#include "cache.h"
#include "dir.h"
#include "string-list.h"

static int inside_git_dir = -1;
static int inside_work_tree = -1;

/*
 * The input parameter must contain an absolute path, and it must already be
 * normalized.
 *
 * Find the part of an absolute path that lies inside the work tree by
 * dereferencing symlinks outside the work tree, for example:
 * /dir1/repo/dir2/file   (work tree is /dir1/repo)      -> dir2/file
 * /dir/file              (work tree is /)               -> dir/file
 * /dir/symlink1/symlink2 (symlink1 points to work tree) -> symlink2
 * /dir/repolink/file     (repolink points to /dir/repo) -> file
 * /dir/repo              (exactly equal to work tree)   -> (empty string)
 */
static int abspath_part_inside_repo(char *path)
{
        size_t len;
        size_t wtlen;
        char *path0;
        int off;
        const char *work_tree = get_git_work_tree();

        if (!work_tree)
                return -1;
        wtlen = strlen(work_tree);
        len = strlen(path);
        off = 0;

        /* check if work tree is already the prefix */
        if (wtlen <= len && !strncmp(path, work_tree, wtlen)) {
                if (path[wtlen] == '/') {
                        memmove(path, path + wtlen + 1, len - wtlen);
                        return 0;
                } else if (path[wtlen - 1] == '/' || path[wtlen] == '\0') {
                        /* work tree is the root, or the whole path */
                        memmove(path, path + wtlen, len - wtlen + 1);
                        return 0;
                }
                /* work tree might match beginning of a symlink to work tree */
                off = wtlen;
        }
        path0 = path;
        path += offset_1st_component(path) + off;

        /* check each '/'-terminated level */
        while (*path) {
                path++;
                if (*path == '/') {
                        *path = '\0';
                        if (strcmp(real_path(path0), work_tree) == 0) {
                                memmove(path0, path + 1, len - (path - path0));
                                return 0;
                        }
                        *path = '/';
                }
        }

        /* check whole path */
        if (strcmp(real_path(path0), work_tree) == 0) {
                *path0 = '\0';
                return 0;
        }

        return -1;
}

/*
 * Normalize "path", prepending the "prefix" for relative paths. If
 * remaining_prefix is not NULL, return the actual prefix still
 * remains in the path. For example, prefix = sub1/sub2/ and path is
 *
 *  foo          -> sub1/sub2/foo  (full prefix)
 *  ../foo       -> sub1/foo       (remaining prefix is sub1/)
 *  ../../bar    -> bar            (no remaining prefix)
 *  ../../sub1/sub2/foo -> sub1/sub2/foo (but no remaining prefix)
 *  `pwd`/../bar -> sub1/bar       (no remaining prefix)
 */
char *prefix_path_gently(const char *prefix, int len,
                         int *remaining_prefix, const char *path)
{
        const char *orig = path;
        char *sanitized;
        if (is_absolute_path(orig)) {
                const char *temp = real_path(path);
                sanitized = xmalloc(len + strlen(temp) + 1);
                strcpy(sanitized, temp);
                if (remaining_prefix)
                        *remaining_prefix = 0;
        } else {
                sanitized = xmalloc(len + strlen(path) + 1);
                if (len)
                        memcpy(sanitized, prefix, len);
                strcpy(sanitized + len, path);
                if (remaining_prefix)
                        *remaining_prefix = len;
        }
        if (normalize_path_copy_len(sanitized, sanitized, remaining_prefix))
                goto error_out;
        if (is_absolute_path(orig)) {
                size_t root_len, len, total;
                const char *work_tree = get_git_work_tree();
                if (!work_tree)
                        goto error_out;
                len = strlen(work_tree);
                root_len = offset_1st_component(work_tree);
                total = strlen(sanitized) + 1;
                if (strncmp(sanitized, work_tree, len) ||
                    (len > root_len && sanitized[len] != '\0' && sanitized[len] != '/')) {
                error_out:
                        free(sanitized);
                        return NULL;
                }
                if (sanitized[len] == '/')
                        len++;
                memmove(sanitized, sanitized + len, total - len);
        }
        return sanitized;
}

char *prefix_path(const char *prefix, int len, const char *path)
{
        char *r = prefix_path_gently(prefix, len, NULL, path);
        if (!r)
                die("'%s' is outside repository", path);
        return r;
}

int path_inside_repo(const char *prefix, const char *path)
{
        int len = prefix ? strlen(prefix) : 0;
        char *r = prefix_path_gently(prefix, len, NULL, path);
        if (r) {
                free(r);
                return 1;
        }
        return 0;
}

int check_filename(const char *prefix, const char *arg)
{
        const char *name;
        struct stat st;

        if (!prefixcmp(arg, ":/")) {
                if (arg[2] == '\0') /* ":/" is root dir, always exists */
                        return 1;
                name = arg + 2;
        } else if (prefix)
                name = prefix_filename(prefix, strlen(prefix), arg);
        else
                name = arg;
        if (!lstat(name, &st))
                return 1; /* file exists */
        if (errno == ENOENT || errno == ENOTDIR)
                return 0; /* file does not exist */
        die_errno("failed to stat '%s'", arg);
}

static void NORETURN die_verify_filename(const char *prefix,
                                         const char *arg,
                                         int diagnose_misspelt_rev)
{
        if (!diagnose_misspelt_rev)
                die("%s: no such path in the working tree.\n"
                    "Use 'git <command> -- <path>...' to specify paths that do not exist locally.",
                    arg);
        /*
         * Saying "'(icase)foo' does not exist in the index" when the
         * user gave us ":(icase)foo" is just stupid.  A magic pathspec
         * begins with a colon and is followed by a non-alnum; do not
         * let maybe_die_on_misspelt_object_name() even trigger.
         */
        if (!(arg[0] == ':' && !isalnum(arg[1])))
                maybe_die_on_misspelt_object_name(arg, prefix);

        /* ... or fall back the most general message. */
        die("ambiguous argument '%s': unknown revision or path not in the working tree.\n"
            "Use '--' to separate paths from revisions, like this:\n"
            "'git <command> [<revision>...] -- [<file>...]'", arg);

}

/*
 * Verify a filename that we got as an argument for a pathspec
 * entry. Note that a filename that begins with "-" never verifies
 * as true, because even if such a filename were to exist, we want
 * it to be preceded by the "--" marker (or we want the user to
 * use a format like "./-filename")
 *
 * The "diagnose_misspelt_rev" is used to provide a user-friendly
 * diagnosis when dying upon finding that "name" is not a pathname.
 * If set to 1, the diagnosis will try to diagnose "name" as an
 * invalid object name (e.g. HEAD:foo). If set to 0, the diagnosis
 * will only complain about an inexisting file.
 *
 * This function is typically called to check that a "file or rev"
 * argument is unambiguous. In this case, the caller will want
 * diagnose_misspelt_rev == 1 when verifying the first non-rev
 * argument (which could have been a revision), and
 * diagnose_misspelt_rev == 0 for the next ones (because we already
 * saw a filename, there's not ambiguity anymore).
 */
void verify_filename(const char *prefix,
                     const char *arg,
                     int diagnose_misspelt_rev)
{
        if (*arg == '-')
                die("bad flag '%s' used after filename", arg);
        if (check_filename(prefix, arg))
                return;
        die_verify_filename(prefix, arg, diagnose_misspelt_rev);
}

/*
 * Opposite of the above: the command line did not have -- marker
 * and we parsed the arg as a refname.  It should not be interpretable
 * as a filename.
 */
void verify_non_filename(const char *prefix, const char *arg)
{
        if (!is_inside_work_tree() || is_inside_git_dir())
                return;
        if (*arg == '-')
                return; /* flag */
        if (!check_filename(prefix, arg))
                return;
        die("ambiguous argument '%s': both revision and filename\n"
            "Use '--' to separate paths from revisions, like this:\n"
            "'git <command> [<revision>...] -- [<file>...]'", arg);
}


