/*
 * Builtin "git clone"
 *
 * Copyright (c) 2007 Kristian Høgsberg <krh@redhat.com>,
 *		 2008 Daniel Barkalow <barkalow@iabervon.org>
 * Based on git-commit.sh by Junio C Hamano and Linus Torvalds
 *
 * Clone a repository into a different directory that does not yet exist.
 */

#include "builtin.h"
#include "lockfile.h"
#include "parse-options.h"
#include "fetch-pack.h"
#include "refs.h"
#include "tree.h"
#include "tree-walk.h"
#include "unpack-trees.h"
#include "transport.h"
#include "strbuf.h"
#include "dir.h"
#include "sigchain.h"
#include "branch.h"
#include "remote.h"
#include "run-command.h"
#include "connected.h"

/*
 * Overall FIXMEs:
 *  - respect DB_ENVIRONMENT for .git/objects.
 *
 * Implementation notes:
 *  - dropping use-separate-remote and no-separate-remote compatibility
 *
 */
static const char * const builtin_clone_usage[] = {
	N_("git clone [<options>] [--] <repo> [<dir>]"),
	NULL
};

static int option_no_checkout, option_bare, option_mirror, option_single_branch = -1;
static int option_local = -1, option_no_hardlinks, option_shared, option_recursive;
static int option_shallow_submodules;
static char *option_template, *option_depth;
static char *option_origin = NULL;
static char *option_branch = NULL;
static const char *real_git_dir;
static char *option_upload_pack = "git-upload-pack";
static int option_verbosity;
static int option_progress = -1;
static enum transport_family family;
static struct string_list option_config = STRING_LIST_INIT_NODUP;
static struct string_list option_reference = STRING_LIST_INIT_NODUP;
static int option_dissociate;
static int max_jobs = -1;

static struct option builtin_clone_options[] = {
	OPT__VERBOSITY(&option_verbosity),
	OPT_BOOL(0, "progress", &option_progress,
		 N_("force progress reporting")),
	OPT_BOOL('n', "no-checkout", &option_no_checkout,
		 N_("don't create a checkout")),
	OPT_BOOL(0, "bare", &option_bare, N_("create a bare repository")),
	OPT_HIDDEN_BOOL(0, "naked", &option_bare,
			N_("create a bare repository")),
	OPT_BOOL(0, "mirror", &option_mirror,
		 N_("create a mirror repository (implies bare)")),
	OPT_BOOL('l', "local", &option_local,
		N_("to clone from a local repository")),
	OPT_BOOL(0, "no-hardlinks", &option_no_hardlinks,
		    N_("don't use local hardlinks, always copy")),
	OPT_BOOL('s', "shared", &option_shared,
		    N_("setup as shared repository")),
	OPT_BOOL(0, "recursive", &option_recursive,
		    N_("initialize submodules in the clone")),
	OPT_BOOL(0, "recurse-submodules", &option_recursive,
		    N_("initialize submodules in the clone")),
	OPT_INTEGER('j', "jobs", &max_jobs,
		    N_("number of submodules cloned in parallel")),
	OPT_STRING(0, "template", &option_template, N_("template-directory"),
		   N_("directory from which templates will be used")),
	OPT_STRING_LIST(0, "reference", &option_reference, N_("repo"),
			N_("reference repository")),
	OPT_BOOL(0, "dissociate", &option_dissociate,
		 N_("use --reference only while cloning")),
	OPT_STRING('o', "origin", &option_origin, N_("name"),
		   N_("use <name> instead of 'origin' to track upstream")),
	OPT_STRING('b', "branch", &option_branch, N_("branch"),
		   N_("checkout <branch> instead of the remote's HEAD")),
	OPT_STRING('u', "upload-pack", &option_upload_pack, N_("path"),
		   N_("path to git-upload-pack on the remote")),
	OPT_STRING(0, "depth", &option_depth, N_("depth"),
		    N_("create a shallow clone of that depth")),
	OPT_BOOL(0, "single-branch", &option_single_branch,
		    N_("clone only one branch, HEAD or --branch")),
	OPT_BOOL(0, "shallow-submodules", &option_shallow_submodules,
		    N_("any cloned submodules will be shallow")),
	OPT_STRING(0, "separate-git-dir", &real_git_dir, N_("gitdir"),
		   N_("separate git dir from working tree")),
	OPT_STRING_LIST('c', "config", &option_config, N_("key=value"),
			N_("set config inside the new repository")),
	OPT_SET_INT('4', "ipv4", &family, N_("use IPv4 addresses only"),
			TRANSPORT_FAMILY_IPV4),
	OPT_SET_INT('6', "ipv6", &family, N_("use IPv6 addresses only"),
			TRANSPORT_FAMILY_IPV6),
	OPT_END()
};

