Rename {setup_py_dir -> unpacked_source_directory}

[pradyunsg]

Why: Because PEP 517 means you won't necessarily have a setup.py in your unpacked sources.

[chrahunt]

Is there a name that would be closer to "the directory which has the setup.py or pyproject.toml file for a project"? As it is it may be confused with "the root of the thing that was unpacked or downloaded", which wouldn't be the case for VCS requirements with subdirectories.

[pradyunsg]

Is there a name that would be closer to "the directory which has the setup.py or pyproject.toml file for a project"?

Naming things is difficult. :(

I couldn't come up with anything better tbh. I do think this, as is, is an improvement over status quo so there's that. If someone has a suggestion that we have consensus on, this name is now unique within the codebase, so changing it is a simple find-replace for me.

[pradyunsg]

Hurrah! Thanks for taking a look @chrahunt! ^>^