chore(3p/git): Unvendor git and track patches instead r/2903

This was vendored a long time ago under the expectation that keeping
it in sync with cgit would be easier this way, but it has proven not
to be a big issue.

On the other hand, a vendored copy of git is an annoying maintenance
burden. It is much easier to rebase the single (dottime) patch that we
have.

This removes the vendored copy of git and instead passes the git
source code to cgit via `pkgs.srcOnly`, which includes the applied
patch so that cgit can continue rendering dottime.

Change-Id: If31f62dea7ce688fd1b9050204e9378019775f2b

1 files changed, 0 insertions, 1538 deletions

diff --git a/third_party/git/path.c b/third_party/git/path.c
deleted file mode 100644
index 7b385e5eb282..000000000000
--- a/third_party/git/path.c
+++ /dev/null
@@ -1,1538 +0,0 @@
-/*
- * 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"
-#include "lockfile.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;
-	/* Belongs to the common dir, though it may contain paths that don't */
-	unsigned is_common:1;
-	const char *path;
-};
-
-static struct common_dir common_list[] = {
-	{ 0, 1, 1, "branches" },
-	{ 0, 1, 1, "common" },
-	{ 0, 1, 1, "hooks" },
-	{ 0, 1, 1, "info" },
-	{ 0, 0, 0, "info/sparse-checkout" },
-	{ 1, 1, 1, "logs" },
-	{ 1, 0, 0, "logs/HEAD" },
-	{ 0, 1, 0, "logs/refs/bisect" },
-	{ 0, 1, 0, "logs/refs/rewritten" },
-	{ 0, 1, 0, "logs/refs/worktree" },
-	{ 0, 1, 1, "lost-found" },
-	{ 0, 1, 1, "objects" },
-	{ 0, 1, 1, "refs" },
-	{ 0, 1, 0, "refs/bisect" },
-	{ 0, 1, 0, "refs/rewritten" },
-	{ 0, 1, 0, "refs/worktree" },
-	{ 0, 1, 1, "remotes" },
-	{ 0, 1, 1, "worktrees" },
-	{ 0, 1, 1, "rr-cache" },
-	{ 0, 1, 1, "svn" },
-	{ 0, 0, 1, "config" },
-	{ 1, 0, 1, "gc.pid" },
-	{ 0, 0, 1, "packed-refs" },
-	{ 0, 0, 1, "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 *value, 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.  If there is
- * no such prefix, return -1.  Otherwise call fn with the unmatched
- * portion of the key and the found value.  If fn returns 0 or
- * positive, then return its return value.  If fn returns negative,
- * then call fn with the next-longest /-terminated prefix of the key
- * (i.e. a parent directory) for which the trie contains a value, and
- * handle its return value the same way.  If there is no shorter
- * /-terminated prefix with a value left, then return the negative
- * return value of the most recent fn invocation.
- *
- * The key is partially normalized: consecutive slashes are skipped.
- *
- * For example, consider the trie containing only [logs,
- * logs/refs/bisect], both with values, but not logs/refs.
- *
- * | key                | unmatched      | prefix to node   | return value |
- * |--------------------|----------------|------------------|--------------|
- * | a                  | not called     | n/a              | -1           |
- * | logstore           | not called     | n/a              | -1           |
- * | logs               | \0             | logs             | as per fn    |
- * | logs/              | /              | logs             | as per fn    |
- * | logs/refs          | /refs          | logs             | as per fn    |
- * | logs/refs/         | /refs/         | logs             | as per fn    |
- * | logs/refs/b        | /refs/b        | logs             | as per fn    |
- * | logs/refs/bisected | /refs/bisected | logs             | as per fn    |
- * | logs/refs/bisect   | \0             | logs/refs/bisect | as per fn    |
- * | logs/refs/bisect/  | /              | logs/refs/bisect | as per fn    |
- * | logs/refs/bisect/a | /a             | logs/refs/bisect | as per fn    |
- * | (If fn in the previous line returns -1, then fn is called once more:) |
- * | logs/refs/bisect/a | /refs/bisect/a | logs             | 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 */
-		if (root->value)
-			return fn(key, root->value, baton);
-		else
-			return -1;
-	}
-
-	/* 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->path; p++)
-		add_to_trie(&common_trie, p->path, 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->is_dir && (unmatched[0] == 0 || unmatched[0] == '/'))
-		return dir->is_common;
-
-	if (!dir->is_dir && unmatched[0] == 0)
-		return dir->is_common;
-
-	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;
-	int has_lock_suffix = strbuf_strip_suffix(buf, LOCK_SUFFIX);
-
-	init_common_trie();
-	if (trie_find(&common_trie, base, check_common, NULL) > 0)
-		replace_dir(buf, git_dir_len, common_dir);
-
-	if (has_lock_suffix)
-		strbuf_addstr(buf, LOCK_SUFFIX);
-}
-
-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->path; p++) {