static const char *get_repo_path_1(struct strbuf *path, int *is_bundle)
{
	static char *suffix[] = { "/.git", "", ".git/.git", ".git" };
	static char *bundle_suffix[] = { ".bundle", "" };
	size_t baselen = path->len;
	struct stat st;
	int i;

	for (i = 0; i < ARRAY_SIZE(suffix); i++) {
		strbuf_setlen(path, baselen);
		strbuf_addstr(path, suffix[i]);
		if (stat(path->buf, &st))
			continue;
		if (S_ISDIR(st.st_mode) && is_git_directory(path->buf)) {
			*is_bundle = 0;
			return path->buf;
		} else if (S_ISREG(st.st_mode) && st.st_size > 8) {
			/* Is it a "gitfile"? */
			char signature[8];
			const char *dst;
			int len, fd = open(path->buf, O_RDONLY);
			if (fd < 0)
				continue;
			len = read_in_full(fd, signature, 8);
			close(fd);
			if (len != 8 || strncmp(signature, "gitdir: ", 8))
				continue;
			dst = read_gitfile(path->buf);
			if (dst) {
				*is_bundle = 0;
				return dst;
			}
		}
	}

	for (i = 0; i < ARRAY_SIZE(bundle_suffix); i++) {
		strbuf_setlen(path, baselen);
		strbuf_addstr(path, bundle_suffix[i]);
		if (!stat(path->buf, &st) && S_ISREG(st.st_mode)) {
			*is_bundle = 1;
			return path->buf;
		}
	}

	return NULL;
}

static char *get_repo_path(const char *repo, int *is_bundle)
{
	struct strbuf path = STRBUF_INIT;
	const char *raw;
	char *canon;

	strbuf_addstr(&path, repo);
	raw = get_repo_path_1(&path, is_bundle);
	canon = raw ? xstrdup(absolute_path(raw)) : NULL;
	strbuf_release(&path);
	return canon;
}

static char *guess_dir_name(const char *repo, int is_bundle, int is_bare)
{
	const char *end = repo + strlen(repo), *start, *ptr;
	size_t len;
	char *dir;

	/*
	 * Skip scheme.
	 */
	start = strstr(repo, "://");
	if (start == NULL)
		start = repo;
	else
		start += 3;

	/*
	 * Skip authentication data. The stripping does happen
	 * greedily, such that we strip up to the last '@' inside
	 * the host part.
	 */
	for (ptr = start; ptr < end && !is_dir_sep(*ptr); ptr++) {
		if (*ptr == '@')
			start = ptr + 1;
	}

	/*
	 * Strip trailing spaces, slashes and /.git
	 */
	while (start < end && (is_dir_sep(end[-1]) || isspace(end[-1])))
		end--;
	if (end - start > 5 && is_dir_sep(end[-5]) &&
	    !strncmp(end - 4, ".git", 4)) {
		end -= 5;
		while (start < end && is_dir_sep(end[-1]))
			end--;
	}

	/*
	 * Strip trailing port number if we've got only a
	 * hostname (that is, there is no dir separator but a
	 * colon). This check is required such that we do not
	 * strip URI's like '/foo/bar:2222.git', which should
	 * result in a dir '2222' being guessed due to backwards
	 * compatibility.
	 */
	if (memchr(start, '/', end - start) == NULL
	    && memchr(start, ':', end - start) != NULL) {
		ptr = end;
		while (start < ptr && isdigit(ptr[-1]) && ptr[-1] != ':')
			ptr--;
		if (start < ptr && ptr[-1] == ':')
			end = ptr - 1;
	}

	/*
	 * Find last component. To remain backwards compatible we
	 * also regard colons as path separators, such that
	 * cloning a repository 'foo:bar.git' would result in a
	 * directory 'bar' being guessed.
	 */
	ptr = end;
	while (start < ptr && !is_dir_sep(ptr[-1]) && ptr[-1] != ':')
		ptr--;
	start = ptr;

