1 files changed, 670 insertions, 227 deletions

diff --git a/setup.c b/setup.c
index f67250b7c1..863ddfd938 100644
--- a/setup.c
+++ b/setup.c
@@ -1,64 +1,134 @@
 #include "cache.h"
 #include "dir.h"
+#include "string-list.h"
 
 static int inside_git_dir = -1;
 static int inside_work_tree = -1;
 
-const char *prefix_path(const char *prefix, int len, const char *path)
+/*
+ * 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 && !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 += 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 = xmalloc(len + strlen(path) + 1);
-	if (is_absolute_path(orig))
-		strcpy(sanitized, path);
-	else {
+	char *sanitized;
+	if (is_absolute_path(orig)) {
+		sanitized = xmalloc(strlen(path) + 1);
+		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 = xmalloc(len + strlen(path) + 1);
 		if (len)
 			memcpy(sanitized, prefix, len);
 		strcpy(sanitized + len, path);
-	}
-	if (normalize_path_copy(sanitized, sanitized))
-		goto error_out;
-	if (is_absolute_path(orig)) {
-		const char *work_tree = get_git_work_tree();
-		size_t len = strlen(work_tree);
-		size_t total = strlen(sanitized) + 1;
-		if (strncmp(sanitized, work_tree, len) ||
-		    (sanitized[len] != '\0' && sanitized[len] != '/')) {
-		error_out:
-			die("'%s' is outside repository", orig);
+		if (remaining_prefix)
+			*remaining_prefix = len;
+		if (normalize_path_copy_len(sanitized, sanitized, remaining_prefix)) {
+			free(sanitized);
+			return NULL;
 		}
-		if (sanitized[len] == '/')
-			len++;
-		memmove(sanitized, sanitized + len, total - len);
 	}
 	return sanitized;
 }
 
-/*
- * Unlike prefix_path, this should be used if the named file does
- * not have to interact with index entry; i.e. name of a random file
- * on the filesystem.
- */
-const char *prefix_filename(const char *pfx, int pfx_len, const char *arg)
-{
-	static char path[PATH_MAX];
-#ifndef WIN32
-	if (!pfx || !*pfx || is_absolute_path(arg))
-		return arg;
-	memcpy(path, pfx, pfx_len);
-	strcpy(path + pfx_len, arg);
-#else
-	char *p;
-	/* don't add prefix to absolute paths, but still replace '\' by '/' */
-	if (is_absolute_path(arg))
-		pfx_len = 0;
-	else
-		memcpy(path, pfx, pfx_len);
-	strcpy(path + pfx_len, arg);
-	for (p = path + pfx_len; *p; p++)
-		if (*p == '\\')
-			*p = '/';
-#endif
-	return path;
+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)
@@ -66,7 +136,16 @@ int check_filename(const char *prefix, const char *arg)
 	const char *name;
 	struct stat st;
 
-	name = prefix ? prefix_filename(prefix, strlen(prefix), arg) : arg;
+	if (starts_with(arg, ":/")) {
+		if (arg[2] == '\0') /* ":/" is root dir, always exists */
+			return 1;
+		name = arg + 2;
+	} else if (!no_wildcard(arg))
+		return 1;
+	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)
@@ -74,21 +153,59 @@ int check_filename(const char *prefix, const char *arg)
 	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)
+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("ambiguous argument '%s': unknown revision or path not in the working tree.\n"
-	    "Use '--' to separate paths from revisions", arg);
+	die_verify_filename(prefix, arg, diagnose_misspelt_rev);
 }
 
 /*
@@ -105,38 +222,39 @@ void verify_non_filename(const char *prefix, const char *arg)
 	if (!check_filename(prefix, arg))
 		return;
 	die("ambiguous argument '%s': both revision and filename\n"
-	    "Use '--' to separate filenames from revisions", arg);
+	    "Use '--' to separate paths from revisions, like this:\n"
+	    "'git <command> [<revision>...] -- [<file>...]'", arg);
 }
 
