Squashed 'third_party/git/' content from commit cb71568594

git-subtree-dir: third_party/git
git-subtree-split: cb715685942260375e1eb8153b0768a376e4ece7

1 files changed, 1458 insertions, 0 deletions

diff --git a/path.c b/path.c
new file mode 100644
index 000000000000..25e97b8c3f76
--- /dev/null
+++ b/path.c
@@ -0,0 +1,1458 @@
+/*
+ * Utilities for paths and pathnames
+ */
+#include "cache.h"
+#include "repository.h"
+#include "strbuf.h"
+#include "string-list.h"
+#include "dir.h"
+#include "worktree.h"
+#include "submodule-config.h"
+#include "path.h"
+#include "packfile.h"
+#include "object-store.h"
+
+static int get_st_mode_bits(const char *path, int *mode)
+{
+	struct stat st;
+	if (lstat(path, &st) < 0)
+		return -1;
+	*mode = st.st_mode;
+	return 0;
+}
+
+static char bad_path[] = "/bad-path/";
+
+static struct strbuf *get_pathname(void)
+{
+	static struct strbuf pathname_array[4] = {
+		STRBUF_INIT, STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
+	};
+	static int index;
+	struct strbuf *sb = &pathname_array[index];
+	index = (index + 1) % ARRAY_SIZE(pathname_array);
+	strbuf_reset(sb);
+	return sb;
+}
+
+static const char *cleanup_path(const char *path)
+{
+	/* Clean it up */
+	if (skip_prefix(path, "./", &path)) {
+		while (*path == '/')
+			path++;
+	}
+	return path;
+}
+
+static void strbuf_cleanup_path(struct strbuf *sb)
+{
+	const char *path = cleanup_path(sb->buf);
+	if (path > sb->buf)
+		strbuf_remove(sb, 0, path - sb->buf);
+}
+
+char *mksnpath(char *buf, size_t n, const char *fmt, ...)
+{
+	va_list args;
+	unsigned len;
+
+	va_start(args, fmt);
+	len = vsnprintf(buf, n, fmt, args);
+	va_end(args);
+	if (len >= n) {
+		strlcpy(buf, bad_path, n);
+		return buf;
+	}
+	return (char *)cleanup_path(buf);
+}
+
+static int dir_prefix(const char *buf, const char *dir)
+{
+	int len = strlen(dir);
+	return !strncmp(buf, dir, len) &&
+		(is_dir_sep(buf[len]) || buf[len] == '\0');
+}
+
+/* $buf =~ m|$dir/+$file| but without regex */
+static int is_dir_file(const char *buf, const char *dir, const char *file)
+{
+	int len = strlen(dir);
+	if (strncmp(buf, dir, len) || !is_dir_sep(buf[len]))
+		return 0;
+	while (is_dir_sep(buf[len]))
+		len++;
+	return !strcmp(buf + len, file);
+}
+
+static void replace_dir(struct strbuf *buf, int len, const char *newdir)
+{
+	int newlen = strlen(newdir);
+	int need_sep = (buf->buf[len] && !is_dir_sep(buf->buf[len])) &&
+		!is_dir_sep(newdir[newlen - 1]);
+	if (need_sep)
+		len--;	 /* keep one char, to be replaced with '/'  */
+	strbuf_splice(buf, 0, len, newdir, newlen);
+	if (need_sep)
+		buf->buf[newlen] = '/';
+}
+
+struct common_dir {
+	/* Not considered garbage for report_linked_checkout_garbage */
+	unsigned ignore_garbage:1;
+	unsigned is_dir:1;
+	/* Not common even though its parent is */
+	unsigned exclude:1;
+	const char *dirname;
+};
+
+static struct common_dir common_list[] = {
+	{ 0, 1, 0, "branches" },
+	{ 0, 1, 0, "common" },
+	{ 0, 1, 0, "hooks" },
+	{ 0, 1, 0, "info" },
+	{ 0, 0, 1, "info/sparse-checkout" },
+	{ 1, 1, 0, "logs" },
+	{ 1, 1, 1, "logs/HEAD" },
+	{ 0, 1, 1, "logs/refs/bisect" },
+	{ 0, 1, 1, "logs/refs/rewritten" },
+	{ 0, 1, 1, "logs/refs/worktree" },
+	{ 0, 1, 0, "lost-found" },
+	{ 0, 1, 0, "objects" },
+	{ 0, 1, 0, "refs" },
+	{ 0, 1, 1, "refs/bisect" },
+	{ 0, 1, 1, "refs/rewritten" },
+	{ 0, 1, 1, "refs/worktree" },
+	{ 0, 1, 0, "remotes" },
+	{ 0, 1, 0, "worktrees" },
+	{ 0, 1, 0, "rr-cache" },
+	{ 0, 1, 0, "svn" },
+	{ 0, 0, 0, "config" },
+	{ 1, 0, 0, "gc.pid" },
+	{ 0, 0, 0, "packed-refs" },
+	{ 0, 0, 0, "shallow" },
+	{ 0, 0, 0, NULL }
+};
+
+/*
+ * A compressed trie.  A trie node consists of zero or more characters that
+ * are common to all elements with this prefix, optionally followed by some
+ * children.  If value is not NULL, the trie node is a terminal node.
+ *
+ * For example, consider the following set of strings:
+ * abc
+ * def
+ * definite
+ * definition
+ *
+ * The trie would look like:
+ * root: len = 0, children a and d non-NULL, value = NULL.
+ *    a: len = 2, contents = bc, value = (data for "abc")
+ *    d: len = 2, contents = ef, children i non-NULL, value = (data for "def")
+ *       i: len = 3, contents = nit, children e and i non-NULL, value = NULL
+ *           e: len = 0, children all NULL, value = (data for "definite")
+ *           i: len = 2, contents = on, children all NULL,
+ *              value = (data for "definition")
+ */
+struct trie {
+	struct trie *children[256];
+	int len;
+	char *contents;
+	void *value;
+};
+
+static struct trie *make_trie_node(const char *key, void *value)
+{
+	struct trie *new_node = xcalloc(1, sizeof(*new_node));
+	new_node->len = strlen(key);
+	if (new_node->len) {
+		new_node->contents = xmalloc(new_node->len);
+		memcpy(new_node->contents, key, new_node->len);
+	}
+	new_node->value = value;
+	return new_node;
+}
+
+/*
+ * Add a key/value pair to a trie.  The key is assumed to be \0-terminated.
+ * If there was an existing value for this key, return it.
+ */
+static void *add_to_trie(struct trie *root, const char *key, void *value)
+{
+	struct trie *child;
+	void *old;
+	int i;
+
+	if (!*key) {
+		/* we have reached the end of the key */
+		old = root->value;
+		root->value = value;
+		return old;
+	}
+
+	for (i = 0; i < root->len; i++) {
+		if (root->contents[i] == key[i])
+			continue;
+
+		/*
+		 * Split this node: child will contain this node's
+		 * existing children.
+		 */
+		child = xmalloc(sizeof(*child));
+		memcpy(child->children, root->children, sizeof(root->children));
+
+		child->len = root->len - i - 1;
+		if (child->len) {
+			child->contents = xstrndup(root->contents + i + 1,
+						   child->len);
+		}
+		child->value = root->value;
+		root->value = NULL;
+		root->len = i;
+
+		memset(root->children, 0, sizeof(root->children));
+		root->children[(unsigned char)root->contents[i]] = child;
+
+		/* This is the newly-added child. */
+		root->children[(unsigned char)key[i]] =
+			make_trie_node(key + i + 1, value);
+		return NULL;
+	}
+
+	/* We have matched the entire compressed section */
+	if (key[i]) {
+		child = root->children[(unsigned char)key[root->len]];
+		if (child) {
+			return add_to_trie(child, key + root->len + 1, value);
+		} else {
+			child = make_trie_node(key + root->len + 1, value);
+			root->children[(unsigned char)key[root->len]] = child;
+			return NULL;
+		}
+	}
+
+	old = root->value;
+	root->value = value;
+	return old;
+}
+
+typedef int (*match_fn)(const char *unmatched, void *data, void *baton);
+
+/*
+ * Search a trie for some key.  Find the longest /-or-\0-terminated
+ * prefix of the key for which the trie contains a value.  Call fn
+ * with the unmatched portion of the key and the found value, and
+ * return its return value.  If there is no such prefix, return -1.
+ *
+ * The key is partially normalized: consecutive slashes are skipped.
+ *
+ * For example, consider the trie containing only [refs,
+ * refs/worktree] (both with values).
+ *
+ * | key             | unmatched  | val from node | return value |
+ * |-----------------|------------|---------------|--------------|
+ * | a               | not called | n/a           | -1           |
+ * | refs            | \0         | refs          | as per fn    |
+ * | refs/           | /          | refs          | as per fn    |
+ * | refs/w          | /w         | refs          | as per fn    |
+ * | refs/worktree   | \0         | refs/worktree | as per fn    |
+ * | refs/worktree/  | /          | refs/worktree | as per fn    |
+ * | refs/worktree/a | /a         | refs/worktree | as per fn    |
+ * |-----------------|------------|---------------|--------------|
+ *
+ */
+static int trie_find(struct trie *root, const char *key, match_fn fn,
+		     void *baton)
+{
+	int i;
+	int result;
+	struct trie *child;
+
+	if (!*key) {
+		/* we have reached the end of the key */
+		if (root->value && !root->len)
+			return fn(key, root->value, baton);
+		else
+			return -1;
+	}
+
+	for (i = 0; i < root->len; i++) {
+		/* Partial path normalization: skip consecutive slashes. */
+		if (key[i] == '/' && key[i+1] == '/') {
+			key++;
+			continue;
+		}
+		if (root->contents[i] != key[i])
+			return -1;
+	}
+
+	/* Matched the entire compressed section */
+	key += i;
+	if (!*key)
+		/* End of key */
+		return fn(key, root->value, baton);
+
+	/* Partial path normalization: skip consecutive slashes */
+	while (key[0] == '/' && key[1] == '/')
+		key++;
+
+	child = root->children[(unsigned char)*key];
+	if (child)
+		result = trie_find(child, key + 1, fn, baton);
+	else
+		result = -1;
+
+	if (result >= 0 || (*key != '/' && *key != 0))
+		return result;
+	if (root->value)
+		return fn(key, root->value, baton);
+	else
+		return -1;
+}
+
+static struct trie common_trie;
+static int common_trie_done_setup;
+
+static void init_common_trie(void)
+{
+	struct common_dir *p;
+
+	if (common_trie_done_setup)
+		return;
+
+	for (p = common_list; p->dirname; p++)
+		add_to_trie(&common_trie, p->dirname, p);
+
+	common_trie_done_setup = 1;
+}
+
+/*
+ * Helper function for update_common_dir: returns 1 if the dir
+ * prefix is common.