	/*
	 * Strip .{bundle,git}.
	 */
	len = end - start;
	strip_suffix_mem(start, &len, is_bundle ? ".bundle" : ".git");

	if (!len || (len == 1 && *start == '/'))
		die(_("No directory name could be guessed.\n"
		      "Please specify a directory on the command line"));

	if (is_bare)
		dir = xstrfmt("%.*s.git", (int)len, start);
	else
		dir = xstrndup(start, len);
	/*
	 * Replace sequences of 'control' characters and whitespace
	 * with one ascii space, remove leading and trailing spaces.
	 */
	if (*dir) {
		char *out = dir;
		int prev_space = 1 /* strip leading whitespace */;
		for (end = dir; *end; ++end) {
			char ch = *end;
			if ((unsigned char)ch < '\x20')
				ch = '\x20';
			if (isspace(ch)) {
				if (prev_space)
					continue;
				prev_space = 1;
			} else
				prev_space = 0;
			*out++ = ch;
		}
		*out = '\0';
		if (out > dir && prev_space)
			out[-1] = '\0';
	}
	return dir;
}

static void strip_trailing_slashes(char *dir)
{
	char *end = dir + strlen(dir);

	while (dir < end - 1 && is_dir_sep(end[-1]))
		end--;
	*end = '\0';
}

static int add_one_reference(struct string_list_item *item, void *cb_data)
{
	char *ref_git;
	const char *repo;
	struct strbuf alternate = STRBUF_INIT;

	/* Beware: read_gitfile(), real_path() and mkpath() return static buffer */
	ref_git = xstrdup(real_path(item->string));

	repo = read_gitfile(ref_git);
	if (!repo)
		repo = read_gitfile(mkpath("%s/.git", ref_git));
	if (repo) {
		free(ref_git);
		ref_git = xstrdup(repo);
	}

	if (!repo && is_directory(mkpath("%s/.git/objects", ref_git))) {
		char *ref_git_git = mkpathdup("%s/.git", ref_git);
		free(ref_git);
		ref_git = ref_git_git;
	} else if (!is_directory(mkpath("%s/objects", ref_git))) {
		struct strbuf sb = STRBUF_INIT;
		if (get_common_dir(&sb, ref_git))
			die(_("reference repository '%s' as a linked checkout is not supported yet."),
			    item->string);
		die(_("reference repository '%s' is not a local repository."),
		    item->string);
	}

	if (!access(mkpath("%s/shallow", ref_git), F_OK))
		die(_("reference repository '%s' is shallow"), item->string);

	if (!access(mkpath("%s/info/grafts", ref_git), F_OK))
		die(_("reference repository '%s' is grafted"), item->string);

	strbuf_addf(&alternate, "%s/objects", ref_git);
	add_to_alternates_file(alternate.buf);
	strbuf_release(&alternate);
	free(ref_git);
	return 0;
}

static void setup_reference(void)
{
	for_each_string_list(&option_reference, add_one_reference, NULL);
}

static void copy_alternates(struct strbuf *src, struct strbuf *dst,
			    const char *src_repo)
{
	/*
	 * Read from the source objects/info/alternates file
	 * and copy the entries to corresponding file in the
	 * destination repository with add_to_alternates_file().
	 * Both src and dst have "$path/objects/info/alternates".
	 *
	 * Instead of copying bit-for-bit from the original,
	 * we need to append to existing one so that the already
	 * created entry via "clone -s" is not lost, and also
	 * to turn entries with paths relative to the original
	 * absolute, so that they can be used in the new repository.
	 */
	FILE *in = fopen(src->buf, "r");
	struct strbuf line = STRBUF_INIT;

	while (strbuf_getline(&line, in) != EOF) {
		char *abs_path;
		if (!line.len || line.buf[0] == '#')
			continue;
		if (is_absolute_path(line.buf)) {
			add_to_alternates_file(line.buf);
			continue;
		}
		abs_path = mkpathdup("%s/objects/%s", src_repo, line.buf);
		if (!normalize_path_copy(abs_path, abs_path))
			add_to_alternates_file(abs_path);
		else
			warning("skipping invalid relative alternate: %s/%s",
				src_repo, line.buf);
		free(abs_path);
	}
	strbuf_release(&line);
	fclose(in);
}

static void copy_or_link_directory(struct strbuf *src, struct strbuf *dest,
				   const char *src_repo, int src_baselen)
{
	struct dirent *de;
	struct stat buf;
	int src_len, dest_len;
	DIR *dir;

	dir = opendir(src->buf);
	if (!dir)
		die_errno(_("failed to open '%s'"), src->buf);

	if (mkdir(dest->buf, 0777)) {
		if (errno != EEXIST)
			die_errno(_("failed to create directory '%s'"), dest->buf);
		else if (stat(dest->buf, &buf))
			die_errno(_("failed to stat '%s'"), dest->buf);
		else if (!S_ISDIR(buf.st_mode))
			die(_("%s exists and is not a directory"), dest->buf);
	}

	strbuf_addch(src, '/');
	src_len = src->len;
	strbuf_addch(dest, '/');
	dest_len = dest->len;

	while ((de = readdir(dir)) != NULL) {
		strbuf_setlen(src, src_len);
		strbuf_addstr(src, de->d_name);
		strbuf_setlen(dest, dest_len);
		strbuf_addstr(dest, de->d_name);
		if (stat(src->buf, &buf)) {
			warning (_("failed to stat %s\n"), src->buf);
			continue;
		}
		if (S_ISDIR(buf.st_mode)) {
			if (de->d_name[0] != '.')
				copy_or_link_directory(src, dest,
						       src_repo, src_baselen);
			continue;
		}

