1 files changed, 1236 insertions, 39 deletions

diff --git a/transport-helper.c b/transport-helper.c
index f57e84c676..5d99a6bc2e 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -1,77 +1,343 @@
 #include "cache.h"
 #include "transport.h"
-
+#include "quote.h"
 #include "run-command.h"
 #include "commit.h"
 #include "diff.h"
 #include "revision.h"
+#include "remote.h"
+#include "string-list.h"
+#include "thread-utils.h"
+#include "sigchain.h"
+#include "argv-array.h"
+#include "refs.h"
 
-struct helper_data
-{
+static int debug;
+
+struct helper_data {
 	const char *name;
 	struct child_process *helper;
-	unsigned fetch : 1;
+	FILE *out;
+	unsigned fetch : 1,
+		import : 1,
+		bidi_import : 1,
+		export : 1,
+		option : 1,
+		push : 1,
+		connect : 1,
+		signed_tags : 1,
+		check_connectivity : 1,
+		no_disconnect_req : 1,
+		no_private_update : 1;
+	char *export_marks;
+	char *import_marks;
+	/* These go from remote name (as in "list") to private name */
+	struct refspec *refspecs;
+	int refspec_nr;
+	/* Transport options for fetch-pack/send-pack (should one of
+	 * those be invoked).
+	 */
+	struct git_transport_options transport_options;
 };
 
+static void sendline(struct helper_data *helper, struct strbuf *buffer)
+{
+	if (debug)
+		fprintf(stderr, "Debug: Remote helper: -> %s", buffer->buf);
+	if (write_in_full(helper->helper->in, buffer->buf, buffer->len)
+		!= buffer->len)
+		die_errno("Full write to remote helper failed");
+}
+
+static int recvline_fh(FILE *helper, struct strbuf *buffer, const char *name)
+{
+	strbuf_reset(buffer);
+	if (debug)
+		fprintf(stderr, "Debug: Remote helper: Waiting...\n");
+	if (strbuf_getline(buffer, helper, '\n') == EOF) {
+		if (debug)
+			fprintf(stderr, "Debug: Remote helper quit.\n");
+		return 1;
+	}
+
+	if (debug)
+		fprintf(stderr, "Debug: Remote helper: <- %s\n", buffer->buf);
+	return 0;
+}
+
+static int recvline(struct helper_data *helper, struct strbuf *buffer)
+{
+	return recvline_fh(helper->out, buffer, helper->name);
+}
+
+static void write_constant(int fd, const char *str)
+{
+	if (debug)
+		fprintf(stderr, "Debug: Remote helper: -> %s", str);
+	if (write_in_full(fd, str, strlen(str)) != strlen(str))
+		die_errno("Full write to remote helper failed");
+}
+
+static const char *remove_ext_force(const char *url)
+{
+	if (url) {
+		const char *colon = strchr(url, ':');
+		if (colon && colon[1] == ':')
+			return colon + 2;
+	}
+	return url;
+}
+
+static void do_take_over(struct transport *transport)
+{
+	struct helper_data *data;
+	data = (struct helper_data *)transport->data;
+	transport_take_over(transport, data->helper);
+	fclose(data->out);
+	free(data);
+}
+
+static void standard_options(struct transport *t);
+
 static struct child_process *get_helper(struct transport *transport)
 {
 	struct helper_data *data = transport->data;
 	struct strbuf buf = STRBUF_INIT;
 	struct child_process *helper;
-	FILE *file;
+	const char **refspecs = NULL;
+	int refspec_nr = 0;
+	int refspec_alloc = 0;
+	int duped;
+	int code;
 
 	if (data->helper)
 		return data->helper;
 
-	helper = xcalloc(1, sizeof(*helper));
+	helper = xmalloc(sizeof(*helper));
+	child_process_init(helper);
 	helper->in = -1;
 	helper->out = -1;
 	helper->err = 0;
-	helper->argv = xcalloc(4, sizeof(*helper->argv));
-	strbuf_addf(&buf, "remote-%s", data->name);
-	helper->argv[0] = strbuf_detach(&buf, NULL);
-	helper->argv[1] = transport->remote->name;
-	helper->argv[2] = transport->url;
-	helper->git_cmd = 1;
-	if (start_command(helper))
-		die("Unable to run helper: git %s", helper->argv[0]);
+	argv_array_pushf(&helper->args, "git-remote-%s", data->name);
+	argv_array_push(&helper->args, transport->remote->name);
+	argv_array_push(&helper->args, remove_ext_force(transport->url));
+	helper->git_cmd = 0;
+	helper->silent_exec_failure = 1;
+
+	argv_array_pushf(&helper->env_array, "%s=%s", GIT_DIR_ENVIRONMENT,
+			 get_git_dir());
+
+	code = start_command(helper);
+	if (code < 0 && errno == ENOENT)
+		die("Unable to find remote helper for '%s'", data->name);
+	else if (code != 0)
+		exit(code);
+
 	data->helper = helper;
+	data->no_disconnect_req = 0;
 
-	write_str_in_full(helper->in, "capabilities\n");
+	/*
+	 * Open the output as FILE* so strbuf_getline() can be used.
+	 * Do this with duped fd because fclose() will close the fd,
+	 * and stuff like taking over will require the fd to remain.
+	 */
+	duped = dup(helper->out);
+	if (duped < 0)
+		die_errno("Can't dup helper output fd");
+	data->out = xfdopen(duped, "r");
+
+	write_constant(helper->in, "capabilities\n");
 
