curl_stream: use CURLINFO_ACTIVESOCKET if curl is recent enough

The `CURLINFO_LASTSOCKET` information has been deprecated since
curl version 7.45.0 as it may result in an overflow in the
returned socket on certain systems, most importantly on 64 bit
Windows. Instead, a new call `CURLINFO_ACTIVESOCKET` has been
added which instead returns a `curl_socket_t`, which is always
sufficiently long to store a socket.

As we need to provide backwards compatibility with curl versions
smaller than 7.45.0, alias CURLINFO_ACTIVESOCKET to
CURLINFO_LASTSOCKET on platforms without CURLINFO_ACTIVESOCKET.

src/curl_stream.c

@@ -15,6 +15,16 @@
 #include "vector.h"
 #include "proxy.h"
 
+/* This is for backwards compatibility with curl<7.45.0. */
+#ifndef CURLINFO_ACTIVESOCKET
+# define CURLINFO_ACTIVESOCKET CURLINFO_LASTSOCKET
+# define GIT_CURL_BADSOCKET -1
+# define git_activesocket_t long
+#else
+# define GIT_CURL_BADSOCKET CURL_SOCKET_BAD
+# define git_activesocket_t curl_socket_t
+#endif
+
 typedef struct {
 	git_stream parent;
 	CURL *handle;
@@ -87,7 +97,8 @@ static int ask_and_apply_proxy_creds(curl_stream *s)
 static int curls_connect(git_stream *stream)
 {
 	curl_stream *s = (curl_stream *) stream;
-	long sockextr, connect_last = 0;
+	git_activesocket_t sockextr;
+	long connect_last = 0;
 	int failed_cert = 0, error;
 	bool retry_connect;
 	CURLcode res;
@@ -117,11 +128,11 @@ static int curls_connect(git_stream *stream)
 	if (res == CURLE_PEER_FAILED_VERIFICATION)
 		failed_cert = 1;
 
-	if ((res = curl_easy_getinfo(s->handle, CURLINFO_LASTSOCKET, &sockextr)) != CURLE_OK) {
+	if ((res = curl_easy_getinfo(s->handle, CURLINFO_ACTIVESOCKET, &sockextr)) != CURLE_OK) {
 		return seterr_curl(s);
 	}
 
-	if (sockextr == -1) {
+	if (sockextr == GIT_CURL_BADSOCKET) {
 		giterr_set(GITERR_NET, "curl socket is no longer valid");
 		return -1;
 	}