/*
 * Test if it looks like we're at a git directory.
 * We want to see:
 *
 *  - either an objects/ directory _or_ the proper
 *    GIT_OBJECT_DIRECTORY environment variable
 *  - a refs/ directory
 *  - either a HEAD symlink or a HEAD file that is formatted as
 *    a proper "ref:", or a regular file HEAD that has a properly
 *    formatted sha1 object name.
 */
int is_git_directory(const char *suspect)
{
        char path[PATH_MAX];
        size_t len = strlen(suspect);

        if (PATH_MAX <= len + strlen("/objects"))
                die("Too long path: %.*s", 60, suspect);
        strcpy(path, suspect);
        if (getenv(DB_ENVIRONMENT)) {
                if (access(getenv(DB_ENVIRONMENT), X_OK))
                        return 0;
        }
        else {
                strcpy(path + len, "/objects");
                if (access(path, X_OK))
                        return 0;
        }

        strcpy(path + len, "/refs");
        if (access(path, X_OK))
                return 0;

        strcpy(path + len, "/HEAD");
        if (validate_headref(path))
                return 0;

        return 1;
}

int is_inside_git_dir(void)
{
        if (inside_git_dir < 0)
                inside_git_dir = is_inside_dir(get_git_dir());
        return inside_git_dir;
}

int is_inside_work_tree(void)
{
        if (inside_work_tree < 0)
                inside_work_tree = is_inside_dir(get_git_work_tree());
        return inside_work_tree;
}

void setup_work_tree(void)
{
        const char *work_tree, *git_dir;
        static int initialized = 0;

        if (initialized)
                return;
        work_tree = get_git_work_tree();
        git_dir = get_git_dir();
        if (!is_absolute_path(git_dir))
                git_dir = real_path(get_git_dir());
        if (!work_tree || chdir(work_tree))
                die("This operation must be run in a work tree");

        /*
         * Make sure subsequent git processes find correct worktree
         * if $GIT_WORK_TREE is set relative
         */
        if (getenv(GIT_WORK_TREE_ENVIRONMENT))
                setenv(GIT_WORK_TREE_ENVIRONMENT, ".", 1);

        set_git_dir(remove_leading_path(git_dir, work_tree));
        initialized = 1;
}

static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
{
        char repo_config[PATH_MAX+1];

        /*
         * git_config() can't be used here because it calls git_pathdup()
         * to get $GIT_CONFIG/config. That call will make setup_git_env()
         * set git_dir to ".git".
         *
         * We are in gitdir setup, no git dir has been found useable yet.
         * Use a gentler version of git_config() to check if this repo
         * is a good one.
         */
        snprintf(repo_config, PATH_MAX, "%s/config", gitdir);
        git_config_early(check_repository_format_version, NULL, repo_config);
        if (GIT_REPO_VERSION < repository_format_version) {
                if (!nongit_ok)
                        die ("Expected git repo version <= %d, found %d",
                             GIT_REPO_VERSION, repository_format_version);
                warning("Expected git repo version <= %d, found %d",
                        GIT_REPO_VERSION, repository_format_version);
                warning("Please upgrade Git");
                *nongit_ok = -1;
                return -1;
        }
        return 0;
}

/*
 * Try to read the location of the git directory from the .git file,
 * return path to git directory if found.
 */
const char *read_gitfile(const char *path)
{
        char *buf;
        char *dir;
        const char *slash;
        struct stat st;
        int fd;
        ssize_t len;

        if (stat(path, &st))
                return NULL;
        if (!S_ISREG(st.st_mode))
                return NULL;
        fd = open(path, O_RDONLY);
        if (fd < 0)
                die_errno("Error opening '%s'", path);
        buf = xmalloc(st.st_size + 1);
        len = read_in_full(fd, buf, st.st_size);
        close(fd);
        if (len != st.st_size)
                die("Error reading %s", path);
        buf[len] = '\0';
        if (prefixcmp(buf, "gitdir: "))
                die("Invalid gitfile format: %s", path);
        while (buf[len - 1] == '\n' || buf[len - 1] == '\r')
                len--;
        if (len < 9)
                die("No path in gitfile: %s", path);
        buf[len] = '\0';
        dir = buf + 8;

