In sbt 0.13.15, in addition to notifying the user about the existence of
sbt's shell, a feature was added to allow the user to switch to sbt's
shell - a more pro-active approach to just displaying a message.
Unfortunately sbt is often unintentionally invoked in shell scripts in
"interactive mode" when no interaction is expected by, for exmaple,
invoking `sbt package` instead of `sbt package < /dev/null`. In that
case hitting [ENTER] would silently trigger sbt to run its shell,
easily wrecking the script. In addition to that I was unhappy with the
implementation as it created a tight coupling between sbt's command
processing abstraction to sbt's shell command.
If you want to stay in sbt's shell after running a task like `package`
then invoke sbt like so:
sbt package shell
Fixes#3091