decided not to include export/import trees

They're only needed to cover a gc edge case, and it's better someone
gets caught by that edge case than that someone who does not know about
them ends up with a filtered git-annex branch that contains such a tree
when some of the files listed in it are ones they wanted to *remove*
from the repository.

Command/FilterBranch.hs

@@ -189,7 +189,6 @@ seek o = withOtherTmp $ \tmpdir -> do
 	cmode <- annexCommitMode <$> Annex.getGitConfig
 	cmessage <- Annex.Branch.commitMessage
 	c <- inRepo $ Git.commitTree cmode cmessage [] t
-	-- TODO export.log trees
 	liftIO $ putStrLn (fromRef c)
   where
 	ww = WarnUnmatchLsFiles