A trailing space signifies that there is nothing else to complete for this argument and the next argument should be started.

Cases where a space is appropriate

• long flags
• values

Cases where a space is not appropriate

• options that allow =
• short flags
• delimiter-separated values

Open questions

• When there is only one option left for a completion and there is "something more", like --opt completing for --option=value, instead of completing to --option should we offer every --option=value possible?
• Can we do that for --option value as well?
• Should we prefer --option=value or --option value? (requires_equals and num_args being more than 1 are times when there isn't a choice)
• When the "something more" is optional (using num_args), should we offer with space and without?

Note: we might be able to defer some of these open questions as "parity with stable, static clap_complete" is the minimum bar