Make function to refill http queue a callback

This eliminates the last function provided by the code using http.h as
a global symbol, so it should be possible to have multiple programs
using http.h in the same executable, and it also adds an argument to
that callback, so that info can be passed into the callback without
being global.

Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

http-push.c

@@ -795,7 +795,7 @@ static void finish_request(struct transfer_request *request)
 }
 
 #ifdef USE_CURL_MULTI
-int fill_active_slot(void)
+static int fill_active_slot(void *unused)
 {
 	struct transfer_request *request = request_queue_head;
 
@@ -2496,6 +2496,7 @@ int main(int argc, char **argv)
 				objects_to_send);
 #ifdef USE_CURL_MULTI
 		fill_active_slots();
+		add_fill_function(NULL, fill_active_slot);
 #endif
 		finish_all_active_slots();