If you’re keeping your Rails application in a source code repository, Tobias Luetke has a script for retrieving the code, running its tests in a deployment directory and copying it to the target directory. All guided by a simple YAML configuration file at ~/.deployrc.
You can likewise checkout from RubyForge CVS with a hack like:
get: cvs -d:pserver:anonymous@rubyforge.org:/var/cvs/bugtrack
export -D now bugtrack; mv bugtrack
I wonder: can RubyGems be easily scripted to pull from CVS or Subversion? Better, I wonder if ViewCVS could be easily hacked to generate snapshot gems? Easily?