		/* Files that cannot be copied bit-for-bit... */
		if (!strcmp(src->buf + src_baselen, "/info/alternates")) {
			copy_alternates(src, dest, src_repo);
			continue;
		}

		if (unlink(dest->buf) && errno != ENOENT)
			die_errno(_("failed to unlink '%s'"), dest->buf);
		if (!option_no_hardlinks) {
			if (!link(src->buf, dest->buf))
				continue;
			if (option_local > 0)
				die_errno(_("failed to create link '%s'"), dest->buf);
			option_no_hardlinks = 1;
		}
		if (copy_file_with_time(dest->buf, src->buf, 0666))
			die_errno(_("failed to copy file to '%s'"), dest->buf);
	}
	closedir(dir);
}

static void clone_local(const char *src_repo, const char *dest_repo)
{
	if (option_shared) {
		struct strbuf alt = STRBUF_INIT;
		strbuf_addf(&alt, "%s/objects", src_repo);
		add_to_alternates_file(alt.buf);
		strbuf_release(&alt);
	} else {
		struct strbuf src = STRBUF_INIT;
		struct strbuf dest = STRBUF_INIT;
		get_common_dir(&src, src_repo);
		get_common_dir(&dest, dest_repo);
		strbuf_addstr(&src, "/objects");
		strbuf_addstr(&dest, "/objects");
		copy_or_link_directory(&src, &dest, src_repo, src.len);
		strbuf_release(&src);
		strbuf_release(&dest);
	}

	if (0 <= option_verbosity)
		fprintf(stderr, _("done.\n"));
}

static const char *junk_work_tree;
static const char *junk_git_dir;
static enum {
	JUNK_LEAVE_NONE,
	JUNK_LEAVE_REPO,
	JUNK_LEAVE_ALL
} junk_mode = JUNK_LEAVE_NONE;

static const char junk_leave_repo_msg[] =
N_("Clone succeeded, but checkout failed.\n"
   "You can inspect what was checked out with 'git status'\n"
   "and retry the checkout with 'git checkout -f HEAD'\n");

static void remove_junk(void)
{
	struct strbuf sb = STRBUF_INIT;

	switch (junk_mode) {
	case JUNK_LEAVE_REPO:
		warning("%s", _(junk_leave_repo_msg));
		/* fall-through */
	case JUNK_LEAVE_ALL:
		return;
	default:
		/* proceed to removal */
		break;
	}

	if (junk_git_dir) {
		strbuf_addstr(&sb, junk_git_dir);
		remove_dir_recursively(&sb, 0);
		strbuf_reset(&sb);
	}
	if (junk_work_tree) {
		strbuf_addstr(&sb, junk_work_tree);
		remove_dir_recursively(&sb, 0);
		strbuf_reset(&sb);
	}
}

static void remove_junk_on_signal(int signo)
{
	remove_junk();
	sigchain_pop(signo);
	raise(signo);
}

static struct ref *find_remote_branch(const struct ref *refs, const char *branch)
{
	struct ref *ref;
	struct strbuf head = STRBUF_INIT;
	strbuf_addstr(&head, "refs/heads/");
	strbuf_addstr(&head, branch);
	ref = find_ref_by_name(refs, head.buf);
	strbuf_release(&head);

	if (ref)
		return ref;

	strbuf_addstr(&head, "refs/tags/");
	strbuf_addstr(&head, branch);
	ref = find_ref_by_name(refs, head.buf);
	strbuf_release(&head);

	return ref;
}

static struct ref *wanted_peer_refs(const struct ref *refs,
		struct refspec *refspec)
{
	struct ref *head = copy_ref(find_ref_by_name(refs, "HEAD"));
	struct ref *local_refs = head;
	struct ref **tail = head ? &head->next : &local_refs;

	if (option_single_branch) {
		struct ref *remote_head = NULL;

		if (!option_branch)
			remote_head = guess_remote_head(head, refs, 0);
		else {
			local_refs = NULL;
			tail = &local_refs;
			remote_head = copy_ref(find_remote_branch(refs, option_branch));
		}

		if (!remote_head && option_branch)
			warning(_("Could not find remote branch %s to clone."),
				option_branch);
		else {
			get_fetch_map(remote_head, refspec, &tail, 0);

