feature request: integrate with github caching action

[ontoneio]

https://github.com/actions/cache

Be nice to speed up the builds using the github cache feature even though its pretty new. Give us bleeding edge! 🚩

Specifically maybe:

• Use the same API
• Allow runtime dependencies or devcontainer features to be automagically cached (seems like the rebuild every time even on prebuild)
• Support application level dependencies caching automagically via the setup-* packages API

Thanks!

[cjam]

Wow this would be amazing. Anyone have any ideas on how the features could be cached? I'm trying to prebuild my devcontainer image which has a number of features but it doesn't seem to use the cache for the features, just always does a rebuild.

There's also this issue #225 to circumvent the long build process and just run the container. I think if we could cache the features layers we'd likely see the build step be much faster.

But I'm not sure what would be necessary to cache the features. It seems like the features are currently being put into a named volume anyways. Perhaps if there was a way to override that volume and put it on disk then the github cache could be used to store it.