merge(third_party/git): Merge squashed git subtree at v2.23.0 r/373

Merge commit '1b593e1ea4d2af0f6444d9a7788d5d99abd6fde5' as 'third_party/git'

1 files changed, 1291 insertions, 0 deletions

diff --git a/third_party/git/setup.c b/third_party/git/setup.c
new file mode 100644
index 0000000000..8dcb4631f7
--- /dev/null
+++ b/third_party/git/setup.c
@@ -0,0 +1,1291 @@
+#include "cache.h"
+#include "repository.h"
+#include "config.h"
+#include "dir.h"
+#include "string-list.h"
+#include "chdir-notify.h"
+
+static int inside_git_dir = -1;
+static int inside_work_tree = -1;
+static int work_tree_config_is_bogus;
+
+static struct startup_info the_startup_info;
+struct startup_info *startup_info = &the_startup_info;
+
+/*
+ * 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 = offset_1st_component(path);
+
+	/* check if work tree is already the prefix */
+	if (wtlen <= len && !fspathncmp(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 += off;
+
+	/* check each '/'-terminated level */
+	while (*path) {
+		path++;
+		if (*path == '/') {
+			*path = '\0';
+			if (fspathcmp(real_path(path0), work_tree) == 0) {
+				memmove(path0, path + 1, len - (path - path0));
+				return 0;
+			}
+			*path = '/';
+		}
+	}
+
+	/* check whole path */
+	if (fspathcmp(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)) {
+		sanitized = xmallocz(strlen(path));
+		if (remaining_prefix)
+			*remaining_prefix = 0;
+		if (normalize_path_copy_len(sanitized, path, remaining_prefix)) {
+			free(sanitized);
+			return NULL;
+		}
+		if (abspath_part_inside_repo(sanitized)) {
+			free(sanitized);
+			return NULL;
+		}
+	} else {
+		sanitized = xstrfmt("%.*s%s", len, len ? prefix : "", path);
+		if (remaining_prefix)
+			*remaining_prefix = len;
+		if (normalize_path_copy_len(sanitized, sanitized, remaining_prefix)) {
+			free(sanitized);
+			return NULL;
+		}
+	}
+	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)
+{
+	char *to_free = NULL;
+	struct stat st;
+
+	if (skip_prefix(arg, ":/", &arg)) {
+		if (!*arg) /* ":/" is root dir, always exists */
+			return 1;
+		prefix = NULL;
+	} else if (skip_prefix(arg, ":!", &arg) ||
+		   skip_prefix(arg, ":^", &arg)) {
+		if (!*arg) /* excluding everything is silly, but allowed */
+			return 1;
+	}
+
+	if (prefix)
+		arg = to_free = prefix_filename(prefix, arg);
+
+	if (!lstat(arg, &st)) {
+		free(to_free);
+		return 1; /* file exists */
+	}
+	if (is_missing_file_error(errno)) {
+		free(to_free);
+		return 0; /* file does not exist */
+	}
+	die_errno(_("failed to stat '%s'"), arg);
+}
+
+static void NORETURN die_verify_filename(struct repository *r,
+					 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(r, 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);
+
+}
+
+/*
+ * Check for arguments that don't resolve as actual files,
+ * but which look sufficiently like pathspecs that we'll consider
+ * them such for the purposes of rev/pathspec DWIM parsing.