+ */
+static int check_common(const char *unmatched, void *value, void *baton)
+{
+	struct common_dir *dir = value;
+
+	if (!dir)
+		return 0;
+
+	if (dir->is_dir && (unmatched[0] == 0 || unmatched[0] == '/'))
+		return !dir->exclude;
+
+	if (!dir->is_dir && unmatched[0] == 0)
+		return !dir->exclude;
+
+	return 0;
+}
+
+static void update_common_dir(struct strbuf *buf, int git_dir_len,
+			      const char *common_dir)
+{
+	char *base = buf->buf + git_dir_len;
+	init_common_trie();
+	if (trie_find(&common_trie, base, check_common, NULL) > 0)
+		replace_dir(buf, git_dir_len, common_dir);
+}
+
+void report_linked_checkout_garbage(void)
+{
+	struct strbuf sb = STRBUF_INIT;
+	const struct common_dir *p;
+	int len;
+
+	if (!the_repository->different_commondir)
+		return;
+	strbuf_addf(&sb, "%s/", get_git_dir());
+	len = sb.len;
+	for (p = common_list; p->dirname; p++) {
+		const char *path = p->dirname;
+		if (p->ignore_garbage)
+			continue;
+		strbuf_setlen(&sb, len);
+		strbuf_addstr(&sb, path);
+		if (file_exists(sb.buf))
+			report_garbage(PACKDIR_FILE_GARBAGE, sb.buf);
+	}
+	strbuf_release(&sb);
+}
+
+static void adjust_git_path(const struct repository *repo,
+			    struct strbuf *buf, int git_dir_len)
+{
+	const char *base = buf->buf + git_dir_len;
+	if (is_dir_file(base, "info", "grafts"))
+		strbuf_splice(buf, 0, buf->len,
+			      repo->graft_file, strlen(repo->graft_file));
+	else if (!strcmp(base, "index"))
+		strbuf_splice(buf, 0, buf->len,
+			      repo->index_file, strlen(repo->index_file));
+	else if (dir_prefix(base, "objects"))
+		replace_dir(buf, git_dir_len + 7, repo->objects->odb->path);
+	else if (git_hooks_path && dir_prefix(base, "hooks"))
+		replace_dir(buf, git_dir_len + 5, git_hooks_path);
+	else if (repo->different_commondir)
+		update_common_dir(buf, git_dir_len, repo->commondir);
+}
+
+static void strbuf_worktree_gitdir(struct strbuf *buf,
+				   const struct repository *repo,
+				   const struct worktree *wt)
+{
+	if (!wt)
+		strbuf_addstr(buf, repo->gitdir);
+	else if (!wt->id)
+		strbuf_addstr(buf, repo->commondir);
+	else
+		strbuf_git_common_path(buf, repo, "worktrees/%s", wt->id);
+}
+
+static void do_git_path(const struct repository *repo,
+			const struct worktree *wt, struct strbuf *buf,
+			const char *fmt, va_list args)
+{
+	int gitdir_len;
+	strbuf_worktree_gitdir(buf, repo, wt);
+	if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
+		strbuf_addch(buf, '/');
+	gitdir_len = buf->len;
+	strbuf_vaddf(buf, fmt, args);
+	if (!wt)
+		adjust_git_path(repo, buf, gitdir_len);
+	strbuf_cleanup_path(buf);
+}
+
+char *repo_git_path(const struct repository *repo,
+		    const char *fmt, ...)
+{
+	struct strbuf path = STRBUF_INIT;
+	va_list args;
+	va_start(args, fmt);
+	do_git_path(repo, NULL, &path, fmt, args);
+	va_end(args);
+	return strbuf_detach(&path, NULL);
+}
+
+void strbuf_repo_git_path(struct strbuf *sb,
+			  const struct repository *repo,
+			  const char *fmt, ...)
+{
+	va_list args;
+	va_start(args, fmt);
+	do_git_path(repo, NULL, sb, fmt, args);
+	va_end(args);
+}
+
+char *git_path_buf(struct strbuf *buf, const char *fmt, ...)
+{
+	va_list args;
+	strbuf_reset(buf);
+	va_start(args, fmt);
+	do_git_path(the_repository, NULL, buf, fmt, args);
+	va_end(args);
+	return buf->buf;
+}
+
+void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
+{
+	va_list args;
+	va_start(args, fmt);
+	do_git_path(the_repository, NULL, sb, fmt, args);
+	va_end(args);
+}
+
+const char *git_path(const char *fmt, ...)
+{
+	struct strbuf *pathname = get_pathname();
+	va_list args;
+	va_start(args, fmt);
+	do_git_path(the_repository, NULL, pathname, fmt, args);
+	va_end(args);
+	return pathname->buf;
+}
+
+char *git_pathdup(const char *fmt, ...)
+{
+	struct strbuf path = STRBUF_INIT;
+	va_list args;
+	va_start(args, fmt);
+	do_git_path(the_repository, NULL, &path, fmt, args);
+	va_end(args);
+	return strbuf_detach(&path, NULL);
+}
+
+char *mkpathdup(const char *fmt, ...)
+{
+	struct strbuf sb = STRBUF_INIT;
+	va_list args;
+	va_start(args, fmt);
+	strbuf_vaddf(&sb, fmt, args);
+	va_end(args);
+	strbuf_cleanup_path(&sb);
+	return strbuf_detach(&sb, NULL);
+}
+
+const char *mkpath(const char *fmt, ...)
+{
+	va_list args;
+	struct strbuf *pathname = get_pathname();
+	va_start(args, fmt);
+	strbuf_vaddf(pathname, fmt, args);
+	va_end(args);
+	return cleanup_path(pathname->buf);
+}
+
+const char *worktree_git_path(const struct worktree *wt, const char *fmt, ...)
+{
+	struct strbuf *pathname = get_pathname();
+	va_list args;
+	va_start(args, fmt);
+	do_git_path(the_repository, wt, pathname, fmt, args);
+	va_end(args);
+	return pathname->buf;
+}
+
+static void do_worktree_path(const struct repository *repo,
+			     struct strbuf *buf,
+			     const char *fmt, va_list args)
+{
+	strbuf_addstr(buf, repo->worktree);
+	if(buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
+		strbuf_addch(buf, '/');
+
+	strbuf_vaddf(buf, fmt, args);
+	strbuf_cleanup_path(buf);
+}
+
+char *repo_worktree_path(const struct repository *repo, const char *fmt, ...)
