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/Expire.hs

@@ -59,12 +59,12 @@ start :: Expire -> Bool -> Log Activity -> M.Map UUID String -> UUID -> CommandS
 start (Expire expire) noact actlog descs u =
 	case lastact of
 		Just ent | notexpired ent -> checktrust (== DeadTrusted) $ do
-			showStart "unexpire" desc
+			showStart' "unexpire" (Just desc)
 			showNote =<< whenactive
 			unless noact $
 				trustSet u SemiTrusted
 		_ -> checktrust (/= DeadTrusted) $ do
-			showStart "expire" desc
+			showStart' "expire" (Just desc)
 			showNote =<< whenactive
 			unless noact $
 				trustSet u DeadTrusted