Fix false positive detection heuristics

[alexzurbonsen]

Context

The newly introduced conditions on rule relevance and copyrights for false positive detections, see f9863e61, contain a bug that makes them detect copyrights and rule relevance if matches do not even have a matched_text or the rule doesn't even have a relevance attribute.

Fixes #4005 (at least for the example I am looking at)

Summary

Correct the any and all conditions to correctly detect copyrights and relevance.

Test plan

I reran the scan of the file from #4005

scancode -l <your path to boost repo>/boost/boost/assign/ptr_list_of.hpp --json scancode.json

and get a scancode.json that has the same contents as on v32.2.1.

scancode_fix.json

Tasks

• Reviewed contribution guidelines
• PR is descriptively titled 📑 and links the original issue above 🔗
• Tests pass -- look for a green checkbox ✔️ a few minutes after opening your PR
  Run tests locally to check for errors.
• Commits are in uniquely-named feature branch and has no merge conflicts 📁
• Updated documentation pages (if applicable)
• Updated CHANGELOG.rst (if applicable)

[alexzurbonsen]

@AyanSinhaMahapatra This should fix the issue with the false positive license detection heuristics. #4005

It feels like there should be a test for this. If so, can you help me write one? It seemed a bit more involved and I wanted to get this out quickly.

[alexzurbonsen]

There is a failing test tests/licensedcode/test_plugin_license_detection.py::test_complicated_license_text_from_ffmpeg It seems that it is relying on the buggy logic. I would be glad for some help on this one @AyanSinhaMahapatra, since I am not sure yet, what the appropriate change is.

[alexzurbonsen]

Update: I scanned plugin_license/scan/ffmpeg-LICENSE.md with the scancode version from this branch and pasted the result into the expected file. The changes seem reasonable to me.

[alexzurbonsen]

@AyanSinhaMahapatra and @pombredanne Would be great to get your feedback on this one. The bug currently blocking us from updating. It would seem that it basically renders the is_false_positive function useless, since it always returns false, and thus torpedoes false positive detection.