showStart variant for when there's no worktree file

Clean up some uses of showStart with "" for the file,
or in some cases, a non-filename description string. That would
generate bad json, although none of the commands doing that
supported --json.

Using "" for the file resulted in output like "foo  rest";
now the extra space is eliminated.

This commit was sponsored by Fernando Jimenez on Patreon.

Command/View.hs

@@ -27,7 +27,7 @@ seek = withWords start
 start :: [String] -> CommandStart
 start [] = giveup "Specify metadata to include in view"
 start ps = do
-	showStart "view" ""
+	showStart' "view" Nothing
 	view <- mkView ps
 	go view  =<< currentView
   where