Support taking over transports

Add support for taking over transports that turn out to be smart.

Signed-off-by: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

transport-helper.c

@@ -22,6 +22,10 @@ struct helper_data
 	/* 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)
@@ -81,6 +85,7 @@ static struct child_process *get_helper(struct transport *transport)
 	const char **refspecs = NULL;
 	int refspec_nr = 0;
 	int refspec_alloc = 0;
+	int duped;
 
 	if (data->helper)
 		return data->helper;
@@ -99,9 +104,19 @@ static struct child_process *get_helper(struct transport *transport)
 		die("Unable to run helper: git %s", helper->argv[0]);
 	data->helper = helper;
 
+	/*
+	 * 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");
 
-	data->out = xfdopen(helper->out, "r");
 	while (1) {
 		const char *capname;
 		int mandatory = 0;
@@ -163,6 +178,7 @@ static int disconnect_helper(struct transport *transport)
 		strbuf_addf(&buf, "\n");
 		sendline(data, &buf);
 		close(data->helper->in);
+		close(data->helper->out);
 		fclose(data->out);
 		finish_command(data->helper);
 		free((char *)data->helper->argv[0]);
@@ -583,5 +599,6 @@ int transport_helper_init(struct transport *transport, const char *name)
 	transport->fetch = fetch;
 	transport->push_refs = push_refs;
 	transport->disconnect = release_helper;
+	transport->smart_options = &(data->transport_options);
 	return 0;
 }

transport.c

@@ -398,6 +398,7 @@ struct git_transport_data {
 	struct git_transport_options options;
 	struct child_process *conn;
 	int fd[2];
+	unsigned got_remote_heads : 1;
 	struct extra_have_objects extra_have;
 };
 
@@ -432,10 +433,15 @@ static int set_git_option(struct git_transport_options *opts,
 static int connect_setup(struct transport *transport, int for_push, int verbose)
 {
 	struct git_transport_data *data = transport->data;
+
+	if (data->conn)
+		return 0;
+
 	data->conn = git_connect(data->fd, transport->url,
 				 for_push ? data->options.receivepack :
 				 data->options.uploadpack,
 				 verbose ? CONNECT_VERBOSE : 0);
+
 	return 0;
 }
 
@@ -447,6 +453,7 @@ static struct ref *get_refs_via_connect(struct transport *transport, int for_pus
 	connect_setup(transport, for_push, 0);
 	get_remote_heads(data->fd[0], &refs, 0, NULL,
 			 for_push ? REF_NORMAL : 0, &data->extra_have);
+	data->got_remote_heads = 1;
 
 	return refs;
 }
@@ -477,9 +484,10 @@ static int fetch_refs_via_pack(struct transport *transport,
 	for (i = 0; i < nr_heads; i++)
 		origh[i] = heads[i] = xstrdup(to_fetch[i]->name);
 
-	if (!data->conn) {
+	if (!data->got_remote_heads) {
 		connect_setup(transport, 0, 0);
 		get_remote_heads(data->fd[0], &refs_tmp, 0, NULL, 0, NULL);
+		data->got_remote_heads = 1;
 	}
 
 	refs = fetch_pack(&args, data->fd, data->conn,
@@ -490,6 +498,7 @@ static int fetch_refs_via_pack(struct transport *transport,
 	if (finish_connect(data->conn))
 		refs = NULL;
 	data->conn = NULL;
+	data->got_remote_heads = 0;
 
 	free_refs(refs_tmp);
 
@@ -718,12 +727,13 @@ static int git_transport_push(struct transport *transport, struct ref *remote_re
 	struct send_pack_args args;
 	int ret;
 
-	if (!data->conn) {
+	if (!data->got_remote_heads) {
 		struct ref *tmp_refs;
 		connect_setup(transport, 1, 0);
 
 		get_remote_heads(data->fd[0], &tmp_refs, 0, NULL, REF_NORMAL,
 				 NULL);
+		data->got_remote_heads = 1;
 	}
 
 	memset(&args, 0, sizeof(args));
@@ -741,6 +751,7 @@ static int git_transport_push(struct transport *transport, struct ref *remote_re
 	close(data->fd[0]);
 	ret |= finish_connect(data->conn);
 	data->conn = NULL;
+	data->got_remote_heads = 0;
 
 	return ret;
 }
@@ -749,7 +760,8 @@ static int disconnect_git(struct transport *transport)
 {
 	struct git_transport_data *data = transport->data;
 	if (data->conn) {
-		packet_flush(data->fd[1]);
+		if (data->got_remote_heads)
+			packet_flush(data->fd[1]);
 		close(data->fd[0]);
 		close(data->fd[1]);
 		finish_connect(data->conn);
@@ -759,6 +771,32 @@ static int disconnect_git(struct transport *transport)
 	return 0;
 }
 
+void transport_take_over(struct transport *transport,
+			 struct child_process *child)
+{
+	struct git_transport_data *data;
+
+	if (!transport->smart_options)
+		die("Bug detected: Taking over transport requires non-NULL "
+		    "smart_options field.");
+
+	data = xcalloc(1, sizeof(*data));
+	data->options = *transport->smart_options;
+	data->conn = child;
+	data->fd[0] = data->conn->out;
+	data->fd[1] = data->conn->in;
+	data->got_remote_heads = 0;
+	transport->data = data;
+
+	transport->set_option = NULL;
+	transport->get_refs_list = get_refs_via_connect;
+	transport->fetch = fetch_refs_via_pack;
+	transport->push = NULL;
+	transport->push_refs = git_transport_push;
+	transport->disconnect = disconnect_git;
+	transport->smart_options = &(data->options);
+}
+
 static int is_local(const char *url)
 {
 	const char *colon = strchr(url, ':');
@@ -867,6 +905,7 @@ struct transport *transport_get(struct remote *remote, const char *url)
 		ret->smart_options = &(data->options);
 
 		data->conn = NULL;
+		data->got_remote_heads = 0;
 	} else if (!prefixcmp(url, "http://")
 		|| !prefixcmp(url, "https://")
 		|| !prefixcmp(url, "ftp://")) {
@@ -927,9 +966,9 @@ int transport_push(struct transport *transport,
 	*nonfastforward = 0;
 	verify_remote_names(refspec_nr, refspec);
 
-	if (transport->push)
+	if (transport->push) {
 		return transport->push(transport, refspec_nr, refspec, flags);
-	if (transport->push_refs) {
+	} else if (transport->push_refs) {
 		struct ref *remote_refs =
 			transport->get_refs_list(transport, 1);
 		struct ref *local_refs = get_local_heads();
@@ -973,6 +1012,7 @@ const struct ref *transport_get_remote_refs(struct transport *transport)
 {
 	if (!transport->remote_refs)
 		transport->remote_refs = transport->get_refs_list(transport, 0);
+
 	return transport->remote_refs;
 }
 
@@ -1007,6 +1047,7 @@ int transport_fetch_refs(struct transport *transport, struct ref *refs)
 	}
 
 	rc = transport->fetch(transport, nr_heads, heads);
+
 	free(heads);
 	return rc;
 }

transport.h

@@ -130,6 +130,8 @@ int transport_fetch_refs(struct transport *transport, struct ref *refs);
 void transport_unlock_pack(struct transport *transport);
 int transport_disconnect(struct transport *transport);
 char *transport_anonymize_url(const char *url);
+void transport_take_over(struct transport *transport,
+			 struct child_process *child);
 
 /* Transport methods defined outside transport.c */
 int transport_helper_init(struct transport *transport, const char *name);