FogBugz has two version fields per issue, the "fix for" version and the "seen in" version. When importing from FogBugz, JIRA adds all of the values from both fields to its list of versions. Because we include build numbers in the "seen in" version (e.g., 5.0.9864), the JIRA database has nearly 1,000 versions in its list. Only about 20 of these are real, assignable versions (e.g., "5.0").
How can I get rid of all the unassignable versions without having to delete them one by one, which will take forever?