Fix: Skip system temp directories in rootdir detection (issue #13822)

[AddyM]

Summary

Fixes #13822

When /tmp/setup.py exists on the system, pytest incorrectly identifies /tmp as the project root, causing test node IDs to include full paths under /tmp instead of relative paths.

Changes

• Added _is_system_temp_or_parent() helper function to detect system temp directories
• Modified determine_setup() to skip system temp directories when searching for setup.py
• Uses tempfile.gettempdir() for cross-platform compatibility

Testing

• Verified helper function correctly identifies system temp directory
• Tested that regular directories are not flagged as temp
• Manual testing confirms /tmp/setup.py no longer affects rootdir detection

Backward Compatibility

• No breaking changes
• Users can still use --rootdir to override if needed
• Only affects systems with setup.py in system temp directories

[nicoddemus]

Thanks @AddyM,

Could you please add a test to ensure this does not regress? You can monkeypatch tempfile.gettempdir() to avoid adding files to the system's temporary directory.

[AddyM]

Thanks @AddyM,

Could you please add a test to ensure this does not regress? You can monkeypatch tempfile.gettempdir() to avoid adding files to the system's temporary directory.

Hello @nicoddemus , thanks a lot for the input , added a regression test .Please help in reviewing . Thanks

[The-Compiler]

@AddyM Could you please take a look at the failing checks? I think the codecov one is fine (I'm actually confused about it being marked as required?) as you can't easily test the corner case, but you should fix the lint issue and add a changelog entry.

Also there seems to be a trivial conflict, would be great if you could resolve it (keeping both imports).