1 files changed, 579 insertions, 274 deletions

diff --git a/builtin/clone.c b/builtin/clone.c
index 0fb5956b48..caae43e7a3 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -9,6 +9,7 @@
  */
 
 #include "builtin.h"
+#include "lockfile.h"
 #include "parse-options.h"
 #include "fetch-pack.h"
 #include "refs.h"
@@ -18,11 +19,11 @@
 #include "transport.h"
 #include "strbuf.h"
 #include "dir.h"
-#include "pack-refs.h"
 #include "sigchain.h"
 #include "branch.h"
 #include "remote.h"
 #include "run-command.h"
+#include "connected.h"
 
 /*
  * Overall FIXMEs:
@@ -33,12 +34,12 @@
  *
  */
 static const char * const builtin_clone_usage[] = {
-	"git clone [options] [--] <repo> [<dir>]",
+	N_("git clone [<options>] [--] <repo> [<dir>]"),
 	NULL
 };
 
-static int option_no_checkout, option_bare, option_mirror;
-static int option_local, option_no_hardlinks, option_shared, option_recursive;
+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 char *option_template, *option_depth;
 static char *option_origin = NULL;
 static char *option_branch = NULL;
@@ -48,54 +49,49 @@ static int option_verbosity;
 static int option_progress = -1;
 static struct string_list option_config;
 static struct string_list option_reference;
-
-static int opt_parse_reference(const struct option *opt, const char *arg, int unset)
-{
-	struct string_list *option_reference = opt->value;
-	if (!arg)
-		return -1;
-	string_list_append(option_reference, arg);
-	return 0;
-}
+static int option_dissociate;
 
 static struct option builtin_clone_options[] = {
 	OPT__VERBOSITY(&option_verbosity),
 	OPT_BOOL(0, "progress", &option_progress,
-		 "force progress reporting"),
-	OPT_BOOLEAN('n', "no-checkout", &option_no_checkout,
-		    "don't create a checkout"),
-	OPT_BOOLEAN(0, "bare", &option_bare, "create a bare repository"),
-	{ OPTION_BOOLEAN, 0, "naked", &option_bare, NULL,
-		"create a bare repository",
-		PARSE_OPT_NOARG | PARSE_OPT_HIDDEN },
-	OPT_BOOLEAN(0, "mirror", &option_mirror,
-		    "create a mirror repository (implies bare)"),
-	OPT_BOOLEAN('l', "local", &option_local,
-		    "to clone from a local repository"),
-	OPT_BOOLEAN(0, "no-hardlinks", &option_no_hardlinks,
-		    "don't use local hardlinks, always copy"),
-	OPT_BOOLEAN('s', "shared", &option_shared,
-		    "setup as shared repository"),
-	OPT_BOOLEAN(0, "recursive", &option_recursive,
-		    "initialize submodules in the clone"),
-	OPT_BOOLEAN(0, "recurse-submodules", &option_recursive,
-		    "initialize submodules in the clone"),
-	OPT_STRING(0, "template", &option_template, "template-directory",
-		   "directory from which templates will be used"),
-	OPT_CALLBACK(0 , "reference", &option_reference, "repo",
-		     "reference repository", &opt_parse_reference),
-	OPT_STRING('o', "origin", &option_origin, "name",
-		   "use <name> instead of 'origin' to track upstream"),
-	OPT_STRING('b', "branch", &option_branch, "branch",
-		   "checkout <branch> instead of the remote's HEAD"),
-	OPT_STRING('u', "upload-pack", &option_upload_pack, "path",
-		   "path to git-upload-pack on the remote"),
-	OPT_STRING(0, "depth", &option_depth, "depth",
-		    "create a shallow clone of that depth"),
-	OPT_STRING(0, "separate-git-dir", &real_git_dir, "gitdir",
-		   "separate git dir from working tree"),
-	OPT_STRING_LIST('c', "config", &option_config, "key=value",
-			"set config inside the new repository"),
+		 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_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_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_END()
 };
 
@@ -103,94 +99,145 @@ static const char *argv_submodule[] = {
 	"submodule", "update", "--init", "--recursive", NULL
 };
 
