path.con commit Merge branch 'rs/fsck-null-return-from-lookup' into maint (b0e5269)
   1/*
   2 * Utilities for paths and pathnames
   3 */
   4#include "cache.h"
   5#include "repository.h"
   6#include "strbuf.h"
   7#include "string-list.h"
   8#include "dir.h"
   9#include "worktree.h"
  10#include "submodule-config.h"
  11#include "path.h"
  12
  13static int get_st_mode_bits(const char *path, int *mode)
  14{
  15        struct stat st;
  16        if (lstat(path, &st) < 0)
  17                return -1;
  18        *mode = st.st_mode;
  19        return 0;
  20}
  21
  22static char bad_path[] = "/bad-path/";
  23
  24static struct strbuf *get_pathname(void)
  25{
  26        static struct strbuf pathname_array[4] = {
  27                STRBUF_INIT, STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
  28        };
  29        static int index;
  30        struct strbuf *sb = &pathname_array[index];
  31        index = (index + 1) % ARRAY_SIZE(pathname_array);
  32        strbuf_reset(sb);
  33        return sb;
  34}
  35
  36static const char *cleanup_path(const char *path)
  37{
  38        /* Clean it up */
  39        if (skip_prefix(path, "./", &path)) {
  40                while (*path == '/')
  41                        path++;
  42        }
  43        return path;
  44}
  45
  46static void strbuf_cleanup_path(struct strbuf *sb)
  47{
  48        const char *path = cleanup_path(sb->buf);
  49        if (path > sb->buf)
  50                strbuf_remove(sb, 0, path - sb->buf);
  51}
  52
  53char *mksnpath(char *buf, size_t n, const char *fmt, ...)
  54{
  55        va_list args;
  56        unsigned len;
  57
  58        va_start(args, fmt);
  59        len = vsnprintf(buf, n, fmt, args);
  60        va_end(args);
  61        if (len >= n) {
  62                strlcpy(buf, bad_path, n);
  63                return buf;
  64        }
  65        return (char *)cleanup_path(buf);
  66}
  67
  68static int dir_prefix(const char *buf, const char *dir)
  69{
  70        int len = strlen(dir);
  71        return !strncmp(buf, dir, len) &&
  72                (is_dir_sep(buf[len]) || buf[len] == '\0');
  73}
  74
  75/* $buf =~ m|$dir/+$file| but without regex */
  76static int is_dir_file(const char *buf, const char *dir, const char *file)
  77{
  78        int len = strlen(dir);
  79        if (strncmp(buf, dir, len) || !is_dir_sep(buf[len]))
  80                return 0;
  81        while (is_dir_sep(buf[len]))
  82                len++;
  83        return !strcmp(buf + len, file);
  84}
  85
  86static void replace_dir(struct strbuf *buf, int len, const char *newdir)
  87{
  88        int newlen = strlen(newdir);
  89        int need_sep = (buf->buf[len] && !is_dir_sep(buf->buf[len])) &&
  90                !is_dir_sep(newdir[newlen - 1]);
  91        if (need_sep)
  92                len--;   /* keep one char, to be replaced with '/'  */
  93        strbuf_splice(buf, 0, len, newdir, newlen);
  94        if (need_sep)
  95                buf->buf[newlen] = '/';
  96}
  97
  98struct common_dir {
  99        /* Not considered garbage for report_linked_checkout_garbage */
 100        unsigned ignore_garbage:1;
 101        unsigned is_dir:1;
 102        /* Not common even though its parent is */
 103        unsigned exclude:1;
 104        const char *dirname;
 105};
 106
 107static struct common_dir common_list[] = {
 108        { 0, 1, 0, "branches" },
 109        { 0, 1, 0, "hooks" },
 110        { 0, 1, 0, "info" },
 111        { 0, 0, 1, "info/sparse-checkout" },
 112        { 1, 1, 0, "logs" },
 113        { 1, 1, 1, "logs/HEAD" },
 114        { 0, 1, 1, "logs/refs/bisect" },
 115        { 0, 1, 0, "lost-found" },
 116        { 0, 1, 0, "objects" },
 117        { 0, 1, 0, "refs" },
 118        { 0, 1, 1, "refs/bisect" },
 119        { 0, 1, 0, "remotes" },
 120        { 0, 1, 0, "worktrees" },
 121        { 0, 1, 0, "rr-cache" },
 122        { 0, 1, 0, "svn" },
 123        { 0, 0, 0, "config" },
 124        { 1, 0, 0, "gc.pid" },
 125        { 0, 0, 0, "packed-refs" },
 126        { 0, 0, 0, "shallow" },
 127        { 0, 0, 0, NULL }
 128};
 129
 130/*
 131 * A compressed trie.  A trie node consists of zero or more characters that
 132 * are common to all elements with this prefix, optionally followed by some
 133 * children.  If value is not NULL, the trie node is a terminal node.
 134 *
 135 * For example, consider the following set of strings:
 136 * abc
 137 * def
 138 * definite
 139 * definition
 140 *
 141 * The trie would look like:
 142 * root: len = 0, children a and d non-NULL, value = NULL.
 143 *    a: len = 2, contents = bc, value = (data for "abc")
 144 *    d: len = 2, contents = ef, children i non-NULL, value = (data for "def")
 145 *       i: len = 3, contents = nit, children e and i non-NULL, value = NULL
 146 *           e: len = 0, children all NULL, value = (data for "definite")
 147 *           i: len = 2, contents = on, children all NULL,
 148 *              value = (data for "definition")
 149 */
 150struct trie {
 151        struct trie *children[256];
 152        int len;
 153        char *contents;
 154        void *value;
 155};
 156
 157static struct trie *make_trie_node(const char *key, void *value)
 158{
 159        struct trie *new_node = xcalloc(1, sizeof(*new_node));
 160        new_node->len = strlen(key);
 161        if (new_node->len) {
 162                new_node->contents = xmalloc(new_node->len);
 163                memcpy(new_node->contents, key, new_node->len);
 164        }
 165        new_node->value = value;
 166        return new_node;
 167}
 168
 169/*
 170 * Add a key/value pair to a trie.  The key is assumed to be \0-terminated.
