tanakh/cmdline — pull request #2 by nanoant (2012-10-22 10:29:17+00:00)
Title: expose default_value stringifier

Allows overriding `cmdline::detail::default_value` to provide own default value string such as **auto** or **none**, for certain type values, so more meaningful help is provided to the user with `--help`.

Actually this is very very little modification that allows for example our program, that calculates automatically options with `0.0` default double values, to show `[=auto]`, using:

```c++
template <>
inline std::string cmdline::detail::default_value(double def) {
if (def == 0.0) return "auto";
return detail::lexical_cast(def);
}
```