        if (!is_absolute_path(dir) && (slash = strrchr(path, '/'))) {
                size_t pathlen = slash+1 - path;
                size_t dirlen = pathlen + len - 8;
                dir = xmalloc(dirlen + 1);
                strncpy(dir, path, pathlen);
                strncpy(dir + pathlen, buf + 8, len - 8);
                dir[dirlen] = '\0';
                free(buf);
                buf = dir;
        }

        if (!is_git_directory(dir))
                die("Not a git repository: %s", dir);
        path = real_path(dir);

        free(buf);
        return path;
}

static const char *setup_explicit_git_dir(const char *gitdirenv,
                                          char *cwd, int len,
                                          int *nongit_ok)
{
        const char *work_tree_env = getenv(GIT_WORK_TREE_ENVIRONMENT);
        const char *worktree;
        char *gitfile;
        int offset;

        if (PATH_MAX - 40 < strlen(gitdirenv))
                die("'$%s' too big", GIT_DIR_ENVIRONMENT);

        gitfile = (char*)read_gitfile(gitdirenv);
        if (gitfile) {
                gitfile = xstrdup(gitfile);
                gitdirenv = gitfile;
        }

        if (!is_git_directory(gitdirenv)) {
                if (nongit_ok) {
                        *nongit_ok = 1;
                        free(gitfile);
                        return NULL;
                }
                die("Not a git repository: '%s'", gitdirenv);
        }

        if (check_repository_format_gently(gitdirenv, nongit_ok)) {
                free(gitfile);
                return NULL;
        }

        /* #3, #7, #11, #15, #19, #23, #27, #31 (see t1510) */
        if (work_tree_env)
                set_git_work_tree(work_tree_env);
        else if (is_bare_repository_cfg > 0) {
                if (git_work_tree_cfg) /* #22.2, #30 */
                        die("core.bare and core.worktree do not make sense");

                /* #18, #26 */
                set_git_dir(gitdirenv);
                free(gitfile);
                return NULL;
        }
        else if (git_work_tree_cfg) { /* #6, #14 */
                if (is_absolute_path(git_work_tree_cfg))
                        set_git_work_tree(git_work_tree_cfg);
                else {
                        char core_worktree[PATH_MAX];
                        if (chdir(gitdirenv))
                                die_errno("Could not chdir to '%s'", gitdirenv);
                        if (chdir(git_work_tree_cfg))
                                die_errno("Could not chdir to '%s'", git_work_tree_cfg);
                        if (!getcwd(core_worktree, PATH_MAX))
                                die_errno("Could not get directory '%s'", git_work_tree_cfg);
                        if (chdir(cwd))
                                die_errno("Could not come back to cwd");
                        set_git_work_tree(core_worktree);
                }
        }
        else if (!git_env_bool(GIT_IMPLICIT_WORK_TREE_ENVIRONMENT, 1)) {
                /* #16d */
                set_git_dir(gitdirenv);
                free(gitfile);
                return NULL;
        }
        else /* #2, #10 */
                set_git_work_tree(".");

        /* set_git_work_tree() must have been called by now */
        worktree = get_git_work_tree();

        /* both get_git_work_tree() and cwd are already normalized */
        if (!strcmp(cwd, worktree)) { /* cwd == worktree */
                set_git_dir(gitdirenv);
                free(gitfile);
                return NULL;
        }

        offset = dir_inside_of(cwd, worktree);
        if (offset >= 0) {      /* cwd inside worktree? */
                set_git_dir(real_path(gitdirenv));
                if (chdir(worktree))
                        die_errno("Could not chdir to '%s'", worktree);
                cwd[len++] = '/';
                cwd[len] = '\0';
                free(gitfile);
                return cwd + offset;
        }