-static char *get_repo_path(const char *repo, int *is_bundle)
+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++) {
-		const char *path;
-		path = mkpath("%s%s", repo, suffix[i]);
-		if (stat(path, &st))
+		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)) {
+		if (S_ISDIR(st.st_mode) && is_git_directory(path->buf)) {
 			*is_bundle = 0;
-			return xstrdup(absolute_path(path));
+			return path->buf;
 		} else if (S_ISREG(st.st_mode) && st.st_size > 8) {
 			/* Is it a "gitfile"? */
 			char signature[8];
-			int len, fd = open(path, O_RDONLY);
+			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;
-			path = read_gitfile(path);
-			if (path) {
+			dst = read_gitfile(path->buf);
+			if (dst) {
 				*is_bundle = 0;
-				return xstrdup(absolute_path(path));
+				return dst;
 			}
 		}
 	}
 
 	for (i = 0; i < ARRAY_SIZE(bundle_suffix); i++) {
-		const char *path;
-		path = mkpath("%s%s", repo, bundle_suffix[i]);
-		if (!stat(path, &st) && S_ISREG(st.st_mode)) {
+		strbuf_setlen(path, baselen);
+		strbuf_addstr(path, bundle_suffix[i]);
+		if (!stat(path->buf, &st) && S_ISREG(st.st_mode)) {
 			*is_bundle = 1;
-			return xstrdup(absolute_path(path));
+			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;
+	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 (repo < end && (is_dir_sep(end[-1]) || isspace(end[-1])))
+	while (start < end && (is_dir_sep(end[-1]) || isspace(end[-1])))
 		end--;
-	if (end - repo > 5 && is_dir_sep(end[-5]) &&
+	if (end - start > 5 && is_dir_sep(end[-5]) &&
 	    !strncmp(end - 4, ".git", 4)) {
 		end -= 5;
-		while (repo < end && is_dir_sep(end[-1]))
+		while (start < end && is_dir_sep(end[-1]))
 			end--;
 	}
 
 	/*
-	 * Find last component, but be prepared that repo could have
-	 * the form  "remote.example.com:foo.git", i.e. no slash
-	 * in the directory part.
+	 * 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.
 	 */
-	start = end;
-	while (repo < start && !is_dir_sep(start[-1]) && start[-1] != ':')
-		start--;
+	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}.
 	 */
-	if (is_bundle) {
-		if (end - start > 7 && !strncmp(end - 7, ".bundle", 7))
-			end -= 7;
-	} else {
-		if (end - start > 4 && !strncmp(end - 4, ".git", 4))
-			end -= 4;
-	}
+	len = end - start;
+	strip_suffix_mem(start, &len, is_bundle ? ".bundle" : ".git");
 
-	if (is_bare) {
-		struct strbuf result = STRBUF_INIT;
-		strbuf_addf(&result, "%.*s.git", (int)(end - start), start);
-		dir = strbuf_detach(&result, NULL);
-	} else
-		dir = xstrndup(start, end - start);
+	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.
@@ -229,32 +276,42 @@ static void strip_trailing_slashes(char *dir)
 static int add_one_reference(struct string_list_item *item, void *cb_data)
 {
 	char *ref_git;
+	const char *repo;
 	struct strbuf alternate = STRBUF_INIT;
-	struct remote *remote;
-	struct transport *transport;
-	const struct ref *extra;
 
-	/* Beware: real_path() and mkpath() return static buffer */
+	/* Beware: read_gitfile(), real_path() and mkpath() return static buffer */
 	ref_git = xstrdup(real_path(item->string));
-	if (is_directory(mkpath("%s/.git/objects", ref_git))) {
-		char *ref_git_git = xstrdup(mkpath("%s/.git", ref_git));
+
+	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)))
-		die(_("reference repository '%s' is not a local directory."),
+	} 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);
-
-	remote = remote_get(ref_git);
-	transport = transport_get(remote, ref_git);
-	for (extra = transport_get_remote_refs(transport); extra;
-	     extra = extra->next)
-		add_extra_ref(extra->name, extra->old_sha1, 0);
-
-	transport_disconnect(transport);
 	free(ref_git);
 	return 0;
 }
@@ -283,16 +340,17 @@ static void copy_alternates(struct strbuf *src, struct strbuf *dst,
 	struct strbuf line = STRBUF_INIT;
 
