i]) {
 957                 if (is_dir_sep(prefix[i])) {
 958                         if (!is_dir_sep(in[j]))
 959                                 return in;
 960                         while (is_dir_sep(prefix[i]))
 961                                 i++;
 962                         while (is_dir_sep(in[j]))
 963                                 j++;
 964                         continue;
 965                 } else if (in[j] != prefix[i]) {
 966                         return in;
 967                 }
 968                 i++;
 969                 j++;
 970         }
 971         if (
 972             /* "/foo" is a prefix of "/foo" */
 973             in[j] &&
 974             /* "/foo" is not a prefix of "/foobar" */
 975             !is_dir_sep(prefix[i-1]) && !is_dir_sep(in[j])
 976            )
 977                 return in;
 978         while (is_dir_sep(in[j]))
 979                 j++;
 980
 981         strbuf_reset(&buf);
 982         if (!in[j])
 983                 strbuf_addstr(&buf, ".");
 984         else
 985                 strbuf_addstr(&buf, in + j);
 986         return buf.buf;
 987 }
 988
 989 /*
 990  * It is okay if dst == src, but they should not overlap otherwise.
 991  *
 992  * Performs the following normalizations on src, storing the result in dst:
 993  * - Ensures that components are separated by '/' (Windows only)
 994  * - Squashes sequences of '/' except "//server/share" on Windows
 995  * - Removes "." components.
 996  * - Removes ".." components, and the components the precede them.
 997  * Returns failure (non-zero) if a ".." component appears as first path
 998  * component anytime during the normalization. Otherwise, returns success (0).
 999  *
1000  * Note that this function is purely textual.  It does not follow symlinks,
1001  * verify the existence of the path, or make any system calls.
1002  *
1003  * prefix_len != NULL is for a specific case of prefix_pathspec():
1004  * assume that src == dst and src[0..prefix_len-1] is already
1005  * normalized, any time "../" eats up to the prefix_len part,
1006  * prefix_len is reduced. In the end prefix_len is the remaining
1007  * prefix that has not been overridden by user pathspec.
1008  *
1009  * NEEDSWORK: This function doesn't perform normalization w.r.t. trailing '/'.
1010  * For everything but the root folder itself, the normalized path should not
1011  * end with a '/', then the callers need to be fixed up accordingly.
1012  *
1013  */
1014 int normalize_path_copy_len(char *dst, const char *src, int *prefix_len)
1015 {
1016         char *dst0;
1017         const char *end;
1018
1019         /*
1020          * Copy initial part of absolute path: "/", "C:/", "//server/share/".
1021          */
1022         end = src + offset_1st_component(src);
1023         while (src < end) {
1024                 char c = *src++;
1025                 if (is_dir_sep(c))
1026                         c = '/';
1027                 *dst++ = c;
1028         }
1029         dst0 = dst;
1030
1031         while (is_dir_sep(*src))
1032                 src++;
1033
1034         for (;;) {
1035                 char c = *src;
1036
1037                 /*
1038                  * A path component that begins with . could be
1039                  * special:
1040                  * (1) "." and ends   -- ignore and terminate.
1041                  * (2) "./"           -- ignore them, eat slash and continue.
1042                  * (3) ".." and ends  -- strip one and terminate.
1043                  * (4) "../"          -- strip one, eat slash and continue.