        /* cwd outside worktree */
        set_git_dir(gitdirenv);
        free(gitfile);
        return NULL;
}

static const char *setup_discovered_git_dir(const char *gitdir,
                                            char *cwd, int offset, int len,
                                            int *nongit_ok)
{
        if (check_repository_format_gently(gitdir, nongit_ok))
                return NULL;

        /* --work-tree is set without --git-dir; use discovered one */
        if (getenv(GIT_WORK_TREE_ENVIRONMENT) || git_work_tree_cfg) {
                if (offset != len && !is_absolute_path(gitdir))
                        gitdir = xstrdup(real_path(gitdir));
                if (chdir(cwd))
                        die_errno("Could not come back to cwd");
                return setup_explicit_git_dir(gitdir, cwd, len, nongit_ok);
        }

        /* #16.2, #17.2, #20.2, #21.2, #24, #25, #28, #29 (see t1510) */
        if (is_bare_repository_cfg > 0) {
                set_git_dir(offset == len ? gitdir : real_path(gitdir));
                if (chdir(cwd))
                        die_errno("Could not come back to cwd");
                return NULL;
        }

        /* #0, #1, #5, #8, #9, #12, #13 */
        set_git_work_tree(".");
        if (strcmp(gitdir, DEFAULT_GIT_DIR_ENVIRONMENT))
                set_git_dir(gitdir);
        inside_git_dir = 0;
        inside_work_tree = 1;
        if (offset == len)
                return NULL;

        /* Make "offset" point to past the '/', and add a '/' at the end */
        offset++;
        cwd[len++] = '/';
        cwd[len] = 0;
        return cwd + offset;
}

/* #16.1, #17.1, #20.1, #21.1, #22.1 (see t1510) */
static const char *setup_bare_git_dir(char *cwd, int offset, int len, int *nongit_ok)
{
        int root_len;

        if (check_repository_format_gently(".", nongit_ok))
                return NULL;

        setenv(GIT_IMPLICIT_WORK_TREE_ENVIRONMENT, "0", 1);

        /* --work-tree is set without --git-dir; use discovered one */
        if (getenv(GIT_WORK_TREE_ENVIRONMENT) || git_work_tree_cfg) {
                const char *gitdir;

                gitdir = offset == len ? "." : xmemdupz(cwd, offset);
                if (chdir(cwd))
                        die_errno("Could not come back to cwd");
                return setup_explicit_git_dir(gitdir, cwd, len, nongit_ok);
        }

        inside_git_dir = 1;
        inside_work_tree = 0;
        if (offset != len) {
                if (chdir(cwd))
                        die_errno("Cannot come back to cwd");
                root_len = offset_1st_component(cwd);
                cwd[offset > root_len ? offset : root_len] = '\0';
                set_git_dir(cwd);
        }
        else
                set_git_dir(".");
        return NULL;
}

static const char *setup_nongit(const char *cwd, int *nongit_ok)
{
        if (!nongit_ok)
                die("Not a git repository (or any of the parent directories): %s", DEFAULT_GIT_DIR_ENVIRONMENT);
        if (chdir(cwd))
                die_errno("Cannot come back to cwd");
        *nongit_ok = 1;
        return NULL;
}

static dev_t get_device_or_die(const char *path, const char *prefix, int prefix_len)
{
        struct stat buf;
        if (stat(path, &buf)) {
                die_errno("failed to stat '%*s%s%s'",
                                prefix_len,
                                prefix ? prefix : "",
                                prefix ? "/" : "", path);
        }
        return buf.st_dev;
}

/*
 * A "string_list_each_func_t" function that canonicalizes an entry
 * from GIT_CEILING_DIRECTORIES using real_path_if_valid(), or
 * discards it if unusable.  The presence of an empty entry in
 * GIT_CEILING_DIRECTORIES turns off canonicalization for all
 * subsequent entries.
 */
static int canonicalize_ceiling_entry(struct string_list_item *item,
                                      void *cb_data)
{
        int *empty_entry_found = cb_data;
        char *ceil = item->string;

        if (!*ceil) {
                *empty_entry_found = 1;
                return 0;
        } else if (!is_absolute_path(ceil)) {
                return 0;
        } else if (*empty_entry_found) {
                /* Keep entry but do not canonicalize it */
                return 1;
        } else {
                const char *real_path = real_path_if_valid(ceil);
                if (!real_path)
                        return 0;
                free(item->string);
                item->string = xstrdup(real_path);
                return 1;
        }
}