+{
+	struct strbuf path = STRBUF_INIT;
+	va_list args;
+
+	if (!repo->worktree)
+		return NULL;
+
+	va_start(args, fmt);
+	do_worktree_path(repo, &path, fmt, args);
+	va_end(args);
+
+	return strbuf_detach(&path, NULL);
+}
+
+void strbuf_repo_worktree_path(struct strbuf *sb,
+			       const struct repository *repo,
+			       const char *fmt, ...)
+{
+	va_list args;
+
+	if (!repo->worktree)
+		return;
+
+	va_start(args, fmt);
+	do_worktree_path(repo, sb, fmt, args);
+	va_end(args);
+}
+
+/* Returns 0 on success, negative on failure. */
+static int do_submodule_path(struct strbuf *buf, const char *path,
+			     const char *fmt, va_list args)
+{
+	struct strbuf git_submodule_common_dir = STRBUF_INIT;
+	struct strbuf git_submodule_dir = STRBUF_INIT;
+	int ret;
+
+	ret = submodule_to_gitdir(&git_submodule_dir, path);
+	if (ret)
+		goto cleanup;
+
+	strbuf_complete(&git_submodule_dir, '/');
+	strbuf_addbuf(buf, &git_submodule_dir);
+	strbuf_vaddf(buf, fmt, args);
+
+	if (get_common_dir_noenv(&git_submodule_common_dir, git_submodule_dir.buf))
+		update_common_dir(buf, git_submodule_dir.len, git_submodule_common_dir.buf);
+
+	strbuf_cleanup_path(buf);
+
+cleanup:
+	strbuf_release(&git_submodule_dir);
+	strbuf_release(&git_submodule_common_dir);
+	return ret;
+}
+
+char *git_pathdup_submodule(const char *path, const char *fmt, ...)
+{
+	int err;
+	va_list args;
+	struct strbuf buf = STRBUF_INIT;
+	va_start(args, fmt);
+	err = do_submodule_path(&buf, path, fmt, args);
+	va_end(args);
+	if (err) {
+		strbuf_release(&buf);
+		return NULL;
+	}
+	return strbuf_detach(&buf, NULL);
+}
+
+int strbuf_git_path_submodule(struct strbuf *buf, const char *path,
+			      const char *fmt, ...)
+{
+	int err;
+	va_list args;
+	va_start(args, fmt);
+	err = do_submodule_path(buf, path, fmt, args);
+	va_end(args);
+
+	return err;
+}
+
+static void do_git_common_path(const struct repository *repo,
+			       struct strbuf *buf,
+			       const char *fmt,
+			       va_list args)
+{
+	strbuf_addstr(buf, repo->commondir);
+	if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
+		strbuf_addch(buf, '/');
+	strbuf_vaddf(buf, fmt, args);
+	strbuf_cleanup_path(buf);
+}
+
+const char *git_common_path(const char *fmt, ...)
+{
+	struct strbuf *pathname = get_pathname();
+	va_list args;
+	va_start(args, fmt);
+	do_git_common_path(the_repository, pathname, fmt, args);
+	va_end(args);
+	return pathname->buf;
+}
+
+void strbuf_git_common_path(struct strbuf *sb,
+			    const struct repository *repo,
+			    const char *fmt, ...)
+{
+	va_list args;
+	va_start(args, fmt);
+	do_git_common_path(repo, sb, fmt, args);
+	va_end(args);
+}
+
+int validate_headref(const char *path)
+{
+	struct stat st;
+	char buffer[256];
+	const char *refname;
+	struct object_id oid;
+	int fd;
+	ssize_t len;
+
+	if (lstat(path, &st) < 0)
+		return -1;
+
+	/* Make sure it is a "refs/.." symlink */
+	if (S_ISLNK(st.st_mode)) {
+		len = readlink(path, buffer, sizeof(buffer)-1);
+		if (len >= 5 && !memcmp("refs/", buffer, 5))
+			return 0;
+		return -1;
+	}
+
+	/*
+	 * Anything else, just open it and try to see if it is a symbolic ref.
+	 */
+	fd = open(path, O_RDONLY);
+	if (fd < 0)
+		return -1;
+	len = read_in_full(fd, buffer, sizeof(buffer)-1);
+	close(fd);
+
+	if (len < 0)
+		return -1;
+	buffer[len] = '\0';
+
+	/*
+	 * Is it a symbolic ref?
+	 */
+	if (skip_prefix(buffer, "ref:", &refname)) {
+		while (isspace(*refname))
+			refname++;
+		if (starts_with(refname, "refs/"))
+			return 0;
+	}
+
+	/*
+	 * Is this a detached HEAD?
+	 */
+	if (!get_oid_hex(buffer, &oid))
+		return 0;
+
+	return -1;
+}
+
+static struct passwd *getpw_str(const char *username, size_t len)
+{
+	struct passwd *pw;
+	char *username_z = xmemdupz(username, len);
+	pw = getpwnam(username_z);
+	free(username_z);
+	return pw;
+}
+
+/*
+ * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
+ * then it is a newly allocated string. Returns NULL on getpw failure or
+ * if path is NULL.
+ *
+ * If real_home is true, real_path($HOME) is used in the expansion.
