Support receiving server capabilities

This patch implements the client side of backward compatible upload-pack
protocol extension, <20051027141619.0e8029f2.vsu@altlinux.ru> by Sergey.

The updated server can append "server_capabilities" which is supposed
to be a string containing space separated features of the server, after
one of elements in the initial list of SHA1-refname line, hidden with
an embedded NUL.

After get_remote_heads(), check if the server supports the feature like

	if (server_supports("multi_ack"))
		do_something();

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

cache.h

@@ -340,6 +340,7 @@ extern int match_refs(struct ref *src, struct ref *dst, struct ref ***dst_tail,
 		      int nr_refspec, char **refspec, int all);
 extern int get_ack(int fd, unsigned char *result_sha1);
 extern struct ref **get_remote_heads(int in, struct ref **list, int nr_match, char **match, int ignore_funny);
+extern int server_supports(const char *feature);
 
 extern struct packed_git *parse_pack_index(unsigned char *sha1);
 extern struct packed_git *parse_pack_index_file(const unsigned char *sha1,

connect.c

@@ -8,6 +8,8 @@
 #include <arpa/inet.h>
 #include <netdb.h>
 
+static char *server_capabilities = "";
+
 /*
  * Read all the refs from the other end
  */
@@ -20,7 +22,7 @@ struct ref **get_remote_heads(int in, struct ref **list,
 		unsigned char old_sha1[20];
 		static char buffer[1000];
 		char *name;
-		int len;
+		int len, name_len;
 
 		len = packet_read_line(in, buffer, sizeof(buffer));
 		if (!len)
@@ -36,6 +38,13 @@ struct ref **get_remote_heads(int in, struct ref **list,
 		    check_ref_format(name + 5))
 			continue;
 
+		name_len = strlen(name);
+		if (len != name_len + 41) {
+			if (server_capabilities)
+				free(server_capabilities);
+			server_capabilities = strdup(name + name_len + 1);
+		}
+
 		if (nr_match && !path_match(name, nr_match, match))
 			continue;
 		ref = xcalloc(1, sizeof(*ref) + len - 40);
@@ -47,6 +56,11 @@ struct ref **get_remote_heads(int in, struct ref **list,
 	return list;
 }
 
+int server_supports(const char *feature)
+{
+	return strstr(feature, server_capabilities) != NULL;
+}
+
 int get_ack(int fd, unsigned char *result_sha1)
 {
 	static char line[1000];