The negative numbers provide a way to refer to the cloned bugs (which
will be assigned proper numbers).
+NB you cannot clone a merged bug. You'd think that trying to do so
+would just give you an unmerged copy of the specified bug number, but no:
+
+http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=474742
+
+You must unmerge, clone, then re-merge.
+
*** To set severity:
severity 123 critical|grave|serious|important|normal|minor|wishlist