anchor.diff:     mime_0.6.tar.gz \
      glue_1.3.1.tar.gz \
      stringr_1.4.0.tar.gz \
  -   highr_0.7.tar.gz \
  +   highr_0.8.tar.gz \
      formatR_1.6.tar.gz \
      evaluate_0.13.tar.gz \
      markdown_0.9.tar.gz \
  
positive.code:    https://archive.linux.duke.edu/cran/src/contrib/glue_1.3.1.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/stringr_1.4.0.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/markdown_0.9.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/highr_0.7.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/formatR_1.6.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/evaluate_0.13.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/mime_0.6.tar.gz \
  
negative.code: RUN rm \
     evaluate_0.13.tar.gz \
     formatR_1.6.tar.gz \
     highr_0.8.tar.gz \
     markdown_0.9.tar.gz \
     stringi_1.4.3.tar.gz \
     magrittr_1.5.tar.gz \
  