travis_fold() implemented this feature in R.
Additionally, the build time for each section will be written after the
section tag. You can use either travis_start() and travis_end()
separately (put R code in between), or a single travis_fold() call
when the R code is short enough.
travis_fold(job, code, ...)
travis_start(job, msg = paste("Running", job))
travis_end(job)travis_start()