-	file = xfdopen(helper->out, "r");
 	while (1) {
-		if (strbuf_getline(&buf, file, '\n') == EOF)
-			exit(128); /* child died, message supplied already */
+		const char *capname, *arg;
+		int mandatory = 0;
+		if (recvline(data, &buf))
+			exit(128);
 
 		if (!*buf.buf)
 			break;
-		if (!strcmp(buf.buf, "fetch"))
+
+		if (*buf.buf == '*') {
+			capname = buf.buf + 1;
+			mandatory = 1;
+		} else
+			capname = buf.buf;
+
+		if (debug)
+			fprintf(stderr, "Debug: Got cap %s\n", capname);
+		if (!strcmp(capname, "fetch"))
 			data->fetch = 1;
+		else if (!strcmp(capname, "option"))
+			data->option = 1;
+		else if (!strcmp(capname, "push"))
+			data->push = 1;
+		else if (!strcmp(capname, "import"))
+			data->import = 1;
+		else if (!strcmp(capname, "bidi-import"))
+			data->bidi_import = 1;
+		else if (!strcmp(capname, "export"))
+			data->export = 1;
+		else if (!strcmp(capname, "check-connectivity"))
+			data->check_connectivity = 1;
+		else if (!data->refspecs && skip_prefix(capname, "refspec ", &arg)) {
+			ALLOC_GROW(refspecs,
+				   refspec_nr + 1,
+				   refspec_alloc);
+			refspecs[refspec_nr++] = xstrdup(arg);
+		} else if (!strcmp(capname, "connect")) {
+			data->connect = 1;
+		} else if (!strcmp(capname, "signed-tags")) {
+			data->signed_tags = 1;
+		} else if (skip_prefix(capname, "export-marks ", &arg)) {
+			data->export_marks = xstrdup(arg);
+		} else if (skip_prefix(capname, "import-marks ", &arg)) {
+			data->import_marks = xstrdup(arg);
+		} else if (starts_with(capname, "no-private-update")) {
+			data->no_private_update = 1;
+		} else if (mandatory) {
+			die("Unknown mandatory capability %s. This remote "
+			    "helper probably needs newer version of Git.",
+			    capname);
+		}
+	}
+	if (refspecs) {
+		int i;
+		data->refspec_nr = refspec_nr;
+		data->refspecs = parse_fetch_refspec(refspec_nr, refspecs);
+		for (i = 0; i < refspec_nr; i++)
+			free((char *)refspecs[i]);
+		free(refspecs);
+	} else if (data->import || data->bidi_import || data->export) {
+		warning("This remote helper should implement refspec capability.");
 	}
+	strbuf_release(&buf);
+	if (debug)
+		fprintf(stderr, "Debug: Capabilities complete.\n");
+	standard_options(transport);
 	return data->helper;
 }
 
 static int disconnect_helper(struct transport *transport)
 {
 	struct helper_data *data = transport->data;
+	int res = 0;
+
 	if (data->helper) {
-		write_str_in_full(data->helper->in, "\n");
+		if (debug)
+			fprintf(stderr, "Debug: Disconnecting.\n");
+		if (!data->no_disconnect_req) {
+			/*
+			 * Ignore write errors; there's nothing we can do,
+			 * since we're about to close the pipe anyway. And the
+			 * most likely error is EPIPE due to the helper dying
+			 * to report an error itself.
+			 */
+			sigchain_push(SIGPIPE, SIG_IGN);
+			xwrite(data->helper->in, "\n", 1);
+			sigchain_pop(SIGPIPE);
+		}
 		close(data->helper->in);
-		finish_command(data->helper);
-		free((char *)data->helper->argv[0]);
-		free(data->helper->argv);
+		close(data->helper->out);
+		fclose(data->out);
+		res = finish_command(data->helper);
 		free(data->helper);
 		data->helper = NULL;
 	}
-	return 0;
+	return res;
+}
+
+static const char *unsupported_options[] = {
+	TRANS_OPT_UPLOADPACK,
+	TRANS_OPT_RECEIVEPACK,
+	TRANS_OPT_THIN,
+	TRANS_OPT_KEEP
+	};
+
+static const char *boolean_options[] = {
+	TRANS_OPT_THIN,
+	TRANS_OPT_KEEP,
+	TRANS_OPT_FOLLOWTAGS,
+	TRANS_OPT_PUSH_CERT
+	};
+
+static int set_helper_option(struct transport *transport,
+			  const char *name, const char *value)
+{
+	struct helper_data *data = transport->data;
+	struct strbuf buf = STRBUF_INIT;
+	int i, ret, is_bool = 0;
+
+	get_helper(transport);
+
+	if (!data->option)
+		return 1;
+
+	for (i = 0; i < ARRAY_SIZE(unsupported_options); i++) {
+		if (!strcmp(name, unsupported_options[i]))
+			return 1;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(boolean_options); i++) {
+		if (!strcmp(name, boolean_options[i])) {
+			is_bool = 1;
+			break;
+		}
+	}
+
+	strbuf_addf(&buf, "option %s ", name);
+	if (is_bool)
+		strbuf_addstr(&buf, value ? "true" : "false");
+	else
+		quote_c_style(value, &buf, NULL, 0);
+	strbuf_addch(&buf, '\n');
+
+	sendline(data, &buf);
+	if (recvline(data, &buf))
+		exit(128);
+
+	if (!strcmp(buf.buf, "ok"))
+		ret = 0;
+	else if (starts_with(buf.buf, "error")) {
+		ret = -1;
+	} else if (!strcmp(buf.buf, "unsupported"))
+		ret = 1;
+	else {
+		warning("%s unexpectedly said: '%s'", data->name, buf.buf);
+		ret = 1;
+	}
+	strbuf_release(&buf);
+	return ret;
+}
+
+static void standard_options(struct transport *t)
+{
+	char buf[16];
+	int n;
+	int v = t->verbose;
+
+	set_helper_option(t, "progress", t->progress ? "true" : "false");
+
+	n = snprintf(buf, sizeof(buf), "%d", v + 1);
+	if (n >= sizeof(buf))
+		die("impossibly large verbosity value");
+	set_helper_option(t, "verbosity", buf);
+}
+
+static int release_helper(struct transport *transport)
+{
+	int res = 0;
+	struct helper_data *data = transport->data;
+	free_refspec(data->refspec_nr, data->refspecs);
+	data->refspecs = NULL;
+	res = disconnect_helper(transport);
+	free(transport->data);
+	return res;
 }
 
 static int fetch_with_fetch(struct transport *transport,
-			    int nr_heads, const struct ref **to_fetch)
+			    int nr_heads, struct ref **to_fetch)
 {
-	struct child_process *helper = get_helper(transport);
-	FILE *file = xfdopen(helper->out, "r");
+	struct helper_data *data = transport->data;
 	int i;
 	struct strbuf buf = STRBUF_INIT;
 