 171 * If there was an existing value for this key, return it.
 172 */
 173static void *add_to_trie(struct trie *root, const char *key, void *value)
 174{
 175        struct trie *child;
 176        void *old;
 177        int i;
 178
 179        if (!*key) {
 180                /* we have reached the end of the key */
 181                old = root->value;
 182                root->value = value;
 183                return old;
 184        }
 185
 186        for (i = 0; i < root->len; i++) {
 187                if (root->contents[i] == key[i])
 188                        continue;
 189
 190                /*
 191                 * Split this node: child will contain this node's
 192                 * existing children.
 193                 */
 194                child = malloc(sizeof(*child));
 195                memcpy(child->children, root->children, sizeof(root->children));
 196
 197                child->len = root->len - i - 1;
 198                if (child->len) {
 199                        child->contents = xstrndup(root->contents + i + 1,
 200                                                   child->len);
 201                }
 202                child->value = root->value;
 203                root->value = NULL;
 204                root->len = i;
 205
 206                memset(root->children, 0, sizeof(root->children));
 207                root->children[(unsigned char)root->contents[i]] = child;
 208
 209                /* This is the newly-added child. */
 210                root->children[(unsigned char)key[i]] =
 211                        make_trie_node(key + i + 1, value);
 212                return NULL;
 213        }
 214
 215        /* We have matched the entire compressed section */
 216        if (key[i]) {
 217                child = root->children[(unsigned char)key[root->len]];
 218                if (child) {
 219                        return add_to_trie(child, key + root->len + 1, value);
 220                } else {
 221                        child = make_trie_node(key + root->len + 1, value);
 222                        root->children[(unsigned char)key[root->len]] = child;
 223                        return NULL;
 224                }
 225        }
 226
 227        old = root->value;
 228        root->value = value;
 229        return old;
 230}
 231
 232typedef int (*match_fn)(const char *unmatched, void *data, void *baton);
 233
 234/*
 235 * Search a trie for some key.  Find the longest /-or-\0-terminated
 236 * prefix of the key for which the trie contains a value.  Call fn
 237 * with the unmatched portion of the key and the found value, and
 238 * return its return value.  If there is no such prefix, return -1.
 239 *
 240 * The key is partially normalized: consecutive slashes are skipped.
 241 *
 242 * For example, consider the trie containing only [refs,
 243 * refs/worktree] (both with values).
 244 *
 245 * | key             | unmatched  | val from node | return value |
 246 * |-----------------|------------|---------------|--------------|
 247 * | a               | not called | n/a           | -1           |
 248 * | refs            | \0         | refs          | as per fn    |
 249 * | refs/           | /          | refs          | as per fn    |
 250 * | refs/w          | /w         | refs          | as per fn    |
 251 * | refs/worktree   | \0         | refs/worktree | as per fn    |
 252 * | refs/worktree/  | /          | refs/worktree | as per fn    |
 253 * | refs/worktree/a | /a         | refs/worktree | as per fn    |
 254 * |-----------------|------------|---------------|--------------|
 255 *
 256 */
 257static int trie_find(struct trie *root, const char *key, match_fn fn,
 258                     void *baton)
 259{
 260        int i;
 261        int result;
 262        struct trie *child;
 263
 264        if (!*key) {
 265                /* we have reached the end of the key */
 266                if (root->value && !root->len)
 267                        return fn(key, root->value, baton);
 268                else
 269                        return -1;
 270        }
 271
 272        for (i = 0; i < root->len; i++) {
 273                /* Partial path normalization: skip consecutive slashes. */
 274                if (key[i] == '/' && key[i+1] == '/') {
 275                        key++;
 276                        continue;
 277                }
 278                if (root->contents[i] != key[i])
 279                        return -1;
 280        }
 281
 282        /* Matched the entire compressed section */
 283        key += i;
 284        if (!*key)
 285                /* End of key */
 286                return fn(key, root->value, baton);
 287
 288        /* Partial path normalization: skip consecutive slashes */
 289        while (key[0] == '/' && key[1] == '/')
 290                key++;
 291
 292        child = root->children[(unsigned char)*key];
 293        if (child)
 294                result = trie_find(child, key + 1, fn, baton);
 295        else
 296                result = -1;
 297
 298        if (result >= 0 || (*key != '/' && *key != 0))
 299                return result;
 300        if (root->value)
 301                return fn(key, root->value, baton);
 302        else
 303                return -1;
 304}
 305
 306static struct trie common_trie;
 307static int common_trie_done_setup;
 308
 309static void init_common_trie(void)
 310{
 311        struct common_dir *p;
 312
 313        if (common_trie_done_setup)
 314                return;
 315
 316        for (p = common_list; p->dirname; p++)
 317                add_to_trie(&common_trie, p->dirname, p);
 318
 319        common_trie_done_setup = 1;
 320}
 321
 322/*
 323 * Helper function for update_common_dir: returns 1 if the dir
 324 * prefix is common.
