add .pre-commit

.pre-commit

@@ -0,0 +1,13 @@
+#!/bin/bash
+set -e
+
+function checkFile() {
+	[[ "$1" =~ \.zone$ ]] || return 0
+	old="$(git show HEAD:"$1"|grep -Po '\d+(?=\s+; serial)')"
+	new="$(git show     :"$1"|grep -Po '\d+(?=\s+; serial)')"
+	[[ "$old" -lt "$new" ]] && return 0 || { echo "serial bump check failed for $1"; return 1; }
+}
+
+ret=0
+while read file; do checkFile "$file" || ret=1; done <<< "$(git diff --name-only --cached)"
+exit $ret