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/EnableTor.hs

@@ -51,7 +51,7 @@ start os = do
 			Nothing -> giveup "Need user-id parameter."
 			Just userid -> go uuid userid
 		else do
-			showStart "enable-tor" ""
+			showStart' "enable-tor" Nothing
 			gitannex <- liftIO readProgramFile
 			let ps = [Param (cmdname cmd), Param (show curruserid)]
 			sucommand <- liftIO $ mkSuCommand gitannex ps