-const char **get_pathspec(const char *prefix, const char **pathspec)
+int get_common_dir(struct strbuf *sb, const char *gitdir)
 {
-	const char *entry = *pathspec;
-	const char **src, **dst;
-	int prefixlen;
-
-	if (!prefix && !entry)
-		return NULL;
-
-	if (!entry) {
-		static const char *spec[2];
-		spec[0] = prefix;
-		spec[1] = NULL;
-		return spec;
-	}
-
-	/* Otherwise we have to re-write the entries.. */
-	src = pathspec;
-	dst = pathspec;
-	prefixlen = prefix ? strlen(prefix) : 0;
-	while (*src) {
-		const char *p = prefix_path(prefix, prefixlen, *src);
-		*(dst++) = p;
-		src++;
+	struct strbuf data = STRBUF_INIT;
+	struct strbuf path = STRBUF_INIT;
+	const char *git_common_dir = getenv(GIT_COMMON_DIR_ENVIRONMENT);
+	int ret = 0;
+	if (git_common_dir) {
+		strbuf_addstr(sb, git_common_dir);
+		return 1;
 	}
-	*dst = NULL;
-	if (!*pathspec)
-		return NULL;
-	return pathspec;
+	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_addstr(sb, real_path(path.buf));
+		ret = 1;
+	} else
+		strbuf_addstr(sb, gitdir);
+	strbuf_release(&data);
+	strbuf_release(&path);
+	return ret;
 }
 
 /*
@@ -150,31 +268,42 @@ const char **get_pathspec(const char *prefix, const char **pathspec)
  *    a proper "ref:", or a regular file HEAD that has a properly
  *    formatted sha1 object name.
  */
-static int is_git_directory(const char *suspect)
+int is_git_directory(const char *suspect)
 {
-	char path[PATH_MAX];
-	size_t len = strlen(suspect);
+	struct strbuf path = STRBUF_INIT;
+	int ret = 0;
+	size_t len;
+
+	/* Check worktree-related signatures */
+	strbuf_addf(&path, "%s/HEAD", suspect);
+	if (validate_headref(path.buf))
+		goto done;
+
+	strbuf_reset(&path);
+	get_common_dir(&path, suspect);
+	len = path.len;
 
-	strcpy(path, suspect);
+	/* Check non-worktree-related signatures */
 	if (getenv(DB_ENVIRONMENT)) {
 		if (access(getenv(DB_ENVIRONMENT), X_OK))
-			return 0;
+			goto done;
 	}
 	else {
-		strcpy(path + len, "/objects");
-		if (access(path, X_OK))
-			return 0;
+		strbuf_setlen(&path, len);
+		strbuf_addstr(&path, "/objects");
+		if (access(path.buf, X_OK))
+			goto done;
 	}
 
-	strcpy(path + len, "/refs");
-	if (access(path, X_OK))
-		return 0;
-
-	strcpy(path + len, "/HEAD");
-	if (validate_headref(path))
-		return 0;
+	strbuf_setlen(&path, len);
+	strbuf_addstr(&path, "/refs");
+	if (access(path.buf, X_OK))
+		goto done;
 
-	return 1;
+	ret = 1;
+done:
+	strbuf_release(&path);
+	return ret;
 }
 
 int is_inside_git_dir(void)
@@ -191,24 +320,6 @@ int is_inside_work_tree(void)
 	return inside_work_tree;
 }
 
-/*
- * set_work_tree() is only ever called if you set GIT_DIR explicitely.
- * The old behaviour (which we retain here) is to set the work tree root
- * to the cwd, unless overridden by the config, the command line, or
- * GIT_WORK_TREE.
- */
-static const char *set_work_tree(const char *dir)
-{
-	char buffer[PATH_MAX + 1];
-
-	if (!getcwd(buffer, sizeof(buffer)))
-		die ("Could not get the current working directory");
-	git_work_tree_cfg = xstrdup(buffer);
-	inside_work_tree = 1;
-
-	return NULL;
-}
-
 void setup_work_tree(void)
 {
 	const char *work_tree, *git_dir;
@@ -219,16 +330,54 @@ void setup_work_tree(void)
 	work_tree = get_git_work_tree();
 	git_dir = get_git_dir();
 	if (!is_absolute_path(git_dir))
-		git_dir = make_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");
-	set_git_dir(make_relative_path(git_dir, 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(int *nongit_ok)
+static int check_repo_format(const char *var, const char *value, void *cb)
 {
-	git_config(check_repository_format_version, NULL);
+	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);
+	return 0;
+}
+
+static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
+{
+	struct strbuf sb = STRBUF_INIT;
+	const char *repo_config;
+	config_fn_t fn;
+	int ret = 0;
+
+	if (get_common_dir(&sb, gitdir))
+		fn = check_repo_format;
+	else
+		fn = check_repository_format_version;
+	strbuf_addstr(&sb, "/config");
+	repo_config = sb.buf;
+
+	/*
+	 * 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.
+	 */
+	git_config_early(fn, NULL, repo_config);
 	if (GIT_REPO_VERSION < repository_format_version) {
 		if (!nongit_ok)
 			die ("Expected git repo version <= %d, found %d",
@@ -237,21 +386,35 @@ static int check_repository_format_gently(int *nongit_ok)
 			GIT_REPO_VERSION, repository_format_version);
 		warning("Please upgrade Git");
 		*nongit_ok = -1;
-		return -1;
+		ret = -1;
 	}
-	return 0;
+	strbuf_release(&sb);
+	return ret;
+}
+
+static void update_linked_gitdir(const char *gitfile, const char *gitdir)
+{
+	struct strbuf path = STRBUF_INIT;
+	struct stat st;
+
+	strbuf_addf(&path, "%s/gitfile", gitdir);
+	if (stat(path.buf, &st) || st.st_mtime + 24 * 3600 < time(NULL))
+		write_file(path.buf, 0, "%s\n", gitfile);
+	strbuf_release(&path);
 }
 
 /*
  * Try to read the location of the git directory from the .git file,
  * return path to git directory if found.
  */
-const char *read_gitfile_gently(const char *path)
+const char *read_gitfile(const char *path)
 {
 	char *buf;
+	char *dir;
+	const char *slash;
 	struct stat st;
 	int fd;
-	size_t len;
+	ssize_t len;
 
 	if (stat(path, &st))
 		return NULL;
@@ -266,32 +429,281 @@ const char *read_gitfile_gently(const char *path)
 	if (len != st.st_size)
 		die("Error reading %s", path);
 	buf[len] = '\0';
-	if (prefixcmp(buf, "gitdir: "))
+	if (!starts_with(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';
-	if (!is_git_directory(buf + 8))
-		die("Not a git repository: %s", buf + 8);
-	path = make_absolute_path(buf + 8);
+	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);
+
+	update_linked_gitdir(path, dir);
+	path = real_path(dir);
+
 	free(buf);
 	return path;
 }
 