+ */
+static int looks_like_pathspec(const char *arg)
+{
+	/* anything with a wildcard character */
+	if (!no_wildcard(arg))
+		return 1;
+
+	/* long-form pathspec magic */
+	if (starts_with(arg, ":("))
+		return 1;
+
+	return 0;
+}
+
+/*
+ * 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(_("option '%s' must come before non-option arguments"), arg);
+	if (looks_like_pathspec(arg) || check_filename(prefix, arg))
+		return;
+	die_verify_filename(the_repository, 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);
+}
+
+int get_common_dir(struct strbuf *sb, const char *gitdir)
+{
+	const char *git_env_common_dir = getenv(GIT_COMMON_DIR_ENVIRONMENT);
+	if (git_env_common_dir) {
+		strbuf_addstr(sb, git_env_common_dir);
+		return 1;
+	} else {
+		return get_common_dir_noenv(sb, gitdir);
+	}
+}
+
+int get_common_dir_noenv(struct strbuf *sb, const char *gitdir)
+{
+	struct strbuf data = STRBUF_INIT;
+	struct strbuf path = STRBUF_INIT;
+	int ret = 0;
+
+	strbuf_addf(&path, "%s/commondir", gitdir);
+	if (file_exists(path.buf)) {
+		if (strbuf_read_file(&data, path.buf, 0) <= 0)
+			die_errno(_("failed to read %s"), path.buf);
+		while (data.len && (data.buf[data.len - 1] == '\n' ||
+				    data.buf[data.len - 1] == '\r'))
+			data.len--;
+		data.buf[data.len] = '\0';
+		strbuf_reset(&path);
+		if (!is_absolute_path(data.buf))
+			strbuf_addf(&path, "%s/", gitdir);
+		strbuf_addbuf(&path, &data);
+		strbuf_add_real_path(sb, path.buf);
+		ret = 1;
+	} else {
+		strbuf_addstr(sb, gitdir);
+	}
+
+	strbuf_release(&data);
+	strbuf_release(&path);
+	return ret;
+}
+
+/*
+ * 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)
+{
+	struct strbuf path = STRBUF_INIT;
+	int ret = 0;
+	size_t len;
+
+	/* Check worktree-related signatures */
+	strbuf_addstr(&path, suspect);
+	strbuf_complete(&path, '/');
+	strbuf_addstr(&path, "HEAD");
+	if (validate_headref(path.buf))
+		goto done;
+
+	strbuf_reset(&path);
+	get_common_dir(&path, suspect);
+	len = path.len;
+
+	/* Check non-worktree-related signatures */
+	if (getenv(DB_ENVIRONMENT)) {
+		if (access(getenv(DB_ENVIRONMENT), X_OK))
+			goto done;
+	}
+	else {
+		strbuf_setlen(&path, len);
+		strbuf_addstr(&path, "/objects");
+		if (access(path.buf, X_OK))
+			goto done;
+	}
+
+	strbuf_setlen(&path, len);
+	strbuf_addstr(&path, "/refs");
+	if (access(path.buf, X_OK))
+		goto done;
+
+	ret = 1;
+done:
+	strbuf_release(&path);
+	return ret;
+}
+
+int is_nonbare_repository_dir(struct strbuf *path)
+{
+	int ret = 0;
+	int gitfile_error;
+	size_t orig_path_len = path->len;
+	assert(orig_path_len != 0);
+	strbuf_complete(path, '/');
+	strbuf_addstr(path, ".git");
+	if (read_gitfile_gently(path->buf, &gitfile_error) || is_git_directory(path->buf))
+		ret = 1;
+	if (gitfile_error == READ_GITFILE_ERR_OPEN_FAILED ||
+	    gitfile_error == READ_GITFILE_ERR_READ_FAILED)
+		ret = 1;
+	strbuf_setlen(path, orig_path_len);
+	return ret;
+}
+
+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;
+	static int initialized = 0;
+
+	if (initialized)
+		return;
+
+	if (work_tree_config_is_bogus)
+		die(_("unable to set up work tree using invalid config"));
+
+	work_tree = get_git_work_tree();
+	if (!work_tree || chdir_notify(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);
+
+	initialized = 1;
+}
+
+static int read_worktree_config(const char *var, const char *value, void *vdata)
+{
+	struct repository_format *data = vdata;
+
+	if (strcmp(var, "core.bare") == 0) {
+		data->is_bare = git_config_bool(var, value);
+	} else if (strcmp(var, "core.worktree") == 0) {
+		if (!value)
+			return config_error_nonbool(var);
+		free(data->work_tree);
