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.

simple_backup/simple_backup.py

@@ -24,6 +24,7 @@ import re
 import shlex
 import sys
 import warnings
+from collections import deque
 from collections.abc import Callable, Iterator
 from datetime import datetime
 from functools import wraps
@@ -774,7 +775,8 @@ class Backup:
             assert p.stdin is not None and isinstance(p.stdout, io.BufferedIOBase)
             p.stdin.close()
 
-            output = []
+            # Without -v, only the summary (the last two lines) is logged
+            output: list[str] | deque[str] = [] if self._verbose else deque(maxlen=2)
 
             try:
                 for r in _read_records(p.stdout):
@@ -790,8 +792,9 @@ class Backup:
             if self._verbose:
                 logger.info('rsync: %s', output)
             else:
-                logger.info('rsync: %s', output[-2])
-                logger.info('rsync: %s', output[-1])
+                # May be fewer than two lines, e.g. with --rsync-options q
+                for r in output:
+                    logger.info('rsync: %s', r)
         else:
             self._returncode_log(returncode)
 

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: