prevent trust commands from trying to do things in a bare repo

Since they need to stage changes, they would actually, if allowed to run,
succeed, but wipe out existing trust.log content.

Command/Untrust.hs

@@ -22,7 +22,7 @@ seek :: [CommandSeek]
 seek = [withString start]
 
 start :: CommandStartString
-start name = do
+start name = notBareRepo $ do
 	showStart "untrust" name
 	Remotes.readConfigs
 	r <- Remotes.byName name