Sometimes I accidentally do a
bundle install while I’m in the default gemset instead of the one for my project (e.g. because it does not define a own gem set).
The following command will remove all installed gems to clean that up:
for i in `gem list --no-versions`; do gem uninstall -aIx $i; done
Note: For me it’s not a big problem to remove all gems, because I usually have nothing important installed in my default gemset.