@@ -81,22 +347,265 @@ static int fetch_with_fetch(struct transport *transport,
 			continue;
 
 		strbuf_addf(&buf, "fetch %s %s\n",
-			    sha1_to_hex(posn->old_sha1), posn->name);
-		write_in_full(helper->in, buf.buf, buf.len);
+			    sha1_to_hex(posn->old_sha1),
+			    posn->symref ? posn->symref : posn->name);
+	}
+
+	strbuf_addch(&buf, '\n');
+	sendline(data, &buf);
+
+	while (1) {
+		if (recvline(data, &buf))
+			exit(128);
+
+		if (starts_with(buf.buf, "lock ")) {
+			const char *name = buf.buf + 5;
+			if (transport->pack_lockfile)
+				warning("%s also locked %s", data->name, name);
+			else
+				transport->pack_lockfile = xstrdup(name);
+		}
+		else if (data->check_connectivity &&
+			 data->transport_options.check_self_contained_and_connected &&
+			 !strcmp(buf.buf, "connectivity-ok"))
+			data->transport_options.self_contained_and_connected = 1;
+		else if (!buf.len)
+			break;
+		else
+			warning("%s unexpectedly said: '%s'", data->name, buf.buf);
+	}
+	strbuf_release(&buf);
+	return 0;
+}
+
+static int get_importer(struct transport *transport, struct child_process *fastimport)
+{
+	struct child_process *helper = get_helper(transport);
+	struct helper_data *data = transport->data;
+	int cat_blob_fd, code;
+	child_process_init(fastimport);
+	fastimport->in = helper->out;
+	argv_array_push(&fastimport->args, "fast-import");
+	argv_array_push(&fastimport->args, debug ? "--stats" : "--quiet");
+
+	if (data->bidi_import) {
+		cat_blob_fd = xdup(helper->in);
+		argv_array_pushf(&fastimport->args, "--cat-blob-fd=%d", cat_blob_fd);
+	}
+	fastimport->git_cmd = 1;
+
+	code = start_command(fastimport);
+	return code;
+}
+
+static int get_exporter(struct transport *transport,
+			struct child_process *fastexport,
+			struct string_list *revlist_args)
+{
+	struct helper_data *data = transport->data;
+	struct child_process *helper = get_helper(transport);
+	int i;
+
+	child_process_init(fastexport);
+
+	/* we need to duplicate helper->in because we want to use it after
+	 * fastexport is done with it. */
+	fastexport->out = dup(helper->in);
+	argv_array_push(&fastexport->args, "fast-export");
+	argv_array_push(&fastexport->args, "--use-done-feature");
+	argv_array_push(&fastexport->args, data->signed_tags ?
+		"--signed-tags=verbatim" : "--signed-tags=warn-strip");
+	if (data->export_marks)
+		argv_array_pushf(&fastexport->args, "--export-marks=%s.tmp", data->export_marks);
+	if (data->import_marks)
+		argv_array_pushf(&fastexport->args, "--import-marks=%s", data->import_marks);
+
+	for (i = 0; i < revlist_args->nr; i++)
+		argv_array_push(&fastexport->args, revlist_args->items[i].string);
+
+	fastexport->git_cmd = 1;
+	return start_command(fastexport);
+}
+
+static int fetch_with_import(struct transport *transport,
+			     int nr_heads, struct ref **to_fetch)
+{
+	struct child_process fastimport;
+	struct helper_data *data = transport->data;
+	int i;
+	struct ref *posn;
+	struct strbuf buf = STRBUF_INIT;
+
+	get_helper(transport);
+
+	if (get_importer(transport, &fastimport))
+		die("Couldn't run fast-import");
+
+	for (i = 0; i < nr_heads; i++) {
+		posn = to_fetch[i];
+		if (posn->status & REF_STATUS_UPTODATE)
+			continue;
+
+		strbuf_addf(&buf, "import %s\n",
+			    posn->symref ? posn->symref : posn->name);
+		sendline(data, &buf);
 		strbuf_reset(&buf);
+	}
+
+	write_constant(data->helper->in, "\n");
+	/*
+	 * remote-helpers that advertise the bidi-import capability are required to
+	 * buffer the complete batch of import commands until this newline before
+	 * sending data to fast-import.
+	 * These helpers read back data from fast-import on their stdin, which could
+	 * be mixed with import commands, otherwise.
+	 */
+
+	if (finish_command(&fastimport))
+		die("Error while running fast-import");
 
