The "test-emailblob-refcheck" command:

Usage: fossil test-emailblob-refcheck [--repair] [--full] [--clean]

Verify that the emailblob.enref field is correct. Report any errors. Use the --repair command to fix up the enref field. The --full option gives a full report showing the enref value on all entries in the emailblob table. If the --clean flags is used together with --repair, then emailblob table entires with enref==0 are removed.