Option to Print only Outdated or Missing Gems

I agree, this would be really nice. Right now, I'm using script/runner under rails to run GemInstaller::autogem, and using that as a conditional in my shell script to determine whether to run geminstaller under sudo. It would be great to have a -n or --no-install or --check or something similar to do this.

I have a patch for this. It's mostly untested but it works really fast since it's only checking against the local gems (no remoteness involved). I've been meaning to get it to Chad and will do so soon.

I'm not sure this exactly fits the request here, but I finally got around to redoing my patch with some test coverage this time. It adds a -o option that acts much like the print-rogue-gems option. It will simply list any local gems you have installed that are newer than the ones specified in the config file.

It will honor the specification and only print gems that do not fit. If you have version >= 1.0.0 for a gem, it will not list a 2.0 gem as outdated in that case, but if the version specification is an exact match it will.