Add prune fallback for GitHub Git Data API 404s

.github/scripts/prune_renders.py

@@ -89,6 +89,33 @@ def collect_paths_under(dir_path: str) -> list[str]:
     return paths
 
 
+def _is_git_data_404(exc: RuntimeError) -> bool:
+    message = str(exc)
+    return (
+        " → 404:" in message
+        and repo_path("/git/") in message
+        and (message.startswith("POST ") or message.startswith("PATCH "))
+    )
+
+
+def delete_via_contents_api(paths_to_delete: list[str]) -> None:
+    for path in paths_to_delete:
+        current = request_api(
+            "GET", repo_path(f"/contents/{path}?ref={BRANCH}"), expect_404=True
+        )
+        if current is None:
+            continue
+        request_api(
+            "DELETE",
+            repo_path(f"/contents/{path}"),
+            {
+                "message": f"Prune stale render file {path}",
+                "branch": BRANCH,
+                "sha": current["sha"],
+            },
+        )
+
+
 def commit_deletions(paths_to_delete: list[str]) -> None:
     """Build a new tree omitting the given paths and push a single commit.
 
@@ -115,27 +142,32 @@ def commit_deletions(paths_to_delete: list[str]) -> None:
     # base_tree is load-bearing: omit it and the new tree contains ONLY the
     # delete-stubs, which the API resolves to an empty tree → next commit
     # wipes the branch. Test test_commit_deletions_payload_shape locks this.
-    new_tree = request_api(
-        "POST",
-        repo_path("/git/trees"),
-        {"base_tree": base_tree_sha, "tree": tree_entries},
-    )
+    try:
+        new_tree = request_api(
+            "POST",
+            repo_path("/git/trees"),
+            {"base_tree": base_tree_sha, "tree": tree_entries},
+        )
 
-    new_commit = request_api(
-        "POST",
-        repo_path("/git/commits"),
-        {
-            "message": f"Prune {len(paths_to_delete)} stale render file(s)",
-            "tree": new_tree["sha"],
-            "parents": [head_sha],
-        },
-    )
+        new_commit = request_api(
+            "POST",
+            repo_path("/git/commits"),
+            {
+                "message": f"Prune {len(paths_to_delete)} stale render file(s)",
+                "tree": new_tree["sha"],
+                "parents": [head_sha],
+            },
+        )
 
-    request_api(
-        "PATCH",
-        repo_path(f"/git/refs/heads/{BRANCH}"),
-        {"sha": new_commit["sha"], "force": False},
-    )
+        request_api(
+            "PATCH",
+            repo_path(f"/git/refs/heads/{BRANCH}"),
+            {"sha": new_commit["sha"], "force": False},
+        )
+    except RuntimeError as exc:
+        if not _is_git_data_404(exc):
+            raise
+        delete_via_contents_api(paths_to_delete)
 
 
 def main() -> int:

tests/github_scripts/test_prune_renders.py

@@ -150,6 +150,66 @@ def test_commit_deletions_at_safety_limit_proceeds():
     assert m.call_count == 5, "all 5 API calls must occur — no early return at the limit"
 
 
+def test_commit_deletions_falls_back_to_contents_api_on_git_data_404():
+    calls = []
+
+    def fake_api(method, path, body=None, **kwargs):
+        calls.append((method, path, body, kwargs))
+        if (method, path) == ("GET", "/repos/owner/repo/git/refs/heads/renders"):
+            return {"object": {"sha": "head_sha"}}
+        if (method, path) == ("GET", "/repos/owner/repo/git/commits/head_sha"):
+            return {"tree": {"sha": "base_tree_sha"}}
+        if (method, path) == ("POST", "/repos/owner/repo/git/trees"):
+            raise RuntimeError(
+                'POST /repos/owner/repo/git/trees → 404: {"message":"Not Found"}'
+            )
+        if (method, path) == ("GET", "/repos/owner/repo/contents/issue-1/a.png?ref=renders"):
+            return {"sha": "sha-a"}
+        if (method, path) == ("GET", "/repos/owner/repo/contents/issue-1/b.png?ref=renders"):
+            return {"sha": "sha-b"}
+        if (method, path) == ("DELETE", "/repos/owner/repo/contents/issue-1/a.png"):
+            return {}
+        if (method, path) == ("DELETE", "/repos/owner/repo/contents/issue-1/b.png"):
+            return {}
+        raise AssertionError(f"unexpected API call: {(method, path, body, kwargs)}")
+
+    with patch.object(prune_renders, "request_api", side_effect=fake_api):
+        prune_renders.commit_deletions(["issue-1/a.png", "issue-1/b.png"])
+
+    assert calls[3] == (
+        "GET",
+        "/repos/owner/repo/contents/issue-1/a.png?ref=renders",
+        None,
+        {"expect_404": True},
+    )
+    assert calls[4] == (
+        "DELETE",
+        "/repos/owner/repo/contents/issue-1/a.png",
+        {
+            "message": "Prune stale render file issue-1/a.png",
+            "branch": "renders",
+            "sha": "sha-a",
+        },
+        {},
+    )
+    assert calls[5] == (
+        "GET",
+        "/repos/owner/repo/contents/issue-1/b.png?ref=renders",
+        None,
+        {"expect_404": True},
+    )
+    assert calls[6] == (
+        "DELETE",
+        "/repos/owner/repo/contents/issue-1/b.png",
+        {
+            "message": "Prune stale render file issue-1/b.png",
+            "branch": "renders",
+            "sha": "sha-b",
+        },
+        {},
+    )
+
+
 def test_list_issue_dirs_ignores_non_issue_entries():
     contents = [
         {"type": "dir", "name": "issue-1", "path": "issue-1"},