1044                  */
1045                 if (c == '.') {
1046                         if (!src[1]) {
1047                                 /* (1) */
1048                                 src++;
1049                         } else if (is_dir_sep(src[1])) {
1050                                 /* (2) */
1051                                 src += 2;
1052                                 while (is_dir_sep(*src))
1053                                         src++;
1054                                 continue;
1055                         } else if (src[1] == '.') {
1056                                 if (!src[2]) {
1057                                         /* (3) */
1058                                         src += 2;
1059                                         goto up_one;
1060                                 } else if (is_dir_sep(src[2])) {
1061                                         /* (4) */
1062                                         src += 3;
1063                                         while (is_dir_sep(*src))
1064                                                 src++;
1065                                         goto up_one;
1066                                 }
1067                         }
1068                 }
1069
1070                 /* copy up to the next '/', and eat all '/' */
1071                 while ((c = *src++) != '\0' && !is_dir_sep(c))
1072                         *dst++ = c;
1073                 if (is_dir_sep(c)) {
1074                         *dst++ = '/';
1075                         while (is_dir_sep(c))
1076                                 c = *src++;
1077                         src--;
1078                 } else if (!c)
1079                         break;
1080                 continue;
1081
1082         up_one:
1083                 /*
1084                  * dst0..dst is prefix portion, and dst[-1] is '/';
1085                  * go up one level.
1086                  */
1087                 dst--;  /* go to trailing '/' */
1088                 if (dst <= dst0)
1089                         return -1;
1090                 /* Windows: dst[-1] cannot be backslash anymore */
1091                 while (dst0 < dst && dst[-1] != '/')
1092                         dst--;
1093                 if (prefix_len && *prefix_len > dst - dst0)
1094                         *prefix_len = dst - dst0;
1095         }
1096         *dst = '\0';
1097         return 0;
1098 }
1099
1100 int normalize_path_copy(char *dst, const char *src)
1101 {
1102         return normalize_path_copy_len(dst, src, NULL);
1103 }
1104
1105 /*
1106  * path = Canonical absolute path
1107  * prefixes = string_list containing normalized, absolute paths without
1108  * trailing slashes (except for the root directory, which is denoted by "/").
1109  *
1110  * Determines, for each path in prefixes, whether the "prefix"
1111  * is an ancestor directory of path.  Returns the length of the longest
1112  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
1113  * is an ancestor.  (Note that this means 0 is returned if prefixes is
1114  * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
1115  * are not considered to be their own ancestors.  path must be in a
1116  * canonical form: empty components, or "." or ".." components are not
1117  * allowed.
1118  */
1119 int longest_ancestor_length(const char *path, struct string_list *prefixes)
1120 {
1121         int i, max_len = -1;
1122
1123         if (!strcmp(path, "/"))
1124                 return -1;
1125
1126         for (i = 0; i < prefixes->nr; i++) {
1127                 const char *ceil = prefixes->items[i].string;
1128                 int len = strlen(ceil);
1129
1130                 if (len == 1 && ceil[0] == '/')
1131                         len = 0; /* root matches anything, with length 0 */
1132                 else if (!strncmp(path, ceil, len) && path[len] == '/')
1133                         ; /* match of length len */
1134                 else
1135                         continue; /* no match */
1136
1137                 if (len > max_len)
1138                         max_len = len;
1139         }
1140
1141         return max_len;
1142 }
1143
1144 /* strip arbitrary amount of directory separators at end of path */
1145 static inline int chomp_trailing_dir_sep(const char *path, int len)
1146 {
1147         while (len && is_dir_sep(path[len - 1]))
1148                 len--;
1149         return len;
1150 }
1151
1152 /*
1153  * If path ends with suffix (complete path components), returns the
1154  * part before suffix (sans trailing directory separators).
1155  * Otherwise returns NULL.
1156  */
1157 char *strip_path_suffix(const char *path, const char *suffix)
1158 {
1159         int path_len = strlen(path), suffix_len = strlen(suffix);
1160
1161         while (suffix_len) {
1162                 if (!path_len)
1163                         return NULL;
1164
1165                 if (is_dir_sep(path[path_len - 1])) {
1166                         if (!is_dir_sep(suffix[suffix_len - 1]))
1167                                 return NULL;
1168                         path_len = chomp_trailing_dir_sep(path, path_len);
1169                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
1170                 }
1171                 else if (path[--path_len] != suffix[--suffix_len])
1172                         return NULL;
1173         }
1174
1175         if (path_len && !is_dir_sep(path[path_len - 1]))
1176                 return NULL;
1177         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
1178 }
1179
1180 int daemon_avoid_alias(const char *p)
1181 {
1182         int sl, ndot;
1183
1184         /*
1185          * This resurrects the belts and suspenders paranoia check by HPA
1186          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
1187          * does not do getcwd() based path canonicalization.
