multiple -m second try

Test suite passes this time. When committing the adjusted branch, use
the old method to make a message that old git-annex can consume. Also
made the code accept the new message, so that eventually
commitTreeExactMessage can be removed.

Sponsored-by: Kevin Mueller on Patreon

Command/FilterBranch.hs

@@ -189,7 +189,7 @@ seek o = withOtherTmp $ \tmpdir -> do
 	liftIO $ removeWhenExistsWith removeLink tmpindex
 	cmode <- annexCommitMode <$> Annex.getGitConfig
 	cmessage <- Annex.Branch.commitMessage
-	c <- inRepo $ Git.commitTree cmode cmessage [] t
+	c <- inRepo $ Git.commitTree cmode [cmessage] [] t
 	liftIO $ putStrLn (fromRef c)
   where
 	ww = WarnUnmatchLsFiles "filter-branch"