Flush output in start_async

This prevents double output in case stdout is redirected.
Signed-off-by: NAnders Melchiorsen <mail@cup.kalibalik.dk>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

run-command.c

@@ -304,6 +304,9 @@ int start_async(struct async *async)
 	async->out = pipe_out[0];
 
 #ifndef __MINGW32__
+	/* Flush stdio before fork() to avoid cloning buffers */
+	fflush(NULL);
+
 	async->pid = fork();
 	if (async->pid < 0) {
 		error("fork (async) failed: %s", strerror(errno));

t/t5601-clone.sh

@@ -31,6 +31,12 @@ test_expect_success 'clone with excess parameters (2)' '
 
 '
 
+test_expect_success 'output from clone' '
+	rm -fr dst &&
+	git clone -n "file://$(pwd)/src" dst >output &&
+	test $(grep Initialized output | wc -l) = 1
+'
+
 test_expect_success 'clone does not keep pack' '
 
 	rm -fr dst &&