+ */
+char *expand_user_path(const char *path, int real_home)
+{
+	struct strbuf user_path = STRBUF_INIT;
+	const char *to_copy = path;
+
+	if (path == NULL)
+		goto return_null;
+	if (path[0] == '~') {
+		const char *first_slash = strchrnul(path, '/');
+		const char *username = path + 1;
+		size_t username_len = first_slash - username;
+		if (username_len == 0) {
+			const char *home = getenv("HOME");
+			if (!home)
+				goto return_null;
+			if (real_home)
+				strbuf_add_real_path(&user_path, home);
+			else
+				strbuf_addstr(&user_path, home);
+#ifdef GIT_WINDOWS_NATIVE
+			convert_slashes(user_path.buf);
+#endif
+		} else {
+			struct passwd *pw = getpw_str(username, username_len);
+			if (!pw)
+				goto return_null;
+			strbuf_addstr(&user_path, pw->pw_dir);
+		}
+		to_copy = first_slash;
+	}
+	strbuf_addstr(&user_path, to_copy);
+	return strbuf_detach(&user_path, NULL);
+return_null:
+	strbuf_release(&user_path);
+	return NULL;
+}
+
+/*
+ * First, one directory to try is determined by the following algorithm.
+ *
+ * (0) If "strict" is given, the path is used as given and no DWIM is
+ *     done. Otherwise:
+ * (1) "~/path" to mean path under the running user's home directory;
+ * (2) "~user/path" to mean path under named user's home directory;
+ * (3) "relative/path" to mean cwd relative directory; or
+ * (4) "/absolute/path" to mean absolute directory.
+ *
+ * Unless "strict" is given, we check "%s/.git", "%s", "%s.git/.git", "%s.git"
+ * in this order. We select the first one that is a valid git repository, and
+ * chdir() to it. If none match, or we fail to chdir, we return NULL.
+ *
+ * If all goes well, we return the directory we used to chdir() (but
+ * before ~user is expanded), avoiding getcwd() resolving symbolic
+ * links.  User relative paths are also returned as they are given,
+ * except DWIM suffixing.
+ */
+const char *enter_repo(const char *path, int strict)
+{
+	static struct strbuf validated_path = STRBUF_INIT;
+	static struct strbuf used_path = STRBUF_INIT;
+
+	if (!path)
+		return NULL;
+
+	if (!strict) {
+		static const char *suffix[] = {
+			"/.git", "", ".git/.git", ".git", NULL,
+		};
+		const char *gitfile;
+		int len = strlen(path);
+		int i;
+		while ((1 < len) && (path[len-1] == '/'))
+			len--;
+
+		/*
+		 * We can handle arbitrary-sized buffers, but this remains as a
+		 * sanity check on untrusted input.
+		 */
+		if (PATH_MAX <= len)
+			return NULL;
+
+		strbuf_reset(&used_path);
+		strbuf_reset(&validated_path);
+		strbuf_add(&used_path, path, len);
+		strbuf_add(&validated_path, path, len);
+
+		if (used_path.buf[0] == '~') {
+			char *newpath = expand_user_path(used_path.buf, 0);
+			if (!newpath)
+				return NULL;
+			strbuf_attach(&used_path, newpath, strlen(newpath),
+				      strlen(newpath));
+		}
+		for (i = 0; suffix[i]; i++) {
+			struct stat st;
+			size_t baselen = used_path.len;
+			strbuf_addstr(&used_path, suffix[i]);
+			if (!stat(used_path.buf, &st) &&
+			    (S_ISREG(st.st_mode) ||
+			    (S_ISDIR(st.st_mode) && is_git_directory(used_path.buf)))) {
+				strbuf_addstr(&validated_path, suffix[i]);
+				break;
+			}
+			strbuf_setlen(&used_path, baselen);
+		}
+		if (!suffix[i])
+			return NULL;
+		gitfile = read_gitfile(used_path.buf);
+		if (gitfile) {
+			strbuf_reset(&used_path);
+			strbuf_addstr(&used_path, gitfile);
+		}
+		if (chdir(used_path.buf))
+			return NULL;
+		path = validated_path.buf;
+	}
+	else {
+		const char *gitfile = read_gitfile(path);
+		if (gitfile)
+			path = gitfile;
+		if (chdir(path))
+			return NULL;
+	}
+
+	if (is_git_directory(".")) {
+		set_git_dir(".");
+		check_repository_format();
+		return path;
+	}
+
+	return NULL;
+}
+
+static int calc_shared_perm(int mode)
+{
+	int tweak;
+
+	if (get_shared_repository() < 0)
+		tweak = -get_shared_repository();
+	else
+		tweak = get_shared_repository();
+
+	if (!(mode & S_IWUSR))
+		tweak &= ~0222;
+	if (mode & S_IXUSR)
+		/* Copy read bits to execute bits */
+		tweak |= (tweak & 0444) >> 2;
+	if (get_shared_repository() < 0)
+		mode = (mode & ~0777) | tweak;
+	else
+		mode |= tweak;
+
+	return mode;
+}
+
+
+int adjust_shared_perm(const char *path)
+{
+	int old_mode, new_mode;
+
+	if (!get_shared_repository())
+		return 0;
+	if (get_st_mode_bits(path, &old_mode) < 0)
+		return -1;
+
+	new_mode = calc_shared_perm(old_mode);
+	if (S_ISDIR(old_mode)) {
+		/* Copy read bits to execute bits */
+		new_mode |= (new_mode & 0444) >> 2;
+		new_mode |= FORCE_DIR_SET_GID;
+	}
+
+	if (((old_mode ^ new_mode) & ~S_IFMT) &&
+			chmod(path, (new_mode & ~S_IFMT)) < 0)
+		return -2;
+	return 0;
+}
+
+void safe_create_dir(const char *dir, int share)
+{
+	if (mkdir(dir, 0777) < 0) {
+		if (errno != EEXIST) {
+			perror(dir);
+			exit(1);
+		}
+	}
+	else if (share && adjust_shared_perm(dir))
+		die(_("Could not make %s writable by group"), dir);
+}
+
+static int have_same_root(const char *path1, const char *path2)
+{
+	int is_abs1, is_abs2;
+
+	is_abs1 = is_absolute_path(path1);
+	is_abs2 = is_absolute_path(path2);
+	return (is_abs1 && is_abs2 && tolower(path1[0]) == tolower(path2[0])) ||
+	       (!is_abs1 && !is_abs2);
+}
+
+/*
+ * Give path as relative to prefix.