-		if (strbuf_getline(&buf, file, '\n') == EOF)
-			exit(128); /* child died, message supplied already */
+	/*
+	 * The fast-import stream of a remote helper that advertises
+	 * the "refspec" capability writes to the refs named after the
+	 * right hand side of the first refspec matching each ref we
+	 * were fetching.
+	 *
+	 * (If no "refspec" capability was specified, for historical
+	 * reasons we default to the equivalent of *:*.)
+	 *
+	 * Store the result in to_fetch[i].old_sha1.  Callers such
+	 * as "git fetch" can use the value to write feedback to the
+	 * terminal, populate FETCH_HEAD, and determine what new value
+	 * should be written to peer_ref if the update is a
+	 * fast-forward or this is a forced update.
+	 */
+	for (i = 0; i < nr_heads; i++) {
+		char *private, *name;
+		posn = to_fetch[i];
+		if (posn->status & REF_STATUS_UPTODATE)
+			continue;
+		name = posn->symref ? posn->symref : posn->name;
+		if (data->refspecs)
+			private = apply_refspecs(data->refspecs, data->refspec_nr, name);
+		else
+			private = xstrdup(name);
+		if (private) {
+			read_ref(private, posn->old_sha1);
+			free(private);
+		}
 	}
+	strbuf_release(&buf);
+	return 0;
+}
+
+static int process_connect_service(struct transport *transport,
+				   const char *name, const char *exec)
+{
+	struct helper_data *data = transport->data;
+	struct strbuf cmdbuf = STRBUF_INIT;
+	struct child_process *helper;
+	int r, duped, ret = 0;
+	FILE *input;
+
+	helper = get_helper(transport);
+
+	/*
+	 * Yes, dup the pipe another time, as we need unbuffered version
+	 * of input pipe as FILE*. fclose() closes the underlying fd and
+	 * stream buffering only can be changed before first I/O operation
+	 * on it.
+	 */
+	duped = dup(helper->out);
+	if (duped < 0)
+		die_errno("Can't dup helper output fd");
+	input = xfdopen(duped, "r");
+	setvbuf(input, NULL, _IONBF, 0);
+
+	/*
+	 * Handle --upload-pack and friends. This is fire and forget...
+	 * just warn if it fails.
+	 */
+	if (strcmp(name, exec)) {
+		r = set_helper_option(transport, "servpath", exec);
+		if (r > 0)
+			warning("Setting remote service path not supported by protocol.");
+		else if (r < 0)
+			warning("Invalid remote service path.");
+	}
+
+	if (data->connect)
+		strbuf_addf(&cmdbuf, "connect %s\n", name);
+	else
+		goto exit;
+
+	sendline(data, &cmdbuf);
+	if (recvline_fh(input, &cmdbuf, name))
+		exit(128);
+
+	if (!strcmp(cmdbuf.buf, "")) {
+		data->no_disconnect_req = 1;
+		if (debug)
+			fprintf(stderr, "Debug: Smart transport connection "
+				"ready.\n");
+		ret = 1;
+	} else if (!strcmp(cmdbuf.buf, "fallback")) {
+		if (debug)
+			fprintf(stderr, "Debug: Falling back to dumb "
+				"transport.\n");
+	} else
+		die("Unknown response to connect: %s",
+			cmdbuf.buf);
+
+exit:
+	fclose(input);
+	return ret;
+}
+
+static int process_connect(struct transport *transport,
+				     int for_push)
+{
+	struct helper_data *data = transport->data;
+	const char *name;
+	const char *exec;
+
+	name = for_push ? "git-receive-pack" : "git-upload-pack";
+	if (for_push)
+		exec = data->transport_options.receivepack;
+	else
+		exec = data->transport_options.uploadpack;
+
+	return process_connect_service(transport, name, exec);
+}
+
+static int connect_helper(struct transport *transport, const char *name,
+		   const char *exec, int fd[2])
+{
+	struct helper_data *data = transport->data;
+
+	/* Get_helper so connect is inited. */
+	get_helper(transport);
+	if (!data->connect)
+		die("Operation not supported by protocol.");
+
+	if (!process_connect_service(transport, name, exec))
+		die("Can't connect to subservice %s.", name);
+
+	fd[0] = data->helper->out;
+	fd[1] = data->helper->in;
 	return 0;
 }
 
 static int fetch(struct transport *transport,
-		 int nr_heads, const struct ref **to_fetch)
+		 int nr_heads, struct ref **to_fetch)
 {
 	struct helper_data *data = transport->data;
 	int i, count;
 
+	if (process_connect(transport, 0)) {
+		do_take_over(transport);
+		return transport->fetch(transport, nr_heads, to_fetch);
+	}
+
 	count = 0;
 	for (i = 0; i < nr_heads; i++)
 		if (!(to_fetch[i]->status & REF_STATUS_UPTODATE))
@@ -105,30 +614,392 @@ static int fetch(struct transport *transport,
 	if (!count)
 		return 0;
 
+	if (data->check_connectivity &&
+	    data->transport_options.check_self_contained_and_connected)
+		set_helper_option(transport, "check-connectivity", "true");
+
+	if (transport->cloning)
+		set_helper_option(transport, "cloning", "true");
+
+	if (data->transport_options.update_shallow)
+		set_helper_option(transport, "update-shallow", "true");
+
 	if (data->fetch)
 		return fetch_with_fetch(transport, nr_heads, to_fetch);
 
+	if (data->import)
+		return fetch_with_import(transport, nr_heads, to_fetch);
+
 	return -1;
 }
 