+static const char *setup_explicit_git_dir(const char *gitdirenv,
+					  struct strbuf *cwd,
+					  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;
+			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);
+			core_worktree = xgetcwd();
+			if (chdir(cwd->buf))
+				die_errno("Could not 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("Could not 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,
+					    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 != cwd->len && !is_absolute_path(gitdir))
+			gitdir = xstrdup(real_path(gitdir));
+		if (chdir(cwd->buf))
+			die_errno("Could not come back to cwd");
+		return setup_explicit_git_dir(gitdir, cwd, 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 == cwd->len ? gitdir : real_path(gitdir));
+		if (chdir(cwd->buf))
+			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 == cwd->len)
+		return NULL;
+
+	/* Make "offset" point to past the '/', and add a '/' at the end */
+	offset++;
+	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,
+				      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 == cwd->len ? "." : xmemdupz(cwd->buf, offset);
+		if (chdir(cwd->buf))
+			die_errno("Could not come back to cwd");
+		return setup_explicit_git_dir(gitdir, cwd, 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 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.
  */
-const char *setup_git_directory_gently(int *nongit_ok)
+static const char *setup_git_directory_gently_1(int *nongit_ok)
 {
-	const char *work_tree_env = getenv(GIT_WORK_TREE_ENVIRONMENT);
 	const char *env_ceiling_dirs = getenv(CEILING_DIRECTORIES_ENVIRONMENT);
-	static char cwd[PATH_MAX+1];
-	const char *gitdirenv;
-	const char *gitfile_dir;
-	int len, offset, ceil_offset;
+	struct string_list ceiling_dirs = STRING_LIST_INIT_DUP;
+	static struct strbuf cwd = STRBUF_INIT;
+	const char *gitdirenv, *ret;
+	char *gitfile;
+	int offset, offset_parent, ceil_offset = -1;
+	dev_t current_device = 0;
+	int one_filesystem = 1;
+
+	/*
+	 * 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.
@@ -301,50 +713,30 @@ const char *setup_git_directory_gently(int *nongit_ok)
 	if (nongit_ok)
 		*nongit_ok = 0;
 
+	if (strbuf_getcwd(&cwd))
+		die_errno("Unable to read current working directory");
+	offset = cwd.len;
+
 	/*
 	 * 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) {
-		if (PATH_MAX - 40 < strlen(gitdirenv))
-			die("'$%s' too big", GIT_DIR_ENVIRONMENT);
-		if (is_git_directory(gitdirenv)) {
-			static char buffer[1024 + 1];
-			const char *retval;
-
-			if (!work_tree_env) {
-				retval = set_work_tree(gitdirenv);
-				/* config may override worktree */
-				if (check_repository_format_gently(nongit_ok))
-					return NULL;
-				return retval;
-			}
-			if (check_repository_format_gently(nongit_ok))
-				return NULL;
-			retval = get_relative_cwd(buffer, sizeof(buffer) - 1,
-					get_git_work_tree());
-			if (!retval || !*retval)
-				return NULL;
-			set_git_dir(make_absolute_path(gitdirenv));
-			if (chdir(work_tree_env) < 0)
-				die_errno ("Could not chdir to '%s'", work_tree_env);
-			strcat(buffer, "/");
-			return retval;
-		}
-		if (nongit_ok) {
-			*nongit_ok = 1;
-			return NULL;
-		}
-		die("Not a git repository: '%s'", gitdirenv);
-	}
+	if (gitdirenv)
+		return setup_explicit_git_dir(gitdirenv, &cwd, nongit_ok);
 
-	if (!getcwd(cwd, sizeof(cwd)-1))
-		die_errno("Unable to read current working directory");
+	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.buf, &ceiling_dirs);
+		string_list_clear(&ceiling_dirs, 0);
+	}
 
-	ceil_offset = longest_ancestor_length(cwd, env_ceiling_dirs);
-	if (ceil_offset < 0 && has_dos_drive_prefix(cwd))
+	if (ceil_offset < 0 && has_dos_drive_prefix(cwd.buf))
 		ceil_offset = 1;
 
