Resynchronizing my gem list with actual gems installed


OS X 10.5.3
Ruby 1.8.6

When I do “gem list” I see a bunch of gem version references that I have
definitely already cleaned off.

How does one force the local gem index to rescan the
RUBY_HOME/Gems/1.8/gems directory to figure out what is actually there?

I keep trying to clean off old versions of gems that have already been
removed and get silly errors about them not being there.