MGS8002: ambiguous output ref prefix
magus query output <ref> accepts a unique prefix of a reference id, the same way git
accepts a short commit hash. This code fires when the prefix you gave matches
more than one stored ref, so the lookup is ambiguous.
Resolution
Add more characters until the prefix is unique. The error lists the matching refs; copy one in full. Full reference ids are printed on each target's result line when it runs.