trim long filenames (have to fit on the sidebar)

30 characters would mostly work, but 20 is safer due to some wider letters
like 'w'. Of course this is very heuristic based on filesize anyway.

(Bootstrap does a surprisingly bad job at dealing with overlong words
in the sidebar.)

Assistant/Alert.hs

@@ -247,11 +247,18 @@ sanityCheckFixAlert msg = Alert
 		combinemessage _ _ = Nothing
 
 addFileAlert :: FilePath -> Alert
-addFileAlert file = (activityAlert (Just "Added") $ takeFileName file)
+addFileAlert file = (activityAlert (Just "Added") $ trim $ takeFileName file)
 	{ alertName = Just AddFileAlert
 	, alertCombiner = messageCombiner combinemessage
 	}
 	where
+		trim f
+			| len < maxlen = f
+			| otherwise = take half f ++ ".." ++ drop (len - half) f
+			where
+				len = length f
+				maxlen = 20
+				half = (maxlen - 2) `div` 2 
 		combinemessage (StringAlert new) (StringAlert old) =
 			Just $ StringAlert $
 				unlines $ take 10 $ new : lines old