Automatically generate roxygen2 documentation. Simply call rox::off() for development, rox::on() before releasing. This is best done in two separate branches, as demonstrated in this repository. The master branch doesn't contain the man directory, but the production branch does. Development happens in master as usual, the production branch is used only for releases. See the documentation for more details.
Packages with rox::off() are still compatible with devtools::install_github(), because the documentation is created as a side effect of R CMD INSTALL. However, users of your packages need to have roxygen2 installed before installing from GitHub.
By the same token, this works with Travis CI but requires the following entry in .travis.yml to trigger the generation of the documentation (code):
before_script: R CMD INSTALL .