 	while (strbuf_getline(&line, in, '\n') != EOF) {
-		char *abs_path, abs_buf[PATH_MAX];
+		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 = mkpath("%s/objects/%s", src_repo, line.buf);
-		normalize_path_copy(abs_buf, abs_path);
-		add_to_alternates_file(abs_buf);
+		abs_path = mkpathdup("%s/objects/%s", src_repo, line.buf);
+		normalize_path_copy(abs_path, abs_path);
+		add_to_alternates_file(abs_path);
+		free(abs_path);
 	}
 	strbuf_release(&line);
 	fclose(in);
@@ -351,7 +409,7 @@ static void copy_or_link_directory(struct strbuf *src, struct strbuf *dest,
 		if (!option_no_hardlinks) {
 			if (!link(src->buf, dest->buf))
 				continue;
-			if (option_local)
+			if (option_local > 0)
 				die_errno(_("failed to create link '%s'"), dest->buf);
 			option_no_hardlinks = 1;
 		}
@@ -361,13 +419,8 @@ static void copy_or_link_directory(struct strbuf *src, struct strbuf *dest,
 	closedir(dir);
 }
 
-static const struct ref *clone_local(const char *src_repo,
-				     const char *dest_repo)
+static void clone_local(const char *src_repo, const char *dest_repo)
 {
-	const struct ref *ret;
-	struct remote *remote;
-	struct transport *transport;
-
 	if (option_shared) {
 		struct strbuf alt = STRBUF_INIT;
 		strbuf_addf(&alt, "%s/objects", src_repo);
@@ -376,31 +429,47 @@ static const struct ref *clone_local(const char *src_repo,
 	} else {
 		struct strbuf src = STRBUF_INIT;
 		struct strbuf dest = STRBUF_INIT;
-		strbuf_addf(&src, "%s/objects", src_repo);
-		strbuf_addf(&dest, "%s/objects", dest_repo);
+		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);
 	}
 
-	remote = remote_get(src_repo);
-	transport = transport_get(remote, src_repo);
-	ret = transport_get_remote_refs(transport);
-	transport_disconnect(transport);
 	if (0 <= option_verbosity)
-		printf(_("done.\n"));
-	return ret;
+		fprintf(stderr, _("done.\n"));
 }
 
 static const char *junk_work_tree;
 static const char *junk_git_dir;
-static pid_t junk_pid;
+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;
-	if (getpid() != junk_pid)
+
+	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);
@@ -420,6 +489,26 @@ static void remove_junk_on_signal(int 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)
 {
@@ -427,8 +516,30 @@ static struct ref *wanted_peer_refs(const struct ref *refs,
 	struct ref *local_refs = head;
 	struct ref **tail = head ? &head->next : &local_refs;
 
-	get_fetch_map(refs, refspec, &tail, 0);
-	if (!option_mirror)
+	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;
@@ -438,14 +549,185 @@ 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;
-		add_extra_ref(r->peer_ref->name, r->old_sha1, 0);
+		if (ref_transaction_create(t, r->peer_ref->name, r->old_sha1,
+					   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_sha1_file(ref->old_sha1))
+			continue;
+		update_ref(msg, ref->name, ref->old_sha1,
+			   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_sha1);
+	*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) {
+		if (transport->progress)
+			fprintf(stderr, _("Checking connectivity... "));
+		if (check_everything_connected_with_transport(iterate_ref_map,
+							      0, &rm, transport))
+			die(_("remote did not send all necessary objects"));
+		if (transport->progress)
+			fprintf(stderr, _("done.\n"));
+	}
+
+	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");
+		create_symref(head_ref.buf,
+			      remote_head_points_at->peer_ref->name,
+			      msg);
+	}
+}
+
+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 */
+		create_symref("HEAD", our->name, NULL);
+		if (!option_bare) {
+			update_ref(msg, "HEAD", our->old_sha1, 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_sha1);
+		/* --branch specifies a non-branch (i.e. tags), detach HEAD */
+		update_ref(msg, "HEAD", c->object.sha1,
+			   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_sha1,
+			   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);
 
-	pack_refs(PACK_REFS_ALL);
-	clear_extra_refs();
+	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)
+		err = run_command_v_opt(argv_submodule, RUN_GIT_CMD);
+
+	return err;
 }
 
 static int write_one_config(const char *key, const char *value, void *data)
@@ -464,6 +746,72 @@ static void write_config(struct string_list *config)
 	}
 }
 
