Keep only rsync's summary lines when not verbose

Every output line was kept in memory although only the last two were logged, and fewer than two lines (e.g. with --rsync-options q) raised an IndexError.

tests/test_local.py

@@ -298,12 +298,13 @@ class FakePopen:
 
     returncode = 0
     calls: list[list[str]] = []
+    output = b'sending incremental file list\nsent 1 bytes  received 2 bytes\ntotal size is 3\n'
 
     def __init__(self, args: list[str], **kwargs: Any) -> None:
         FakePopen.calls.append(args)
         os.makedirs(args[args.index('/') + 1])
         self.stdin = io.BytesIO()
-        self.stdout = io.BytesIO(b'sending incremental file list\nsent 1 bytes  received 2 bytes\ntotal size is 3\n')
+        self.stdout = io.BytesIO(FakePopen.output)
 
     def __enter__(self) -> 'FakePopen':
         return self
@@ -343,6 +344,18 @@ class TestReturnCodes:
         assert f'--link-dest={out}/simple_backup/{old_backups[-1]}' in args
         assert args[args.index('/') + 1] == f'{out}/simple_backup/2026-10-14_10-00-00'
 
+    @pytest.mark.parametrize('lines, logged', [
+        ([f'file{n}' for n in range(5)] + ['sent 1 bytes', 'total size is 3'], ['sent 1 bytes', 'total size is 3']),
+        ([], []),
+        (['total size is 3'], ['total size is 3']),
+    ])
+    def test_summary_logged(self, src: Path, out: Path, fake_popen: type[FakePopen], monkeypatch: pytest.MonkeyPatch,
+                            caplog: pytest.LogCaptureFixture, lines: list[str], logged: list[str]) -> None:
+        monkeypatch.setattr(fake_popen, 'output', ''.join(f'{line}\n' for line in lines).encode())
+
+        assert run_backup(out, [str(src)]) == 0
+        assert [m[7:] for m in caplog.messages if m.startswith('rsync: ')] == logged
+
     def test_rsync_missing(self, src: Path, out: Path, tmp_path: Path, fake_popen: type[FakePopen],
                            old_backups: list[str], monkeypatch: pytest.MonkeyPatch,
                            caplog: pytest.LogCaptureFixture) -> None: