remote-curl: supports git-upload-archive service

Add new service (git-upload-archive) support in remote-curl, so we can
support remote archive over HTTP/HTTPS protocols. Differences between
git-upload-archive and other services:

 1. The git-archive program does not expect to see protocol version and
    capabilities when connecting to remote-helper, so do not send them
    in remote-curl for the git-upload-archive service.

 2. We need to detect protocol version by calling discover_refs().
    Fallback to use the git-upload-pack service (which, like
    git-upload-archive, is a read-only operation) to discover protocol
    version.

Signed-off-by: Jiang Xin <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: jiangxin

remote-curl.c

@@ -1447,8 +1447,14 @@ static int stateless_connect(const char *service_name)
 	 * establish a stateless connection, otherwise we need to tell the
 	 * client to fallback to using other transport helper functions to
 	 * complete their request.
+	 *
+	 * The "git-upload-archive" service is a read-only operation. Fallback
+	 * to use "git-upload-pack" service to discover protocol version.
 	 */
-	discover = discover_refs(service_name, 0);
+	if (!strcmp(service_name, "git-upload-archive"))
+		discover = discover_refs("git-upload-pack", 0);
+	else
+		discover = discover_refs(service_name, 0);
 	if (discover->version != protocol_v2) {
 		printf("fallback\n");
 		fflush(stdout);
@@ -1486,9 +1492,11 @@ static int stateless_connect(const char *service_name)
 
 	/*
 	 * Dump the capability listing that we got from the server earlier
-	 * during the info/refs request.
+	 * during the info/refs request. This does not work with the
+	 * "git-upload-archive" service.
 	 */
-	write_or_die(rpc.in, discover->buf, discover->len);
+	if (strcmp(service_name, "git-upload-archive"))
+		write_or_die(rpc.in, discover->buf, discover->len);
 
 	/* Until we see EOF keep sending POSTs */
 	while (1) {