[R-pkg-team] Bug#912254: Wrong culprit

[Gordon Ball]

I turns out I picked up on the wrong origin for the HTML in this
package. It's not from `pkgdown`; that is just used to generate their
upstream website and isn't shipped in the CRAN tarball. Mea culpa.

The HTML in this case (`inst/doc/*.html`) appears in fact to be
generated by RMarkdown when upstream built this package, from the
corresponding files in `vignettes/*.Rmd`.

Two of these documents (`extending-ggplot2` and `ggplot2-specs`) contain
only a short code highlighting script (inserted by Pandoc) and a
generated link to Mathjax. These links are likely to be common to any
RMarkdown documentation prebuilt by upstream. They could be fixed by
regex, but these HTML files are in any case not source and should be
removed (and ideally rebuilt).

`profiling` contains a huge pile of minified javascript, which appears
to be generated by the `profvis` library. This generates an HTML widget
in the RMarkdown output including all the necessary inlined libraries.
Rebuilding this vignette would be hard, but I think is probably of
pretty marginal interest.

`dh-r` already supports rebuilding vignettes (`dh $@ --buildsystem R --with
vignette`), but this functionality has never been much tested or used, I
think. It means adding a bunch of extra build dependencies (either
pandoc or texlive, depending on the output format, in addition to any
extra packages needed for the vignette). I also doesn't currently have
any mechanism to only build a subset of vignettes if some are known to
break, require exotic dependencies of take too long to run. I'm a bit
concerned that trying to enable this more broadly is a bit of a rabbit
hole which risks making a lot of packages slower and more flaky to
build.