Documented all shell/indexer.php arguments with dashes (#2930)

Author: loekvangool

shell/indexer.php

@@ -199,10 +199,10 @@ public function usageHelp()
   --mode-realtime <indexer>     Set index mode type "Update on Save"
   --mode-manual <indexer>       Set index mode type "Manual Update"
   --reindex <indexer>           Reindex Data
-  info                          Show allowed indexers
-  reindexall                    Reindex Data by all indexers
-  reindexallrequired            Reindex Data only if required by all indexers
-  help                          This help
+  --info                        Show allowed indexers
+  --reindexall                  Reindex Data by all indexers
+  --reindexallrequired          Reindex Data only if required by all indexers
+  --help                        This help
 
   <indexer>     Comma separated indexer codes or value "all" for all indexers