+		data->work_tree = xstrdup(value);
+	}
+	return 0;
+}
+
+static int check_repo_format(const char *var, const char *value, void *vdata)
+{
+	struct repository_format *data = vdata;
+	const char *ext;
+
+	if (strcmp(var, "core.repositoryformatversion") == 0)
+		data->version = git_config_int(var, value);
+	else if (skip_prefix(var, "extensions.", &ext)) {
+		/*
+		 * record any known extensions here; otherwise,
+		 * we fall through to recording it as unknown, and
+		 * check_repository_format will complain
+		 */
+		if (!strcmp(ext, "noop"))
+			;
+		else if (!strcmp(ext, "preciousobjects"))
+			data->precious_objects = git_config_bool(var, value);
+		else if (!strcmp(ext, "partialclone")) {
+			if (!value)
+				return config_error_nonbool(var);
+			data->partial_clone = xstrdup(value);
+		} else if (!strcmp(ext, "worktreeconfig"))
+			data->worktree_config = git_config_bool(var, value);
+		else
+			string_list_append(&data->unknown_extensions, ext);
+	}
+
+	return read_worktree_config(var, value, vdata);
+}
+
+static int check_repository_format_gently(const char *gitdir, struct repository_format *candidate, int *nongit_ok)
+{
+	struct strbuf sb = STRBUF_INIT;
+	struct strbuf err = STRBUF_INIT;
+	int has_common;
+
+	has_common = get_common_dir(&sb, gitdir);
+	strbuf_addstr(&sb, "/config");
+	read_repository_format(candidate, sb.buf);
+	strbuf_release(&sb);
+
+	/*
+	 * For historical use of check_repository_format() in git-init,
+	 * we treat a missing config as a silent "ok", even when nongit_ok
+	 * is unset.
+	 */
+	if (candidate->version < 0)
+		return 0;
+
+	if (verify_repository_format(candidate, &err) < 0) {
+		if (nongit_ok) {
+			warning("%s", err.buf);
+			strbuf_release(&err);
+			*nongit_ok = -1;
+			return -1;
+		}
+		die("%s", err.buf);
+	}
+
+	repository_format_precious_objects = candidate->precious_objects;
+	repository_format_partial_clone = xstrdup_or_null(candidate->partial_clone);
+	repository_format_worktree_config = candidate->worktree_config;
+	string_list_clear(&candidate->unknown_extensions, 0);
+
+	if (repository_format_worktree_config) {
+		/*
+		 * pick up core.bare and core.worktree from per-worktree
+		 * config if present
+		 */
+		strbuf_addf(&sb, "%s/config.worktree", gitdir);
+		git_config_from_file(read_worktree_config, sb.buf, candidate);
+		strbuf_release(&sb);
+		has_common = 0;
+	}
+
+	if (!has_common) {
+		if (candidate->is_bare != -1) {
+			is_bare_repository_cfg = candidate->is_bare;
+			if (is_bare_repository_cfg == 1)
+				inside_work_tree = -1;
+		}
+		if (candidate->work_tree) {
+			free(git_work_tree_cfg);
+			git_work_tree_cfg = xstrdup(candidate->work_tree);
+			inside_work_tree = -1;
+		}
+	}
+
+	return 0;
+}
+
+static void init_repository_format(struct repository_format *format)
+{
+	const struct repository_format fresh = REPOSITORY_FORMAT_INIT;
+
+	memcpy(format, &fresh, sizeof(fresh));
+}
+
+int read_repository_format(struct repository_format *format, const char *path)
+{
+	clear_repository_format(format);
+	git_config_from_file(check_repo_format, path, format);
+	if (format->version == -1)
+		clear_repository_format(format);
+	return format->version;
+}
+
+void clear_repository_format(struct repository_format *format)
+{
+	string_list_clear(&format->unknown_extensions, 0);
+	free(format->work_tree);
+	free(format->partial_clone);
+	init_repository_format(format);
+}
+
+int verify_repository_format(const struct repository_format *format,
+			     struct strbuf *err)
+{
+	if (GIT_REPO_VERSION_READ < format->version) {
+		strbuf_addf(err, _("Expected git repo version <= %d, found %d"),
