Affected: gitpython-developers GitPython

GitPython versions before 3.1.59 contain an incomplete denylist in the unsafe_git_revision_options guard that omits --contents and -S options, allowing attackers to read arbitrary files by passing these options to Repo.blame(). Attackers can supply revision values like --contents=/etc/passwd to leak file contents through the blame result returned to the caller.

Affected: PyPI: GitPython

## Summary `Repo.blame()` / `Repo.blame_incremental()` guard forwarded revision options against `unsafe_git_revision_options`, but that denylist only contains the file-WRITE options `--output`/`-o`. `git blame` also honors `--contents <file>` and `-S <file>`, which cause the file's lines to be echoed into the blame result — an arbitrary file READ. Neither option is in the denylist, so a caller-influenced revision value of `--contents=<path>` passes the guard and leaks file contents. This is a distinct sink-option and impact class (READ) from GHSA-956x-8gvw-wg5v (which addressed the blame `--output` WRITE), directly analogous to GHSA-539m-9xh6-q6rr (archive READ gap accepted separately from the archive write/exec advisory).

## Root Cause `unsafe_git_revision_options = ["--output","-o"]` (`git/repo/base.py:188`). The `rev` string is passed to `_option_candidates([rev], kwargs)` and placed BEFORE the `--` separator (base.py:841). The canonical name of `--contents=...` is `contents`, which is not on the denylist, so no `UnsafeOptionError` is raised. The trailing `--` protects only the pathspec, not the option before the revision.

## Impact Arbitrary local file read at the privileges of the host process; the file's line contents appear in the blame result returned to the caller. Pure VALUE control (the caller forwards a user-influenced revision string). Default `allow_unsafe_options=False`.

## Proof of Concept ```python result = repo.blame("--contents=/etc/passwd", "a.txt") #…

Affected: PyPI: gitpython

GitPython versions before 3.1.59 contain an incomplete denylist in the unsafe_git_revision_options guard that omits --contents and -S options, allowing attackers to read arbitrary files by passing these options to Repo.blame(). Attackers can supply revision values like --contents=/etc/passwd to leak file contents through the blame result returned to the caller.