+static int push_update_ref_status(struct strbuf *buf,
+				   struct ref **ref,
+				   struct ref *remote_refs)
+{
+	char *refname, *msg;
+	int status, forced = 0;
+
+	if (starts_with(buf->buf, "ok ")) {
+		status = REF_STATUS_OK;
+		refname = buf->buf + 3;
+	} else if (starts_with(buf->buf, "error ")) {
+		status = REF_STATUS_REMOTE_REJECT;
+		refname = buf->buf + 6;
+	} else
+		die("expected ok/error, helper said '%s'", buf->buf);
+
+	msg = strchr(refname, ' ');
+	if (msg) {
+		struct strbuf msg_buf = STRBUF_INIT;
+		const char *end;
+
+		*msg++ = '\0';
+		if (!unquote_c_style(&msg_buf, msg, &end))
+			msg = strbuf_detach(&msg_buf, NULL);
+		else
+			msg = xstrdup(msg);
+		strbuf_release(&msg_buf);
+
+		if (!strcmp(msg, "no match")) {
+			status = REF_STATUS_NONE;
+			free(msg);
+			msg = NULL;
+		}
+		else if (!strcmp(msg, "up to date")) {
+			status = REF_STATUS_UPTODATE;
+			free(msg);
+			msg = NULL;
+		}
+		else if (!strcmp(msg, "non-fast forward")) {
+			status = REF_STATUS_REJECT_NONFASTFORWARD;
+			free(msg);
+			msg = NULL;
+		}
+		else if (!strcmp(msg, "already exists")) {
+			status = REF_STATUS_REJECT_ALREADY_EXISTS;
+			free(msg);
+			msg = NULL;
+		}
+		else if (!strcmp(msg, "fetch first")) {
+			status = REF_STATUS_REJECT_FETCH_FIRST;
+			free(msg);
+			msg = NULL;
+		}
+		else if (!strcmp(msg, "needs force")) {
+			status = REF_STATUS_REJECT_NEEDS_FORCE;
+			free(msg);
+			msg = NULL;
+		}
+		else if (!strcmp(msg, "stale info")) {
+			status = REF_STATUS_REJECT_STALE;
+			free(msg);
+			msg = NULL;
+		}
+		else if (!strcmp(msg, "forced update")) {
+			forced = 1;
+			free(msg);
+			msg = NULL;
+		}
+	}
+
+	if (*ref)
+		*ref = find_ref_by_name(*ref, refname);
+	if (!*ref)
+		*ref = find_ref_by_name(remote_refs, refname);
+	if (!*ref) {
+		warning("helper reported unexpected status of %s", refname);
+		return 1;
+	}
+
+	if ((*ref)->status != REF_STATUS_NONE) {
+		/*
+		 * Earlier, the ref was marked not to be pushed, so ignore the ref
+		 * status reported by the remote helper if the latter is 'no match'.
+		 */
+		if (status == REF_STATUS_NONE)
+			return 1;
+	}
+
+	(*ref)->status = status;
+	(*ref)->forced_update |= forced;
+	(*ref)->remote_status = msg;
+	return !(status == REF_STATUS_OK);
+}
+
+static int push_update_refs_status(struct helper_data *data,
+				    struct ref *remote_refs,
+				    int flags)
+{
+	struct strbuf buf = STRBUF_INIT;
+	struct ref *ref = remote_refs;
+	int ret = 0;
+
+	for (;;) {
+		char *private;
+
+		if (recvline(data, &buf)) {
+			ret = 1;
+			break;
+		}
+
+		if (!buf.len)
+			break;
+
+		if (push_update_ref_status(&buf, &ref, remote_refs))
+			continue;
+
+		if (flags & TRANSPORT_PUSH_DRY_RUN || !data->refspecs || data->no_private_update)
+			continue;
+
+		/* propagate back the update to the remote namespace */
+		private = apply_refspecs(data->refspecs, data->refspec_nr, ref->name);
+		if (!private)
+			continue;
+		update_ref("update by helper", private, ref->new_sha1, NULL, 0, 0);
+		free(private);
+	}
+	strbuf_release(&buf);
+	return ret;
+}
+
+static int push_refs_with_push(struct transport *transport,
+			       struct ref *remote_refs, int flags)
+{
+	int force_all = flags & TRANSPORT_PUSH_FORCE;
+	int mirror = flags & TRANSPORT_PUSH_MIRROR;
+	struct helper_data *data = transport->data;
+	struct strbuf buf = STRBUF_INIT;
+	struct ref *ref;
+	struct string_list cas_options = STRING_LIST_INIT_DUP;
+	struct string_list_item *cas_option;
+
+	get_helper(transport);
+	if (!data->push)
+		return 1;
+
+	for (ref = remote_refs; ref; ref = ref->next) {
+		if (!ref->peer_ref && !mirror)
+			continue;
+
+		/* Check for statuses set by set_ref_status_for_push() */
+		switch (ref->status) {
+		case REF_STATUS_REJECT_NONFASTFORWARD:
+		case REF_STATUS_REJECT_STALE:
+		case REF_STATUS_REJECT_ALREADY_EXISTS:
+		case REF_STATUS_UPTODATE:
+			continue;
+		default:
+			; /* do nothing */
+		}
+
+		if (force_all)
+			ref->force = 1;
+
+		strbuf_addstr(&buf, "push ");
+		if (!ref->deletion) {
+			if (ref->force)
+				strbuf_addch(&buf, '+');
+			if (ref->peer_ref)
+				strbuf_addstr(&buf, ref->peer_ref->name);
+			else
+				strbuf_addstr(&buf, sha1_to_hex(ref->new_sha1));
+		}
+		strbuf_addch(&buf, ':');
+		strbuf_addstr(&buf, ref->name);
+		strbuf_addch(&buf, '\n');
+
+		/*
+		 * The "--force-with-lease" options without explicit
+		 * values to expect have already been expanded into
+		 * the ref->old_sha1_expect[] field; we can ignore
+		 * transport->smart_options->cas altogether and instead
+		 * can enumerate them from the refs.
+		 */
+		if (ref->expect_old_sha1) {
+			struct strbuf cas = STRBUF_INIT;