+			    GIT_REPO_VERSION_READ, format->version);
+		return -1;
+	}
+
+	if (format->version >= 1 && format->unknown_extensions.nr) {
+		int i;
+
+		strbuf_addstr(err, _("unknown repository extensions found:"));
+
+		for (i = 0; i < format->unknown_extensions.nr; i++)
+			strbuf_addf(err, "\n\t%s",
+				    format->unknown_extensions.items[i].string);
+		return -1;
+	}
+
+	return 0;
+}
+
+void read_gitfile_error_die(int error_code, const char *path, const char *dir)
+{
+	switch (error_code) {
+	case READ_GITFILE_ERR_STAT_FAILED:
+	case READ_GITFILE_ERR_NOT_A_FILE:
+		/* non-fatal; follow return path */
+		break;
+	case READ_GITFILE_ERR_OPEN_FAILED:
+		die_errno(_("error opening '%s'"), path);
+	case READ_GITFILE_ERR_TOO_LARGE:
+		die(_("too large to be a .git file: '%s'"), path);
+	case READ_GITFILE_ERR_READ_FAILED:
+		die(_("error reading %s"), path);
+	case READ_GITFILE_ERR_INVALID_FORMAT:
+		die(_("invalid gitfile format: %s"), path);
+	case READ_GITFILE_ERR_NO_PATH:
+		die(_("no path in gitfile: %s"), path);
+	case READ_GITFILE_ERR_NOT_A_REPO:
+		die(_("not a git repository: %s"), dir);
+	default:
+		BUG("unknown error code");
+	}
+}
+
+/*
+ * Try to read the location of the git directory from the .git file,
+ * return path to git directory if found. The return value comes from
+ * a shared buffer.
+ *
+ * On failure, if return_error_code is not NULL, return_error_code
+ * will be set to an error code and NULL will be returned. If
+ * return_error_code is NULL the function will die instead (for most
+ * cases).
+ */
+const char *read_gitfile_gently(const char *path, int *return_error_code)
+{
+	const int max_file_size = 1 << 20;  /* 1MB */
+	int error_code = 0;
+	char *buf = NULL;
+	char *dir = NULL;
+	const char *slash;
+	struct stat st;
+	int fd;
+	ssize_t len;
+
+	if (stat(path, &st)) {
+		/* NEEDSWORK: discern between ENOENT vs other errors */
+		error_code = READ_GITFILE_ERR_STAT_FAILED;
+		goto cleanup_return;
+	}
+	if (!S_ISREG(st.st_mode)) {
+		error_code = READ_GITFILE_ERR_NOT_A_FILE;
+		goto cleanup_return;
+	}
+	if (st.st_size > max_file_size) {
+		error_code = READ_GITFILE_ERR_TOO_LARGE;
+		goto cleanup_return;
+	}
+	fd = open(path, O_RDONLY);
+	if (fd < 0) {
+		error_code = READ_GITFILE_ERR_OPEN_FAILED;
+		goto cleanup_return;
+	}
+	buf = xmallocz(st.st_size);
+	len = read_in_full(fd, buf, st.st_size);
+	close(fd);
+	if (len != st.st_size) {
+		error_code = READ_GITFILE_ERR_READ_FAILED;
+		goto cleanup_return;
+	}
+	if (!starts_with(buf, "gitdir: ")) {
+		error_code = READ_GITFILE_ERR_INVALID_FORMAT;
+		goto cleanup_return;
+	}
+	while (buf[len - 1] == '\n' || buf[len - 1] == '\r')
+		len--;
+	if (len < 9) {
+		error_code = READ_GITFILE_ERR_NO_PATH;
+		goto cleanup_return;
+	}
+	buf[len] = '\0';
+	dir = buf + 8;
+
+	if (!is_absolute_path(dir) && (slash = strrchr(path, '/'))) {
+		size_t pathlen = slash+1 - path;
+		dir = xstrfmt("%.*s%.*s", (int)pathlen, path,
+			      (int)(len - 8), buf + 8);
+		free(buf);
+		buf = dir;
+	}
+	if (!is_git_directory(dir)) {
+		error_code = READ_GITFILE_ERR_NOT_A_REPO;
+		goto cleanup_return;
+	}
+	path = real_path(dir);
+
+cleanup_return:
+	if (return_error_code)
+		*return_error_code = error_code;
+	else if (error_code)
+		read_gitfile_error_die(error_code, path, dir);
+
+	free(buf);
+	return error_code ? NULL : path;
+}
+
+static const char *setup_explicit_git_dir(const char *gitdirenv,
+					  struct strbuf *cwd,
+					  struct repository_format *repo_fmt,
+					  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, repo_fmt, 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 */
+			warning("core.bare and core.worktree do not make sense");
