rmarkdown::render() for .Rmd at a URL

Is there any way to knit a hosted file (for instance, a .Rmd hosted at GitHub - or standing alone at a dedicated URL) that isn't on the local machine? I've got a job scheduler that I can use to run .R scripts, but doesn't handle .Rmd, and doesn't have any sense of other files past the script it's currently executing.
Is there any way to pass render() a hosted file?