Help me understand which default shell is used in Bitbucket pipelines.
We defines Docker images with `step.image` and several steps in `script`.
Healthy conclusion is that each `script` line is sent to shell, defiled by Docket image which can vary.
I see that `.` / `source` operator is working for sh like-shells. That mean each `script` command reuses same sh session.
Is it correct that there is no predefined shell executors?
Is it correct that each line of step executed within same shell session?