+			work_tree_config_is_bogus = 1;
+		}
+
+		/* #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;
+			if (chdir(gitdirenv))
+				die_errno(_("cannot chdir to '%s'"), gitdirenv);
+			if (chdir(git_work_tree_cfg))
+				die_errno(_("cannot chdir to '%s'"), git_work_tree_cfg);
+			core_worktree = xgetcwd();
+			if (chdir(cwd->buf))
+				die_errno(_("cannot come back to cwd"));
+			set_git_work_tree(core_worktree);
+			free(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->buf, worktree)) { /* cwd == worktree */
+		set_git_dir(gitdirenv);
+		free(gitfile);
+		return NULL;
+	}
+
+	offset = dir_inside_of(cwd->buf, worktree);
+	if (offset >= 0) {	/* cwd inside worktree? */
+		set_git_dir(real_path(gitdirenv));
+		if (chdir(worktree))
+			die_errno(_("cannot chdir to '%s'"), worktree);
+		strbuf_addch(cwd, '/');
+		free(gitfile);
+		return cwd->buf + offset;
+	}
+
+	/* cwd outside worktree */
+	set_git_dir(gitdirenv);
+	free(gitfile);
+	return NULL;
+}
+
+static const char *setup_discovered_git_dir(const char *gitdir,
+					    struct strbuf *cwd, int offset,
+					    struct repository_format *repo_fmt,
+					    int *nongit_ok)
+{
+	if (check_repository_format_gently(gitdir, repo_fmt, nongit_ok))
+		return NULL;
+
+	/* --work-tree is set without --git-dir; use discovered one */
+	if (getenv(GIT_WORK_TREE_ENVIRONMENT) || git_work_tree_cfg) {
+		char *to_free = NULL;
+		const char *ret;
+
+		if (offset != cwd->len && !is_absolute_path(gitdir))
+			gitdir = to_free = real_pathdup(gitdir, 1);
+		if (chdir(cwd->buf))
+			die_errno(_("cannot come back to cwd"));
+		ret = setup_explicit_git_dir(gitdir, cwd, repo_fmt, nongit_ok);
+		free(to_free);
+		return ret;
+	}
+
+	/* #16.2, #17.2, #20.2, #21.2, #24, #25, #28, #29 (see t1510) */
+	if (is_bare_repository_cfg > 0) {
+		set_git_dir(offset == cwd->len ? gitdir : real_path(gitdir));
+		if (chdir(cwd->buf))
+			die_errno(_("cannot 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 == cwd->len)
+		return NULL;
+
+	/* Make "offset" point past the '/' (already the case for root dirs) */
+	if (offset != offset_1st_component(cwd->buf))
+		offset++;
+	/* Add a '/' at the end */
+	strbuf_addch(cwd, '/');
+	return cwd->buf + offset;
+}
+
+/* #16.1, #17.1, #20.1, #21.1, #22.1 (see t1510) */
+static const char *setup_bare_git_dir(struct strbuf *cwd, int offset,
+				      struct repository_format *repo_fmt,
+				      int *nongit_ok)
+{
+	int root_len;
+
+	if (check_repository_format_gently(".", repo_fmt, 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) {
+		static const char *gitdir;
+
+		gitdir = offset == cwd->len ? "." : xmemdupz(cwd->buf, offset);
+		if (chdir(cwd->buf))
+			die_errno(_("cannot come back to cwd"));
+		return setup_explicit_git_dir(gitdir, cwd, repo_fmt, nongit_ok);
+	}
+
+	inside_git_dir = 1;
+	inside_work_tree = 0;
+	if (offset != cwd->len) {
+		if (chdir(cwd->buf))
+			die_errno(_("cannot come back to cwd"));
+		root_len = offset_1st_component(cwd->buf);
+		strbuf_setlen(cwd, offset > root_len ? offset : root_len);
+		set_git_dir(cwd->buf);
+	}
+	else
+		set_git_dir(".");
+	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 {
+		char *real_path = real_pathdup(ceil, 0);
+		if (!real_path) {
+			return 0;
+		}
+		free(item->string);
+		item->string = real_path;
+		return 1;
+	}
+}
+
+enum discovery_result {
+	GIT_DIR_NONE = 0,
+	GIT_DIR_EXPLICIT,
+	GIT_DIR_DISCOVERED,
+	GIT_DIR_BARE,
+	/* these are errors */
+	GIT_DIR_HIT_CEILING = -1,
+	GIT_DIR_HIT_MOUNT_POINT = -2,
+	GIT_DIR_INVALID_GITFILE = -3
+};
+
+/*
+ * 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.
