* fix: set default shell for containers to sh
This matches GitHub Actions behaviour where,
runners use bash since it's guaranteed to exist there
while containers use sh for compatibility
* tests: fixup for default shell
* fix: typo
* fix: remove debug for git references
it generates a massive amount of logs
* feat: read values from env
allows to test act on GHA when it's not a main repo
* fix: merge extrapath with PATH
* fix(tests): add additional shells for testing
* fix(image): update images
pin node to major version only, current node version: 12.22.1
replace most images with `node:12-buster-slim` to prevent
errors on macOS runner due to DockerHub pull limit
replace ocaml image
Co-authored-by: Casey Lee <cplee@nektos.com>