+			strbuf_addf(&cas, "%s:%s",
+				    ref->name, sha1_to_hex(ref->old_sha1_expect));
+			string_list_append(&cas_options, strbuf_detach(&cas, NULL));
+		}
+	}
+	if (buf.len == 0) {
+		string_list_clear(&cas_options, 0);
+		return 0;
+	}
+
+	for_each_string_list_item(cas_option, &cas_options)
+		set_helper_option(transport, "cas", cas_option->string);
+
+	if (flags & TRANSPORT_PUSH_DRY_RUN) {
+		if (set_helper_option(transport, "dry-run", "true") != 0)
+			die("helper %s does not support dry-run", data->name);
+	} else if (flags & TRANSPORT_PUSH_CERT) {
+		if (set_helper_option(transport, TRANS_OPT_PUSH_CERT, "true") != 0)
+			die("helper %s does not support --signed", data->name);
+	}
+
+	strbuf_addch(&buf, '\n');
+	sendline(data, &buf);
+	strbuf_release(&buf);
+
+	return push_update_refs_status(data, remote_refs, flags);
+}
+
+static int push_refs_with_export(struct transport *transport,
+		struct ref *remote_refs, int flags)
+{
+	struct ref *ref;
+	struct child_process *helper, exporter;
+	struct helper_data *data = transport->data;
+	struct string_list revlist_args = STRING_LIST_INIT_DUP;
+	struct strbuf buf = STRBUF_INIT;
+
+	if (!data->refspecs)
+		die("remote-helper doesn't support push; refspec needed");
+
+	if (flags & TRANSPORT_PUSH_DRY_RUN) {
+		if (set_helper_option(transport, "dry-run", "true") != 0)
+			die("helper %s does not support dry-run", data->name);
+	} else if (flags & TRANSPORT_PUSH_CERT) {
+		if (set_helper_option(transport, TRANS_OPT_PUSH_CERT, "true") != 0)
+			die("helper %s does not support --signed", data->name);
+	}
+
+	if (flags & TRANSPORT_PUSH_FORCE) {
+		if (set_helper_option(transport, "force", "true") != 0)
+			warning("helper %s does not support 'force'", data->name);
+	}
+
+	helper = get_helper(transport);
+
+	write_constant(helper->in, "export\n");
+
+	for (ref = remote_refs; ref; ref = ref->next) {
+		char *private;
+		unsigned char sha1[20];
+
+		private = apply_refspecs(data->refspecs, data->refspec_nr, ref->name);
+		if (private && !get_sha1(private, sha1)) {
+			strbuf_addf(&buf, "^%s", private);
+			string_list_append(&revlist_args, strbuf_detach(&buf, NULL));
+			hashcpy(ref->old_sha1, sha1);
+		}
+		free(private);
+
+		if (ref->peer_ref) {
+			if (strcmp(ref->name, ref->peer_ref->name)) {
+				if (!ref->deletion) {
+					const char *name;
+					int flag;
+
+					/* Follow symbolic refs (mainly for HEAD). */
+					name = resolve_ref_unsafe(
+						 ref->peer_ref->name,
+						 RESOLVE_REF_READING,
+						 sha1, &flag);
+					if (!name || !(flag & REF_ISSYMREF))
+						name = ref->peer_ref->name;
+
+					strbuf_addf(&buf, "%s:%s", name, ref->name);
+				} else
+					strbuf_addf(&buf, ":%s", ref->name);
+
+				string_list_append(&revlist_args, "--refspec");
+				string_list_append(&revlist_args, buf.buf);
+				strbuf_release(&buf);
+			}
+			if (!ref->deletion)
+				string_list_append(&revlist_args, ref->peer_ref->name);
+		}
+	}
+
+	if (get_exporter(transport, &exporter, &revlist_args))
+		die("Couldn't run fast-export");
+
+	string_list_clear(&revlist_args, 1);
+
+	if (finish_command(&exporter))
+		die("Error while running fast-export");
+	if (push_update_refs_status(data, remote_refs, flags))
+		return 1;
+
+	if (data->export_marks) {
+		strbuf_addf(&buf, "%s.tmp", data->export_marks);
+		rename(buf.buf, data->export_marks);
+		strbuf_release(&buf);
+	}
+
+	return 0;
+}
+
+static int push_refs(struct transport *transport,
+		struct ref *remote_refs, int flags)
+{
+	struct helper_data *data = transport->data;
+
+	if (process_connect(transport, 1)) {
+		do_take_over(transport);
+		return transport->push_refs(transport, remote_refs, flags);
+	}
+
+	if (!remote_refs) {
+		fprintf(stderr, "No refs in common and none specified; doing nothing.\n"
+			"Perhaps you should specify a branch such as 'master'.\n");
+		return 0;
+	}
+
+	if (data->push)
+		return push_refs_with_push(transport, remote_refs, flags);
+
+	if (data->export)
+		return push_refs_with_export(transport, remote_refs, flags);
+
+	return -1;
+}
+
+
+static int has_attribute(const char *attrs, const char *attr) {
+	int len;
+	if (!attrs)
+		return 0;
+
+	len = strlen(attr);
+	for (;;) {
+		const char *space = strchrnul(attrs, ' ');
+		if (len == space - attrs && !strncmp(attrs, attr, len))
+			return 1;
+		if (!*space)
+			return 0;
+		attrs = space + 1;
+	}
+}
+
 static struct ref *get_refs_list(struct transport *transport, int for_push)
 {
+	struct helper_data *data = transport->data;
 	struct child_process *helper;
 	struct ref *ret = NULL;
 	struct ref **tail = &ret;
 	struct ref *posn;
 	struct strbuf buf = STRBUF_INIT;
-	FILE *file;
 
