PYSEC-2026-2465 Dulwich's submodule path traversal in porcelain.submodule_update / porcelain.clone(recurse_submodules=True) yields RCE via attacker-dropped .git/hooks payload

Summary dulwich.porcelain.submoduleupdate, and by extension porcelain.clone..., recursesubmodules=True, materializes attacker-controlled submodule paths from a crafted upstream repository without path validation. A malicious .gitmodules plus a matching tree gitlink whose path is .git/hooks or any...