You're right, that argument was added a while ago (not by me); I also don't think it's used, and I wouldn't be surprised if it was accidentally broken.

This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

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I tried the --revision option here in a test import and everything worked fine, so I guess we can close this one.