+ *
+ * The strbuf may or may not be used, so do not assume it contains the
+ * returned path.
+ */
+const char *relative_path(const char *in, const char *prefix,
+			  struct strbuf *sb)
+{
+	int in_len = in ? strlen(in) : 0;
+	int prefix_len = prefix ? strlen(prefix) : 0;
+	int in_off = 0;
+	int prefix_off = 0;
+	int i = 0, j = 0;
+
+	if (!in_len)
+		return "./";
+	else if (!prefix_len)
+		return in;
+
+	if (have_same_root(in, prefix))
+		/* bypass dos_drive, for "c:" is identical to "C:" */
+		i = j = has_dos_drive_prefix(in);
+	else {
+		return in;
+	}
+
+	while (i < prefix_len && j < in_len && prefix[i] == in[j]) {
+		if (is_dir_sep(prefix[i])) {
+			while (is_dir_sep(prefix[i]))
+				i++;
+			while (is_dir_sep(in[j]))
+				j++;
+			prefix_off = i;
+			in_off = j;
+		} else {
+			i++;
+			j++;
+		}
+	}
+
+	if (
+	    /* "prefix" seems like prefix of "in" */
+	    i >= prefix_len &&
+	    /*
+	     * but "/foo" is not a prefix of "/foobar"
+	     * (i.e. prefix not end with '/')
+	     */
+	    prefix_off < prefix_len) {
+		if (j >= in_len) {
+			/* in="/a/b", prefix="/a/b" */
+			in_off = in_len;
+		} else if (is_dir_sep(in[j])) {
+			/* in="/a/b/c", prefix="/a/b" */
+			while (is_dir_sep(in[j]))
+				j++;
+			in_off = j;
+		} else {
+			/* in="/a/bbb/c", prefix="/a/b" */
+			i = prefix_off;
+		}
+	} else if (
+		   /* "in" is short than "prefix" */
+		   j >= in_len &&
+		   /* "in" not end with '/' */
+		   in_off < in_len) {
+		if (is_dir_sep(prefix[i])) {
+			/* in="/a/b", prefix="/a/b/c/" */
+			while (is_dir_sep(prefix[i]))
+				i++;
+			in_off = in_len;
+		}
+	}
+	in += in_off;
+	in_len -= in_off;
+
+	if (i >= prefix_len) {
+		if (!in_len)
+			return "./";
+		else
+			return in;
+	}
+
+	strbuf_reset(sb);
+	strbuf_grow(sb, in_len);
+
+	while (i < prefix_len) {
+		if (is_dir_sep(prefix[i])) {
+			strbuf_addstr(sb, "../");
+			while (is_dir_sep(prefix[i]))
+				i++;
+			continue;
+		}
+		i++;
+	}
+	if (!is_dir_sep(prefix[prefix_len - 1]))
+		strbuf_addstr(sb, "../");
+
+	strbuf_addstr(sb, in);
+
+	return sb->buf;
+}
+
+/*
+ * A simpler implementation of relative_path
+ *
+ * Get relative path by removing "prefix" from "in". This function
+ * first appears in v1.5.6-1-g044bbbc, and makes git_dir shorter
+ * to increase performance when traversing the path to work_tree.
+ */
+const char *remove_leading_path(const char *in, const char *prefix)
+{
+	static struct strbuf buf = STRBUF_INIT;
+	int i = 0, j = 0;
+
+	if (!prefix || !prefix[0])
+		return in;
+	while (prefix[i]) {
+		if (is_dir_sep(prefix[i])) {
+			if (!is_dir_sep(in[j]))
+				return in;
+			while (is_dir_sep(prefix[i]))
+				i++;
+			while (is_dir_sep(in[j]))
+				j++;
+			continue;
+		} else if (in[j] != prefix[i]) {
+			return in;
+		}
+		i++;
+		j++;
+	}
+	if (
+	    /* "/foo" is a prefix of "/foo" */
+	    in[j] &&
+	    /* "/foo" is not a prefix of "/foobar" */
+	    !is_dir_sep(prefix[i-1]) && !is_dir_sep(in[j])
+	   )
+		return in;
+	while (is_dir_sep(in[j]))
+		j++;
+
+	strbuf_reset(&buf);
+	if (!in[j])
+		strbuf_addstr(&buf, ".");
+	else
+		strbuf_addstr(&buf, in + j);
+	return buf.buf;
+}
+
+/*
+ * It is okay if dst == src, but they should not overlap otherwise.
+ *
+ * Performs the following normalizations on src, storing the result in dst:
+ * - Ensures that components are separated by '/' (Windows only)
+ * - Squashes sequences of '/' except "//server/share" on Windows
+ * - Removes "." components.
+ * - Removes ".." components, and the components the precede them.
+ * Returns failure (non-zero) if a ".." component appears as first path
+ * component anytime during the normalization. Otherwise, returns success (0).
+ *
+ * Note that this function is purely textual.  It does not follow symlinks,
+ * verify the existence of the path, or make any system calls.
+ *
+ * prefix_len != NULL is for a specific case of prefix_pathspec():
+ * assume that src == dst and src[0..prefix_len-1] is already
+ * normalized, any time "../" eats up to the prefix_len part,
+ * prefix_len is reduced. In the end prefix_len is the remaining
+ * prefix that has not been overridden by user pathspec.
+ *
+ * NEEDSWORK: This function doesn't perform normalization w.r.t. trailing '/'.
+ * For everything but the root folder itself, the normalized path should not
+ * end with a '/', then the callers need to be fixed up accordingly.
