Give a clear recommendation on what sdists should contain

There is currently confusion in the ecosystem around what sdists should contain, and specifically

• whether they should contain tests and documentation
• whether they should contain auxiliary files (e.g., maintenance scripts)

This is an issue for downstream packagers, who normally want at least the tests. If sdists should contain tests, downstream packagers should be able to use sdists from PyPI and sdists which currently do not contain tests should be changed by upstream authors. If sdists should not contain tests, packagers should migrate to using upstream sources like VCS checkouts.

There has been no real consensus so far, AFAICS. The discussions were

https://discuss.python.org/t/should-sdists-include-docs-and-tests/14578

and

https://discuss.python.org/t/sdists-for-pure-python-projects/25191/40

Once a consensus is reached, it should be reflected in the guide.

Start by reading the two linked discussions about whether sdists should include tests, documentation, and auxiliary files. Determine whether a consensus has been reached and what recommendation it supports. Done means reflecting that recommendation in the packaging guide; the issue does not name a specific guide file.