+ *
+ * Also, we avoid changing any global state (such as the current working
+ * directory) to allow early callers.
+ *
+ * The directory where the search should start needs to be passed in via the
+ * `dir` parameter; upon return, the `dir` buffer will contain the path of
+ * the directory where the search ended, and `gitdir` will contain the path of
+ * the discovered .git/ directory, if any. If `gitdir` is not absolute, it
+ * is relative to `dir` (i.e. *not* necessarily the cwd).
+ */
+static enum discovery_result setup_git_directory_gently_1(struct strbuf *dir,
+							  struct strbuf *gitdir,
+							  int die_on_error)
+{
+	const char *env_ceiling_dirs = getenv(CEILING_DIRECTORIES_ENVIRONMENT);
+	struct string_list ceiling_dirs = STRING_LIST_INIT_DUP;
+	const char *gitdirenv;
+	int ceil_offset = -1, min_offset = has_dos_drive_prefix(dir->buf) ? 3 : 1;
+	dev_t current_device = 0;
+	int one_filesystem = 1;
+
+	/*
+	 * 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) {
+		strbuf_addstr(gitdir, gitdirenv);
+		return GIT_DIR_EXPLICIT;
+	}
+
+	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(dir->buf, &ceiling_dirs);
+		string_list_clear(&ceiling_dirs, 0);
+	}
+
+	if (ceil_offset < 0)
+		ceil_offset = min_offset - 2;
+
+	/*
+	 * Test in the following order (relative to the dir):
+	 * - .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(dir->buf, NULL, 0);
+	for (;;) {
+		int offset = dir->len, error_code = 0;
+
+		if (offset > min_offset)
+			strbuf_addch(dir, '/');
+		strbuf_addstr(dir, DEFAULT_GIT_DIR_ENVIRONMENT);
+		gitdirenv = read_gitfile_gently(dir->buf, die_on_error ?
+						NULL : &error_code);
+		if (!gitdirenv) {
+			if (die_on_error ||
+			    error_code == READ_GITFILE_ERR_NOT_A_FILE) {
+				/* NEEDSWORK: fail if .git is not file nor dir */
+				if (is_git_directory(dir->buf))
+					gitdirenv = DEFAULT_GIT_DIR_ENVIRONMENT;
+			} else if (error_code != READ_GITFILE_ERR_STAT_FAILED)
+				return GIT_DIR_INVALID_GITFILE;
+		}
+		strbuf_setlen(dir, offset);
+		if (gitdirenv) {
+			strbuf_addstr(gitdir, gitdirenv);
+			return GIT_DIR_DISCOVERED;
+		}
+
+		if (is_git_directory(dir->buf)) {
+			strbuf_addstr(gitdir, ".");
+			return GIT_DIR_BARE;
+		}
+
+		if (offset <= min_offset)
+			return GIT_DIR_HIT_CEILING;
+
+		while (--offset > ceil_offset && !is_dir_sep(dir->buf[offset]))
+			; /* continue */
+		if (offset <= ceil_offset)
+			return GIT_DIR_HIT_CEILING;
+
+		strbuf_setlen(dir, offset > min_offset ?  offset : min_offset);
+		if (one_filesystem &&
+		    current_device != get_device_or_die(dir->buf, NULL, offset))
+			return GIT_DIR_HIT_MOUNT_POINT;
+	}
+}
+
+int discover_git_directory(struct strbuf *commondir,
+			   struct strbuf *gitdir)
+{
+	struct strbuf dir = STRBUF_INIT, err = STRBUF_INIT;
+	size_t gitdir_offset = gitdir->len, cwd_len;
+	size_t commondir_offset = commondir->len;
+	struct repository_format candidate = REPOSITORY_FORMAT_INIT;
+
+	if (strbuf_getcwd(&dir))
+		return -1;
+
+	cwd_len = dir.len;
+	if (setup_git_directory_gently_1(&dir, gitdir, 0) <= 0) {
+		strbuf_release(&dir);
+		return -1;
+	}
+
+	/*
+	 * The returned gitdir is relative to dir, and if dir does not reflect
+	 * the current working directory, we simply make the gitdir absolute.