 325 */
 326static int check_common(const char *unmatched, void *value, void *baton)
 327{
 328        struct common_dir *dir = value;
 329
 330        if (!dir)
 331                return 0;
 332
 333        if (dir->is_dir && (unmatched[0] == 0 || unmatched[0] == '/'))
 334                return !dir->exclude;
 335
 336        if (!dir->is_dir && unmatched[0] == 0)
 337                return !dir->exclude;
 338
 339        return 0;
 340}
 341
 342static void update_common_dir(struct strbuf *buf, int git_dir_len,
 343                              const char *common_dir)
 344{
 345        char *base = buf->buf + git_dir_len;
 346        init_common_trie();
 347        if (trie_find(&common_trie, base, check_common, NULL) > 0)
 348                replace_dir(buf, git_dir_len, common_dir);
 349}
 350
 351void report_linked_checkout_garbage(void)
 352{
 353        struct strbuf sb = STRBUF_INIT;
 354        const struct common_dir *p;
 355        int len;
 356
 357        if (!the_repository->different_commondir)
 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
 373static void adjust_git_path(const struct repository *repo,
 374                            struct strbuf *buf, int git_dir_len)
 375{
 376        const char *base = buf->buf + git_dir_len;
 377        if (is_dir_file(base, "info", "grafts"))
 378                strbuf_splice(buf, 0, buf->len,
 379                              repo->graft_file, strlen(repo->graft_file));
 380        else if (!strcmp(base, "index"))
 381                strbuf_splice(buf, 0, buf->len,
 382                              repo->index_file, strlen(repo->index_file));
 383        else if (dir_prefix(base, "objects"))
 384                replace_dir(buf, git_dir_len + 7, repo->objectdir);
 385        else if (git_hooks_path && dir_prefix(base, "hooks"))
 386                replace_dir(buf, git_dir_len + 5, git_hooks_path);
 387        else if (repo->different_commondir)
 388                update_common_dir(buf, git_dir_len, repo->commondir);
 389}
 390
 391static void strbuf_worktree_gitdir(struct strbuf *buf,
 392                                   const struct repository *repo,
 393                                   const struct worktree *wt)
 394{
 395        if (!wt)
 396                strbuf_addstr(buf, repo->gitdir);
 397        else if (!wt->id)
 398                strbuf_addstr(buf, repo->commondir);
 399        else
 400                strbuf_git_common_path(buf, repo, "worktrees/%s", wt->id);
 401}
 402
 403static void do_git_path(const struct repository *repo,
 404                        const struct worktree *wt, struct strbuf *buf,
 405                        const char *fmt, va_list args)
 406{
 407        int gitdir_len;
 408        strbuf_worktree_gitdir(buf, repo, wt);
 409        if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 410                strbuf_addch(buf, '/');
 411        gitdir_len = buf->len;
 412        strbuf_vaddf(buf, fmt, args);
 413        if (!wt)
 414                adjust_git_path(repo, buf, gitdir_len);
 415        strbuf_cleanup_path(buf);
 416}
 417
 418char *repo_git_path(const struct repository *repo,
 419                    const char *fmt, ...)
 420{
 421        struct strbuf path = STRBUF_INIT;
 422        va_list args;
 423        va_start(args, fmt);
 424        do_git_path(repo, NULL, &path, fmt, args);
 425        va_end(args);
 426        return strbuf_detach(&path, NULL);
 427}
 428
 429void strbuf_repo_git_path(struct strbuf *sb,
 430                          const struct repository *repo,
 431                          const char *fmt, ...)
 432{
 433        va_list args;
 434        va_start(args, fmt);
 435        do_git_path(repo, NULL, sb, fmt, args);
 436        va_end(args);
 437}
 438
 439char *git_path_buf(struct strbuf *buf, const char *fmt, ...)
 440{
 441        va_list args;
 442        strbuf_reset(buf);
 443        va_start(args, fmt);
 444        do_git_path(the_repository, NULL, buf, fmt, args);
 445        va_end(args);
 446        return buf->buf;
 447}
 448
 449void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
 450{
 451        va_list args;
 452        va_start(args, fmt);
 453        do_git_path(the_repository, NULL, sb, fmt, args);
 454        va_end(args);
 455}
 456
 457const char *git_path(const char *fmt, ...)
 458{
 459        struct strbuf *pathname = get_pathname();
 460        va_list args;
 461        va_start(args, fmt);
 462        do_git_path(the_repository, NULL, pathname, fmt, args);
 463        va_end(args);
 464        return pathname->buf;
 465}
 466
 467char *git_pathdup(const char *fmt, ...)
 468{
 469        struct strbuf path = STRBUF_INIT;
 470        va_list args;
 471        va_start(args, fmt);
 472        do_git_path(the_repository, NULL, &path, fmt, args);
 473        va_end(args);
 474        return strbuf_detach(&path, NULL);
 475}
 476
 477char *mkpathdup(const char *fmt, ...)
 478{
 479        struct strbuf sb = STRBUF_INIT;
 480        va_list args;
 481        va_start(args, fmt);
 482        strbuf_vaddf(&sb, fmt, args);
 483        va_end(args);
 484        strbuf_cleanup_path(&sb);
 485        return strbuf_detach(&sb, NULL);
 486}
 487
 488const char *mkpath(const char *fmt, ...)
 489{
 490        va_list args;
 491        struct strbuf *pathname = get_pathname();
 492        va_start(args, fmt);
 493        strbuf_vaddf(pathname, fmt, args);
 494        va_end(args);
 495        return cleanup_path(pathname->buf);
 496}
 497
 498const char *worktree_git_path(const struct worktree *wt, const char *fmt, ...)
 499{
 500        struct strbuf *pathname = get_pathname();
 501        va_list args;
 502        va_start(args, fmt);
 503        do_git_path(the_repository, wt, pathname, fmt, args);
 504        va_end(args);
 505        return pathname->buf;
 506}
 507
 508static void do_worktree_path(const struct repository *repo,
 509                             struct strbuf *buf,
 510                             const char *fmt, va_list args)
 511{
 512        strbuf_addstr(buf, repo->worktree);
 513        if(buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 514                strbuf_addch(buf, '/');
 515
 516        strbuf_vaddf(buf, fmt, args);
 517        strbuf_cleanup_path(buf);
 518}
 519
 520char *repo_worktree_path(const struct repository *repo, const char *fmt, ...)
