Desired git reference. Could be a commit, tag, or branch
name. Defaults to "master".
subdir
A subdirectory in the repository that contains the app. By
default, this function will run an app from the top level of the repo, but
you can use a path such as `"inst/shinyapp".
port
The TCP port that the application should listen on. Defaults to
choosing a random port.
launch.browser
If true, the system's default web browser will be
launched automatically after the app is started. Defaults to true in
interactive sessions only.