Jade is supposed to come with a command line utility that does exactly that.
See here https://github.com/visionmedia/jade#jade1
Or see just above it for a make file that runs it.
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Edit – it seems Jade was renamed to Pug – see https://github.com/pugjs/pug/issues/2184
but the answer remains – Pug comes with a command line tool – install it with npm install pug-cli -g
Then you can run pug my_template.pug which will produce my_template.html