+	 */
+	if (dir.len < cwd_len && !is_absolute_path(gitdir->buf + gitdir_offset)) {
+		/* Avoid a trailing "/." */
+		if (!strcmp(".", gitdir->buf + gitdir_offset))
+			strbuf_setlen(gitdir, gitdir_offset);
+		else
+			strbuf_addch(&dir, '/');
+		strbuf_insert(gitdir, gitdir_offset, dir.buf, dir.len);
+	}
+
+	get_common_dir(commondir, gitdir->buf + gitdir_offset);
+
+	strbuf_reset(&dir);
+	strbuf_addf(&dir, "%s/config", commondir->buf + commondir_offset);
+	read_repository_format(&candidate, dir.buf);
+	strbuf_release(&dir);
+
+	if (verify_repository_format(&candidate, &err) < 0) {
+		warning("ignoring git dir '%s': %s",
+			gitdir->buf + gitdir_offset, err.buf);
+		strbuf_release(&err);
+		strbuf_setlen(commondir, commondir_offset);
+		strbuf_setlen(gitdir, gitdir_offset);
+		clear_repository_format(&candidate);
+		return -1;
+	}
+
+	clear_repository_format(&candidate);
+	return 0;
+}
+
+const char *setup_git_directory_gently(int *nongit_ok)
+{
+	static struct strbuf cwd = STRBUF_INIT;
+	struct strbuf dir = STRBUF_INIT, gitdir = STRBUF_INIT;
+	const char *prefix = NULL;
+	struct repository_format repo_fmt = REPOSITORY_FORMAT_INIT;
+
+	/*
+	 * We may have read an incomplete configuration before
+	 * setting-up the git directory. If so, clear the cache so
+	 * that the next queries to the configuration reload complete
+	 * configuration (including the per-repo config file that we
+	 * ignored previously).
+	 */
+	git_config_clear();
+
+	/*
+	 * 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 (strbuf_getcwd(&cwd))
+		die_errno(_("Unable to read current working directory"));
+	strbuf_addbuf(&dir, &cwd);
+
+	switch (setup_git_directory_gently_1(&dir, &gitdir, 1)) {
+	case GIT_DIR_EXPLICIT:
+		prefix = setup_explicit_git_dir(gitdir.buf, &cwd, &repo_fmt, nongit_ok);
+		break;
+	case GIT_DIR_DISCOVERED:
+		if (dir.len < cwd.len && chdir(dir.buf))
+			die(_("cannot change to '%s'"), dir.buf);
+		prefix = setup_discovered_git_dir(gitdir.buf, &cwd, dir.len,
+						  &repo_fmt, nongit_ok);
+		break;
+	case GIT_DIR_BARE:
+		if (dir.len < cwd.len && chdir(dir.buf))
+			die(_("cannot change to '%s'"), dir.buf);
+		prefix = setup_bare_git_dir(&cwd, dir.len, &repo_fmt, nongit_ok);
+		break;
+	case GIT_DIR_HIT_CEILING:
+		if (!nongit_ok)
+			die(_("not a git repository (or any of the parent directories): %s"),
+			    DEFAULT_GIT_DIR_ENVIRONMENT);
+		*nongit_ok = 1;
+		break;
+	case GIT_DIR_HIT_MOUNT_POINT:
+		if (!nongit_ok)
+			die(_("not a git repository (or any parent up to mount point %s)\n"
+			      "Stopping at filesystem boundary (GIT_DISCOVERY_ACROSS_FILESYSTEM not set)."),
+			    dir.buf);
+		*nongit_ok = 1;
+		break;
+	case GIT_DIR_NONE:
+		/*
+		 * As a safeguard against setup_git_directory_gently_1 returning
+		 * this value, fallthrough to BUG. Otherwise it is possible to
+		 * set startup_info->have_repository to 1 when we did nothing to
+		 * find a repository.
