facilitate deletion of coafile.green on running pytest

[ishanSrt]

*Identification of tests is required which create coafile.green files
after which they must be deleted in those tests

• Even though add .coafile.green to .gitignore #309 adds them to the .gitignore, coafile.green should be created when actually running the --green-mode on the repository, not by pytest

[jayvdb]

The test suite should be using a separate working directory

[ishanSrt]

I needed some actual code to test upon and dummy test directories and files (either mocked or sometimes created) was a tedious task. We need some actual (not completely random) code for the green mode to run tests upon.

[jayvdb]

Clone a repository into a test working directory

or copy stuff into a test working directory.