repl -b option is missing tests

There are quite a few nuances to the `repl -b` option, adding some tests for the feature would be a good first contribution.

1: Does it work in a project context?
2. What happens in a script context?
3. Does it work with multi-repl (I imagine the answer is no)
4. Does -b bring the whole transitive closure of the dependency into scope, or just the specified package?
5. Does the `--no-transitive-deps` option work?

Start by locating the existing repl -b implementation and its test suite. Run the five scenarios described in the issue: project and script contexts, multi-repl, transitive dependencies, and --no-transitive-deps. Done means tests document the observed behavior for each case.

Written by the indexing model from the issue text.