			/* if --branch=tag, pull the requested tag explicitly */
			get_fetch_map(remote_head, tag_refspec, &tail, 0);
		}
	} else
		get_fetch_map(refs, refspec, &tail, 0);

	if (!option_mirror && !option_single_branch)
		get_fetch_map(refs, tag_refspec, &tail, 0);

	return local_refs;
}

static void write_remote_refs(const struct ref *local_refs)
{
	const struct ref *r;

	struct ref_transaction *t;
	struct strbuf err = STRBUF_INIT;

	t = ref_transaction_begin(&err);
	if (!t)
		die("%s", err.buf);

	for (r = local_refs; r; r = r->next) {
		if (!r->peer_ref)
			continue;
		if (ref_transaction_create(t, r->peer_ref->name, r->old_oid.hash,
					   0, NULL, &err))
			die("%s", err.buf);
	}

	if (initial_ref_transaction_commit(t, &err))
		die("%s", err.buf);

	strbuf_release(&err);
	ref_transaction_free(t);
}

static void write_followtags(const struct ref *refs, const char *msg)
{
	const struct ref *ref;
	for (ref = refs; ref; ref = ref->next) {
		if (!starts_with(ref->name, "refs/tags/"))
			continue;
		if (ends_with(ref->name, "^{}"))
			continue;
		if (!has_object_file(&ref->old_oid))
			continue;
		update_ref(msg, ref->name, ref->old_oid.hash,
			   NULL, 0, UPDATE_REFS_DIE_ON_ERR);
	}
}

static int iterate_ref_map(void *cb_data, unsigned char sha1[20])
{
	struct ref **rm = cb_data;
	struct ref *ref = *rm;

	/*
	 * Skip anything missing a peer_ref, which we are not
	 * actually going to write a ref for.
	 */
	while (ref && !ref->peer_ref)
		ref = ref->next;
	/* Returning -1 notes "end of list" to the caller. */
	if (!ref)
		return -1;

	hashcpy(sha1, ref->old_oid.hash);
	*rm = ref->next;
	return 0;
}

static void update_remote_refs(const struct ref *refs,
			       const struct ref *mapped_refs,
			       const struct ref *remote_head_points_at,
			       const char *branch_top,
			       const char *msg,
			       struct transport *transport,
			       int check_connectivity)
{
	const struct ref *rm = mapped_refs;

	if (check_connectivity) {
		struct check_connected_options opt = CHECK_CONNECTED_INIT;

		opt.transport = transport;
		opt.progress = transport->progress;

		if (check_connected(iterate_ref_map, &rm, &opt))
			die(_("remote did not send all necessary objects"));
	}

	if (refs) {
		write_remote_refs(mapped_refs);
		if (option_single_branch)
			write_followtags(refs, msg);
	}

	if (remote_head_points_at && !option_bare) {
		struct strbuf head_ref = STRBUF_INIT;
		strbuf_addstr(&head_ref, branch_top);
		strbuf_addstr(&head_ref, "HEAD");
		if (create_symref(head_ref.buf,
				  remote_head_points_at->peer_ref->name,
				  msg) < 0)
			die(_("unable to update %s"), head_ref.buf);
		strbuf_release(&head_ref);
	}
}

static void update_head(const struct ref *our, const struct ref *remote,
			const char *msg)
{
	const char *head;
	if (our && skip_prefix(our->name, "refs/heads/", &head)) {
		/* Local default branch link */
		if (create_symref("HEAD", our->name, NULL) < 0)
			die(_("unable to update HEAD"));
		if (!option_bare) {
			update_ref(msg, "HEAD", our->old_oid.hash, NULL, 0,
				   UPDATE_REFS_DIE_ON_ERR);
			install_branch_config(0, head, option_origin, our->name);
		}
	} else if (our) {
		struct commit *c = lookup_commit_reference(our->old_oid.hash);
		/* --branch specifies a non-branch (i.e. tags), detach HEAD */
		update_ref(msg, "HEAD", c->object.oid.hash,
			   NULL, REF_NODEREF, UPDATE_REFS_DIE_ON_ERR);
	} else if (remote) {
		/*
		 * We know remote HEAD points to a non-branch, or
		 * HEAD points to a branch but we don't know which one.
		 * Detach HEAD in all these cases.
		 */
		update_ref(msg, "HEAD", remote->old_oid.hash,
			   NULL, REF_NODEREF, UPDATE_REFS_DIE_ON_ERR);
	}
}

static int checkout(void)
{
	unsigned char sha1[20];
	char *head;
	struct lock_file *lock_file;
	struct unpack_trees_options opts;
	struct tree *tree;
	struct tree_desc t;
	int err = 0;

	if (option_no_checkout)
		return 0;

	head = resolve_refdup("HEAD", RESOLVE_REF_READING, sha1, NULL);
	if (!head) {
		warning(_("remote HEAD refers to nonexistent ref, "
			  "unable to checkout.\n"));
		return 0;
	}
	if (!strcmp(head, "HEAD")) {
		if (advice_detached_head)
			detach_advice(sha1_to_hex(sha1));
	} else {
		if (!starts_with(head, "refs/heads/"))
			die(_("HEAD not found below refs/heads!"));
	}
	free(head);

