anchor.diff:  # R packages we need for devtools - and we need devtools to be able to update the rmarkdown package
   RUN DEBIAN_FRONTEND=noninteractive wget \
      https://archive.linux.duke.edu/cran/src/contrib/rstudioapi_0.10.tar.gz \
  -   https://archive.linux.duke.edu/cran/src/contrib/openssl_1.0.2.tar.gz \
  +   https://archive.linux.duke.edu/cran/src/contrib/openssl_1.2.2.tar.gz \
      https://archive.linux.duke.edu/cran/src/contrib/withr_2.1.2.tar.gz \
      https://archive.linux.duke.edu/cran/src/contrib/brew_1.0-6.tar.gz \
      https://archive.linux.duke.edu/cran/src/contrib/magrittr_1.5.tar.gz \
      https://archive.linux.duke.edu/cran/src/contrib/Archive/roxygen2/roxygen2_5.0.1.tar.gz \
      https://archive.linux.duke.edu/cran/src/contrib/rversions_1.0.3.tar.gz \
  -   https://archive.linux.duke.edu/cran/src/contrib/git2r_0.23.0.tar.gz \
  -   https://archive.linux.duke.edu/cran/src/contrib/devtools_1.13.6.tar.gz \
  -   https://archive.linux.duke.edu/cran/src/contrib/R6_2.2.2.tar.gz \
  -   https://archive.linux.duke.edu/cran/src/contrib/httr_1.3.1.tar.gz \
  -   https://archive.linux.duke.edu/cran/src/contrib/RCurl_1.95-4.11.tar.gz \
  -   https://archive.linux.duke.edu/cran/src/contrib/BH_1.66.0-1.tar.gz \
  +   https://archive.linux.duke.edu/cran/src/contrib/git2r_0.25.2.tar.gz \
  +   https://archive.linux.duke.edu/cran/src/contrib/devtools_2.0.1.tar.gz \
  +   https://archive.linux.duke.edu/cran/src/contrib/R6_2.4.0.tar.gz \
  +   https://archive.linux.duke.edu/cran/src/contrib/httr_1.4.0.tar.gz \
  +   https://archive.linux.duke.edu/cran/src/contrib/RCurl_1.95-4.12.tar.gz \
  +   https://archive.linux.duke.edu/cran/src/contrib/BH_1.69.0-1.tar.gz \
      https://archive.linux.duke.edu/cran/src/contrib/xml2_1.2.0.tar.gz \
  -   https://archive.linux.duke.edu/cran/src/contrib/curl_3.2.tar.gz \
  -   https://archive.linux.duke.edu/cran/src/contrib/jsonlite_1.5.tar.gz \
  +   https://archive.linux.duke.edu/cran/src/contrib/curl_3.3.tar.gz \
  +   https://archive.linux.duke.edu/cran/src/contrib/jsonlite_1.6.tar.gz \
      https://archive.linux.duke.edu/cran/src/contrib/downloader_0.4.tar.gz \
      https://archive.linux.duke.edu/cran/src/contrib/memoise_1.1.0.tar.gz \
      https://archive.linux.duke.edu/cran/src/contrib/plyr_1.8.4.tar.gz \
  -   https://archive.linux.duke.edu/cran/src/contrib/XML_3.98-1.16.tar.gz \
  +   https://archive.linux.duke.edu/cran/src/contrib/XML_3.98-1.19.tar.gz \
      https://archive.linux.duke.edu/cran/src/contrib/whisker_0.3-2.tar.gz \
      https://archive.linux.duke.edu/cran/src/contrib/bitops_1.0-6.tar.gz
   
   RUN DEBIAN_FRONTEND=noninteractive R CMD INSTALL \
  -   jsonlite_1.5.tar.gz \
  +   jsonlite_1.6.tar.gz \
      memoise_1.1.0.tar.gz \
      whisker_0.3-2.tar.gz \
      bitops_1.0-6.tar.gz \
  -   RCurl_1.95-4.11.tar.gz \
  +   RCurl_1.95-4.12.tar.gz \
      plyr_1.8.4.tar.gz \
  -   R6_2.2.2.tar.gz \
  -   curl_3.2.tar.gz \
  -   openssl_1.0.2.tar.gz \
  -   httr_1.3.1.tar.gz \
  +   R6_2.4.0.tar.gz \
  +   curl_3.3.tar.gz \
  +   openssl_1.2.2.tar.gz \
  +   httr_1.4.0.tar.gz \
      rstudioapi_0.10.tar.gz \
      withr_2.1.2.tar.gz \
  -   git2r_0.23.0.tar.gz \
  -   devtools_1.13.6.tar.gz \
  +   git2r_0.25.2.tar.gz \
  +   devtools_2.0.1.tar.gz \
      brew_1.0-6.tar.gz \
      magrittr_1.5.tar.gz \
      roxygen2_5.0.1.tar.gz \
  -   XML_3.98-1.16.tar.gz \
  -   BH_1.66.0-1.tar.gz \
  +   XML_3.98-1.19.tar.gz \
  +   BH_1.69.0-1.tar.gz \
      xml2_1.2.0.tar.gz \
      rversions_1.0.3.tar.gz \
      downloader_0.4.tar.gz
   
   RUN rm \
  -   jsonlite_1.5.tar.gz \
  +   jsonlite_1.6.tar.gz \
      memoise_1.1.0.tar.gz \
      whisker_0.3-2.tar.gz \
      bitops_1.0-6.tar.gz \
  -   RCurl_1.95-4.11.tar.gz \
  +   RCurl_1.95-4.12.tar.gz \
      plyr_1.8.4.tar.gz \
  -   R6_2.2.2.tar.gz \
  -   httr_1.3.1.tar.gz \
  +   R6_2.4.0.tar.gz \
  +   httr_1.4.0.tar.gz \
      rstudioapi_0.10.tar.gz \
  -   openssl_1.0.2.tar.gz \
  +   openssl_1.2.2.tar.gz \
      withr_2.1.2.tar.gz \
      brew_1.0-6.tar.gz \
      magrittr_1.5.tar.gz \
      roxygen2_5.0.1.tar.gz \
  -   BH_1.66.0-1.tar.gz \
  -   XML_3.98-1.16.tar.gz \
  +   BH_1.69.0-1.tar.gz \
  +   XML_3.98-1.19.tar.gz \
      xml2_1.2.0.tar.gz \
  -   curl_3.2.tar.gz \
  +   curl_3.3.tar.gz \
      rversions_1.0.3.tar.gz \
  -   git2r_0.23.0.tar.gz \
  -   devtools_1.13.6.tar.gz \
  +   git2r_0.25.2.tar.gz \
  +   devtools_2.0.1.tar.gz \
      downloader_0.4.tar.gz
   
   # the CRAN install from source fails because a server at MIT will not respond
  
positive.code: RUN rm \
     openintro_1.7.1.tar.gz \
     assertthat_0.2.0.tar.gz \
     R6_2.2.2.tar.gz \
     magrittr_1.5.tar.gz \
     lazyeval_0.2.1.tar.gz \
     DBI_1.0.0.tar.gz \
  
negative.code: RUN DEBIAN_FRONTEND=noninteractive R CMD INSTALL \
     openintro_1.7.1.tar.gz \
     assertthat_0.2.0.tar.gz \
     magrittr_1.5.tar.gz \
     lazyeval_0.2.1.tar.gz \
     DBI_1.0.0.tar.gz \
  