Inspired by a question of Stephane Bortzmeyer <bortzmeyer@nic.fr> on 
@darcs-users, I ventured the idea that Darcs could recognize, during log 
-v, when there are adjacent patches that are inverses. Given some 
suitable option, Darcs could show such a pair "squashed", i.e. replace 
both changes with a short message to indicate that we dropped a change 
and its inverse. The example in question was deletion of a file in the 
past and subsequent resurrection via the rollback command.