remaining

.remaining can be used for capturing pass-through flags. For example, for a parsable type defined as @Option(parsing: .remaining) var passthrough: [String]:

$ cmd --passthrough --foo 1 --bar 2 -xvf
------------
options.passthrough == ["--foo", "1", "--bar", "2", "-xvf"]

Consider using a trailing @Argument instead and letting users explicitly turn off parsing through the terminator --. That is the more common approach. For example:

struct Options: ParsableArguments {
    @Option var title: String
    @Argument var remainder: [String]
}

would parse the input --title Foo -- Bar --baz such that the remainder would hold the value ["Bar", "--baz"].