+ *
+ */
+int normalize_path_copy_len(char *dst, const char *src, int *prefix_len)
+{
+	char *dst0;
+	const char *end;
+
+	/*
+	 * Copy initial part of absolute path: "/", "C:/", "//server/share/".
+	 */
+	end = src + offset_1st_component(src);
+	while (src < end) {
+		char c = *src++;
+		if (is_dir_sep(c))
+			c = '/';
+		*dst++ = c;
+	}
+	dst0 = dst;
+
+	while (is_dir_sep(*src))
+		src++;
+
+	for (;;) {
+		char c = *src;
+
+		/*
+		 * A path component that begins with . could be
+		 * special:
+		 * (1) "." and ends   -- ignore and terminate.
+		 * (2) "./"           -- ignore them, eat slash and continue.
+		 * (3) ".." and ends  -- strip one and terminate.
+		 * (4) "../"          -- strip one, eat slash and continue.
+		 */
+		if (c == '.') {
+			if (!src[1]) {
+				/* (1) */
+				src++;
+			} else if (is_dir_sep(src[1])) {
+				/* (2) */
+				src += 2;
+				while (is_dir_sep(*src))
+					src++;
+				continue;
+			} else if (src[1] == '.') {
+				if (!src[2]) {
+					/* (3) */
+					src += 2;
+					goto up_one;
+				} else if (is_dir_sep(src[2])) {
+					/* (4) */
+					src += 3;
+					while (is_dir_sep(*src))
+						src++;
+					goto up_one;
+				}
+			}
+		}
+
+		/* copy up to the next '/', and eat all '/' */
+		while ((c = *src++) != '\0' && !is_dir_sep(c))
+			*dst++ = c;
+		if (is_dir_sep(c)) {
+			*dst++ = '/';
+			while (is_dir_sep(c))
+				c = *src++;
+			src--;
+		} else if (!c)
+			break;
+		continue;
+
+	up_one:
+		/*
+		 * dst0..dst is prefix portion, and dst[-1] is '/';
+		 * go up one level.
+		 */
+		dst--;	/* go to trailing '/' */
+		if (dst <= dst0)
+			return -1;
+		/* Windows: dst[-1] cannot be backslash anymore */
+		while (dst0 < dst && dst[-1] != '/')
+			dst--;
+		if (prefix_len && *prefix_len > dst - dst0)
+			*prefix_len = dst - dst0;
+	}
+	*dst = '\0';
+	return 0;
+}
+
+int normalize_path_copy(char *dst, const char *src)
+{
+	return normalize_path_copy_len(dst, src, NULL);
+}
+
+/*
+ * path = Canonical absolute path
+ * prefixes = string_list containing normalized, absolute paths without
+ * trailing slashes (except for the root directory, which is denoted by "/").
+ *
+ * Determines, for each path in prefixes, whether the "prefix"
+ * is an ancestor directory of path.  Returns the length of the longest
+ * ancestor directory, excluding any trailing slashes, or -1 if no prefix
+ * is an ancestor.  (Note that this means 0 is returned if prefixes is
+ * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
+ * are not considered to be their own ancestors.  path must be in a
+ * canonical form: empty components, or "." or ".." components are not
+ * allowed.
+ */
+int longest_ancestor_length(const char *path, struct string_list *prefixes)
+{
+	int i, max_len = -1;
+
+	if (!strcmp(path, "/"))
+		return -1;
+
+	for (i = 0; i < prefixes->nr; i++) {
+		const char *ceil = prefixes->items[i].string;
+		int len = strlen(ceil);
+
+		if (len == 1 && ceil[0] == '/')
+			len = 0; /* root matches anything, with length 0 */
+		else if (!strncmp(path, ceil, len) && path[len] == '/')
+			; /* match of length len */
+		else
+			continue; /* no match */
+
+		if (len > max_len)
+			max_len = len;
+	}
+
+	return max_len;
+}
+
+/* strip arbitrary amount of directory separators at end of path */
+static inline int chomp_trailing_dir_sep(const char *path, int len)
+{
+	while (len && is_dir_sep(path[len - 1]))
+		len--;
+	return len;
+}
+
+/*
+ * If path ends with suffix (complete path components), returns the
+ * part before suffix (sans trailing directory separators).
+ * Otherwise returns NULL.
+ */
+char *strip_path_suffix(const char *path, const char *suffix)
+{
+	int path_len = strlen(path), suffix_len = strlen(suffix);
+
+	while (suffix_len) {
+		if (!path_len)
+			return NULL;
+
+		if (is_dir_sep(path[path_len - 1])) {
+			if (!is_dir_sep(suffix[suffix_len - 1]))
+				return NULL;
+			path_len = chomp_trailing_dir_sep(path, path_len);
+			suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
+		}
+		else if (path[--path_len] != suffix[--suffix_len])
+			return NULL;
+	}
+
+	if (path_len && !is_dir_sep(path[path_len - 1]))
+		return NULL;
+	return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
+}
+
+int daemon_avoid_alias(const char *p)
+{
+	int sl, ndot;
+
+	/*
+	 * This resurrects the belts and suspenders paranoia check by HPA
+	 * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
+	 * does not do getcwd() based path canonicalization.
+	 *
+	 * sl becomes true immediately after seeing '/' and continues to
+	 * be true as long as dots continue after that without intervening
+	 * non-dot character.
+	 */
+	if (!p || (*p != '/' && *p != '~'))
+		return -1;
+	sl = 1; ndot = 0;
+	p++;
+
+	while (1) {
+		char ch = *p++;
+		if (sl) {
+			if (ch == '.')