1188          *
1189          * sl becomes true immediately after seeing '/' and continues to
1190          * be true as long as dots continue after that without intervening
1191          * non-dot character.
1192          */
1193         if (!p || (*p != '/' && *p != '~'))
1194                 return -1;
1195         sl = 1; ndot = 0;
1196         p++;
1197
1198         while (1) {
1199                 char ch = *p++;
1200                 if (sl) {
1201                         if (ch == '.')
1202                                 ndot++;
1203                         else if (ch == '/') {
1204                                 if (ndot < 3)
1205                                         /* reject //, /./ and /../ */
1206                                         return -1;
1207                                 ndot = 0;
1208                         }
1209                         else if (ch == 0) {
1210                                 if (0 < ndot && ndot < 3)
1211                                         /* reject /.$ and /..$ */
1212                                         return -1;
1213                                 return 0;
1214                         }
1215                         else
1216                                 sl = ndot = 0;
1217                 }
1218                 else if (ch == 0)
1219                         return 0;
1220                 else if (ch == '/') {
1221                         sl = 1;
1222                         ndot = 0;
1223                 }
1224         }
1225 }
1226
1227 static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
1228 {
1229         if (len < skip)
1230                 return 0;
1231         len -= skip;
1232         path += skip;
1233         while (len-- > 0) {
1234                 char c = *(path++);
1235                 if (c != ' ' && c != '.')
1236                         return 0;
1237         }
1238         return 1;
1239 }
1240
1241 int is_ntfs_dotgit(const char *name)
1242 {
1243         int len;
1244
1245         for (len = 0; ; len++)
1246                 if (!name[len] || name[len] == '\\' || is_dir_sep(name[len])) {
1247                         if (only_spaces_and_periods(name, len, 4) &&
1248                                         !strncasecmp(name, ".git", 4))
1249                                 return 1;
1250                         if (only_spaces_and_periods(name, len, 5) &&
1251                                         !strncasecmp(name, "git~1", 5))
1252                                 return 1;
1253                         if (name[len] != '\\')
1254                                 return 0;
1255                         name += len + 1;
1256                         len = -1;
1257                 }
1258 }
1259
1260 char *xdg_config_home(const char *filename)
1261 {
1262         const char *home, *config_home;
1263
1264         assert(filename);
1265         config_home = getenv("XDG_CONFIG_HOME");
1266         if (config_home && *config_home)
1267                 return mkpathdup("%s/git/%s", config_home, filename);
1268
1269         home = getenv("HOME");
1270         if (home)
1271                 return mkpathdup("%s/.config/git/%s", home, filename);
1272         return NULL;
1273 }
1274
1275 GIT_PATH_FUNC(git_path_cherry_pick_head, "CHERRY_PICK_HEAD")
1276 GIT_PATH_FUNC(git_path_revert_head, "REVERT_HEAD")
1277 GIT_PATH_FUNC(git_path_squash_msg, "SQUASH_MSG")
1278 GIT_PATH_FUNC(git_path_merge_msg, "MERGE_MSG")
1279 GIT_PATH_FUNC(git_path_merge_rr, "MERGE_RR")
1280 GIT_PATH_FUNC(git_path_merge_mode, "MERGE_MODE")
1281 GIT_PATH_FUNC(git_path_merge_head, "MERGE_HEAD")
1282 GIT_PATH_FUNC(git_path_fetch_head, "FETCH_HEAD")
1283 GIT_PATH_FUNC(git_path_shallow, "shallow")