/*
 * We cannot decide in this function whether we are in the work tree or
 * not, since the config can only be read _after_ this function was called.
 */
static const char *setup_git_directory_gently_1(int *nongit_ok)
{
        const char *env_ceiling_dirs = getenv(CEILING_DIRECTORIES_ENVIRONMENT);
        struct string_list ceiling_dirs = STRING_LIST_INIT_DUP;
        static char cwd[PATH_MAX + 1];
        const char *gitdirenv, *ret;
        char *gitfile;
        int len, offset, offset_parent, ceil_offset = -1;
        dev_t current_device = 0;
        int one_filesystem = 1;

        /*
         * Let's assume that we are in a git repository.
         * If it turns out later that we are somewhere else, the value will be
         * updated accordingly.
         */
        if (nongit_ok)
                *nongit_ok = 0;

        if (!getcwd(cwd, sizeof(cwd) - 1))
                die_errno("Unable to read current working directory");
        offset = len = strlen(cwd);

        /*
         * If GIT_DIR is set explicitly, we're not going
         * to do any discovery, but we still do repository
         * validation.
         */
        gitdirenv = getenv(GIT_DIR_ENVIRONMENT);
        if (gitdirenv)
                return setup_explicit_git_dir(gitdirenv, cwd, len, nongit_ok);

        if (env_ceiling_dirs) {
                int empty_entry_found = 0;

                string_list_split(&ceiling_dirs, env_ceiling_dirs, PATH_SEP, -1);
                filter_string_list(&ceiling_dirs, 0,
                                   canonicalize_ceiling_entry, &empty_entry_found);
                ceil_offset = longest_ancestor_length(cwd, &ceiling_dirs);
                string_list_clear(&ceiling_dirs, 0);
        }

        if (ceil_offset < 0 && has_dos_drive_prefix(cwd))
                ceil_offset = 1;

        /*
         * Test in the following order (relative to the cwd):
         * - .git (file containing "gitdir: <path>")
         * - .git/
         * - ./ (bare)
         * - ../.git
         * - ../.git/
         * - ../ (bare)
         * - ../../.git/
         *   etc.
         */
        one_filesystem = !git_env_bool("GIT_DISCOVERY_ACROSS_FILESYSTEM", 0);
        if (one_filesystem)
                current_device = get_device_or_die(".", NULL, 0);
        for (;;) {
                gitfile = (char*)read_gitfile(DEFAULT_GIT_DIR_ENVIRONMENT);
                if (gitfile)
                        gitdirenv = gitfile = xstrdup(gitfile);
                else {
                        if (is_git_directory(DEFAULT_GIT_DIR_ENVIRONMENT))
                                gitdirenv = DEFAULT_GIT_DIR_ENVIRONMENT;
                }

                if (gitdirenv) {
                        ret = setup_discovered_git_dir(gitdirenv,
                                                       cwd, offset, len,
                                                       nongit_ok);
                        free(gitfile);
                        return ret;
                }
                free(gitfile);

                if (is_git_directory("."))
                        return setup_bare_git_dir(cwd, offset, len, nongit_ok);

                offset_parent = offset;
                while (--offset_parent > ceil_offset && cwd[offset_parent] != '/');
                if (offset_parent <= ceil_offset)
                        return setup_nongit(cwd, nongit_ok);
                if (one_filesystem) {
                        dev_t parent_device = get_device_or_die("..", cwd, offset);
                        if (parent_device != current_device) {
                                if (nongit_ok) {
                                        if (chdir(cwd))
                                                die_errno("Cannot come back to cwd");
                                        *nongit_ok = 1;
                                        return NULL;
                                }
                                cwd[offset] = '\0';
                                die("Not a git repository (or any parent up to mount point %s)\n"
                                "Stopping at filesystem boundary (GIT_DISCOVERY_ACROSS_FILESYSTEM not set).", cwd);
                        }
                }
                if (chdir("..")) {
                        cwd[offset] = '\0';
                        die_errno("Cannot change to '%s/..'", cwd);
                }
                offset = offset_parent;
        }
}