+				ndot++;
+			else if (ch == '/') {
+				if (ndot < 3)
+					/* reject //, /./ and /../ */
+					return -1;
+				ndot = 0;
+			}
+			else if (ch == 0) {
+				if (0 < ndot && ndot < 3)
+					/* reject /.$ and /..$ */
+					return -1;
+				return 0;
+			}
+			else
+				sl = ndot = 0;
+		}
+		else if (ch == 0)
+			return 0;
+		else if (ch == '/') {
+			sl = 1;
+			ndot = 0;
+		}
+	}
+}
+
+static int only_spaces_and_periods(const char *path, size_t len, size_t skip)
+{
+	if (len < skip)
+		return 0;
+	len -= skip;
+	path += skip;
+	while (len-- > 0) {
+		char c = *(path++);
+		if (c != ' ' && c != '.')
+			return 0;
+	}
+	return 1;
+}
+
+int is_ntfs_dotgit(const char *name)
+{
+	size_t len;
+
+	for (len = 0; ; len++)
+		if (!name[len] || name[len] == '\\' || is_dir_sep(name[len])) {
+			if (only_spaces_and_periods(name, len, 4) &&
+					!strncasecmp(name, ".git", 4))
+				return 1;
+			if (only_spaces_and_periods(name, len, 5) &&
+					!strncasecmp(name, "git~1", 5))
+				return 1;
+			if (name[len] != '\\')
+				return 0;
+			name += len + 1;
+			len = -1;
+		}
+}
+
+static int is_ntfs_dot_generic(const char *name,
+			       const char *dotgit_name,
+			       size_t len,
+			       const char *dotgit_ntfs_shortname_prefix)
+{
+	int saw_tilde;
+	size_t i;
+
+	if ((name[0] == '.' && !strncasecmp(name + 1, dotgit_name, len))) {
+		i = len + 1;
+only_spaces_and_periods:
+		for (;;) {
+			char c = name[i++];
+			if (!c)
+				return 1;
+			if (c != ' ' && c != '.')
+				return 0;
+		}
+	}
+
+	/*
+	 * Is it a regular NTFS short name, i.e. shortened to 6 characters,
+	 * followed by ~1, ... ~4?
+	 */
+	if (!strncasecmp(name, dotgit_name, 6) && name[6] == '~' &&
+	    name[7] >= '1' && name[7] <= '4') {
+		i = 8;
+		goto only_spaces_and_periods;
+	}
+
+	/*
+	 * Is it a fall-back NTFS short name (for details, see
+	 * https://en.wikipedia.org/wiki/8.3_filename?
+	 */
+	for (i = 0, saw_tilde = 0; i < 8; i++)
+		if (name[i] == '\0')
+			return 0;
+		else if (saw_tilde) {
+			if (name[i] < '0' || name[i] > '9')
+				return 0;
+		} else if (name[i] == '~') {
+			if (name[++i] < '1' || name[i] > '9')
+				return 0;
+			saw_tilde = 1;
+		} else if (i >= 6)
+			return 0;
+		else if (name[i] & 0x80) {
+			/*
+			 * We know our needles contain only ASCII, so we clamp
+			 * here to make the results of tolower() sane.
+			 */
+			return 0;
+		} else if (tolower(name[i]) != dotgit_ntfs_shortname_prefix[i])
+			return 0;
+
+	goto only_spaces_and_periods;
+}
+
+/*
+ * Inline helper to make sure compiler resolves strlen() on literals at
+ * compile time.
+ */
+static inline int is_ntfs_dot_str(const char *name, const char *dotgit_name,
+				  const char *dotgit_ntfs_shortname_prefix)
+{
+	return is_ntfs_dot_generic(name, dotgit_name, strlen(dotgit_name),
+				   dotgit_ntfs_shortname_prefix);
+}
+
+int is_ntfs_dotgitmodules(const char *name)
+{
+	return is_ntfs_dot_str(name, "gitmodules", "gi7eba");
+}
+
+int is_ntfs_dotgitignore(const char *name)
+{
+	return is_ntfs_dot_str(name, "gitignore", "gi250a");
+}
+
+int is_ntfs_dotgitattributes(const char *name)
+{
+	return is_ntfs_dot_str(name, "gitattributes", "gi7d29");
+}
+
+int looks_like_command_line_option(const char *str)
+{
+	return str && str[0] == '-';
+}
+
+char *xdg_config_home(const char *filename)
+{
+	const char *home, *config_home;
+
+	assert(filename);
+	config_home = getenv("XDG_CONFIG_HOME");
+	if (config_home && *config_home)
+		return mkpathdup("%s/git/%s", config_home, filename);
+
+	home = getenv("HOME");
+	if (home)
+		return mkpathdup("%s/.config/git/%s", home, filename);
+	return NULL;
+}
+
+char *xdg_cache_home(const char *filename)
+{
+	const char *home, *cache_home;
+
+	assert(filename);
+	cache_home = getenv("XDG_CACHE_HOME");
+	if (cache_home && *cache_home)
+		return mkpathdup("%s/git/%s", cache_home, filename);
+
+	home = getenv("HOME");
+	if (home)
+		return mkpathdup("%s/.cache/git/%s", home, filename);
+	return NULL;
+}
+
+REPO_GIT_PATH_FUNC(cherry_pick_head, "CHERRY_PICK_HEAD")
+REPO_GIT_PATH_FUNC(revert_head, "REVERT_HEAD")
+REPO_GIT_PATH_FUNC(squash_msg, "SQUASH_MSG")
+REPO_GIT_PATH_FUNC(merge_msg, "MERGE_MSG")
+REPO_GIT_PATH_FUNC(merge_rr, "MERGE_RR")
+REPO_GIT_PATH_FUNC(merge_mode, "MERGE_MODE")
+REPO_GIT_PATH_FUNC(merge_head, "MERGE_HEAD")
+REPO_GIT_PATH_FUNC(fetch_head, "FETCH_HEAD")
+REPO_GIT_PATH_FUNC(shallow, "shallow")