 521{
 522        struct strbuf path = STRBUF_INIT;
 523        va_list args;
 524
 525        if (!repo->worktree)
 526                return NULL;
 527
 528        va_start(args, fmt);
 529        do_worktree_path(repo, &path, fmt, args);
 530        va_end(args);
 531
 532        return strbuf_detach(&path, NULL);
 533}
 534
 535void strbuf_repo_worktree_path(struct strbuf *sb,
 536                               const struct repository *repo,
 537                               const char *fmt, ...)
 538{
 539        va_list args;
 540
 541        if (!repo->worktree)
 542                return;
 543
 544        va_start(args, fmt);
 545        do_worktree_path(repo, sb, fmt, args);
 546        va_end(args);
 547}
 548
 549/* Returns 0 on success, negative on failure. */
 550static int do_submodule_path(struct strbuf *buf, const char *path,
 551                             const char *fmt, va_list args)
 552{
 553        struct strbuf git_submodule_common_dir = STRBUF_INIT;
 554        struct strbuf git_submodule_dir = STRBUF_INIT;
 555        int ret;
 556
 557        ret = submodule_to_gitdir(&git_submodule_dir, path);
 558        if (ret)
 559                goto cleanup;
 560
 561        strbuf_complete(&git_submodule_dir, '/');
 562        strbuf_addbuf(buf, &git_submodule_dir);
 563        strbuf_vaddf(buf, fmt, args);
 564
 565        if (get_common_dir_noenv(&git_submodule_common_dir, git_submodule_dir.buf))
 566                update_common_dir(buf, git_submodule_dir.len, git_submodule_common_dir.buf);
 567
 568        strbuf_cleanup_path(buf);
 569
 570cleanup:
 571        strbuf_release(&git_submodule_dir);
 572        strbuf_release(&git_submodule_common_dir);
 573        return ret;
 574}
 575
 576char *git_pathdup_submodule(const char *path, const char *fmt, ...)
 577{
 578        int err;
 579        va_list args;
 580        struct strbuf buf = STRBUF_INIT;
 581        va_start(args, fmt);
 582        err = do_submodule_path(&buf, path, fmt, args);
 583        va_end(args);
 584        if (err) {
 585                strbuf_release(&buf);
 586                return NULL;
 587        }
 588        return strbuf_detach(&buf, NULL);
 589}
 590
 591int strbuf_git_path_submodule(struct strbuf *buf, const char *path,
 592                              const char *fmt, ...)
 593{
 594        int err;
 595        va_list args;
 596        va_start(args, fmt);
 597        err = do_submodule_path(buf, path, fmt, args);
 598        va_end(args);
 599
 600        return err;
 601}
 602
 603static void do_git_common_path(const struct repository *repo,
 604                               struct strbuf *buf,
 605                               const char *fmt,
 606                               va_list args)
 607{
 608        strbuf_addstr(buf, repo->commondir);
 609        if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 610                strbuf_addch(buf, '/');
 611        strbuf_vaddf(buf, fmt, args);
 612        strbuf_cleanup_path(buf);
 613}
 614
 615const char *git_common_path(const char *fmt, ...)
 616{
 617        struct strbuf *pathname = get_pathname();
 618        va_list args;
 619        va_start(args, fmt);
 620        do_git_common_path(the_repository, pathname, fmt, args);
 621        va_end(args);
 622        return pathname->buf;
 623}
 624
 625void strbuf_git_common_path(struct strbuf *sb,
 626                            const struct repository *repo,
 627                            const char *fmt, ...)
 628{
 629        va_list args;
 630        va_start(args, fmt);
 631        do_git_common_path(repo, sb, fmt, args);
 632        va_end(args);
 633}
 634
 635int validate_headref(const char *path)
 636{
 637        struct stat st;
 638        char buffer[256];
 639        const char *refname;
 640        struct object_id oid;
 641        int fd;
 642        ssize_t len;
 643
 644        if (lstat(path, &st) < 0)
 645                return -1;
 646
 647        /* Make sure it is a "refs/.." symlink */
 648        if (S_ISLNK(st.st_mode)) {
 649                len = readlink(path, buffer, sizeof(buffer)-1);
 650                if (len >= 5 && !memcmp("refs/", buffer, 5))
 651                        return 0;
 652                return -1;
 653        }
 654
 655        /*
 656         * Anything else, just open it and try to see if it is a symbolic ref.
 657         */
 658        fd = open(path, O_RDONLY);
 659        if (fd < 0)
 660                return -1;
 661        len = read_in_full(fd, buffer, sizeof(buffer)-1);
 662        close(fd);
 663
 664        if (len < 0)
 665                return -1;
 666        buffer[len] = '\0';
 667
 668        /*
 669         * Is it a symbolic ref?
 670         */
 671        if (skip_prefix(buffer, "ref:", &refname)) {
 672                while (isspace(*refname))
 673                        refname++;
 674                if (starts_with(refname, "refs/"))
 675                        return 0;
 676        }
 677
 678        /*
 679         * Is this a detached HEAD?
 680         */
 681        if (!get_oid_hex(buffer, &oid))
 682                return 0;
 683
 684        return -1;
 685}
 686
 687static struct passwd *getpw_str(const char *username, size_t len)
 688{
 689        struct passwd *pw;
 690        char *username_z = xmemdupz(username, len);
 691        pw = getpwnam(username_z);
 692        free(username_z);
 693        return pw;
 694}
 695
 696/*
 697 * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 698 * then it is a newly allocated string. Returns NULL on getpw failure or
 699 * if path is NULL.