 	helper = get_helper(transport);
 
-	write_str_in_full(helper->in, "list\n");
+	if (process_connect(transport, for_push)) {
+		do_take_over(transport);
+		return transport->get_refs_list(transport, for_push);
+	}
+
+	if (data->push && for_push)
+		write_str_in_full(helper->in, "list for-push\n");
+	else
+		write_str_in_full(helper->in, "list\n");
 
-	file = xfdopen(helper->out, "r");
 	while (1) {
 		char *eov, *eon;
-		if (strbuf_getline(&buf, file, '\n') == EOF)
-			exit(128); /* child died, message supplied already */
+		if (recvline(data, &buf))
+			exit(128);
 
 		if (!*buf.buf)
 			break;
@@ -145,8 +1016,16 @@ static struct ref *get_refs_list(struct transport *transport, int for_push)
 			(*tail)->symref = xstrdup(buf.buf + 1);
 		else if (buf.buf[0] != '?')
 			get_sha1_hex(buf.buf, (*tail)->old_sha1);
+		if (eon) {
+			if (has_attribute(eon + 1, "unchanged")) {
+				(*tail)->status |= REF_STATUS_UPTODATE;
+				read_ref((*tail)->name, (*tail)->old_sha1);
+			}
+		}
 		tail = &((*tail)->next);
 	}
+	if (debug)
+		fprintf(stderr, "Debug: Read ref listing.\n");
 	strbuf_release(&buf);
 
 	for (posn = ret; posn; posn = posn->next)
@@ -157,12 +1036,330 @@ static struct ref *get_refs_list(struct transport *transport, int for_push)
 
 int transport_helper_init(struct transport *transport, const char *name)
 {
-	struct helper_data *data = xcalloc(sizeof(*data), 1);
+	struct helper_data *data = xcalloc(1, sizeof(*data));
 	data->name = name;
 
