Restrict license checks to staged/committed files only

[marklysze]

Why are these changes needed?

In my previous implementation of the license check, #90, when running the check locally with pre-commit run it would check all python files, irrespective of whether they were staged or not.

This update fixes that.

Also, when this runs as a GitHub action it will check against the base branch.

Related issue number

N/A

Checks

• I've included any doc changes needed for https://ag2ai.github.io/ag2/. See https://ag2ai.github.io/ag2/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[qingyun-wu]

LGTM. Thanks1

[qingyun-wu]

There is code formating problem.

[marklysze]

There is code formatting problem.

Yep, thanks - let me make sure it goes through as the code covers both local use and GitHub action use - so need to make sure it's working in GitHub too :)

[marklysze]

Okay, passed!