 	/*
@@ -358,56 +750,73 @@ const char *setup_git_directory_gently(int *nongit_ok)
 	 * - ../../.git/
 	 *   etc.
 	 */
-	offset = len = strlen(cwd);
+	one_filesystem = !git_env_bool("GIT_DISCOVERY_ACROSS_FILESYSTEM", 0);
+	if (one_filesystem)
+		current_device = get_device_or_die(".", NULL, 0);
 	for (;;) {
-		gitfile_dir = read_gitfile_gently(DEFAULT_GIT_DIR_ENVIRONMENT);
-		if (gitfile_dir) {
-			if (set_git_dir(gitfile_dir))
-				die("Repository setup failed");
-			break;
+		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 (is_git_directory(DEFAULT_GIT_DIR_ENVIRONMENT))
-			break;
-		if (is_git_directory(".")) {
-			inside_git_dir = 1;
-			if (!work_tree_env)
-				inside_work_tree = 0;
-			if (offset != len) {
-				cwd[offset] = '\0';
-				setenv(GIT_DIR_ENVIRONMENT, cwd, 1);
-			} else
-				setenv(GIT_DIR_ENVIRONMENT, ".", 1);
-			check_repository_format_gently(nongit_ok);
-			return NULL;
+
+		if (gitdirenv) {
+			ret = setup_discovered_git_dir(gitdirenv,
+						       &cwd, offset,
+						       nongit_ok);
+			free(gitfile);
+			return ret;
 		}
-		while (--offset > ceil_offset && cwd[offset] != '/');
-		if (offset <= ceil_offset) {
-			if (nongit_ok) {
-				if (chdir(cwd))
-					die_errno("Cannot come back to cwd");
-				*nongit_ok = 1;
-				return NULL;
+		free(gitfile);
+
+		if (is_git_directory("."))
+			return setup_bare_git_dir(&cwd, offset, nongit_ok);
+
+		offset_parent = offset;
+		while (--offset_parent > ceil_offset && cwd.buf[offset_parent] != '/');
+		if (offset_parent <= ceil_offset)
+			return setup_nongit(cwd.buf, nongit_ok);
+		if (one_filesystem) {
+			dev_t parent_device = get_device_or_die("..", cwd.buf,
+								offset);
+			if (parent_device != current_device) {
+				if (nongit_ok) {
+					if (chdir(cwd.buf))
+						die_errno("Cannot come back to cwd");
+					*nongit_ok = 1;
+					return NULL;
+				}
+				strbuf_setlen(&cwd, offset);
+				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.buf);
 			}
-			die("Not a git repository (or any of the parent directories): %s", DEFAULT_GIT_DIR_ENVIRONMENT);
 		}
-		if (chdir(".."))
-			die_errno("Cannot change to '%s/..'", cwd);
+		if (chdir("..")) {
+			strbuf_setlen(&cwd, offset);
+			die_errno("Cannot change to '%s/..'", cwd.buf);
+		}
+		offset = offset_parent;
 	}
+}
 
-	inside_git_dir = 0;
-	if (!work_tree_env)
-		inside_work_tree = 1;
-	git_work_tree_cfg = xstrndup(cwd, offset);
-	if (check_repository_format_gently(nongit_ok))
-		return NULL;
-	if (offset == len)
-		return NULL;
+const char *setup_git_directory_gently(int *nongit_ok)
+{
+	const char *prefix;
 
-	/* Make "offset" point to past the '/', and add a '/' at the end */
-	offset++;
-	cwd[len++] = '/';
-	cwd[len] = 0;
-	return cwd + offset;
+	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)
@@ -463,11 +872,10 @@ int git_config_perm(const char *var, const char *value)
 
 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) {
+	int ret = check_repo_format(var, value, cb);
+	if (ret)
+		return ret;
+	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;
@@ -483,24 +891,59 @@ int check_repository_format_version(const char *var, const char *value, void *cb
 
 int check_repository_format(void)
 {
-	return check_repository_format_gently(NULL);
+	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)
 {
-	const char *retval = setup_git_directory_gently(NULL);
-
-	/* If the work tree is not the default one, recompute prefix */
-	if (inside_work_tree < 0) {
-		static char buffer[PATH_MAX + 1];
-		char *rel;
-		if (retval && chdir(retval))
-			die_errno ("Could not jump back into original cwd");
-		rel = get_relative_cwd(buffer, PATH_MAX, get_git_work_tree());
-		if (rel && *rel && chdir(get_git_work_tree()))
-			die_errno ("Could not jump to working directory");
-		return rel && *rel ? strcat(rel, "/") : NULL;
-	}
+	return setup_git_directory_gently(NULL);
+}
+
+const char *resolve_gitdir(const char *suspect)
+{
+	if (is_git_directory(suspect))
+		return suspect;
+	return read_gitfile(suspect);
+}
 
-	return retval;
+/* 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
 }