anchor.diff:  
   RUN rm \
      jsonlite_1.5.tar.gz \
  -   digest_0.6.12.tar.gz \
  +   digest_0.6.13.tar.gz \
      memoise_1.1.0.tar.gz \
      whisker_0.3-2.tar.gz \
      bitops_1.0-6.tar.gz \
  
positive.code: RUN DEBIAN_FRONTEND=noninteractive R CMD INSTALL \
     bitops_1.0-6.tar.gz \
     caTools_1.17.1.tar.gz \
     digest_0.6.12.tar.gz \
     Rcpp_0.12.14.tar.gz \
     htmltools_0.3.6.tar.gz \
     yaml_2.1.16.tar.gz \
  
negative.code:    https://mirrors.nics.utk.edu/cran/src/contrib/htmltools_0.3.6.tar.gz \
     https://mirrors.nics.utk.edu/cran/src/contrib/caTools_1.17.1.tar.gz \
     https://mirrors.nics.utk.edu/cran/src/contrib/bitops_1.0-6.tar.gz \
     https://mirrors.nics.utk.edu/cran/src/contrib/digest_0.6.13.tar.gz \
     https://mirrors.nics.utk.edu/cran/src/contrib/stringr_1.2.0.tar.gz \
     https://mirrors.nics.utk.edu/cran/src/contrib/markdown_0.8.tar.gz \
     https://mirrors.nics.utk.edu/cran/src/contrib/highr_0.6.tar.gz \
  