original link
http://stackoverflow.com/questions/5337010/how-to-add-meta-inf-context-xml-in-warbler
I finally figure out a way to copy context.xml to META-INF:
create META-INF/context.xml under your rails app root folder
uncomment and change the following line in config/warble.rb
config.public_html = FileList["public/**/*", "doc/**/*", "META-INF/context.xml" ]
Basically treat META-INF as public_html, and it will be copied to webapps/youapp/META-INF.
