diff --git a/bin/git-alias b/bin/git-alias
index 20f5a9f..fbc9d2e 100755
--- a/bin/git-alias
+++ b/bin/git-alias
@@ -1,7 +1,16 @@
 #!/usr/bin/env bash
 
+usage() {
+cat <<HERE
+usage: git alias                         # list all aliases
+   or: git alias <search-pattern>        # show aliases matching pattern
+   or: git alias <alias-name> <command>  # alias a command
+HERE
+}
+
 case $# in
   0) git config --get-regexp 'alias.*' | sed 's/^alias\.//' | sed 's/[ ]/ = /' | sort ;;
   1) git alias | grep -e "$1" ;;
-  *) git config --global alias."$1" "$2" ;;
+  2) git config --global alias."$1" "$2" ;;
+  *) >&2 echo "error: too many arguments." && usage && exit 1 ;;
 esac