Why is there no ->capture_default_str() modifier for app.add_flag(...)?

[jpeter42]

I am wondering why there is no ->capture_default_str() modifier (or similar) for flags. How can I show the default values of flags in the help?

[phlptp]

flags are most commonly binary, so in most cases a default value isn't meaningful. You can of course make a an option that behaves just like a flag using the expected(0,1) modifier. then it can have a default value and capture_default_str works.