	/* We need to be in the new work tree for the checkout */
	setup_work_tree();

	lock_file = xcalloc(1, sizeof(struct lock_file));
	hold_locked_index(lock_file, 1);

	memset(&opts, 0, sizeof opts);
	opts.update = 1;
	opts.merge = 1;
	opts.fn = oneway_merge;
	opts.verbose_update = (option_verbosity >= 0);
	opts.src_index = &the_index;
	opts.dst_index = &the_index;

	tree = parse_tree_indirect(sha1);
	parse_tree(tree);
	init_tree_desc(&t, tree->buffer, tree->size);
	if (unpack_trees(1, &t, &opts) < 0)
		die(_("unable to checkout working tree"));

	if (write_locked_index(&the_index, lock_file, COMMIT_LOCK))
		die(_("unable to write new index file"));

	err |= run_hook_le(NULL, "post-checkout", sha1_to_hex(null_sha1),
			   sha1_to_hex(sha1), "1", NULL);

	if (!err && option_recursive) {
		struct argv_array args = ARGV_ARRAY_INIT;
		argv_array_pushl(&args, "submodule", "update", "--init", "--recursive", NULL);

		if (option_shallow_submodules == 1)
			argv_array_push(&args, "--depth=1");

		if (max_jobs != -1)
			argv_array_pushf(&args, "--jobs=%d", max_jobs);

		err = run_command_v_opt(args.argv, RUN_GIT_CMD);
		argv_array_clear(&args);
	}

	return err;
}

static int write_one_config(const char *key, const char *value, void *data)
{
	return git_config_set_multivar_gently(key, value ? value : "true", "^$", 0);
}

static void write_config(struct string_list *config)
{
	int i;

	for (i = 0; i < config->nr; i++) {
		if (git_config_parse_parameter(config->items[i].string,
					       write_one_config, NULL) < 0)
			die(_("unable to write parameters to config file"));
	}
}

static void write_refspec_config(const char *src_ref_prefix,
		const struct ref *our_head_points_at,
		const struct ref *remote_head_points_at,
		struct strbuf *branch_top)
{
	struct strbuf key = STRBUF_INIT;
	struct strbuf value = STRBUF_INIT;

	if (option_mirror || !option_bare) {
		if (option_single_branch && !option_mirror) {
			if (option_branch) {
				if (starts_with(our_head_points_at->name, "refs/tags/"))
					strbuf_addf(&value, "+%s:%s", our_head_points_at->name,
						our_head_points_at->name);
				else
					strbuf_addf(&value, "+%s:%s%s", our_head_points_at->name,
						branch_top->buf, option_branch);
			} else if (remote_head_points_at) {
				const char *head = remote_head_points_at->name;
				if (!skip_prefix(head, "refs/heads/", &head))
					die("BUG: remote HEAD points at non-head?");

				strbuf_addf(&value, "+%s:%s%s", remote_head_points_at->name,
						branch_top->buf, head);
			}
			/*
			 * otherwise, the next "git fetch" will
			 * simply fetch from HEAD without updating
			 * any remote-tracking branch, which is what
			 * we want.
			 */
		} else {
			strbuf_addf(&value, "+%s*:%s*", src_ref_prefix, branch_top->buf);
		}
		/* Configure the remote */
		if (value.len) {
			strbuf_addf(&key, "remote.%s.fetch", option_origin);
			git_config_set_multivar(key.buf, value.buf, "^$", 0);
			strbuf_reset(&key);

			if (option_mirror) {
				strbuf_addf(&key, "remote.%s.mirror", option_origin);
				git_config_set(key.buf, "true");
				strbuf_reset(&key);
			}
		}
	}

	strbuf_release(&key);
	strbuf_release(&value);
}

static void dissociate_from_references(void)
{
	static const char* argv[] = { "repack", "-a", "-d", NULL };
	char *alternates = git_pathdup("objects/info/alternates");

