Adjust reflog filemode in shared repository

Without this, committing in a group-shared repository would not work
even though all developers are in the same group.

Signed-off-by: Matthias Kestenholz <matthias@spinlock.ch>
Signed-off-by: Junio C Hamano <junkio@cox.net>

refs.c

@@ -921,6 +921,8 @@ static int log_ref_write(const char *ref_name, const unsigned char *old_sha1,
 				     log_file, strerror(errno));
 	}
 
+	adjust_shared_perm(log_file);
+
 	msglen = 0;
 	if (msg) {
 		/* clean up the message and make sure it is a single line */