Prevent non-source files from being added into source-only directories

[arhadthedev]

Feature or enhancement

Proposal:

gh-118159 accidentally added Include/incl.tar with a full copy of Include. Since this addition fell through the cracks, we need to help both contributors and triagers by .gitignore-ing non-source files in the most edited directories:

• anything different from *.h in Include
• anything different from *.py in Lib (except Lib/test where code is bundled with test data)

Modules and Objects require more complex rules so I skipped them. However, it'll be great if anyone defines and adds them.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-118189: Revert accidentally added incl.tar #118190

[JelleZijlstra]

I don't think it's worth adding automated rules here. Adding such rules has a cost in that it can cause confusion when a future change relies on adding files that don't match the pattern we expect. And the benefit is low because it's rare that we accidentally add files and if we do, we can easily fix the mistake later.