.check_valid_command_path
                        Checks path is valid
.check_valid_util       Checks for valid members of subdirectory
cmd_args_all            Return all named arguments and arguments passed
                        as dots from parent function call
cmd_args_dots           return function dots from parent function as
                        named list
cmd_args_named          Return all named arguments from parent function
                        call
cmd_error_if_missing    Check that file(s) exist, error if not
cmd_file_combn          Generates list of expected output files
cmd_file_expect         Creates list of paths by file extension &
                        checks they exist
cmd_help_flags_similar
                        Suggest alternative name by minimizing
                        Levenshtein edit distance between valid and
                        invalid arguments
cmd_help_flags_suggest
                        Error & Suggest different flag name to user
cmd_help_parse_flags    Parses commandline help options to return
                        vector of valid flag names
cmd_install_check       Wrapper function for checking an install
cmd_install_is_valid    Macro for constructing boolean check for valid
                        path
cmd_list_drop           Drop entries from list of flags by name,
                        name/value pair, or index
cmd_list_drop_named     Drop items by name from list
cmd_list_interp         Convert list of function arguments to list of
                        command flags
cmd_list_keep           keep entries from list of flags by name,
                        name/value pair, or index
cmd_list_keep_named     Keep items by name from list
cmd_list_to_flags       Convert flag list to vector of command flags
cmd_path_search         Macro for constructing target path validators
cmd_ui_file_exists      Checks if file exists, returns pretty status
                        message
