test(git): httpx-mock coverage for list_open_prs + get_pr_diff

Covers the inbound-PR read surface: list_open_prs normalization + fork/internal
classification (and the recent _fetch_open_prs/_normalize_open_pr refactor),
plus get_pr_diff's diff-media-type request — both with their safe-empty paths
on missing token / GitHub error. The DB-backed paths
(ingest/complete_review/pr_review_claim/supersede umbrella) are covered
separately.

tests/unit/services/test_git_inbound_pr.py

@@ -0,0 +1,160 @@
+"""GitService inbound-PR reads — list_open_prs + get_pr_diff (httpx fully mocked).
+
+``list_open_prs`` is the discovery surface for the inbound-PR reviewer: it lists
+ALL open PRs and normalizes each (number, url, title, head_ref, head_sha,
+is_fork, user_login, author_association). ``get_pr_diff`` fetches a PR's unified
+diff read-only. Both return safe empties ([] / "") on a missing token or any
+GitHub error so the poll/claim never crash.
+"""
+
+from __future__ import annotations
+
+from typing import Any
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+from roboco.services.git import GitService
+
+_PR = 7
+
+
+def _service() -> GitService:
+    session = MagicMock()
+    session.execute = AsyncMock()
+    svc = GitService(session)
+    object.__setattr__(svc, "_token_for_project", AsyncMock(return_value="tok"))
+    return svc
+
+
+def _resp(status_code: int, *, json_payload: Any = None, text: str = "") -> MagicMock:
+    resp = MagicMock()
+    resp.status_code = status_code
+    resp.is_success = 200 <= status_code < 300  # noqa: PLR2004
+    resp.json.return_value = json_payload
+    resp.text = text
+    return resp
+
+
+def _client(get_resp: MagicMock) -> MagicMock:
+    client = MagicMock()
+    client.__aenter__ = AsyncMock(return_value=client)
+    client.__aexit__ = AsyncMock(return_value=False)
+    client.get = AsyncMock(return_value=get_resp)
+    return client
+
+
+def _patch_project() -> Any:
+    fake = MagicMock()
+    fake.get_by_slug = AsyncMock(
+        return_value=MagicMock(git_url="https://github.com/acme/repo.git")
+    )
+    return patch("roboco.services.git.get_project_service", return_value=fake)
+
+
+def _pr(*, number: int, head_full: str, login: str, assoc: str) -> dict[str, Any]:
+    return {
+        "number": number,
+        "html_url": f"https://github.com/acme/repo/pull/{number}",
+        "title": f"PR {number}",
+        "head": {
+            "ref": "feature-x",
+            "sha": "deadbeef",
+            "repo": {"full_name": head_full},
+        },
+        "user": {"login": login},
+        "author_association": assoc,
+    }
+
+
+# ---------------------------------------------------------------------------
+# list_open_prs
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.asyncio
+async def test_list_open_prs_normalizes_and_flags_fork() -> None:
+    svc = _service()
+    payload = [
+        _pr(number=7, head_full="forkowner/repo", login="corey", assoc="CONTRIBUTOR"),
+        _pr(number=8, head_full="acme/repo", login="be-dev-1", assoc="MEMBER"),
+    ]
+    client = _client(_resp(200, json_payload=payload))
+    with (
+        _patch_project(),
+        patch("roboco.services.git.httpx.AsyncClient", return_value=client),
+    ):
+        out = await svc.list_open_prs("roboco")
+    assert len(out) == 2  # noqa: PLR2004
+    fork, internal = out
+    assert fork == {
+        "number": 7,
+        "url": "https://github.com/acme/repo/pull/7",
+        "title": "PR 7",
+        "head_ref": "feature-x",
+        "head_sha": "deadbeef",
+        "is_fork": True,
+        "user_login": "corey",
+        "author_association": "CONTRIBUTOR",
+    }
+    # Same-repo head → not a fork.
+    assert internal["is_fork"] is False
+    assert internal["author_association"] == "MEMBER"
+
+
+@pytest.mark.asyncio
+async def test_list_open_prs_empty_on_missing_token() -> None:
+    svc = _service()
+    object.__setattr__(svc, "_token_for_project", AsyncMock(return_value=None))
+    with _patch_project():
+        assert await svc.list_open_prs("roboco") == []
+
+
+@pytest.mark.asyncio
+async def test_list_open_prs_empty_on_github_error() -> None:
+    svc = _service()
+    client = _client(_resp(403, text="forbidden"))
+    with (
+        _patch_project(),
+        patch("roboco.services.git.httpx.AsyncClient", return_value=client),
+    ):
+        assert await svc.list_open_prs("roboco") == []
+
+
+# ---------------------------------------------------------------------------
+# get_pr_diff
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.asyncio
+async def test_get_pr_diff_returns_diff_text() -> None:
+    svc = _service()
+    diff = "diff --git a/x b/x\n+added line\n"
+    client = _client(_resp(200, text=diff))
+    with (
+        _patch_project(),
+        patch("roboco.services.git.httpx.AsyncClient", return_value=client),
+    ):
+        out = await svc.get_pr_diff("roboco", _PR)
+    assert out == diff
+    call = client.get.await_args
+    assert f"/pulls/{_PR}" in call.args[0]
+    assert call.kwargs["headers"]["Accept"] == "application/vnd.github.v3.diff"
+
+
+@pytest.mark.asyncio
+async def test_get_pr_diff_empty_on_missing_token() -> None:
+    svc = _service()
+    object.__setattr__(svc, "_token_for_project", AsyncMock(return_value=None))
+    with _patch_project():
+        assert await svc.get_pr_diff("roboco", _PR) == ""
+
+
+@pytest.mark.asyncio
+async def test_get_pr_diff_empty_on_non_2xx() -> None:
+    svc = _service()
+    client = _client(_resp(404, text="not found"))
+    with (
+        _patch_project(),
+        patch("roboco.services.git.httpx.AsyncClient", return_value=client),
+    ):
+        assert await svc.get_pr_diff("roboco", _PR) == ""