marking a bug as duplicate of a bug does not work, if other bugs have been marked as duplicate of this bug

[j^]

you have a bug with several bugs marked as duplicate of this bug.
now it turns out this bug infact is a duplicate of another bug.
trying to to mark this bug as duplicate and change all dups to dups of the new bug is not possible.

bug a, with bug b and c makred as dub of a
now it turns out bug a is a dub of A.
trying to mark bug a as dub of A, bug b and c should be makred as dub of A too.

right now one gets a waring and has to manulay(!) move bugs b and c to A before one can move bug a.

[James Henstridge (jamesh)]

This behaviour is by design. Perhaps the design should be changed though.