Reduce unnecessary pull requests with incremental fetching

tests/test_pull_incremental_pagination.py

@@ -0,0 +1,85 @@
+"""Tests for incremental pull request pagination."""
+
+import json
+import os
+from unittest.mock import patch
+
+from github_backup import github_backup
+
+
+class MockHTTPResponse:
+    def __init__(self, data, link_header=None):
+        self._content = json.dumps(data).encode("utf-8")
+        self._link_header = link_header
+        self._read = False
+        self.reason = "OK"
+
+    def getcode(self):
+        return 200
+
+    def read(self):
+        if self._read:
+            return b""
+        self._read = True
+        return self._content
+
+    @property
+    def headers(self):
+        headers = {"x-ratelimit-remaining": "5000"}
+        if self._link_header:
+            headers["Link"] = self._link_header
+        return headers
+
+
+def test_backup_pulls_incremental_stops_before_fetching_old_pages(
+    create_args, tmp_path
+):
+    args = create_args(include_pulls=True, incremental=True)
+    args.since = "2026-04-26T08:13:46Z"
+    repository = {"full_name": "owner/repo"}
+
+    responses = [
+        MockHTTPResponse([]),
+        MockHTTPResponse(
+            [
+                {
+                    "number": 2,
+                    "title": "new pull",
+                    "updated_at": "2026-04-26T09:00:00Z",
+                },
+                {
+                    "number": 1,
+                    "title": "old pull",
+                    "updated_at": "2026-04-26T07:00:00Z",
+                },
+            ],
+            link_header='<https://api.github.com/repos/owner/repo/pulls?per_page=100&state=closed&page=2>; rel="next"',
+        ),
+        MockHTTPResponse(
+            [
+                {
+                    "number": 0,
+                    "title": "older pull on page 2",
+                    "updated_at": "2026-04-25T07:00:00Z",
+                }
+            ]
+        ),
+    ]
+    requests_made = []
+
+    def mock_urlopen(request, *args, **kwargs):
+        requests_made.append(request.get_full_url())
+        return responses[len(requests_made) - 1]
+
+    with patch("github_backup.github_backup.urlopen", side_effect=mock_urlopen):
+        github_backup.backup_pulls(
+            args, tmp_path, repository, "https://api.github.com/repos"
+        )
+
+    assert len(requests_made) == 2
+    assert "state=open" in requests_made[0]
+    assert "state=closed" in requests_made[1]
+    assert all("page=2" not in url for url in requests_made)
+    assert os.path.exists(tmp_path / "pulls" / "2.json")
+    assert not os.path.exists(tmp_path / "pulls" / "1.json")
+    assert not os.path.exists(tmp_path / "pulls" / "0.json")