daemon: support <directory> arguments again

Ever since v1.7.4-rc0~125^2~8 (daemon: use run-command api for async
serving, 2010-11-04), git daemon spawns child processes instead of
forking to serve requests.  The child processes learn that they are
being run for this purpose from the presence of the --serve command
line flag.

When running with <ok_path> arguments, the --serve flag is treated
as one of the path arguments and the special child behavior does
not kick in.  So the child becomes an ordinary git daemon process,
notices that all the addresses it needs are in use, and exits with
the message "fatal: unable to allocate any listen sockets on port
9418".

Fix it by putting --serve at the beginning of the command line,
where the flag cannot be mistaken for a path argument.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Acked-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

daemon.c

@@ -1226,9 +1226,10 @@ int main(int argc, char **argv)
 
 	/* prepare argv for serving-processes */
 	cld_argv = xmalloc(sizeof (char *) * (argc + 2));
-	for (i = 0; i < argc; ++i)
-		cld_argv[i] = argv[i];
-	cld_argv[argc] = "--serve";
+	cld_argv[0] = argv[0];	/* git-daemon */
+	cld_argv[1] = "--serve";
+	for (i = 1; i < argc; ++i)
+		cld_argv[i+1] = argv[i];
 	cld_argv[argc+1] = NULL;
 
 	return serve(&listen_addr, listen_port, cred);