	if (!access(alternates, F_OK)) {
		if (run_command_v_opt(argv, RUN_GIT_CMD|RUN_COMMAND_NO_STDIN))
			die(_("cannot repack to clean up"));
		if (unlink(alternates) && errno != ENOENT)
			die_errno(_("cannot unlink temporary alternates file"));
	}
	free(alternates);
}

int cmd_clone(int argc, const char **argv, const char *prefix)
{
	int is_bundle = 0, is_local;
	struct stat buf;
	const char *repo_name, *repo, *work_tree, *git_dir;
	char *path, *dir;
	int dest_exists;
	const struct ref *refs, *remote_head;
	const struct ref *remote_head_points_at;
	const struct ref *our_head_points_at;
	struct ref *mapped_refs;
	const struct ref *ref;
	struct strbuf key = STRBUF_INIT, value = STRBUF_INIT;
	struct strbuf branch_top = STRBUF_INIT, reflog_msg = STRBUF_INIT;
	struct transport *transport = NULL;
	const char *src_ref_prefix = "refs/heads/";
	struct remote *remote;
	int err = 0, complete_refs_before_fetch = 1;

	struct refspec *refspec;
	const char *fetch_pattern;

	packet_trace_identity("clone");
	argc = parse_options(argc, argv, prefix, builtin_clone_options,
			     builtin_clone_usage, 0);

	if (argc > 2)
		usage_msg_opt(_("Too many arguments."),
			builtin_clone_usage, builtin_clone_options);

	if (argc == 0)
		usage_msg_opt(_("You must specify a repository to clone."),
			builtin_clone_usage, builtin_clone_options);

	if (option_single_branch == -1)
		option_single_branch = option_depth ? 1 : 0;

	if (option_mirror)
		option_bare = 1;

	if (option_bare) {
		if (option_origin)
			die(_("--bare and --origin %s options are incompatible."),
			    option_origin);
		if (real_git_dir)
			die(_("--bare and --separate-git-dir are incompatible."));
		option_no_checkout = 1;
	}

	if (!option_origin)
		option_origin = "origin";

	repo_name = argv[0];

	path = get_repo_path(repo_name, &is_bundle);
	if (path)
		repo = xstrdup(absolute_path(repo_name));
	else if (!strchr(repo_name, ':'))
		die(_("repository '%s' does not exist"), repo_name);
	else
		repo = repo_name;

	/* no need to be strict, transport_set_option() will validate it again */
	if (option_depth && atoi(option_depth) < 1)
		die(_("depth %s is not a positive number"), option_depth);

	if (argc == 2)
		dir = xstrdup(argv[1]);
	else
		dir = guess_dir_name(repo_name, is_bundle, option_bare);
	strip_trailing_slashes(dir);

	dest_exists = !stat(dir, &buf);
	if (dest_exists && !is_empty_dir(dir))
		die(_("destination path '%s' already exists and is not "
			"an empty directory."), dir);

	strbuf_addf(&reflog_msg, "clone: from %s", repo);

	if (option_bare)
		work_tree = NULL;
	else {
		work_tree = getenv("GIT_WORK_TREE");
		if (work_tree && !stat(work_tree, &buf))
			die(_("working tree '%s' already exists."), work_tree);
	}

	if (option_bare || work_tree)
		git_dir = xstrdup(dir);
	else {
		work_tree = dir;
		git_dir = mkpathdup("%s/.git", dir);
	}

	atexit(remove_junk);
	sigchain_push_common(remove_junk_on_signal);

	if (!option_bare) {
		if (safe_create_leading_directories_const(work_tree) < 0)
			die_errno(_("could not create leading directories of '%s'"),
				  work_tree);
		if (!dest_exists && mkdir(work_tree, 0777))
			die_errno(_("could not create work tree dir '%s'"),
				  work_tree);
		junk_work_tree = work_tree;
		set_git_work_tree(work_tree);
	}

	junk_git_dir = git_dir;
	if (safe_create_leading_directories_const(git_dir) < 0)
		die(_("could not create leading directories of '%s'"), git_dir);

	set_git_dir_init(git_dir, real_git_dir, 0);
	if (real_git_dir) {
		git_dir = real_git_dir;
		junk_git_dir = real_git_dir;
	}

	if (0 <= option_verbosity) {
		if (option_bare)
			fprintf(stderr, _("Cloning into bare repository '%s'...\n"), dir);
		else
			fprintf(stderr, _("Cloning into '%s'...\n"), dir);
	}
	init_db(option_template, INIT_DB_QUIET);
	write_config(&option_config);

	git_config(git_default_config, NULL);

	if (option_bare) {
		if (option_mirror)
			src_ref_prefix = "refs/";
		strbuf_addstr(&branch_top, src_ref_prefix);