-		const char *path = p->path;
-		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, strbuf_realpath($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(".", 0);
-		check_repository_format(NULL);
-		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.
- * The "dst" buffer must be at least as long as "src"; normalizing may shrink
- * the size of the path, but will never grow it.
- *
- * 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 offset of
- * the last character in the path before the suffix (sans trailing directory
- * separators), and -1 otherwise.
- */
-static ssize_t stripped_path_suffix_offset(const char *path, const char *suffix)
-{
-	int path_len = strlen(path), suffix_len = strlen(suffix);
-
-	while (suffix_len) {
-		if (!path_len)
-			return -1;
-
-		if (is_dir_sep(path[path_len - 1])) {
-			if (!is_dir_sep(suffix[suffix_len - 1]))
-				return -1;
-			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 -1;
-	}
-
-	if (path_len && !is_dir_sep(path[path_len - 1]))
-		return -1;
-	return chomp_trailing_dir_sep(path, path_len);
-}
-
-/*
- * Returns true if the path ends with components, considering only complete path
- * components, and false otherwise.
- */
-int ends_with_path_components(const char *path, const char *components)
-{
-	return stripped_path_suffix_offset(path, components) != -1;
-}
-
-/*
- * 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)
-{
-	ssize_t offset = stripped_path_suffix_offset(path, suffix);
-
-	return offset == -1 ? NULL : xstrndup(path, offset);
-}
-
-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;
-		}
-	}
-}
-
-/*
- * On NTFS, we need to be careful to disallow certain synonyms of the `.git/`
- * directory:
- *
- * - For historical reasons, file names that end in spaces or periods are
- *   automatically trimmed. Therefore, `.git . . ./` is a valid way to refer
- *   to `.git/`.
- *
- * - For other historical reasons, file names that do not conform to the 8.3
- *   format (up to eight characters for the basename, three for the file
- *   extension, certain characters not allowed such as `+`, etc) are associated
- *   with a so-called "short name", at least on the `C:` drive by default.
- *   Which means that `git~1/` is a valid way to refer to `.git/`.
- *
- *   Note: Technically, `.git/` could receive the short name `git~2` if the
- *   short name `git~1` were already used. In Git, however, we guarantee that
- *   `.git` is the first item in a directory, therefore it will be associated
- *   with the short name `git~1` (unless short names are disabled).
- *
- * - For yet other historical reasons, NTFS supports so-called "Alternate Data
- *   Streams", i.e. metadata associated with a given file, referred to via
- *   `<filename>:<stream-name>:<stream-type>`. There exists a default stream
- *   type for directories, allowing `.git/` to be accessed via
- *   `.git::$INDEX_ALLOCATION/`.
- *
- * When this function returns 1, it indicates that the specified file/directory
- * name refers to a `.git` file or directory, or to any of these synonyms, and
- * Git should therefore not track it.
- *
- * For performance reasons, _all_ Alternate Data Streams of `.git/` are
- * forbidden, not just `::$INDEX_ALLOCATION`.
- *
- * This function is intended to be used by `git fsck` even on platforms where
- * the backslash is a regular filename character, therefore it needs to handle
- * backlash characters in the provided `name` specially: they are interpreted
- * as directory separators.
- */
-int is_ntfs_dotgit(const char *name)
-{
-	char c;
-
-	/*
-	 * Note that when we don't find `.git` or `git~1` we end up with `name`
-	 * advanced partway through the string. That's okay, though, as we
-	 * return immediately in those cases, without looking at `name` any
-	 * further.
-	 */
-	c = *(name++);
-	if (c == '.') {
-		/* .git */
-		if (((c = *(name++)) != 'g' && c != 'G') ||
-		    ((c = *(name++)) != 'i' && c != 'I') ||
-		    ((c = *(name++)) != 't' && c != 'T'))
-			return 0;
-	} else if (c == 'g' || c == 'G') {
-		/* git ~1 */
-		if (((c = *(name++)) != 'i' && c != 'I') ||
-		    ((c = *(name++)) != 't' && c != 'T') ||
-		    *(name++) != '~' ||
-		    *(name++) != '1')
-			return 0;
-	} else
-		return 0;
-
-	for (;;) {
-		c = *(name++);
-		if (!c || c == '\\' || c == '/' || c == ':')
-			return 1;
-		if (c != '.' && c != ' ')
-			return 0;
-	}
-}
-
-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 || 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(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(merge_autostash, "MERGE_AUTOSTASH")
-REPO_GIT_PATH_FUNC(fetch_head, "FETCH_HEAD")
-REPO_GIT_PATH_FUNC(shallow, "shallow")