fix: reconstruct diff from per-file patches when GitHub 406s on large PRs

[jainakshay93]

Problem

_fetch_pr_once fetches the PR diff via Accept: application/vnd.github.v3.diff. GitHub returns 406 Not Acceptable when the diff is too large to generate — reproduced on a 722-file PR. diff_resp.raise_for_status() then aborts the whole review, so large PRs can't be reviewed at all.

Fix

The per-file patches are already fetched from the /pulls/{n}/files API a few lines above. On a 406, reconstruct an equivalent unified diff from those patches instead of failing:

except httpx.HTTPStatusError as exc:
    if exc.response.status_code != 406:
        raise
    full_diff = "\n".join(
        f"diff --git a/{f.path} b/{f.path}\n--- a/{f.path}\n+++ b/{f.path}\n{f.patch}"
        for f in changed_files if f.patch
    )

Small/normal PRs are unchanged — the real .diff media type is still used whenever it succeeds.

Testing

A 722-file PR that previously 406'd now fetches (≈3.5 MB reconstructed diff) and reviews to completion.

Note

GitHub's /files API caps at 3000 files and omits patch for individually huge files, so extreme PRs may have partial diffs — but a partial diff is strictly better than a hard failure.

🤖 Generated with Claude Code