		git_config_set("core.bare", "true");
	} else {
		strbuf_addf(&branch_top, "refs/remotes/%s/", option_origin);
	}

	strbuf_addf(&value, "+%s*:%s*", src_ref_prefix, branch_top.buf);
	strbuf_addf(&key, "remote.%s.url", option_origin);
	git_config_set(key.buf, repo);
	strbuf_reset(&key);

	if (option_reference.nr)
		setup_reference();

	fetch_pattern = value.buf;
	refspec = parse_fetch_refspec(1, &fetch_pattern);

	strbuf_reset(&value);

	remote = remote_get(option_origin);
	transport = transport_get(remote, remote->url[0]);
	transport_set_verbosity(transport, option_verbosity, option_progress);
	transport->family = family;

	path = get_repo_path(remote->url[0], &is_bundle);
	is_local = option_local != 0 && path && !is_bundle;
	if (is_local) {
		if (option_depth)
			warning(_("--depth is ignored in local clones; use file:// instead."));
		if (!access(mkpath("%s/shallow", path), F_OK)) {
			if (option_local > 0)
				warning(_("source repository is shallow, ignoring --local"));
			is_local = 0;
		}
	}
	if (option_local > 0 && !is_local)
		warning(_("--local is ignored"));
	transport->cloning = 1;

	if (!transport->get_refs_list || (!is_local && !transport->fetch))
		die(_("Don't know how to clone %s"), transport->url);

	transport_set_option(transport, TRANS_OPT_KEEP, "yes");

	if (option_depth)
		transport_set_option(transport, TRANS_OPT_DEPTH,
				     option_depth);
	if (option_single_branch)
		transport_set_option(transport, TRANS_OPT_FOLLOWTAGS, "1");

	if (option_upload_pack)
		transport_set_option(transport, TRANS_OPT_UPLOADPACK,
				     option_upload_pack);

	if (transport->smart_options && !option_depth)
		transport->smart_options->check_self_contained_and_connected = 1;

	refs = transport_get_remote_refs(transport);

	if (refs) {
		mapped_refs = wanted_peer_refs(refs, refspec);
		/*
		 * transport_get_remote_refs() may return refs with null sha-1
		 * in mapped_refs (see struct transport->get_refs_list
		 * comment). In that case we need fetch it early because
		 * remote_head code below relies on it.
		 *
		 * for normal clones, transport_get_remote_refs() should
		 * return reliable ref set, we can delay cloning until after
		 * remote HEAD check.
		 */
		for (ref = refs; ref; ref = ref->next)
			if (is_null_oid(&ref->old_oid)) {
				complete_refs_before_fetch = 0;
				break;
			}

		if (!is_local && !complete_refs_before_fetch)
			transport_fetch_refs(transport, mapped_refs);

		remote_head = find_ref_by_name(refs, "HEAD");
		remote_head_points_at =
			guess_remote_head(remote_head, mapped_refs, 0);

		if (option_branch) {
			our_head_points_at =
				find_remote_branch(mapped_refs, option_branch);

			if (!our_head_points_at)
				die(_("Remote branch %s not found in upstream %s"),
				    option_branch, option_origin);
		}
		else
			our_head_points_at = remote_head_points_at;
	}
	else {
		if (option_branch)
			die(_("Remote branch %s not found in upstream %s"),
					option_branch, option_origin);

		warning(_("You appear to have cloned an empty repository."));
		mapped_refs = NULL;
		our_head_points_at = NULL;
		remote_head_points_at = NULL;
		remote_head = NULL;
		option_no_checkout = 1;
		if (!option_bare)
			install_branch_config(0, "master", option_origin,
					      "refs/heads/master");
	}

	write_refspec_config(src_ref_prefix, our_head_points_at,
			remote_head_points_at, &branch_top);

	if (is_local)
		clone_local(path, git_dir);
	else if (refs && complete_refs_before_fetch)
		transport_fetch_refs(transport, mapped_refs);

	update_remote_refs(refs, mapped_refs, remote_head_points_at,
			   branch_top.buf, reflog_msg.buf, transport, !is_local);

	update_head(our_head_points_at, remote_head, reflog_msg.buf);

	transport_unlock_pack(transport);
	transport_disconnect(transport);

	if (option_dissociate) {
		close_all_packs();
		dissociate_from_references();
	}

	junk_mode = JUNK_LEAVE_REPO;
	err = checkout();

	strbuf_release(&reflog_msg);
	strbuf_release(&branch_top);
	strbuf_release(&key);
	strbuf_release(&value);
	junk_mode = JUNK_LEAVE_ALL;

	free(refspec);
	return err;
}