devtools::document() requires a DESCRIPTION file, which in general we don't
include in analysis projects. Sometimes we want to produce development
documentation for functions in analysis projects so we can describe options
and behaviour. pkgtools::document will also work in a non package project
to produce .Rd files in the man directory for any functions declared in
the R subfolder. It also override the default behaviour of ? to return
the development documentation of matching functions in the current project.