Build .md vignette using devtools

Question

I’m using knitr::rmarkdown (but knitr::knitr does the same) as my VignetteEngine. I then build my package vignette using devtool

Answer 1

The only output formats for vignettes are HTML and PDF (and LaTeX, but it is converted to PDF, not displayed). Markdown isn't supported.

You can have arbitrary documentation files in your package (by convention you put them in inst/doc), but they aren't considered to be vignettes, so they won't be automatically built, functions like browseVignettes() will ignore them, etc.

To convert an Rmd file to md, just run knitr::knit on it.