Enable the use of MPTCP on Linux (when available)

IPPROTO_MPTCP v1 (not the old v0) has been improved to go about the
limitations of middleboxes.

MPTCP protocol is an extension of standard TCP which enables multiple
IP to aggregate bandwidth at layer 4 of the OSI stack across
as said IP(s).

Similar to link aggregation which works at layer 2. MPTCP works on top
of IP layer.

Other than aggregating bandwidth, MPTCP also allows seamless failover
when one network path is down between the client and server.

This patch is optional and detects if IPPROTO_MPTCP is available and
uses it when the Linux system supports it.

Signed-off-by: Muhammad Nuzaihan Bin Kamal Luddin <zaihan@unrealasia.net>

Author: muhammadn

connect.c

@@ -827,8 +827,11 @@ static int git_tcp_connect_sock(char *host, int flags)
 	else if (flags & CONNECT_IPV6)
 		hints.ai_family = AF_INET6;
 	hints.ai_socktype = SOCK_STREAM;
-	hints.ai_protocol = IPPROTO_TCP;
-
+#ifdef IPPROTO_MPTCP
+        hints.ai_protocol = IPPROTO_MPTCP;
+#else
+        hints.ai_protocol = IPPROTO_TCP;
+#endif
 	if (flags & CONNECT_VERBOSE)
 		fprintf(stderr, _("Looking up %s ... "), host);