gate few deps only used in bin by cli feature

[klensy]

This adds cli feature (added to default list to prevent possible break) which gates deps used only by mdbook bin. This technically breaks users of bin with default-features = false, are they exist?

[ehuss]

Unfortunately we won't be able to make a change like this because it would break cargo install --no-default-features.

The main change in the 0.5 release is intended to fix this. I really want to get that rolling soon, it's just been hard to make time.

[klensy]

Looking at 0.5 milestone (https://github.com/rust-lang/mdBook/milestone/11) and don't see similar change, is there list with planned breaking changes somewhere else?

[klensy]

Something like #1937, which is not labeled :-(

[ehuss]

I don't think there is a list besides the milestone. The primary thing is to split it into multiple packages, and do some API cleanup to fix backwards-compatibility issues to make it easier to update things.