add date hook to resolve the $DATE$ magic keyword

.gitattributes

@@ -0,0 +1,2 @@
+*.js filter=dateHook.sh
+*.html filter=dateHook.sh

dateHook.sh

@@ -0,0 +1,4 @@
+#!/bin/bash
+
+lastDate=$(git log --pretty=format:"%ad" -1)
+sed -e "s/\$DATE[^\$]\$/$DATE: ${lastDate}$/"