Fixing usage string in ansible-galaxy install for role files

bin/ansible-galaxy

@@ -173,7 +173,7 @@ def build_option_parser(action):
             help='The path in which the skeleton role will be created.'
                  'The default is the current working directory.')
     elif action == "install":
-        parser.set_usage("usage: %prog install [options] [-f FILE | role_name(s)[,version] | tar_file(s)]")
+        parser.set_usage("usage: %prog install [options] [-r FILE | role_name(s)[,version] | tar_file(s)]")
         parser.add_option(
             '-i', '--ignore-errors', dest='ignore_errors', action='store_true', default=False,
             help='Ignore errors and continue with the next specified role.')