prevent out-of-repo access when manipulating references. by Byron · Pull Request #2134 · gitpython-developers/GitPython

This previously made it possible to create, modify and delete files outside outside
of the repository, which is a problem if inputs aren't trusted.

Co-authored-by: Sebastian Thiel <sebastian.thiel@icloud.com>

Consolidate follow-up fixes from review and CI:

- fix lint and mypy issues in reference log path handling
- validate remote reference paths before invoking git branch deletion
- add symlink escape coverage where realpath resolves symlinks
- ensure temporary test repositories release git resources during cleanup

Co-authored-by: Sebastian Thiel <sebastian.thiel@icloud.com>