 700 *
 701 * If real_home is true, real_path($HOME) is used in the expansion.
 702 */
 703char *expand_user_path(const char *path, int real_home)
 704{
 705        struct strbuf user_path = STRBUF_INIT;
 706        const char *to_copy = path;
 707
 708        if (path == NULL)
 709                goto return_null;
 710        if (path[0] == '~') {
 711                const char *first_slash = strchrnul(path, '/');
 712                const char *username = path + 1;
 713                size_t username_len = first_slash - username;
 714                if (username_len == 0) {
 715                        const char *home = getenv("HOME");
 716                        if (!home)
 717                                goto return_null;
 718                        if (real_home)
 719                                strbuf_addstr(&user_path, real_path(home));
 720                        else
 721                                strbuf_addstr(&user_path, home);
 722#ifdef GIT_WINDOWS_NATIVE
 723                        convert_slashes(user_path.buf);
 724#endif
 725                } else {
 726                        struct passwd *pw = getpw_str(username, username_len);
 727                        if (!pw)
 728                                goto return_null;
 729                        strbuf_addstr(&user_path, pw->pw_dir);
 730                }
 731                to_copy = first_slash;
 732        }
 733        strbuf_addstr(&user_path, to_copy);
 734        return strbuf_detach(&user_path, NULL);
 735return_null:
 736        strbuf_release(&user_path);
 737        return NULL;
 738}
 739
 740/*
 741 * First, one directory to try is determined by the following algorithm.
 742 *
 743 * (0) If "strict" is given, the path is used as given and no DWIM is
 744 *     done. Otherwise:
 745 * (1) "~/path" to mean path under the running user's home directory;
 746 * (2) "~user/path" to mean path under named user's home directory;
 747 * (3) "relative/path" to mean cwd relative directory; or
 748 * (4) "/absolute/path" to mean absolute directory.
 749 *
 750 * Unless "strict" is given, we check "%s/.git", "%s", "%s.git/.git", "%s.git"
 751 * in this order. We select the first one that is a valid git repository, and
 752 * chdir() to it. If none match, or we fail to chdir, we return NULL.
 753 *
 754 * If all goes well, we return the directory we used to chdir() (but
 755 * before ~user is expanded), avoiding getcwd() resolving symbolic
 756 * links.  User relative paths are also returned as they are given,
 757 * except DWIM suffixing.
 758 */
 759const char *enter_repo(const char *path, int strict)
 760{
 761        static struct strbuf validated_path = STRBUF_INIT;
 762        static struct strbuf used_path = STRBUF_INIT;
 763
 764        if (!path)
 765                return NULL;
 766
 767        if (!strict) {
 768                static const char *suffix[] = {
 769                        "/.git", "", ".git/.git", ".git", NULL,
 770                };
 771                const char *gitfile;
 772                int len = strlen(path);
 773                int i;
 774                while ((1 < len) && (path[len-1] == '/'))
 775                        len--;
 776
 777                /*
 778                 * We can handle arbitrary-sized buffers, but this remains as a
 779                 * sanity check on untrusted input.
 780                 */
 781                if (PATH_MAX <= len)
 782                        return NULL;
 783
 784                strbuf_reset(&used_path);
 785                strbuf_reset(&validated_path);
 786                strbuf_add(&used_path, path, len);
 787                strbuf_add(&validated_path, path, len);
 788
 789                if (used_path.buf[0] == '~') {
 790                        char *newpath = expand_user_path(used_path.buf, 0);
 791                        if (!newpath)
 792                                return NULL;
 793                        strbuf_attach(&used_path, newpath, strlen(newpath),
 794                                      strlen(newpath));
 795                }
 796                for (i = 0; suffix[i]; i++) {
 797                        struct stat st;
 798                        size_t baselen = used_path.len;
 799                        strbuf_addstr(&used_path, suffix[i]);
 800                        if (!stat(used_path.buf, &st) &&
 801                            (S_ISREG(st.st_mode) ||
 802                            (S_ISDIR(st.st_mode) && is_git_directory(used_path.buf)))) {
 803                                strbuf_addstr(&validated_path, suffix[i]);
 804                                break;
 805                        }
 806                        strbuf_setlen(&used_path, baselen);
 807                }
 808                if (!suffix[i])
 809                        return NULL;
 810                gitfile = read_gitfile(used_path.buf);
 811                if (gitfile) {
 812                        strbuf_reset(&used_path);
 813                        strbuf_addstr(&used_path, gitfile);
 814                }
 815                if (chdir(used_path.buf))
 816                        return NULL;
 817                path = validated_path.buf;
 818        }
 819        else {
 820                const char *gitfile = read_gitfile(path);
 821                if (gitfile)
 822                        path = gitfile;
 823                if (chdir(path))
 824                        return NULL;
 825        }
 826
 827        if (is_git_directory(".")) {
 828                set_git_dir(".");
 829                check_repository_format();
 830                return path;
 831        }
 832
 833        return NULL;
 834}
 835
 836static int calc_shared_perm(int mode)
 837{
 838        int tweak;
 839
 840        if (get_shared_repository() < 0)
 841                tweak = -get_shared_repository();
 842        else
 843                tweak = get_shared_repository();
 844
 845        if (!(mode & S_IWUSR))
 846                tweak &= ~0222;
 847        if (mode & S_IXUSR)
 848                /* Copy read bits to execute bits */
 849                tweak |= (tweak & 0444) >> 2;
 850        if (get_shared_repository() < 0)
 851                mode = (mode & ~0777) | tweak;
 852        else
 853                mode |= tweak;
 854
 855        return mode;
 856}
 857
 858
 859int adjust_shared_perm(const char *path)
 860{
 861        int old_mode, new_mode;
 862
 863        if (!get_shared_repository())
 864                return 0;
 865        if (get_st_mode_bits(path, &old_mode) < 0)
 866                return -1;
 867
 868        new_mode = calc_shared_perm(old_mode);
 869        if (S_ISDIR(old_mode)) {
 870                /* Copy read bits to execute bits */
 871                new_mode |= (new_mode & 0444) >> 2;
 872                new_mode |= FORCE_DIR_SET_GID;
 873        }
 874
 875        if (((old_mode ^ new_mode) & ~S_IFMT) &&
 876                        chmod(path, (new_mode & ~S_IFMT)) < 0)
 877                return -2;
 878        return 0;
 879}
 880
 881void safe_create_dir(const char *dir, int share)
 882{
 883        if (mkdir(dir, 0777) < 0) {
 884                if (errno != EEXIST) {
 885                        perror(dir);
 886                        exit(1);
 887                }
 888        }
 889        else if (share && adjust_shared_perm(dir))
 890                die(_("Could not make %s writable by group"), dir);
 891}
 892
 893static int have_same_root(const char *path1, const char *path2)
 894{
 895        int is_abs1, is_abs2;
 896
 897        is_abs1 = is_absolute_path(path1);
 898        is_abs2 = is_absolute_path(path2);
 899        return (is_abs1 && is_abs2 && tolower(path1[0]) == tolower(path2[0])) ||
 900               (!is_abs1 && !is_abs2);
 901}
 902
 903/*
 904 * Give path as relative to prefix.
 905 *
 906 * The strbuf may or may not be used, so do not assume it contains the
 907 * returned path.
 908 */
 909const char *relative_path(const char *in, const char *prefix,
 910                          struct strbuf *sb)
 911{
 912        int in_len = in ? strlen(in) : 0;
 913        int prefix_len = prefix ? strlen(prefix) : 0;
 914        int in_off = 0;
 915        int prefix_off = 0;
 916        int i = 0, j = 0;
 917
 918        if (!in_len)
 919                return "./";
 920        else if (!prefix_len)
 921                return in;
 922
 923        if (have_same_root(in, prefix))
 924                /* bypass dos_drive, for "c:" is identical to "C:" */
 925                i = j = has_dos_drive_prefix(in);
 926        else {
 927                return in;
 928        }
 929
 930        while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
 931                if (is_dir_sep(prefix[i])) {
 932                        while (is_dir_sep(prefix[i]))
 933                                i++;
 934                        while (is_dir_sep(in[j]))
 935                                j++;
 936                        prefix_off = i;
 937                        in_off = j;
 938                } else {
 939                        i++;
 940                        j++;
 941                }
 942        }
 943
 944        if (
 945            /* "prefix" seems like prefix of "in" */
 946            i >= prefix_len &&
 947            /*
 948             * but "/foo" is not a prefix of "/foobar"
 949             * (i.e. prefix not end with '/')
 950             */
 951            prefix_off < prefix_len) {
 952                if (j >= in_len) {
 953                        /* in="/a/b", prefix="/a/b" */
 954                        in_off = in_len;
 955                } else if (is_dir_sep(in[j])) {
 956                        /* in="/a/b/c", prefix="/a/b" */
 957                        while (is_dir_sep(in[j]))
 958                                j++;
 959                        in_off = j;
 960                } else {
 961                        /* in="/a/bbb/c", prefix="/a/b" */
 962                        i = prefix_off;
 963                }
 964        } else if (
 965                   /* "in" is short than "prefix" */
 966                   j >= in_len &&
 967                   /* "in" not end with '/' */
 968                   in_off < in_len) {
 969                if (is_dir_sep(prefix[i])) {
 970                        /* in="/a/b", prefix="/a/b/c/" */
 971                        while (is_dir_sep(prefix[i]))
 972                                i++;
 973                        in_off = in_len;
 974                }
 975        }
 976        in += in_off;
 977        in_len -= in_off;
 978
 979        if (i >= prefix_len) {
 980                if (!in_len)
 981                        return "./";
 982                else
 983                        return in;
 984        }
 985
 986        strbuf_reset(sb);
 987        strbuf_grow(sb, in_len);
 988
 989        while (i < prefix_len) {
 990                if (is_dir_sep(prefix[i])) {
 991                        strbuf_addstr(sb, "../");
 992                        while (is_dir_sep(prefix[i]))
 993                                i++;
 994                        continue;
 995                }
 996                i++;
 997        }
 998        if (!is_dir_sep(prefix[prefix_len - 1]))
 999                strbuf_addstr(sb, "../");
1000
1001        strbuf_addstr(sb, in);
1002
1003        return sb->buf;
1004}
1005
1006/*
1007 * A simpler implementation of relative_path
1008 *
1009 * Get relative path by removing "prefix" from "in". This function
1010 * first appears in v1.5.6-1-g044bbbc, and makes git_dir shorter
1011 * to increase performance when traversing the path to work_tree.
1012 */
1013const char *remove_leading_path(const char *in, const char *prefix)
1014{
1015        static struct strbuf buf = STRBUF_INIT;
1016        int i = 0, j = 0;
1017
1018        if (!prefix || !prefix[0])
1019                return in;
1020        while (prefix[i]) {
1021                if (is_dir_sep(prefix[i])) {
1022                        if (!is_dir_sep(in[j]))
1023                                return in;
1024                        while (is_dir_sep(prefix[i]))
1025                                i++;
1026                        while (is_dir_sep(in[j]))
1027                                j++;
1028                        continue;
1029                } else if (in[j] != prefix[i]) {
1030                        return in;
1031                }
1032                i++;
1033                j++;
1034        }
1035        if (
1036            /* "/foo" is a prefix of "/foo" */
1037            in[j] &&
1038            /* "/foo" is not a prefix of "/foobar" */
1039            !is_dir_sep(prefix[i-1]) && !is_dir_sep(in[j])
1040           )
1041                return in;
1042        while (is_dir_sep(in[j]))
1043                j++;
1044
1045        strbuf_reset(&buf);
1046        if (!in[j])
1047                strbuf_addstr(&buf, ".");
1048        else
1049                strbuf_addstr(&buf, in + j);
1050        return buf.buf;
1051}
1052
1053/*
1054 * It is okay if dst == src, but they should not overlap otherwise.
1055 *
1056 * Performs the following normalizations on src, storing the result in dst:
1057 * - Ensures that components are separated by '/' (Windows only)
1058 * - Squashes sequences of '/' except "//server/share" on Windows
1059 * - Removes "." components.
1060 * - Removes ".." components, and the components the precede them.
1061 * Returns failure (non-zero) if a ".." component appears as first path
1062 * component anytime during the normalization. Otherwise, returns success (0).
1063 *
1064 * Note that this function is purely textual.  It does not follow symlinks,
1065 * verify the existence of the path, or make any system calls.
1066 *
1067 * prefix_len != NULL is for a specific case of prefix_pathspec():
1068 * assume that src == dst and src[0..prefix_len-1] is already
1069 * normalized, any time "../" eats up to the prefix_len part,
1070 * prefix_len is reduced. In the end prefix_len is the remaining
1071 * prefix that has not been overridden by user pathspec.
1072 *
1073 * NEEDSWORK: This function doesn't perform normalization w.r.t. trailing '/'.
1074 * For everything but the root folder itself, the normalized path should not
1075 * end with a '/', then the callers need to be fixed up accordingly.
1076 *
1077 */
1078int normalize_path_copy_len(char *dst, const char *src, int *prefix_len)
1079{
1080        char *dst0;
1081        const char *end;
1082
1083        /*
1084         * Copy initial part of absolute path: "/", "C:/", "//server/share/".
1085         */
1086        end = src + offset_1st_component(src);
1087        while (src < end) {
1088                char c = *src++;
1089                if (is_dir_sep(c))
1090                        c = '/';
1091                *dst++ = c;
1092        }
1093        dst0 = dst;
1094
1095        while (is_dir_sep(*src))
1096                src++;
1097
1098        for (;;) {
1099                char c = *src;
1100
1101                /*
1102                 * A path component that begins with . could be
1103                 * special:
1104                 * (1) "." and ends   -- ignore and terminate.
1105                 * (2) "./"           -- ignore them, eat slash and continue.
1106                 * (3) ".." and ends  -- strip one and terminate.
1107                 * (4) "../"          -- strip one, eat slash and continue.
1108                 */
1109                if (c == '.') {
1110                        if (!src[1]) {
1111                                /* (1) */
1112                                src++;
1113                        } else if (is_dir_sep(src[1])) {
1114                                /* (2) */
1115                                src += 2;
1116                                while (is_dir_sep(*src))
1117                                        src++;
1118                                continue;
1119                        } else if (src[1] == '.') {
1120                                if (!src[2]) {
1121                                        /* (3) */
1122                                        src += 2;
1123                                        goto up_one;
1124                                } else if (is_dir_sep(src[2])) {
1125                                        /* (4) */
1126                                        src += 3;
1127                                        while (is_dir_sep(*src))
1128                                                src++;
1129                                        goto up_one;
1130                                }
1131                        }
1132                }
1133
1134                /* copy up to the next '/', and eat all '/' */
1135                while ((c = *src++) != '\0' && !is_dir_sep(c))
1136                        *dst++ = c;
1137                if (is_dir_sep(c)) {
1138                        *dst++ = '/';
1139                        while (is_dir_sep(c))
1140                                c = *src++;
1141                        src--;
1142                } else if (!c)
1143                        break;
1144                continue;
1145
1146        up_one:
1147                /*
1148                 * dst0..dst is prefix portion, and dst[-1] is '/';
1149                 * go up one level.
1150                 */
1151                dst--;  /* go to trailing '/' */
1152                if (dst <= dst0)
1153                        return -1;
1154                /* Windows: dst[-1] cannot be backslash anymore */
1155                while (dst0 < dst && dst[-1] != '/')
1156                        dst--;
1157                if (prefix_len && *prefix_len > dst - dst0)
1158                        *prefix_len = dst - dst0;
1159        }
1160        *dst = '\0';
1161        return 0;
1162}
1163
1164int normalize_path_copy(char *dst, const char *src)
1165{
1166        return normalize_path_copy_len(dst, src, NULL);
1167}
1168
1169/*
1170 * path = Canonical absolute path
1171 * prefixes = string_list containing normalized, absolute paths without
1172 * trailing slashes (except for the root directory, which is denoted by "/").
1173 *
1174 * Determines, for each path in prefixes, whether the "prefix"
1175 * is an ancestor directory of path.  Returns the length of the longest
1176 * ancestor directory, excluding any trailing slashes, or -1 if no prefix
1177 * is an ancestor.  (Note that this means 0 is returned if prefixes is
1178 * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
1179 * are not considered to be their own ancestors.  path must be in a
1180 * canonical form: empty components, or "." or ".." components are not
1181 * allowed.