+		 */
+	default:
+		BUG("unhandled setup_git_directory_1() result");
+	}
+
+	/*
+	 * At this point, nongit_ok is stable. If it is non-NULL and points
+	 * to a non-zero value, then this means that we haven't found a
+	 * repository and that the caller expects startup_info to reflect
+	 * this.
+	 *
+	 * Regardless of the state of nongit_ok, startup_info->prefix and
+	 * the GIT_PREFIX environment variable must always match. For details
+	 * see Documentation/config/alias.txt.
+	 */
+	if (nongit_ok && *nongit_ok) {
+		startup_info->have_repository = 0;
+		startup_info->prefix = NULL;
+		setenv(GIT_PREFIX_ENVIRONMENT, "", 1);
+	} else {
+		startup_info->have_repository = 1;
+		startup_info->prefix = prefix;
+		if (prefix)
+			setenv(GIT_PREFIX_ENVIRONMENT, prefix, 1);
+		else
+			setenv(GIT_PREFIX_ENVIRONMENT, "", 1);
+	}
+
+	/*
+	 * Not all paths through the setup code will call 'set_git_dir()' (which
+	 * directly sets up the environment) so in order to guarantee that the
+	 * environment is in a consistent state after setup, explicitly setup
+	 * the environment if we have a repository.
+	 *
+	 * NEEDSWORK: currently we allow bogus GIT_DIR values to be set in some
+	 * code paths so we also need to explicitly setup the environment if
+	 * the user has set GIT_DIR.  It may be beneficial to disallow bogus
+	 * GIT_DIR values at some point in the future.
+	 */
+	if (/* GIT_DIR_EXPLICIT, GIT_DIR_DISCOVERED, GIT_DIR_BARE */
+	    startup_info->have_repository ||
+	    /* GIT_DIR_EXPLICIT */
+	    getenv(GIT_DIR_ENVIRONMENT)) {
+		if (!the_repository->gitdir) {
+			const char *gitdir = getenv(GIT_DIR_ENVIRONMENT);
+			if (!gitdir)
+				gitdir = DEFAULT_GIT_DIR_ENVIRONMENT;
+			setup_git_env(gitdir);
+		}
+		if (startup_info->have_repository)
+			repo_set_hash_algo(the_repository, repo_fmt.hash_algo);
+	}
+
+	strbuf_release(&dir);
+	strbuf_release(&gitdir);
+	clear_repository_format(&repo_fmt);
+
+	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);
+}
+
+void check_repository_format(void)
+{
+	struct repository_format repo_fmt = REPOSITORY_FORMAT_INIT;
+	check_repository_format_gently(get_git_dir(), &repo_fmt, NULL);
+	startup_info->have_repository = 1;
+	clear_repository_format(&repo_fmt);
+}
+
+/*
+ * 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_gently(const char *suspect, int *return_error_code)
+{
+	if (is_git_directory(suspect))
+		return suspect;
+	return read_gitfile_gently(suspect, return_error_code);
+}
+
+/* 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);
+}
+
+int daemonize(void)
+{
+#ifdef NO_POSIX_GOODIES
+	errno = ENOSYS;
+	return -1;
+#else
+	switch (fork()) {
+		case 0:
+			break;
+		case -1:
+			die_errno(_("fork failed"));
+		default:
+			exit(0);
+	}
+	if (setsid() == -1)
+		die_errno(_("setsid failed"));
+	close(0);
+	close(1);
+	close(2);
+	sanitize_stdfds();
+	return 0;
+#endif
+}