Allow to specify where to put default options in option desciption

[Kubuxu]

Resolves #2702

License: MIT
Signed-off-by: Jakub Sztandera kubuxu@protonmail.ch

[RichardLitt]

Good idea!

[Kubuxu]

Should I change the tag to <<default>> we are using sometimes things like <date> in the descriptions. I hope there won't be <default> anywhere.

[whyrusleeping]

This LGTM, good idea :)

[jbenet]

Should I change the tag to <<default>> we are using sometimes things like <date> in the descriptions. I hope there won't be <default> anywhere.

@Kubuxu valid concern. I'm not sure-- we may have <default> somewhere. if we don't want it there, we should endeavor to make it obvious to devs somehow. right not it would just silently replace and i may not notice.

[Kubuxu]

I think chaining it to<<default>> has lower cost than writing a document and remembering it. I will follow it up.