GHSA-w8jc-g24h-crhw: GitPython command wrappers omit unsafe protocol and option checks

GitPython has spent 2022-2026 rolling out two reusable guards method-by-method: Git.check_unsafe_protocols(url) (raises UnsafeProtocolError for <transport>:: remote-helper URLs - CVE-2022-24439) and Git.check_unsafe_options(...) (raises UnsafeOptionError for denylisted option spellings - CVE-2023-40267, CVE-2026-42215, CVE-2026-67323). Three wrapper methods that build a git argv from caller-controlled values still have neither:

1. Git.ls_remote (git/cmd.py:1128-1143) - checks options (:1139-1141) but forwards the URL positional unchecked; no allow_unsafe_protocols parameter exists. The same URL through clone_from raises UnsafeProtocolError.
2. Repo.merge_base (git/repo/base.py:895-936) - forwards **kwargs/*rev to self.git.merge_base with no guard; guarded sibling iter_commits sits 12 lines up. Its exception handler additionally swallows every non-128 GitCommandError into [], masking the injection.
3. IndexFile.move (git/index/base.py:1092-1168) - forwards **kwargs to git mv twice (:1147, :1167); guarded sibling remove() is 23 lines above.

Verified unfixed on main @ a54d159 (2026-09-21), post-dating latest release 3.1.62 (2026-09-07) - all three sites re-verified today.