Bundler 1.1 introduced a new ‘outdated’ feature, which is exactly what I was looking for. Pat Shaughnessy has a great write-up on the new features. In his words, bundle outdated:
displays the gems it would download and install, but without actually
doing it. This gives me the freedom to inspect the list and update
just the gems I would like to.
This should make it a snap to see what gems are due for an update without actually modifying your source and local gems. Thanks Bundler!