Server side includes on app engine (<!-- include virtual="header.html" -->)?

I have been trying to figure this out a while. I would like to make my app engine website use basic html and shtml whenever in order to avoid the slow warm-up phase of jsp apps on app engine. This is so that my landing pages load instantly.

Basically, I am trying to include an html file into my main html file (index.html - I tried index.shtml). This is the command I try:

<!-- include virtual="header.html" -->

However it does not work. The server side includes to not s开发者_Go百科eem to get executed in app engine. Do I need to enable these commands somewhere first - or does app engine simply not allow them?

SSI is a web-server-specific feature that GAE appears not to support.

(This per Nick Johnson, who's quite active on this site.)