Fix preservation of rename information on evolve (#33)
Following what rebase itself does, call duplicatecopies between
rebasenode and concludenode.
Should fix
https://bitbucket.org/marmoute/mutable-history/issue/33/evolve-command-loses-copy-metadata
tests: fix test-prune.t breakage
test-prune.t was broken due to 91d28bd0e04e in upstream Mercurial, which made
hidden commits visible when a local tag made the commit reachable. The fix is to
delete the tag in the test.