How to auto-yes "drush features-revert-all" ... via terminus On a local machine

drush features-revert-all


will convert all features to codebase definition.
On a local machine ...

drush -y


will auto-yes any command.
On a local machine

terminus -y command


will auto-yes as well.

But when combined, even

terminus -y drush -y yoursite.dev -y features-revert-all -y


... will still ask for a key-press.

How can it be forced to run non-interactively?
You need to add a -- separator to your command. The options for Terminus come before this marker, and the options for Drush come after.

In other words:

terminus -y drush site.dev -- features-revert-all -y


Explanation:

In programs that support it, -- means "all of the options that come after should be treated as arguements". The command terminus drush passes all of its arguments through to Drush.