Option to not saving cache for paritial match cache keys on feature branches.

[huxuan]

It would be great if there is an option to only restore cache on pull requests, since the cases that reusing caches from feature branch are really rare. IMO, reuse the cache from the main branch should be enough.

Currently, the paritial match cache keys works fine, so I suppose we only need an option to not saving the cache when primary key and matched key are not equal.

BTW, the corresponding option in GitLab CI/CD is policy: https://docs.gitlab.com/ee/ci/yaml/#cachepolicy.