+	if (getenv("GIT_TRANSPORT_HELPER_DEBUG"))
+		debug = 1;
+
 	transport->data = data;
+	transport->set_option = set_helper_option;
 	transport->get_refs_list = get_refs_list;
 	transport->fetch = fetch;
-	transport->disconnect = disconnect_helper;
+	transport->push_refs = push_refs;
+	transport->disconnect = release_helper;
+	transport->connect = connect_helper;
+	transport->smart_options = &(data->transport_options);
 	return 0;
 }
+
+/*
+ * Linux pipes can buffer 65536 bytes at once (and most platforms can
+ * buffer less), so attempt reads and writes with up to that size.
+ */
+#define BUFFERSIZE 65536
+/* This should be enough to hold debugging message. */
+#define PBUFFERSIZE 8192
+
+/* Print bidirectional transfer loop debug message. */
+__attribute__((format (printf, 1, 2)))
+static void transfer_debug(const char *fmt, ...)
+{
+	va_list args;
+	char msgbuf[PBUFFERSIZE];
+	static int debug_enabled = -1;
+
+	if (debug_enabled < 0)
+		debug_enabled = getenv("GIT_TRANSLOOP_DEBUG") ? 1 : 0;
+	if (!debug_enabled)
+		return;
+
+	va_start(args, fmt);
+	vsnprintf(msgbuf, PBUFFERSIZE, fmt, args);
+	va_end(args);
+	fprintf(stderr, "Transfer loop debugging: %s\n", msgbuf);
+}
+
+/* Stream state: More data may be coming in this direction. */
+#define SSTATE_TRANSFERING 0
+/*
+ * Stream state: No more data coming in this direction, flushing rest of
+ * data.
+ */
+#define SSTATE_FLUSHING 1
+/* Stream state: Transfer in this direction finished. */
+#define SSTATE_FINISHED 2
+
+#define STATE_NEEDS_READING(state) ((state) <= SSTATE_TRANSFERING)
+#define STATE_NEEDS_WRITING(state) ((state) <= SSTATE_FLUSHING)
+#define STATE_NEEDS_CLOSING(state) ((state) == SSTATE_FLUSHING)
+
+/* Unidirectional transfer. */
+struct unidirectional_transfer {
+	/* Source */
+	int src;
+	/* Destination */
+	int dest;
+	/* Is source socket? */
+	int src_is_sock;
+	/* Is destination socket? */
+	int dest_is_sock;
+	/* Transfer state (TRANSFERRING/FLUSHING/FINISHED) */
+	int state;
+	/* Buffer. */
+	char buf[BUFFERSIZE];
+	/* Buffer used. */
+	size_t bufuse;
+	/* Name of source. */
+	const char *src_name;
+	/* Name of destination. */
+	const char *dest_name;
+};
+
+/* Closes the target (for writing) if transfer has finished. */
+static void udt_close_if_finished(struct unidirectional_transfer *t)
+{
+	if (STATE_NEEDS_CLOSING(t->state) && !t->bufuse) {
+		t->state = SSTATE_FINISHED;
+		if (t->dest_is_sock)
+			shutdown(t->dest, SHUT_WR);
+		else
+			close(t->dest);
+		transfer_debug("Closed %s.", t->dest_name);
+	}
+}
+
+/*
+ * Tries to read read data from source into buffer. If buffer is full,
+ * no data is read. Returns 0 on success, -1 on error.
+ */
+static int udt_do_read(struct unidirectional_transfer *t)
+{
+	ssize_t bytes;
+
+	if (t->bufuse == BUFFERSIZE)
+		return 0;	/* No space for more. */
+
+	transfer_debug("%s is readable", t->src_name);
+	bytes = read(t->src, t->buf + t->bufuse, BUFFERSIZE - t->bufuse);
+	if (bytes < 0 && errno != EWOULDBLOCK && errno != EAGAIN &&
+		errno != EINTR) {
+		error("read(%s) failed: %s", t->src_name, strerror(errno));
+		return -1;
+	} else if (bytes == 0) {
+		transfer_debug("%s EOF (with %i bytes in buffer)",
+			t->src_name, (int)t->bufuse);
+		t->state = SSTATE_FLUSHING;
+	} else if (bytes > 0) {
+		t->bufuse += bytes;
+		transfer_debug("Read %i bytes from %s (buffer now at %i)",
+			(int)bytes, t->src_name, (int)t->bufuse);
+	}
+	return 0;
+}
+
+/* Tries to write data from buffer into destination. If buffer is empty,
+ * no data is written. Returns 0 on success, -1 on error.
+ */
+static int udt_do_write(struct unidirectional_transfer *t)
+{
+	ssize_t bytes;
+
+	if (t->bufuse == 0)
+		return 0;	/* Nothing to write. */
+
+	transfer_debug("%s is writable", t->dest_name);
+	bytes = xwrite(t->dest, t->buf, t->bufuse);
+	if (bytes < 0 && errno != EWOULDBLOCK) {
+		error("write(%s) failed: %s", t->dest_name, strerror(errno));
+		return -1;
+	} else if (bytes > 0) {
+		t->bufuse -= bytes;
+		if (t->bufuse)
+			memmove(t->buf, t->buf + bytes, t->bufuse);
+		transfer_debug("Wrote %i bytes to %s (buffer now at %i)",
+			(int)bytes, t->dest_name, (int)t->bufuse);
+	}
+	return 0;
+}
+
+
+/* State of bidirectional transfer loop. */
+struct bidirectional_transfer_state {
+	/* Direction from program to git. */
+	struct unidirectional_transfer ptg;
+	/* Direction from git to program. */
+	struct unidirectional_transfer gtp;
+};
+
+static void *udt_copy_task_routine(void *udt)
+{
+	struct unidirectional_transfer *t = (struct unidirectional_transfer *)udt;
+	while (t->state != SSTATE_FINISHED) {
+		if (STATE_NEEDS_READING(t->state))
+			if (udt_do_read(t))
+				return NULL;
+		if (STATE_NEEDS_WRITING(t->state))
+			if (udt_do_write(t))
+				return NULL;
+		if (STATE_NEEDS_CLOSING(t->state))
+			udt_close_if_finished(t);
+	}
+	return udt;	/* Just some non-NULL value. */
+}
+
+#ifndef NO_PTHREADS
+
+/*
+ * Join thread, with appropriate errors on failure. Name is name for the
+ * thread (for error messages). Returns 0 on success, 1 on failure.
+ */
+static int tloop_join(pthread_t thread, const char *name)
+{
+	int err;
+	void *tret;
+	err = pthread_join(thread, &tret);
+	if (!tret) {
+		error("%s thread failed", name);
+		return 1;
+	}
+	if (err) {
+		error("%s thread failed to join: %s", name, strerror(err));
+		return 1;
+	}
+	return 0;
+}
+
+/*
+ * Spawn the transfer tasks and then wait for them. Returns 0 on success,
+ * -1 on failure.
+ */
+static int tloop_spawnwait_tasks(struct bidirectional_transfer_state *s)
+{
+	pthread_t gtp_thread;
+	pthread_t ptg_thread;
+	int err;
+	int ret = 0;
+	err = pthread_create(&gtp_thread, NULL, udt_copy_task_routine,
+		&s->gtp);
+	if (err)
+		die("Can't start thread for copying data: %s", strerror(err));
+	err = pthread_create(&ptg_thread, NULL, udt_copy_task_routine,
+		&s->ptg);
+	if (err)
+		die("Can't start thread for copying data: %s", strerror(err));
+
+	ret |= tloop_join(gtp_thread, "Git to program copy");
+	ret |= tloop_join(ptg_thread, "Program to git copy");
+	return ret;
+}
+#else
+
+/* Close the source and target (for writing) for transfer. */
+static void udt_kill_transfer(struct unidirectional_transfer *t)
+{
+	t->state = SSTATE_FINISHED;
+	/*
+	 * Socket read end left open isn't a disaster if nobody
+	 * attempts to read from it (mingw compat headers do not
+	 * have SHUT_RD)...
+	 *
+	 * We can't fully close the socket since otherwise gtp
+	 * task would first close the socket it sends data to
+	 * while closing the ptg file descriptors.
+	 */
+	if (!t->src_is_sock)
+		close(t->src);
+	if (t->dest_is_sock)
+		shutdown(t->dest, SHUT_WR);
+	else
+		close(t->dest);
+}
+
+/*
+ * Join process, with appropriate errors on failure. Name is name for the
+ * process (for error messages). Returns 0 on success, 1 on failure.
+ */
+static int tloop_join(pid_t pid, const char *name)
+{
+	int tret;
+	if (waitpid(pid, &tret, 0) < 0) {
+		error("%s process failed to wait: %s", name, strerror(errno));
+		return 1;
+	}
+	if (!WIFEXITED(tret) || WEXITSTATUS(tret)) {
+		error("%s process failed", name);
+		return 1;
+	}
+	return 0;
+}
+
+/*
+ * Spawn the transfer tasks and then wait for them. Returns 0 on success,
+ * -1 on failure.
+ */
+static int tloop_spawnwait_tasks(struct bidirectional_transfer_state *s)
+{
+	pid_t pid1, pid2;
+	int ret = 0;
+
+	/* Fork thread #1: git to program. */
+	pid1 = fork();
+	if (pid1 < 0)
+		die_errno("Can't start thread for copying data");
+	else if (pid1 == 0) {
+		udt_kill_transfer(&s->ptg);
+		exit(udt_copy_task_routine(&s->gtp) ? 0 : 1);
+	}
+
+	/* Fork thread #2: program to git. */
+	pid2 = fork();
+	if (pid2 < 0)
+		die_errno("Can't start thread for copying data");
+	else if (pid2 == 0) {
+		udt_kill_transfer(&s->gtp);
+		exit(udt_copy_task_routine(&s->ptg) ? 0 : 1);
+	}
+
+	/*
+	 * Close both streams in parent as to not interfere with
+	 * end of file detection and wait for both tasks to finish.
+	 */
+	udt_kill_transfer(&s->gtp);
+	udt_kill_transfer(&s->ptg);
+	ret |= tloop_join(pid1, "Git to program copy");
+	ret |= tloop_join(pid2, "Program to git copy");
+	return ret;
+}
+#endif
+
+/*
+ * Copies data from stdin to output and from input to stdout simultaneously.
+ * Additionally filtering through given filter. If filter is NULL, uses
+ * identity filter.
+ */
+int bidirectional_transfer_loop(int input, int output)
+{
+	struct bidirectional_transfer_state state;
+
+	/* Fill the state fields. */
+	state.ptg.src = input;
+	state.ptg.dest = 1;
+	state.ptg.src_is_sock = (input == output);
+	state.ptg.dest_is_sock = 0;
+	state.ptg.state = SSTATE_TRANSFERING;
+	state.ptg.bufuse = 0;
+	state.ptg.src_name = "remote input";
+	state.ptg.dest_name = "stdout";
+
+	state.gtp.src = 0;
+	state.gtp.dest = output;
+	state.gtp.src_is_sock = 0;
+	state.gtp.dest_is_sock = (input == output);
+	state.gtp.state = SSTATE_TRANSFERING;
+	state.gtp.bufuse = 0;
+	state.gtp.src_name = "stdin";
+	state.gtp.dest_name = "remote output";
+
+	return tloop_spawnwait_tasks(&state);
+}