1182 */
1183int longest_ancestor_length(const char *path, struct string_list *prefixes)
1184{
1185        int i, max_len = -1;
1186
1187        if (!strcmp(path, "/"))
1188                return -1;
1189
1190        for (i = 0; i < prefixes->nr; i++) {
1191                const char *ceil = prefixes->items[i].string;
1192                int len = strlen(ceil);
1193
1194                if (len == 1 && ceil[0] == '/')
1195                        len = 0; /* root matches anything, with length 0 */
1196                else if (!strncmp(path, ceil, len) && path[len] == '/')
1197                        ; /* match of length len */
1198                else
1199                        continue; /* no match */
1200
1201                if (len > max_len)
1202                        max_len = len;
1203        }
1204
1205        return max_len;
1206}
1207
1208/* strip arbitrary amount of directory separators at end of path */
1209static inline int chomp_trailing_dir_sep(const char *path, int len)
1210{
1211        while (len && is_dir_sep(path[len - 1]))
1212                len--;
1213        return len;
1214}
1215
1216/*
1217 * If path ends with suffix (complete path components), returns the
1218 * part before suffix (sans trailing directory separators).
1219 * Otherwise returns NULL.
1220 */
1221char *strip_path_suffix(const char *path, const char *suffix)
1222{
1223        int path_len = strlen(path), suffix_len = strlen(suffix);
1224
1225        while (suffix_len) {
1226                if (!path_len)
1227                        return NULL;
1228
1229                if (is_dir_sep(path[path_len - 1])) {
1230                        if (!is_dir_sep(suffix[suffix_len - 1]))
1231                                return NULL;
1232                        path_len = chomp_trailing_dir_sep(path, path_len);
1233                        suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
1234                }
1235                else if (path[--path_len] != suffix[--suffix_len])
1236                        return NULL;
1237        }
1238
1239        if (path_len && !is_dir_sep(path[path_len - 1]))
1240                return NULL;
1241        return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
1242}
1243
1244int daemon_avoid_alias(const char *p)
1245{
1246        int sl, ndot;
1247
1248        /*
1249         * This resurrects the belts and suspenders paranoia check by HPA
1250         * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
1251         * does not do getcwd() based path canonicalization.
1252         *
1253         * sl becomes true immediately after seeing '/' and continues to
1254         * be true as long as dots continue after that without intervening
1255         * non-dot character.
1256         */
1257        if (!p || (*p != '/' && *p != '~'))
1258                return -1;
1259        sl = 1; ndot = 0;
1260        p++;
1261
1262        while (1) {
1263                char ch = *p++;
1264                if (sl) {
1265                        if (ch == '.')
1266                                ndot++;
1267                        else if (ch == '/') {
1268                                if (ndot < 3)
1269                                        /* reject //, /./ and /../ */
1270                                        return -1;
1271                                ndot = 0;
1272                        }
1273                        else if (ch == 0) {
1274                                if (0 < ndot && ndot < 3)
1275                                        /* reject /.$ and /..$ */
1276                                        return -1;
1277                                return 0;
1278                        }
1279                        else
1280                                sl = ndot = 0;
1281                }
1282                else if (ch == 0)
1283                        return 0;
1284                else if (ch == '/') {
1285                        sl = 1;
1286                        ndot = 0;
1287                }
1288        }
1289}
1290
1291static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
1292{
1293        if (len < skip)
1294                return 0;
1295        len -= skip;
1296        path += skip;
1297        while (len-- > 0) {
1298                char c = *(path++);
1299                if (c != ' ' && c != '.')
1300                        return 0;
1301        }
1302        return 1;
1303}
1304
1305int is_ntfs_dotgit(const char *name)
1306{
1307        int len;
1308
1309        for (len = 0; ; len++)
1310                if (!name[len] || name[len] == '\\' || is_dir_sep(name[len])) {
1311                        if (only_spaces_and_periods(name, len, 4) &&
1312                                        !strncasecmp(name, ".git", 4))
1313                                return 1;
1314                        if (only_spaces_and_periods(name, len, 5) &&
1315                                        !strncasecmp(name, "git~1", 5))
1316                                return 1;
1317                        if (name[len] != '\\')
1318                                return 0;
1319                        name += len + 1;
1320                        len = -1;
1321                }
1322}
1323
1324int looks_like_command_line_option(const char *str)
1325{
1326        return str && str[0] == '-';
1327}
1328
1329char *xdg_config_home(const char *filename)
1330{
1331        const char *home, *config_home;
1332
1333        assert(filename);
1334        config_home = getenv("XDG_CONFIG_HOME");
1335        if (config_home && *config_home)
1336                return mkpathdup("%s/git/%s", config_home, filename);
1337
1338        home = getenv("HOME");
1339        if (home)
1340                return mkpathdup("%s/.config/git/%s", home, filename);
1341        return NULL;
1342}
1343
1344char *xdg_cache_home(const char *filename)
1345{
1346        const char *home, *cache_home;
1347
1348        assert(filename);
1349        cache_home = getenv("XDG_CACHE_HOME");
1350        if (cache_home && *cache_home)
1351                return mkpathdup("%s/git/%s", cache_home, filename);
1352
1353        home = getenv("HOME");
1354        if (home)
1355                return mkpathdup("%s/.cache/git/%s", home, filename);
1356        return NULL;
1357}
1358
1359GIT_PATH_FUNC(git_path_cherry_pick_head, "CHERRY_PICK_HEAD")
1360GIT_PATH_FUNC(git_path_revert_head, "REVERT_HEAD")
1361GIT_PATH_FUNC(git_path_squash_msg, "SQUASH_MSG")
1362GIT_PATH_FUNC(git_path_merge_msg, "MERGE_MSG")
1363GIT_PATH_FUNC(git_path_merge_rr, "MERGE_RR")
1364GIT_PATH_FUNC(git_path_merge_mode, "MERGE_MODE")
1365GIT_PATH_FUNC(git_path_merge_head, "MERGE_HEAD")
1366GIT_PATH_FUNC(git_path_fetch_head, "FETCH_HEAD")
1367GIT_PATH_FUNC(git_path_shallow, "shallow")