+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;
@@ -475,17 +823,17 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	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;
-	char *src_ref_prefix = "refs/heads/";
-	int err = 0;
+	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;
 
-	junk_pid = getpid();
-
 	packet_trace_identity("clone");
 	argc = parse_options(argc, argv, prefix, builtin_clone_options,
 			     builtin_clone_usage, 0);
@@ -498,6 +846,9 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 		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;
 
@@ -505,6 +856,8 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 		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;
 	}
 
@@ -520,9 +873,10 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 		die(_("repository '%s' does not exist"), repo_name);
 	else
 		repo = repo_name;
-	is_local = path && !is_bundle;
-	if (is_local && option_depth)
-		warning(_("--depth is ignored in local clones; use file:// instead."));
+
+	/* 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]);
@@ -549,48 +903,42 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 		git_dir = xstrdup(dir);
 	else {
 		work_tree = dir;
-		git_dir = xstrdup(mkpath("%s/.git", dir));
+		git_dir = mkpathdup("%s/.git", dir);
 	}
 
+	atexit(remove_junk);
+	sigchain_push_common(remove_junk_on_signal);
+
 	if (!option_bare) {
-		junk_work_tree = work_tree;
 		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, 0755))
-			die_errno(_("could not create work tree dir '%s'."),
+		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;
-	atexit(remove_junk);
-	sigchain_push_common(remove_junk_on_signal);
-
-	setenv(CONFIG_ENVIRONMENT, mkpath("%s/config", git_dir), 1);
 
+	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)
+	if (real_git_dir) {
 		git_dir = real_git_dir;
+		junk_git_dir = real_git_dir;
+	}
 
 	if (0 <= option_verbosity) {
 		if (option_bare)
-			printf(_("Cloning into bare repository '%s'...\n"), dir);
+			fprintf(stderr, _("Cloning into bare repository '%s'...\n"), dir);
 		else
-			printf(_("Cloning into '%s'...\n"), dir);
+			fprintf(stderr, _("Cloning into '%s'...\n"), dir);
 	}
 	init_db(option_template, INIT_DB_QUIET);
 	write_config(&option_config);
 
-	/*
-	 * At this point, the config exists, so we do not need the
-	 * environment variable.  We actually need to unset it, too, to
-	 * re-enable parsing of the global configs.
-	 */
-	unsetenv(CONFIG_ENVIRONMENT);
-
 	git_config(git_default_config, NULL);
 
 	if (option_bare) {
@@ -604,20 +952,6 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	}
 
 	strbuf_addf(&value, "+%s*:%s*", src_ref_prefix, branch_top.buf);
-
-	if (option_mirror || !option_bare) {
-		/* Configure the remote */
-		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_addf(&key, "remote.%s.url", option_origin);
 	git_config_set(key.buf, repo);
 	strbuf_reset(&key);
@@ -630,64 +964,88 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 
 	strbuf_reset(&value);
 
+	remote = remote_get(option_origin);
+	transport = transport_get(remote, remote->url[0]);
+	transport_set_verbosity(transport, option_verbosity, option_progress);
+
+	path = get_repo_path(remote->url[0], &is_bundle);
+	is_local = option_local != 0 && path && !is_bundle;
 	if (is_local) {
-		refs = clone_local(path, git_dir);
-		mapped_refs = wanted_peer_refs(refs, refspec);
-	} else {
-		struct remote *remote = remote_get(option_origin);
-		transport = transport_get(remote, remote->url[0]);
+		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 || !transport->fetch)
-			die(_("Don't know how to clone %s"), transport->url);
+	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");
+	transport_set_option(transport, TRANS_OPT_KEEP, "yes");
 
-		if (option_depth)
-			transport_set_option(transport, TRANS_OPT_DEPTH,
-					     option_depth);
+	if (option_depth)
+		transport_set_option(transport, TRANS_OPT_DEPTH,
+				     option_depth);
+	if (option_single_branch)
+		transport_set_option(transport, TRANS_OPT_FOLLOWTAGS, "1");
 
-		transport_set_verbosity(transport, option_verbosity, option_progress);
+	if (option_upload_pack)
+		transport_set_option(transport, TRANS_OPT_UPLOADPACK,
+				     option_upload_pack);
 
