bundler-cache with several Gemfiles

[alexeyr-ci2]

Our repo https://github.com/shakacode/react_on_rails includes both root Gemfile.lock and spec/dummy/Gemfile.lock for a demo/test app. So commands like bundle install need to be run in both directories.

Currently we use actions/cache, but while fixing a problem with it I've noticed your documentation saying

It is also possible to cache gems manually, but this is not recommended because it is verbose and very difficult to do correctly. There are many concerns which means using actions/cache is never enough for caching gems (e.g., incomplete cache key, cleaning old gems when restoring from another key, correctly hashing the lockfile if not checked in, OS versions, ABI compatibility for ruby-head, etc). So, please use bundler-cache: true instead and report any issue.

I'd be happy to switch but the scenario with running and caching bundle install in multiple directories doesn't seem to be covered. Am I missing something?

Or is my best option to only use bundler-cache: true for the root and still manually cache the spec/dummy gems?

[eregon]

See #170 (comment)