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/Direct.hs

@@ -31,7 +31,7 @@ start = ifM versionSupportsDirectMode
 
 perform :: CommandPerform
 perform = do
-	showStart "commit" ""
+	showStart' "commit" Nothing
 	showOutput
 	_ <- inRepo $ Git.Branch.commitCommand Git.Branch.ManualCommit
 		[ Param "-a"
@@ -65,6 +65,6 @@ perform = do
 
 cleanup :: CommandCleanup
 cleanup = do
-	showStart "direct" ""
+	showStart' "direct" Nothing
 	setDirect True
 	return True