const char *setup_git_directory_gently(int *nongit_ok)
{
        const char *prefix;

        prefix = setup_git_directory_gently_1(nongit_ok);
        if (prefix)
                setenv(GIT_PREFIX_ENVIRONMENT, prefix, 1);
        else
                setenv(GIT_PREFIX_ENVIRONMENT, "", 1);

        if (startup_info) {
                startup_info->have_repository = !nongit_ok || !*nongit_ok;
                startup_info->prefix = prefix;
        }
        return prefix;
}

int git_config_perm(const char *var, const char *value)
{
        int i;
        char *endptr;

        if (value == NULL)
                return PERM_GROUP;

        if (!strcmp(value, "umask"))
                return PERM_UMASK;
        if (!strcmp(value, "group"))
                return PERM_GROUP;
        if (!strcmp(value, "all") ||
            !strcmp(value, "world") ||
            !strcmp(value, "everybody"))
                return PERM_EVERYBODY;

        /* Parse octal numbers */
        i = strtol(value, &endptr, 8);

        /* If not an octal number, maybe true/false? */
        if (*endptr != 0)
                return git_config_bool(var, value) ? PERM_GROUP : PERM_UMASK;

        /*
         * Treat values 0, 1 and 2 as compatibility cases, otherwise it is
         * a chmod value to restrict to.
         */
        switch (i) {
        case PERM_UMASK:               /* 0 */
                return PERM_UMASK;
        case OLD_PERM_GROUP:           /* 1 */
                return PERM_GROUP;
        case OLD_PERM_EVERYBODY:       /* 2 */
                return PERM_EVERYBODY;
        }

        /* A filemode value was given: 0xxx */

        if ((i & 0600) != 0600)
                die("Problem with core.sharedRepository filemode value "
                    "(0%.3o).\nThe owner of files must always have "
                    "read and write permissions.", i);

        /*
         * Mask filemode value. Others can not get write permission.
         * x flags for directories are handled separately.
         */
        return -(i & 0666);
}

int check_repository_format_version(const char *var, const char *value, void *cb)
{
        if (strcmp(var, "core.repositoryformatversion") == 0)
                repository_format_version = git_config_int(var, value);
        else if (strcmp(var, "core.sharedrepository") == 0)
                shared_repository = git_config_perm(var, value);
        else if (strcmp(var, "core.bare") == 0) {
                is_bare_repository_cfg = git_config_bool(var, value);
                if (is_bare_repository_cfg == 1)
                        inside_work_tree = -1;
        } else if (strcmp(var, "core.worktree") == 0) {
                if (!value)
                        return config_error_nonbool(var);
                free(git_work_tree_cfg);
                git_work_tree_cfg = xstrdup(value);
                inside_work_tree = -1;
        }
        return 0;
}

int check_repository_format(void)
{
        return check_repository_format_gently(get_git_dir(), NULL);
}

/*
 * Returns the "prefix", a path to the current working directory
 * relative to the work tree root, or NULL, if the current working
 * directory is not a strict subdirectory of the work tree root. The
 * prefix always ends with a '/' character.
 */
const char *setup_git_directory(void)
{
        return setup_git_directory_gently(NULL);
}

const char *resolve_gitdir(const char *suspect)
{
        if (is_git_directory(suspect))
                return suspect;
        return read_gitfile(suspect);
}

/* if any standard file descriptor is missing open it to /dev/null */
void sanitize_stdfds(void)
{
        int fd = open("/dev/null", O_RDWR, 0);
        while (fd != -1 && fd < 2)
                fd = dup(fd);
        if (fd == -1)
                die_errno("open /dev/null or dup failed");
        if (fd > 2)
                close(fd);
}