Tests now only work on v1.0.3+, lower versions will get an error saying
that there are multiple versions of Documenter available. This doesn't
break usage on older Julia versions, though.
Use Pkg to generate Project.toml and the src entrypoint, and add the
Test package from the stdlib.
Also remove some options to generate that added complexity: force,
temp_dir, and ssh. Trying to create a package at an already-existent path
is now an error no matter what. The ssh keyword to generate has been
moved to Template.
TODO:
- Update the file templates to current standards.
- Clean up the gen_plugin signature and update those docs.
- Pkg.add requirements provided to the template.
- Update interactive_template's requirements gathering to use a loop.
- **Make smaller commits.**