-		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_fetch_refs(transport, mapped_refs);
-		}
-	}
+	refs = transport_get_remote_refs(transport);
 
 	if (refs) {
-		clear_extra_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_sha1(ref->old_sha1)) {
+				complete_refs_before_fetch = 0;
+				break;
+			}
 
-		write_remote_refs(mapped_refs);
+		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) {
-			struct strbuf head = STRBUF_INIT;
-			strbuf_addstr(&head, src_ref_prefix);
-			strbuf_addstr(&head, option_branch);
 			our_head_points_at =
-				find_ref_by_name(mapped_refs, head.buf);
-			strbuf_release(&head);
+				find_remote_branch(mapped_refs, option_branch);
 
-			if (!our_head_points_at) {
-				warning(_("Remote branch %s not found in "
-					"upstream %s, using HEAD instead"),
-					option_branch, option_origin);
-				our_head_points_at = remote_head_points_at;
-			}
+			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;
@@ -697,89 +1055,36 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 					      "refs/heads/master");
 	}
 
-	if (remote_head_points_at && !option_bare) {
-		struct strbuf head_ref = STRBUF_INIT;
-		strbuf_addstr(&head_ref, branch_top.buf);
-		strbuf_addstr(&head_ref, "HEAD");
-		create_symref(head_ref.buf,
-			      remote_head_points_at->peer_ref->name,
-			      reflog_msg.buf);
-	}
+	write_refspec_config(src_ref_prefix, our_head_points_at,
+			remote_head_points_at, &branch_top);
 
-	if (our_head_points_at) {
-		/* Local default branch link */
-		create_symref("HEAD", our_head_points_at->name, NULL);
-		if (!option_bare) {
-			const char *head = skip_prefix(our_head_points_at->name,
-						       "refs/heads/");
-			update_ref(reflog_msg.buf, "HEAD",
-				   our_head_points_at->old_sha1,
-				   NULL, 0, DIE_ON_ERR);
-			install_branch_config(0, head, option_origin,
-					      our_head_points_at->name);
-		}
-	} else if (remote_head) {
-		/* Source had detached HEAD pointing somewhere. */
-		if (!option_bare) {
-			update_ref(reflog_msg.buf, "HEAD",
-				   remote_head->old_sha1,
-				   NULL, REF_NODEREF, DIE_ON_ERR);
-			our_head_points_at = remote_head;
-		}
-	} else {
-		/* Nothing to checkout out */
-		if (!option_no_checkout)
-			warning(_("remote HEAD refers to nonexistent ref, "
-				"unable to checkout.\n"));
-		option_no_checkout = 1;
-	}
-
-	if (transport) {
-		transport_unlock_pack(transport);
-		transport_disconnect(transport);
-	}
-
-	if (!option_no_checkout) {
-		struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
-		struct unpack_trees_options opts;
-		struct tree *tree;
-		struct tree_desc t;
-		int fd;
+	if (is_local)
+		clone_local(path, git_dir);
+	else if (refs && complete_refs_before_fetch)
+		transport_fetch_refs(transport, mapped_refs);
 
-		/* We need to be in the new work tree for the checkout */
-		setup_work_tree();
+	update_remote_refs(refs, mapped_refs, remote_head_points_at,
+			   branch_top.buf, reflog_msg.buf, transport, !is_local);
 
-		fd = hold_locked_index(lock_file, 1);
+	update_head(our_head_points_at, remote_head, reflog_msg.buf);
 
-		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(our_head_points_at->old_sha1);
-		parse_tree(tree);
-		init_tree_desc(&t, tree->buffer, tree->size);
-		unpack_trees(1, &t, &opts);
-
-		if (write_cache(fd, active_cache, active_nr) ||
-		    commit_locked_index(lock_file))
-			die(_("unable to write new index file"));
-
-		err |= run_hook(NULL, "post-checkout", sha1_to_hex(null_sha1),
-				sha1_to_hex(our_head_points_at->old_sha1), "1",
-				NULL);
+	transport_unlock_pack(transport);
+	transport_disconnect(transport);
 
-		if (!err && option_recursive)
-			err = run_command_v_opt(argv_submodule, RUN_GIT_CMD);
+	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_pid = 0;
+	junk_mode = JUNK_LEAVE_ALL;
+
+	free(refspec);
 	return err;
 }