GHSA-hh9p-6wh2-4mfc

## Summary `IndexFile.remove()` and `Head.checkout()` forward `**kwargs` into `git rm` and `git checkout` with no guard. Passing `--pathspec-from-file=<file>` **together with `--pathspec-file-nul`** makes Git treat the whole file as a single NUL-delimited pathspec, and the unmatched-pathspec error quotes it verbatim. GitPython surfaces that through `GitCommandError.stderr`, so the entire contents of a caller-chosen file are returned to the caller in band. This is the same primitive as Instance 2 of [GHSA-3f7w-8rr8-f37f](https://github.com/advisories/GHSA-3f7w-8rr8-f37f) - `TagReference.create()` with `-F`, arbitrary file read returned in band - at two sites that advisory assessed and cleared. ## Prior art, and why I am filing rather than commenting GHSA-3f7w-8rr8-f37f's sweep table lists these four sites with the assessment *"`--pathspec-from-file` only reads a pathspec; no write or disclosure primitive found"*: | Call site | git command | that advisory's assessment | |---|---|---| | `IndexFile.remove()` | `rm` | `--pathspec-from-file` only reads a pathspec; no write or disclosure primitive found | | `IndexFile.move()` | `mv` | same | | `HEAD.reset()` | `reset` | same | | `HEAD.checkout()` | `checkout` | same | That assessment is very nearly right, and I think that is why it held: with `--pathspec-from-file` alone, Git splits on newlines and the error quotes only the **first line**, which reads as an uninteresting partial. Adding `--pathspec-file-nul` - a sibling flag of the same option, and the documented way to handle paths containing newlines - makes the whole file one pathspec. ## Root cause `git/index/base.py:991-1043`: ```python def remove(self, items, working_tree=False, **kwargs): ... removed_paths = self.repo.git.rm(args, paths, **kwargs).splitlines() # line 1043 ``` `git/refs/head.py:237-268`: ```python def checkout(self, force: bool = False, **kwargs: Any): ... self.repo.git.checkout(self, **kwargs)