improve usage message

diff --git a/etckeeper b/etckeeper
index 5606b72cb46b8639d45fa62e75b07c81a781869c..e5be32ffab7369c4d099835ae5f87be78c63ab6c 100755 (executable)
--- a/etckeeper
+++ b/etckeeper
@@ -2,7 +2,7 @@
 set -e
 
 if [ -z "$1" ]; then
-       echo "usage: etckeeper command" >&2
+       echo "usage: etckeeper command [directory]" >&2
        exit 1
 fi
 command="$1"