GHSA-p538-c434-8v24: GitPython: Arbitrary file truncation via git rev-list --output argument injection in unguarded Commit.count

Commit.count() forwards **kwargs into rev_list with no check_unsafe_options guard (the guard exists only in the sibling iter_items, commit.py:341). git rev-list --output=<path> opens and truncates the target file to 0 bytes before revision parsing, so count(output='/victim') destroys/blanks an arbitrary file.