Close the index file between writing and committing

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/builtin-add.c b/builtin-add.c
index bfbbb1b..2d25698 100644
--- a/builtin-add.c
+++ b/builtin-add.c
@@ -181,7 +181,7 @@
 
 	if (active_cache_changed) {
 		if (write_cache(newfd, active_cache, active_nr) ||
-		    commit_lock_file(&lock_file))
+		    close(newfd) || commit_lock_file(&lock_file))
 			die("Unable to write new index file");
 	}